Phenotyping the Immune Response to Trauma: A Multiparametric Systems Immunology Approach

An immune signature of postoperative cognitive decline: a prospective cohort study

BACKGROUND

Postoperative cognitive decline (POCD) is the predominant complication affecting patients over 60 years old following major surgery, yet its prediction and prevention remain challenging. Understanding the biological processes underlying the pathogenesis of POCD is essential for identifying mechanistic biomarkers to advance diagnostics and therapeutics. This study aimed to provide a comprehensive analysis of immune cell trajectories differentiating patients with and without POCD and to derive a predictive score enabling the identification of high-risk patients during the preoperative period.

MATERIAL AND METHODS

Twenty-six patients aged 60 years old and older undergoing elective major orthopedic surgery were enrolled in a prospective longitudinal study, and the occurrence of POCD was assessed 7 days after surgery. Serial samples collected before surgery, and 1, 7, and 90 days after surgery were analyzed using a combined single-cell mass cytometry and plasma proteomic approach. Unsupervised clustering of the high-dimensional mass cytometry data was employed to characterize time-dependent trajectories of all major innate and adaptive immune cell frequencies and signaling responses. Sparse machine learning coupled with data-driven feature selection was applied to the presurgery immunological dataset to classify patients at risk for POCD.

RESULTS

The analysis identified cell-type and signaling-specific immune trajectories differentiating patients with and without POCD. The most prominent trajectory features revealed early exacerbation of JAK/STAT and dampening of inhibitory κB and nuclear factor-κB immune signaling responses in patients with POCD. Further analyses integrating immunological and clinical data collected before surgery identified a preoperative predictive model comprising one plasma protein and 10 immune cell features that classified patients at risk for POCD with excellent accuracy (AUC=0.80, P =2.21e-02 U -test).

CONCLUSION

Immune system-wide monitoring of patients over 60 years old undergoing surgery unveiled a peripheral immune signature of POCD. A predictive model built on immunological data collected before surgery demonstrated greater accuracy in predicting POCD compared to known clinical preoperative risk factors, offering a concise list of biomarker candidates to personalize perioperative management.

NETWORK ANALYSIS OF SINGLE-NUCLEOTIDE POLYMORPHISMS ASSOCIATED WITH ABERRANT INFLAMMATION IN TRAUMA PATIENTS SUGGESTS A ROLE FOR VESICLE-ASSOCIATED INFLAMMATORY PROGRAMS INVOLVING CD55

ABSTRACT

Background: Critical illness stemming from severe traumatic injury is a leading cause of morbidity and mortality worldwide and involves the dysfunction of multiple organ systems, driven, at least in part, by dysregulated inflammation. We and others have shown a key role for genetic predisposition to dysregulated inflammation and downstream adverse critical illness outcomes. Recently, we demonstrated an association among genotypes at the single-nucleotide polymorphism (SNP) rs10404939 in LYPD4 , dysregulated systemic inflammation, and adverse clinical outcomes in a broad sample of ~1,000 critically ill patients. Methods: We sought to gain mechanistic insights into the role of LYPD4 in critical illness by bioinformatically analyzing potential interactions among rs10404939 and other SNPs. We analyzed a dataset of common (i.e., not rare) SNPs previously defined to be associated with genotype-specific, significantly dysregulated systemic inflammation trajectories in trauma patients, in comparison to a control dataset of common SNPs determined to exhibit an absence of genotype-specific inflammatory responses. Results: In the control dataset, this analysis implicated SNPs associated with phosphatidylinositol and various membrane transport proteins, but not LYPD4. In the patient subset with genotypically dysregulated inflammation, our analysis suggested the co-localization to lipid rafts of LYPD4 and the complement receptor CD55, as well as the neurally related CNTNAP2 and RIMS4. Segregation of trauma patients based on genotype of the CD55 SNP rs11117564 showed distinct trajectories of organ dysfunction and systemic inflammation despite similar demographics and injury characteristics. Conclusion: These analyses define novel interactions among SNPs that could enhance our understanding of the response to traumatic injury and critical illness.

Clinical features, cerebrospinal fluid changes, and prognosis in Chinese patients with autoimmune encephalitis

INTRODUCTION

Autoimmune encephalitis (AE) is a rare, treatable disease of the central nervous system (CNS) caused by an antibody-related immune response. This study is to investigate the correlation of clinical features, cerebrospinal fluid (CSF) characteristics, and prognosis in patients with AE.

METHODS

A total of 71 patients diagnosed with antibody-positive AE were retrospectively analyzed. The patients were divided into three groups: anti-NMDAR group, anti-LGI1 group, and other types. Clinical data were collected to analyze clinical features and CSF results, and prognosis was determined by modified Rankin Scale (mRS).

RESULTS

There was statistical difference in the incidences of decreased consciousness level (P < 0.001), memory loss (P = 0.017), speech disorders (P = 0.035), and dyskinesia (P = 0.001) in different antibodies groups. Younger age (P = 0.018), elevated CSF chloride content (P = 0.006), and white blood cells > 50/mm3 (P = 0.026) were highly correlated with ICU admission. Anti-LGI1 encephalitis had a relatively small risk for ICU admission (P = 0.034), and a lower risk of poor functional recovery (P = 0.048) and recurrence (P = 0.041). Patients with first-line treatment failure (P = 0.021) had an increased risk of poor functional recovery. Delayed treatment (P = 0.011) would increase the risk of recurrence.

CONCLUSION

There are differences in age, gender, clinical characteristics, and CSF results in different subtypes of AE. First-line therapy failure would have poor functional recovery, and delayed therapy would increase the risk of relapse. Chloride ion content and white blood cell count in cerebrospinal fluid are positively correlated with the patient's exacerbation and admission to ICU. These indicators have certain clinical value for the prognosis of AE patients.

Digital twin mathematical models suggest individualized hemorrhagic shock resuscitation strategies

BACKGROUND

Optimizing resuscitation to reduce inflammation and organ dysfunction following human trauma-associated hemorrhagic shock is a major clinical hurdle. This is limited by the short duration of pre-clinical studies and the sparsity of early data in the clinical setting.

METHODS

We sought to bridge this gap by linking preclinical data in a porcine model with clinical data from patients from the Prospective, Observational, Multicenter, Major Trauma Transfusion (PROMMTT) study via a three-compartment ordinary differential equation model of inflammation and coagulation.

RESULTS

The mathematical model accurately predicts physiologic, inflammatory, and laboratory measures in both the porcine model and patients, as well as the outcome and time of death in the PROMMTT cohort. Model simulation suggests that resuscitation with plasma and red blood cells outperformed resuscitation with crystalloid or plasma alone, and that earlier plasma resuscitation reduced injury severity and increased survival time.

CONCLUSIONS

This workflow may serve as a translational bridge from pre-clinical to clinical studies in trauma-associated hemorrhagic shock and other complex disease settings.

The contribution of the meningeal immune interface to neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI) is a major cause of disability and mortality worldwide, particularly among the elderly, yet our mechanistic understanding of what renders the post-traumatic brain vulnerable to poor outcomes, and susceptible to neurological disease, is incomplete. It is well established that dysregulated and sustained immune responses elicit negative consequences after TBI; however, our understanding of the neuroimmune interface that facilitates crosstalk between central and peripheral immune reservoirs is in its infancy. The meninges serve as the interface between the brain and the immune system, facilitating important bi-directional roles in both healthy and disease settings. It has been previously shown that disruption of this system exacerbates neuroinflammation in age-related neurodegenerative disorders such as Alzheimer's disease; however, we have an incomplete understanding of how the meningeal compartment influences immune responses after TBI. In this manuscript, we will offer a detailed overview of the holistic nature of neuroinflammatory responses in TBI, including hallmark features observed across clinical and animal models. We will highlight the structure and function of the meningeal lymphatic system, including its role in immuno-surveillance and immune responses within the meninges and the brain. We will provide a comprehensive update on our current knowledge of meningeal-derived responses across the spectrum of TBI, and identify new avenues for neuroimmune modulation within the neurotrauma field.

An immune signature of postoperative cognitive decline in elderly patients

Postoperative cognitive decline (POCD) is the predominant complication affecting elderly patients following major surgery, yet its prediction and prevention remain challenging. Understanding biological processes underlying the pathogenesis of POCD is essential for identifying mechanistic biomarkers to advance diagnostics and therapeutics. This longitudinal study involving 26 elderly patients undergoing orthopedic surgery aimed to characterize the impact of peripheral immune cell responses to surgical trauma on POCD. Trajectory analyses of single-cell mass cytometry data highlighted early JAK/STAT signaling exacerbation and diminished MyD88 signaling post-surgery in patients who developed POCD. Further analyses integrating single-cell and plasma proteomic data collected before surgery with clinical variables yielded a sparse predictive model that accurately identified patients who would develop POCD (AUC = 0.80). The resulting POCD immune signature included one plasma protein and ten immune cell features, offering a concise list of biomarker candidates for developing point-of-care prognostic tests to personalize perioperative management of at-risk patients. The code and the data are documented and available at https://github.com/gregbellan/POCD .

Teaser

Modeling immune cell responses and plasma proteomic data predicts postoperative cognitive decline.

CD4 + T cells ferroptosis is associated with the development of sepsis in severe polytrauma patients

BACKGROUND

Immunological disorder remains a great challenge in severe poly-trauma, in which lymphopenia is an important contributor. The purpose of present study is to explore whether ferroptosis, a new manner of programmed cell death (PCD), is involved in the lymphocyte depletion and predictive to the adverse prognosis of severe injuries.

PATIENTS AND METHODS

Severe polytrauma patients admitted from January 2022 to December 2022 in our trauma center were prospectively investigated. Peripheral blood samples were collected at admission (day 1), day 3 and day 7 from them. Included patients were classified based on whether they developed sepsis or not. Clinical outcomes, systematic inflammatory response, lymphocyte subpopulation, CD4 + T cell ferroptosis were collected, detected and analyzed.

RESULTS

Notable lymphopenia was observed on the first day after severe trauma and failed to normalize on the 7th day if patients were complicated with sepsis, in which CD4 + T cell was the subset of lymphocyte that depleted most pronouncedly. Lymphocyte loss was significantly correlated with the acute and biphasic systemic inflammatory response. Ferroptosis participated in the death of CD4 + T cells, potentially mediated by the downregulation of xCT-GSH-GPX4 pathway. CD4 + T cells ferroptosis had a conducive predicting value for the development of sepsis following severe trauma.

CONCLUSIONS

CD4 + T cells ferroptosis occurs early in the acute stage of severe polytrauma, which may become a promising biomarker and therapeutic target for post-traumatic sepsis.

Elevation of White Blood Cell Subtypes in Adult Trauma Patients with Stress-Induced Hyperglycemia

BACKGROUND

Blood immune cell subset alterations following trauma can indicate a patient's immune-inflammatory status. This research explored the influence of stress-induced hyperglycemia (SIH) on platelet counts and white blood cell (WBC) subtypes, including the derived indices of the monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), in trauma patients.

METHODS

We studied 15,480 adult trauma patients admitted from 1 January 1998 to 31 December 2022. They were categorized into four groups: nondiabetic normoglycemia (NDN, n = 11,602), diabetic normoglycemia (DN, n = 1750), SIH (n = 716), and diabetic hyperglycemia (DH, n = 1412). A propensity score-matched cohort was formed after adjusting for age, sex, and comorbidities, allowing for comparing the WBC subtypes and platelet counts.

RESULTS

Patients with SIH exhibited significantly increased counts of monocytes, neutrophils, and lymphocytes in contrast to NDN patients. However, no significant rise in platelet counts was noted in the SIH group. There were no observed increases in these cell counts in either the DN or DH groups.

CONCLUSIONS

Our results demonstrated that trauma patients with SIH showed significantly higher counts of monocytes, neutrophils, and lymphocytes when compared to NDN patients, whereas the DN and DH groups remained unaffected. This underscores the profound association between SIH and elevated levels of specific WBC subtypes.

Interleukin-17 as a spatiotemporal bridge from acute to chronic inflammation: Novel insights from computational modeling

A systematic review of several acute inflammatory diseases ranging from sepsis and trauma/hemorrhagic shock to the relevant pathology of the decade, COVID-19, points to the cytokine interleukin (IL)-17A as being centrally involved in the propagation of inflammation. We summarize the role of IL-17A in acute inflammation, leveraging insights made possible by biological network analysis and novel computational methodologies aimed at defining the spatiotemporal spread of inflammation in both experimental animal models and humans. These studies implicate IL-17A in the cross-tissue spread of inflammation, a process that appears to be in part regulated through neural mechanisms. Although acute inflammatory diseases are currently considered distinct from chronic inflammatory pathologies, we suggest that chronic inflammation may represent repeated, cyclical episodes of acute inflammation driven by mechanisms involving IL-17A. Thus, insights from computational modeling of acute inflammatory diseases may improve diagnosis and treatment of chronic inflammation; in turn, therapeutics developed for chronic/autoimmune disease may be of benefit in acute inflammation. This article is categorized under: Immune System Diseases > Computational Models.

Central role for neurally dysregulated IL-17A in dynamic networks of systemic and local inflammation in combat casualties

Dynamic Network Analysis (DyNA) and Dynamic Hypergraphs (DyHyp) were used to define protein-level inflammatory networks at the local (wound effluent) and systemic circulation (serum) levels from 140 active-duty, injured service members (59 with TBI and 81 non-TBI). Interleukin (IL)-17A was the only biomarker elevated significantly in both serum and effluent in TBI vs. non-TBI casualties, and the mediator with the most DyNA connections in TBI wounds. DyNA combining serum and effluent data to define cross-compartment correlations suggested that IL-17A bridges local and systemic circulation at late time points. DyHyp suggested that systemic IL-17A upregulation in TBI patients was associated with tumor necrosis factor-α, while IL-17A downregulation in non-TBI patients was associated with interferon-γ. Correlation analysis suggested differential upregulation of pathogenic Th17 cells, non-pathogenic Th17 cells, and memory/effector T cells. This was associated with reduced procalcitonin in both effluent and serum of TBI patients, in support of an antibacterial effect of Th17 cells in TBI patients. Dysregulation of Th17 responses following TBI may drive cross-compartment inflammation following combat injury, counteracting wound infection at the cost of elevated systemic inflammation.

Multi-omic molecular profiling and network biology for precision anaesthesiology: a narrative review

Technological advancement, data democratisation, and decreasing costs have led to a revolution in molecular biology in which the entire set of DNA, RNA, proteins, and various other molecules - the 'multi-omic' profile - can be measured in humans. Sequencing 1 million bases of human DNA now costs US$0.01, and emerging technologies soon promise to reduce the cost of sequencing the whole genome to US$100. These trends have made it feasible to sample the multi-omic profile of millions of people, much of which is publicly available for medical research. Can anaesthesiologists use these data to improve patient care? This narrative review brings together a rapidly growing literature in multi-omic profiling across numerous fields that points to the future of precision anaesthesiology. Here, we discuss how DNA, RNA, proteins, and other molecules interact in molecular networks that can be used for preoperative risk stratification, intraoperative optimisation, and postoperative monitoring. This literature provides evidence for four fundamental insights: (1) Clinically similar patients have different molecular profiles and, as a consequence, different outcomes. (2) Vast, publicly available, and rapidly growing molecular datasets have been generated in chronic disease patients and can be repurposed to estimate perioperative risk. (3) Multi-omic networks are altered in the perioperative period and influence postoperative outcomes. (4) Multi-omic networks can serve as empirical, molecular measurements of a successful postoperative course. With this burgeoning universe of molecular data, the anaesthesiologist-of-the-future will tailor their clinical management to an individual's multi-omic profile to optimise postoperative outcomes and long-term health.

MACROPHAGE SWITCHING: POLARIZATION AND MOBILIZATION AFTER TRAUMA

ABSTRACT

Introduction: Trauma alters the immune response in numerous ways, affecting both the innate and adaptive responses. Macrophages play an important role in inflammation and wound healing following injury. We hypothesize that macrophages mobilize from the circulation to the site of injury and secondary sites after trauma, with a transition from proinflammatory (M1) shortly after trauma to anti-inflammatory (M2) at later time points. Methods: C57Bl6 mice (n = 6/group) underwent a polytrauma model using cardiac puncture/hemorrhage, pseudofemoral fracture, and liver crush injury. The animals were killed at several time points: uninjured, 24 h, and 7 days. Peripheral blood mononuclear cells, spleen, liver nonparenchymal cells, and lung were harvested, processed, and stained for flow cytometry. Macrophages were identified as CD68 + ; M1 macrophages were identified as iNOS + ; M2 macrophages as arginase 1 + . Results: We saw a slight presence of M1 macrophages at baseline in peripheral blood mononuclear cells (6.6%), with no significant change at 24 h and 7 days after polytrauma. In contrast, the spleen has a larger population of M1 macrophages at baseline (27.7%), with levels decreasing at 24 h and 7 days after trauma (20.6% and 12.6%, respectively). A similar trend is seen in the lung where at baseline 14.9% of CD68 + macrophages are M1, with subsequent continual decrease reaching 8.7% at 24 h and 4.4% at 7 days after polytrauma. M1 macrophages in the liver represent 14.3% of CD68 + population in the liver nonparenchymal cells at baseline. This percentage increases to 20.8% after trauma and decreases at 7 days after polytrauma (13.4%). There are few M2 macrophages in circulating peripheral blood mononuclear cells and in spleen at baseline and after trauma. The percentage of M2 macrophages in the lungs remains constant after trauma (7.2% at 24 h and 9.2% at 7 days). In contrast, a large proportion of M2 macrophages are seen in the liver at baseline (36.0%). This percentage trends upward and reaches 45.6% acutely after trauma and drops to 21.4% at 7 days. The phenotypic changes in macrophages seen in the lungs did not correlate with a functional change in the ability of the macrophages to perform oxidative burst, with an increase from 2.0% at baseline to 22.1% at 7 days after polytrauma ( P = 0.0258). Conclusion: Macrophage phenotypic changes after polytrauma are noted, especially with a decrease in the lung M1 phenotype and a short-term increase in the M2 phenotype in the liver. However, macrophage function as measured by oxidative burst increased over the time course of trauma, which may signify a change in subset polarization after injury not captured by the typical macrophage phenotypes.

Neutrophil phenotypes implicated in the pathophysiology of post-traumatic sepsis

BACKGROUND

The disruption of immune homeostasis after trauma is a major cause of post-traumatic organ dysfunction and/or sepsis. Recently, a variety of neutrophil phenotypes with distinct functions have been identified and suggested as involved in various clinical conditions. The association between neutrophil phenotypes and post-traumatic immunodeficiency has also been reported, yet the specific neutrophil phenotypes and their functional significance in post-traumatic sepsis have not been fully clarified. Therefore, we sought to investigate neutrophil phenotypic changes in a murine model, as these may hold prognostic value in post-traumatic sepsis.

MATERIALS AND METHODS

Third-degree burns affecting 25% of the body surface area were used to establish trauma model, and sepsis was induced 24 h later through cecal ligation and puncture (CLP). The Burn/CLP post-traumatic sepsis model and the Sham/CLP control model were established to assess the immunological status after trauma. Histopathological evaluation was performed on the spleen, liver, kidneys, and lung tissues. Immunological evaluation included the assessment of neutrophil markers using mass cytometry as well as cytokine measurements in serum and ascitic fluid through multiplex analysis using LUMINEX®.

RESULTS

The Burn/CLP group had a lower survival rate than the Sham/CLP group. Histopathological examination revealed an impaired immune response and more advanced organ damage in the Burn/CLP group. Furthermore, the Burn/CLP group exhibited higher levels of transforming growth factor-beta 1 in the blood and generally lower levels of cytokines than the Sham/CLP group. CD11b, which is involved in neutrophil adhesion and migration, was highly expressed on neutrophils in the Burn/CLP group. The expression of CD172a, which is related to the inhibition of phagocytosis, was also upregulated on neutrophils in the Burn/CLP group. The expression of sialic acid-binding lg-like lectin F and CD68 also differed between the two groups.

CONCLUSION

Different neutrophil phenotypes were observed between Burn/CLP and Sham/CLP groups, suggesting that neutrophils are implicated in the immune imbalance following trauma. However, further studies are needed to prove the causal relationships between neutrophil phenotypes and outcomes, including survival rate and organ dysfunction.

Immune modulation after traumatic brain injury

Traumatic brain injury (TBI) induces instant activation of innate immunity in brain tissue, followed by a systematization of the inflammatory response. The subsequent response, evolved to limit an overwhelming systemic inflammatory response and to induce healing, involves the autonomic nervous system, hormonal systems, and the regulation of immune cells. This physiological response induces an immunosuppression and tolerance state that promotes to the occurrence of secondary infections. This review describes the immunological consequences of TBI and highlights potential novel therapeutic approaches using immune modulation to restore homeostasis between the nervous system and innate immunity.

Importance of the neutrophil‑to‑lymphocyte ratio as a prognostic factor in patients with spleen trauma: A single center experience

Abdominal trauma is a common diagnosis for patients admitted to the emergency room. Evaluation of the severity of such patients can sometimes be difficult due to rapid hemodynamic changes caused by the activation of inflammatory and anti-inflammatory regulatory mechanisms. To evaluate the prognosis of trauma patients, it is crucial to identify these changes and adapt various treatment strategies. Using the records of the Mures County Emergency Clinical Hospital, 126 patients were included in the present study with traumatic splenic injury admitted over 6 years. Blood parameters such as the neutrophil, lymphocyte, and platelet counts, the neutrophil to lymphocyte ratio (NLR), and the platelet to lymphocyte ratio (PLR) were determined, and the association between these and the severity of the traumatic injury [quantified as the injury severity score (ISS)] was calculated. We used linear and multiple regression analyses to identify and quantify the relationships. We found statistically significant associations between the ISS and the NLR (P=0.002), with an AUC of 0.816 and a cut-off value of NLR=6.075 (sensitivity=76.7%, specificity=74.3%), and between the ISS and hemoglobin (P<0.0001), hematocrit (P<0.0001), neutrophil count (P<0.0001), lymphocyte count (P=0.0224), and platelet count (P=0.0163). No association was found between the PLR and the severity of trauma. An elevated NLR at admission in trauma patients had significant predictive power for the severity of trauma. Patients with an NLR greater than the cut-off value of 6.075 were more likely to have suffered serious injuries and undergone deterioration.

Genetic and immune crosstalk between severe burns and blunt trauma: A study of transcriptomic data

Background: Severe burns and blunt trauma can lead to multiple organ dysfunction syndrome, the leading cause of death in intensive care units. In addition to infection, the degree of immune inflammatory response also affects prognosis. However, the characteristics and clinical relevance of the common mechanisms of these major diseases are still underexplored.

Methods: In the present study, we performed microarray data analysis to identify immune-related differentially expressed genes (DEGs) involved in both disease progression in burns and blunt trauma. Six analyses were subsequently performed, including gene enrichment analysis, protein‐protein interaction (PPI) network construction, immune cell infiltration analysis, core gene identification, co-expression network analysis, and clinical correlation analysis.

Results: A total of 117 common immune-related DEGs was selected for subsequent analyses. Functional analysis emphasizes the important role of Th17 cell differentiation, Th1 and Th2 cell differentiation, Cytokine-cytokine receptor interaction and T cell receptor signaling pathway in these two diseases. Finally, eight core DEGs were identified using cytoHubba, including CD8A, IL10, CCL5, CD28, LCK, CCL4, IL2RB, and STAT1. The correlation analysis showed that the identified core DEGs were more or less significantly associated with simultaneous dysregulation of immune cells in blunt trauma and sepsis patients. Of these, the downregulation of CD8A and CD28 had a worse prognosis.

Conclusion: Our analysis lays the groundwork for future studies to elucidate molecular mechanisms shared in burns and blunt trauma. The functional roles of identified core immune-related DEGs and dysregulated immune cell subsets warrant further in-depth study.

Inferring Tissue-Specific, TLR4-Dependent Type 17 Immune Interactions in Experimental Trauma/Hemorrhagic Shock and Resuscitation Using Computational Modeling

Trauma/hemorrhagic shock followed by resuscitation (T/HS-R) results in multi-system inflammation and organ dysfunction, in part driven by binding of damage-associated molecular pattern molecules to Toll-like Receptor 4 (TLR4). We carried out experimental T/HS-R (pseudo-fracture plus 2 h of shock followed by 0-22 h of resuscitation) in C57BL/6 (wild type [WT]) and TLR4-null (TLR4^-/-) mice, and then defined the dynamics of 20 protein-level inflammatory mediators in the heart, gut, lung, liver, spleen, kidney, and systemic circulation. Cross-correlation and Principal Component Analysis (PCA) on data from the 7 tissues sampled suggested that TLR4^-/- samples express multiple inflammatory mediators in a small subset of tissue compartments as compared to the WT samples, in which many inflammatory mediators were localized non-specifically to nearly all compartments. We and others have previously defined a central role for type 17 immune cells in human trauma. Accordingly, correlations between IL-17A and GM-CSF (indicative of pathogenic Th17 cells); between IL-17A and IL-10 (indicative of non-pathogenic Th17 cells); and IL-17A and TNF (indicative of memory/effector T cells) were assessed across all tissues studied. In both WT and TLR4^-/- mice, positive correlations were observed between IL-17A and GM-CSF, IL-10, and TNF in the kidney and gut. In contrast, the variable and dynamic presence of both pathogenic and non-pathogenic Th17 cells was inferred in the systemic circulation of TLR4^-/- mice over time, suggesting a role for TLR4 in efflux of these cells into peripheral tissues. Hypergraph analysis - used to define dynamic, cross compartment networks - in concert with PCA-suggested that IL-17A was present persistently in all tissues at all sampled time points except for its absence in the plasma at 0.5h in the WT group, supporting the hypothesis that T/HS-R induces efflux of Th17 cells from the circulation and into specific tissues. These analyses suggest a complex, context-specific role for TLR4 and type 17 immunity following T/HS-R.

Elevated monocyte distribution width in trauma: An early cellular biomarker of organ dysfunction

INTRODUCTION

Traumatic injury elicits an inflammatory response such as the one occurring during systemic infection. Monocyte distribution width (MDW) has been found to distinguish sepsis in a pool of patients with suspected infection. We hypothesized that an elevated MDW in trauma patients would be associated with the development of multiple organ dysfunction syndrome (MODS) and an increased mortality.

MATERIALS AND METHODS

Observational study in a dedicated trauma Intensive Care Unit (ICU) in Madrid during 2019-2020. Patients were classified according to their first MDW value on admission, as greater or lesser than 21 U. Clinical data was obtained and univariate and multivariate analysis were realized, as well as a test performance analysis.

RESULTS

354 patients were studied, with a median age of 46 years, 78% male. Half presented with severe trauma ISS > 15, mostly with a blunt mechanism of injury. A MDW ≥ 21 U on admission was found in 17% of cases. These patients were more likely to present with hemodynamic instability and MODS. They had a higher length of stay (3.8 vs 2 days) and higher mortality (21 vs 5%) compared to the low MDW group. These findings remained statistically significant in the multivariate analysis, with an OR 4.6 (IC 95% 1.7-12) for MODS and 3.1 (IC 95% 1.2-8.3) for mortality.

CONCLUSIONS

In trauma patients, a MDW ≥ 21 U on admission was independently associated with a greater risk of MODS, a higher mortality and a higher length of stay. This biomarker could be useful in predicting severity in the initial evaluation of trauma patients.

Integrated Single-cell and Plasma Proteomic Modeling to Predict Surgical Site Complications: A Prospective Cohort Study

OBJECTIVE

The aim of this study was to determine whether single-cell and plasma proteomic elements of the host's immune response to surgery accurately identify patients who develop a surgical site complication (SSC) after major abdominal surgery.

SUMMARY BACKGROUND DATA

SSCs may occur in up to 25% of patients undergoing bowel resection, resulting in significant morbidity and economic burden. However, the accurate prediction of SSCs remains clinically challenging. Leveraging high-content proteomic technologies to comprehensively profile patients' immune response to surgery is a promising approach to identify predictive biological factors of SSCs.

METHODS

Forty-one patients undergoing non-cancer bowel resection were prospectively enrolled. Blood samples collected before surgery and on postoperative day one (POD1) were analyzed using a combination of single-cell mass cytometry and plasma proteomics. The primary outcome was the occurrence of an SSC, including surgical site infection, anastomotic leak, or wound dehiscence within 30 days of surgery.

RESULTS

A multiomic model integrating the single-cell and plasma proteomic data collected on POD1 accurately differentiated patients with (n = 11) and without (n = 30) an SSC [area under the curve (AUC) = 0.86]. Model features included coregulated proinflammatory (eg, IL-6- and MyD88- signaling responses in myeloid cells) and immunosuppressive (eg, JAK/STAT signaling responses in M-MDSCs and Tregs) events preceding an SSC. Importantly, analysis of the immunological data obtained before surgery also yielded a model accurately predicting SSCs (AUC = 0.82).

CONCLUSIONS

The multiomic analysis of patients' immune response after surgery and immune state before surgery revealed systemic immune signatures preceding the development of SSCs. Our results suggest that integrating immunological data in perioperative risk assessment paradigms is a plausible strategy to guide individualized clinical care.

Potential Immune Indicators for Predicting the Prognosis of COVID-19 and Trauma: Similarities and Disparities

Although cellular and molecular mediators of the immune system have the potential to be prognostic indicators of disease outcomes, temporal interference between diseases might affect the immune mediators, and make them difficult to predict disease complications. Today one of the most important challenges is predicting the prognosis of COVID-19 in the context of other inflammatory diseases such as traumatic injuries. Many diseases with inflammatory properties are usually polyphasic and the kinetics of inflammatory mediators in various inflammatory diseases might be different. To find the most appropriate evaluation time of immune mediators to accurately predict COVID-19 prognosis in the trauma environment, researchers must investigate and compare cellular and molecular alterations based on their kinetics after the start of COVID-19 symptoms and traumatic injuries. The current review aimed to investigate the similarities and differences of common inflammatory mediators (C-reactive protein, procalcitonin, ferritin, and serum amyloid A), cytokine/chemokine levels (IFNs, IL-1, IL-6, TNF-α, IL-10, and IL-4), and immune cell subtypes (neutrophil, monocyte, Th1, Th2, Th17, Treg and CTL) based on the kinetics between patients with COVID-19 and trauma. The mediators may help us to accurately predict the severity of COVID-19 complications and follow up subsequent clinical interventions. These findings could potentially help in a better understanding of COVID-19 and trauma pathogenesis.

Immunomonitoring of Monocyte and Neutrophil Function in Critically Ill Patients: From Sepsis and/or Trauma to COVID-19

Immune cells and mediators play a crucial role in the critical care setting but are understudied. This review explores the concept of sepsis and/or injury-induced immunosuppression and immuno-inflammatory response in COVID-19 and reiterates the need for more accurate functional immunomonitoring of monocyte and neutrophil function in these critically ill patients. in addition, the feasibility of circulating and cell-surface immune biomarkers as predictors of infection and/or outcome in critically ill patients is explored. It is clear that, for critically ill, one size does not fit all and that immune phenotyping of critically ill patients may allow the development of a more personalized approach with tailored immunotherapy for the specific patient. In addition, at this point in time, caution is advised regarding the quality of evidence of some COVID-19 studies in the literature.

Therapeutic Potential of Mesenchymal Stromal Cell-Derived Extracellular Vesicles in the Prevention of Organ Injuries Induced by Traumatic Hemorrhagic Shock

Severe trauma is the principal cause of death among young people worldwide. Hemorrhagic shock is the leading cause of death after severe trauma. Traumatic hemorrhagic shock (THS) is a complex phenomenon associating an absolute hypovolemia secondary to a sudden and significant extravascular blood loss, tissue injury, and, eventually, hypoxemia. These phenomena are responsible of secondary injuries such as coagulopathy, endotheliopathy, microcirculation failure, inflammation, and immune activation. Collectively, these dysfunctions lead to secondary organ failures and multi-organ failure (MOF). The development of MOF after severe trauma is one of the leading causes of morbidity and mortality, where immunological dysfunction plays a central role. Damage-associated molecular patterns induce an early and exaggerated activation of innate immunity and a suppression of adaptive immunity. Severe complications are associated with a prolonged and dysregulated immune–inflammatory state. The current challenge in the management of THS patients is preventing organ injury, which currently has no etiological treatment available. Modulating the immune response is a potential therapeutic strategy for preventing the complications of THS. Mesenchymal stromal cells (MSCs) are multipotent cells found in a large number of adult tissues and used in clinical practice as therapeutic agents for immunomodulation and tissue repair. There is growing evidence that their efficiency is mainly attributed to the secretion of a wide range of bioactive molecules and extracellular vesicles (EVs). Indeed, different experimental studies revealed that MSC-derived EVs (MSC-EVs) could modulate local and systemic deleterious immune response. Therefore, these new cell-free therapeutic products, easily stored and available immediately, represent a tremendous opportunity in the emergency context of shock. In this review, the pathophysiological environment of THS and, in particular, the crosstalk between the immune system and organ function are described. The potential therapeutic benefits of MSCs or their EVs in treating THS are discussed based on the current knowledge. Understanding the key mechanisms of immune deregulation leading to organ damage is a crucial element in order to optimize the preparation of EVs and potentiate their therapeutic effect.

Polymorphonuclear myeloid-derived suppressor cells link inflammation and damage response after trauma

Elimination of the posttraumatic inflammatory response and recovery of homeostasis are crucial for the positive prognosis of trauma patients. Myeloid-derived suppressor cells (MDSCs) are known to play a regulatory role in the posttraumatic immune response in mice, but their induction source and involved potential mechanism are poorly understood. Here, we report that polymorphonuclear MDSCs (PMN-MDSCs) are activated after trauma and are closely associated with the progression of the posttraumatic inflammatory response. In humans, lectin-type oxidized LDL receptor 1 (LOX1) was used to specifically characterize LOX1⁺ PMN-MDSCs. Trauma patients showed high intracellular reactive oxygen species (ROS) production, as well as activation of LOX1⁺ PMN-MDSCs. These MDSCs contribute to the anti-inflammatory immune response by regulating the Treg/Th17 and Th2/Th1 balances after trauma, increasing the levels of anti-inflammatory factors, and decreasing the levels of proinflammatory factors. The number of LOX1⁺ PMN-MDSCs was positively correlated with the positive clinical prognosis of trauma patients with infection. Activation of LOX1⁺ PMN-MDSCs is mediated by NF-κB signal, and TGF-β1 may be as an important inducer for LOX1⁺ PMN-MDSCs in the posttraumatic cytokine environment. In a pseudofracture trauma mouse model, we also observed the activation of PMN-MDSCs, accompanying high levels of intracellular ROS production, NF-κB phosphorylation, and changes in the inflammatory environment, in particularly by regulating the Treg/Th17 and Th2/Th1 balance. And more significantly, posttraumatic inflammation was alleviated in mice after transferring trauma-derived PMN-MDSCs, but aggravated after injecting with Gr1 agonistic antibody. These findings provide evidence for the specific role of PMN-MDSCs in the regulation of posttraumatic inflammation.

Severe Traumatic Injury Induces Phenotypic and Functional Changes of Neutrophils and Monocytes

Background: Severe traumatic injury has been associated with high susceptibility for the development of secondary complications caused by dysbalanced immune response. As the first line of the cellular immune response, neutrophils and monocytes recruited to the site of tissue damage and/or infection, are divided into three different subsets according to their CD16/CD62L and CD16/CD14 expression, respectively. Their differential functions have not yet been clearly understood. Thus, we evaluated the phenotypic changes of neutrophil and monocyte subsets among their functionality regarding oxidative burst and the phagocytic capacity in severely traumatized patients. Methods: Peripheral blood was withdrawn from severely injured trauma patients (TP; n = 15, ISS ≥ 16) within the first 12 h post-trauma and from healthy volunteers (HV; n = 15) and stimulated with fMLP and PMA. CD16^dimCD62L^bright (immature), CD16^brightCD62L^bright (mature) and CD16^brightCD62L^dim (CD62L^low) neutrophil subsets and CD14^brightCD16⁻ (classical), CD14^brightCD16⁺ (intermediate) and CD14^dimCD16⁺ (non-classical) monocyte subsets of HV and TP were either directly analyzed by flow cytometry or the examined subsets of HV were sorted first by fluorescence-activated cell sorting and subsequently analyzed. Subset-specific generation of reactive oxygen species (ROS) and of E. coli bioparticle phagocytosis were evaluated. Results: In TP, the counts of immature neutrophils were significantly increased vs. HV. The numbers of mature and CD62L^dim neutrophils remained unchanged but the production of ROS was significantly enhanced in TP vs. HV and the stimulation with fMLP significantly increased the generation of ROS in the mature and CD62L^dim neutrophils of HV. The counts of phagocyting neutrophils did not change but the mean phagocytic capacity showed an increasing trend in TP. In TP, the monocytes shifted toward the intermediate phenotype, whereas the classical and non-classical monocytes became less abundant. ROS generation was significantly increased in all monocyte subsets in TP vs. HV and PMA stimulation significantly increased those level in both, HV and TP. However, the PMA-induced mean ROS generation was significantly lower in intermediate monocytes of TP vs. HV. Sorting of monocyte and neutrophil subsets revealed a significant increase of ROS and decrease of phagocytic capacity vs. whole blood analysis. Conclusions: Neutrophils and monocytes display a phenotypic shift following severe injury. The increased functional abnormalities of certain subsets may contribute to the dysbalanced immune response and attenuate the antimicrobial function and thus, may represent a potential therapeutic target. Further studies on isolated subsets are necessary for evaluation of their physiological role after severe traumatic injury.

Deep immune profiling of whole blood to identify early immune signatures that correlate to patient outcome after major trauma

BACKGROUND

Major injury results in an early cascade of immunologic responses that increase susceptibility to infection and multiorgan dysfunction. Detailed immune profiling by mass cytometry has the potential to identify immune signatures that correspond to patient outcomes. Our objective was to determine the prognostic value of immune signatures early after major trauma injury.

METHODS

Trauma patients (n = 17) were prospectively enrolled between September 2018 and December 2019. Serial whole blood samples were obtained from trauma patients (mean Injury Severity Score, 26.2; standard error of the mean, 3.7) at Days 1 and 3 after injury, and from age- and sex-matched uninjured controls using a standardized protocol for fixation, storage, and labeling. Computational analyses including K-nearest neighbor automated clustering of immune cells and Spearman's correlation analysis were used to identify correlations between cell populations, clinical measures, and patient outcomes.

RESULTS

Analysis revealed nine immune cell clusters that correlated with one or more clinical outcomes. On Days 1 and 3 postinjury, the abundance of immature neutrophil and classical monocytes exhibited a strong positive correlation with increased intensive care unit and hospital length of stay. Conversely, the abundance of CD4 T-cell subsets, namely Th17 cells, is associated with improved patient outcomes including decreased ventilator days (r = -0.76), hospital-acquired pneumonia (r = -0.69), and acute kidney injury (r = -0.73).

CONCLUSION

Here, we provide a comprehensive multitime point immunophenotyping analysis of whole blood from patients soon after traumatic injury to determine immune correlates of adverse outcomes. Our findings indicate that alterations in myeloid-origin cell types may contribute to immune dysfunction after injury. Conversely, the presence of effector T cell populations corresponds with decreased hospital length of stay and organ dysfunction. Overall, these data identify novel immune signatures following traumatic injury that support the view that monitoring of immune (sub)-populations may provide clinical decision-making support for at-risk patients early in their hospital course.

LEVEL OF EVIDENCE

Prognostic/Epidemiologic, Level IV.

A putative "chemokine switch" that regulates systemic acute inflammation in humans

Systemic inflammation is complex and likely drives clinical outcomes in critical illness such as that which ensues following severe injury. We obtained time course data on multiple inflammatory mediators in the blood of blunt trauma patients. Using dynamic network analyses, we inferred a novel control architecture for systemic inflammation: a three-way switch comprising the chemokines MCP-1/CCL2, MIG/CXCL9, and IP-10/CXCL10. To test this hypothesis, we created a logical model comprising this putative architecture. This model predicted key qualitative features of systemic inflammation in patient sub-groups, as well as the different patterns of hospital discharge of moderately vs. severely injured patients. Thus, a rational transition from data to data-driven models to mechanistic models suggests a novel, chemokine-based mechanism for control of acute inflammation in humans and points to the potential utility of this workflow in defining novel features in other complex diseases.

Alterations of Phagocytic Activity and Capacity in Granulocytes and Monocytes Depend on the Pathogen Strain in Porcine Polytrauma

Background: Polytraumatized patients undergo a strong immunological stress upon insult. Phagocytes (granulocytes and monocytes) play a substantial role in immunological defense against bacteria, fungi and yeast, and in the clearance of cellular debris after tissue injury. We have reported a reduced monocytes phagocytic activity early after porcine polytrauma before. However, it is unknown if both phagocyte types undergo those functional alterations, and if there is a pathogen-specific phagocytic behavior. We characterized the phagocytic activity and capacity of granulocytes and monocytes after polytrauma.

Methods: Eight pigs (Sus scrofa) underwent polytrauma consisting of lung contusion, liver laceration, tibial fracture and hemorrhagic shock with fluid resuscitation and fracture fixation with external fixator. Intensive care treatment including mechanical ventilation for 72 h followed. Phagocytic activity and capacity were investigated using an in vitro ex vivo whole blood stimulation phagocytosis assays before trauma, after surgery, 24, 48, and 72 h after trauma. Blood samples were stimulated with Phorbol-12-myristate-13-acetate and incubated with FITC-labeled E. coli, S. aureus or S. cerevisiae for phagocytosis assessment by flow cytometry.

Results: Early polytrauma-induced significant increase of granulocytes and monocytes declined to baseline values within 24 h. Percentage of E. coli-phagocytizing granulocytes significantly decreased after polytrauma and during further intensive care treatment, while their capacity significantly increased. Interestingly, both granulocytic phagocytic activity and capacity of S. aureus significantly decreased after trauma, although a recovery was observed after 24 h and yet was followed by another decrease. The percentage of S. cerevisiae-phagocytizing granulocytes significantly increased after 24 h, while their impaired capacity after surgery and 72 h later was detected. Monocytic E. coli-phagocytizing percentage did not change, while their capacity increased after 24–72 h. After a significant decrease in S. aureus-phagocytizing monocytes after surgery, a significant increase after 24 and 48 h was observed without capacity alterations. No significant changes in S. cerevisiae-phagocytizing monocytes occurred, but their capacity dropped 48 and 72 h.

Conclusion: Phagocytic activity and capacity of granulocytes and monocytes follow a different pattern and significantly change within 72 h after polytrauma. Both phagocytic activity and capacity show significantly different alterations depending on the pathogen strain, thus potentially indicating at certain and possibly more relevant infection causes after polytrauma.

A road map from single-cell transcriptome to patient classification for the immune response to trauma

Immune dysfunction is an important factor driving mortality and adverse outcomes after trauma but remains poorly understood, especially at the cellular level. To deconvolute the trauma-induced immune response, we applied single-cell RNA sequencing to circulating and bone marrow mononuclear cells in injured mice and circulating mononuclear cells in trauma patients. In mice, the greatest changes in gene expression were seen in monocytes across both compartments. After systemic injury, the gene expression pattern of monocytes markedly deviated from steady state with corresponding changes in critical transcription factors, which can be traced back to myeloid progenitors. These changes were largely recapitulated in the human single-cell analysis. We generalized the major changes in human CD14⁺ monocytes into 6 signatures, which further defined 2 trauma patient subtypes (SG1 vs. SG2) identified in the whole-blood leukocyte transcriptome in the initial 12 hours after injury. Compared with SG2, SG1 patients exhibited delayed recovery, more severe organ dysfunction, and a higher incidence of infection and noninfectious complications. The 2 patient subtypes were also recapitulated in burn and sepsis patients, revealing a shared pattern of immune response across critical illness. Our data will be broadly useful to further explore the immune response to inflammatory diseases and critical illness.

Computational Derivation of Core, Dynamic Human Blunt Trauma Inflammatory Endotypes

Systemic inflammation ensues following traumatic injury, driving immune dysregulation and multiple organ dysfunction (MOD). While a balanced immune/inflammatory response is ideal for promoting tissue regeneration, most trauma patients exhibit variable and either overly exuberant or overly damped responses that likely drive adverse clinical outcomes. We hypothesized that these inflammatory phenotypes occur in the context of severe injury, and therefore sought to define clinically distinct endotypes of trauma patients based on their systemic inflammatory responses. Using Patient-Specific Principal Component Analysis followed by unsupervised hierarchical clustering of circulating inflammatory mediators obtained in the first 24 h after injury, we segregated a cohort of 227 blunt trauma survivors into three core endotypes exhibiting significant differences in requirement for mechanical ventilation, duration of ventilation, and MOD over 7 days. Nine non-survivors co-segregated with survivors. Dynamic network inference, Fisher Score analysis, and correlations of IL-17A with GM-CSF, IL-10, and IL-22 in the three survivor sub-groups suggested a role for type 3 immunity, in part regulated by Th17 and γδ 17 cells, and related tissue-protective cytokines as a key feature of systemic inflammation following injury. These endotypes may represent archetypal adaptive, over-exuberant, and overly damped inflammatory responses.

Cellular and molecular mechanisms of IMMunE dysfunction and Recovery from SEpsis-related critical illness in adults: An observational cohort study (IMMERSE) protocol paper

Sepsis is a common illness. Immune responses are considered major drivers of sepsis illness and outcomes. However, there are no proven immunomodulator therapies in sepsis. We hypothesised that in-depth characterisation of sepsis-specific immune trajectory may inform immunomodulation in sepsis-related critical illness. We describe the protocol of the IMMERSE study to address this hypothesis. We include critically ill sepsis patients without documented immune comorbidity and age–sex matched cardiac surgical patients as controls. We plan to perform an in-depth biological characterisation of innate and adaptive immune systems, platelet function, humoral components and transcriptional determinants of the immune system responses in sepsis. This will be done at pre-specified time points during their critical illness to generate an illness trajectory. The sample size for each biological assessment is different and is described in detail. In summary, the overall aim of the IMMERSE study is to increase the granularity of longitudinal immunology model of sepsis to inform future immunomodulation trials.

Peripheral cytokines are not influenced by the type of surgical approach for non-small cell lung cancer by four weeks postoperatively

OBJECTIVES

The influence of surgical approach on systemic inflammatory response and the subsequent oncologic impact for non-small cell lung cancer is debated. We aimed to measure the effects of thoracic surgical approach on peripheral cytokine milieu over time.

METHODS

Patients undergoing primary lung resection without neoadjuvant therapy (2016-2018) were evaluated. A panel of 43 cytokines, angiogenic factors, and inflammatory molecules (CAFs) were evaluated in peripheral blood preoperatively, at 24 -hs and 4-weeks postoperatively. Differences between CAFs in patients undergoing thoracotomy versus video-assisted thoracoscopic surgery (VATS) at all timepoints were assessed using Student's t-test.

RESULTS

76 patients with available peripheral CAF panels met inclusion criteria. Thoracotomy was performed in 53 (70 %) patients while VATS was undertaken in 23 (30 %). Upon examination of known inflammatory CAFs, including IL-1β, IL-6, IL-8, IL-10, IFN-γ, and soluble (s) CD27, no differences were detected at 24 h or 4 weeks postoperatively between surgical groups. Examination of trends over time did not demonstrate any temporal derangements for these CAFs, with return to baseline levels by 4 weeks postoperatively for both groups. Evaluation of soluble (s) checkpoint molecules, including sPD-1, sPD-L1, sTIM-3, and sCTLA-4, did not reveal any differences in the immediate postoperative or long-term recovery period.

CONCLUSIONS

Peripheral immune profiles following pulmonary resection do not appear to differ between VATS and thoracotomy postoperatively. CAF fluctuations are transient and recover rapidly. These results, at the peripheral cytokine level, suggest that the surgical approach for lung cancer is unlikely to alter the effectiveness of novel immune-modulating systemic therapies, although more studies are needed to validate these findings.

Preferential inhibition of adaptive immune system dynamics by glucocorticoids in patients after acute surgical trauma

Glucocorticoids (GC) are a controversial yet commonly used intervention in the clinical management of acute inflammatory conditions, including sepsis or traumatic injury. In the context of major trauma such as surgery, concerns have been raised regarding adverse effects from GC, thereby necessitating a better understanding of how GCs modulate the immune response. Here we report the results of a randomized controlled trial (NCT02542592) in which we employ a high-dimensional mass cytometry approach to characterize innate and adaptive cell signaling dynamics after a major surgery (primary outcome) in patients treated with placebo or methylprednisolone (MP). A robust, unsupervised bootstrap clustering of immune cell subsets coupled with random forest analysis shows profound (AUC = 0.92, p-value = 3.16E-8) MP-induced alterations of immune cell signaling trajectories, particularly in the adaptive compartments. By contrast, key innate signaling responses previously associated with pain and functional recovery after surgery, including STAT3 and CREB phosphorylation, are not affected by MP. These results imply cell-specific and pathway-specific effects of GCs, and also prompt future studies to examine GCs' effects on clinical outcomes likely dependent on functional adaptive immune responses.

An Inverse Relationship Between c-Kit/CD117 and mTOR Confers NK Cell Dysregulation Late After Severe Injury

Major trauma-induced tissue injury causes a dysregulation of the immune system. Severe systemic inflammation occurs early after the insult. Later on, an enhanced risk for life-threatening opportunistic infections develops that culminates at the end of the first week after trauma. CD56^bright Natural killer (NK) cells play a key role in the defense against infection due to their rapid release of Interferon (IFN) γ in response to Interleukin (IL) 12. NK cells are impaired in IFN-γ synthesis after severe injury due to a disturbed IL-12/IFN-γ axis. Thereby, a circulating factor mediates extrinsic suppression of NK cells. Yet unknown cell-intrinsic mechanisms manifest by day 8 after trauma and render NK cells unresponsive to stimulatory cytokines. In the present study, we investigated the origin of such late NK cell-intrinsic suppression after major trauma. Peripheral blood mononuclear cells (PBMC) were isolated from patients 8 day after severe injury and from healthy control subjects and were stimulated with inactivated Staphylococcus aureus. The expression of diverse cytokine receptors, intracellular signaling molecules, and the secretion of IFN-γ by CD56^bright NK cells were examined. After stimulation with S. aureus, NK cells from patients expressed enhanced levels of c-kit/CD117 that inversely correlated with IFN-γ synthesis and IL-12 receptor (IL-12R) β2 expression. Supplementation with IL-15 and inhibition of the transforming growth factor receptor (TGF-βR) I reduced CD117 expression and increased the level of IL-12Rβ2 and IFN-γ. NK cells from patients showed reduced phosphorylation of mammalian target of rapamycin (mTOR). Addition of IL-15 at least partly restored mTOR phosphorylation and increased IL-12Rβ2 expression. The reduced mTOR phosphorylation after severe injury was cell-intrinsic as it was not induced by serum factors. Inhibition of mTOR in purified NK cells from healthy donors by rapamycin decreased the synthesis of IFN-γ. Thus, impaired mTOR phosphorylation in response to a microbial challenge contributes to the cell-intrinsic mechanisms that underlie NK cell dysregulation after trauma. Restoration of the mTOR phosphorylation capacity along with inhibition of the TGF-βRI signaling in NK cells after severe injury might improve the immune defense against opportunistic infections.

Circulating Factors in Trauma Plasma Activate Specific Human Immune Cell Subsets

BACKGROUND

Trauma causes tissue injury that results in the release of damage associated molecular patterns (DAMPs) and other mediators at the site of injury and systemically. Such mediators disrupt immune system homeostasis and may activate multicellular immune responses with downstream complications such as the development of infections and sepsis. To characterize these alterations, we used time-of-flight mass cytometry to determine how trauma plasma affects normal peripheral blood mononuclear cell (PBMC) activation to gain insights into the kinetics and nature of trauma-induced circulating factors on human immune cell populations. A better understanding of the components that activate cells in trauma may aid in the discovery of therapeutic targets.

METHODS

PBMCs from healthy volunteers were cultured with 5% plasma (healthy, trauma-1day, or trauma-3day) or known DAMPs for 24 h. Samples were stained with a broad immunophenotyping CyTOF antibody panel. Multiplex (Luminex) cytokine assays were used to measure differences in multiple cytokine levels in healthy and trauma plasma samples.

RESULTS

Plasma from day 1, but not day 3 trauma patients induced the acute expansion of CD11c+ NK cells and CD73+/CCR7+ CD8 T cell subpopulations. Additionally, trauma plasma did not induce CD4+ T cell expansion but did cause a phenotypic shift towards CD38+/CCR7+ expressing CD4+ T cells. Multiplex analysis of cytokines by Luminex showed increased levels of IL-1RA, IL-6 and IL-15 in trauma-1day plasma. Similar to trauma day 1 plasma, PBMC stimulation with known DAMPs showed activation and expansion of CD11c+ NK cells.

CONCLUSIONS

We hypothesized that circulating factors in trauma plasma would induce phenotypic activation of normal human immune cell subsets. Using an unbiased approach, we identified specific changes in immune cell subsets that respond to trauma plasma. Additionally, CD11c+ NK cells expanded in response to DAMPs and LPS, suggesting they may also be responding to similar components in trauma plasma. Collectively, our data demonstrate that the normal PBMC response to trauma plasma involves marked changes in specific subsets of NK and CD8+ T cell populations. Future studies will target the function of these trauma plasma reactive immune cell subsets. These findings have important implications for the field of acute traumatic injuries.

Characterization of pulmonary immune responses to hyperoxia by high-dimensional mass cytometry analyses

Prolonged exposure to hyperoxia has deleterious effects on the lung, provoking both inflammation and alveolar injury. The elements of hyperoxic injury, which result in high rates of lethality in experimental models, are thought to include multicellular immune responses. To characterize these alterations in immune cell populations, we performed time-of-flight mass cytometry (CyTOF) analysis of CD45-expressing immune cells in whole lung parenchyma and the bronchoalveolar space of mice, exposed to 48 hours of hyperoxia together with normoxic controls. At the tested time point, hyperoxia exposure resulted in decreased abundance of immunoregulatory populations (regulatory B cells, myeloid regulatory cells) in lung parenchyma and markedly decreased proliferation rates of myeloid regulatory cells, monocytes and alveolar macrophages. Additionally, hyperoxia caused a shift in the phenotype of alveolar macrophages, increasing proportion of cells with elevated CD68, CD44, CD11c, PD-L1, and CD205 expression levels. These changes occurred in the absence of histologically evident alveolar damage and abundance of neutrophils in the parenchyma or alveolar space did not change at these time points. Collectively, these findings demonstrate that pulmonary response to hyperoxia involves marked changes in specific subsets of myeloid and lymphoid populations. These findings have important implications for therapeutic targeting in acute lung injury.

Serum Copeptin levels in the emergency department predict major clinical outcomes in adult trauma patients

BACKGROUND

Early prognostication in trauma patients is challenging, but particularly important. We wanted to explore the ability of copeptin, the C-terminal fragment of arginine vasopressin, to identify major trauma, defined as Injury Severity Score (ISS) > 15, in a heterogeneous cohort of trauma patients and to compare its performances with lactate. We also evaluated copeptin performance in predicting other clinical outcomes: mortality, hospital admission, blood transfusion, emergency surgery, and Intensive Care Unit (ICU) admission.

METHODS

This single center, pragmatic, prospective observational study was conducted at Arcispedale Santa Maria Nuova, a level II trauma center in Reggio Emilia, Italy. Copeptin determination was obtained on Emergency Department (ED) arrival, together with venous lactate. Different outcomes were measured including ISS, Revised Trauma Score (RTS), hospital and ICU admission, blood transfusion, emergency surgery, and mortality.

RESULTS

One hundred and twenty five adult trauma patients admitted to the ED between June 2017 and March 2018. Copeptin showed a good ability to identify patients with ISS > 15 (AUC 0.819). Similar good performances were recorded also in predicting other outcomes. Copeptin was significantly superior to lactate in identifying patients with ISS > 15 (P 0.0015), and in predicting hospital admission (P 0.0002) and blood transfusion (P 0.016). Comparable results were observed in a subgroup of patients with RTS 7.84.

CONCLUSIONS

In a heterogeneous group of trauma patients, a single copeptin determination at the time of ED admission proved to be an accurate biomarker, statistically superior to lactate for the identification of major trauma, hospital admission, and blood transfusion, while no statistical difference was observed for ICU admission and emergency surgery. These results, if confirmed, may support a role for copeptin during early management of trauma patients.

Cytotoxic Immunity in Peripheral Nerve Injury and Pain

Cytotoxicity and consequent cell death pathways are a critical component of the immune response to infection, disease or injury. While numerous examples of inflammation causing neuronal sensitization and pain have been described, there is a growing appreciation of the role of cytotoxic immunity in response to painful nerve injury. In this review we highlight the functions of cytotoxic immune effector cells, focusing in particular on natural killer (NK) cells, and describe the consequent action of these cells in the injured nerve as well as other chronic pain conditions and peripheral neuropathies. We describe how targeted delivery of cytotoxic factors via the immune synapse operates alongside Wallerian degeneration to allow local axon degeneration in the absence of cell death and is well-placed to support the restoration of homeostasis within the nerve. We also summarize the evidence for the expression of endogenous ligands and receptors on injured nerve targets and infiltrating immune cells that facilitate direct neuro-immune interactions, as well as modulation of the surrounding immune milieu. A number of chronic pain and peripheral neuropathies appear comorbid with a loss of function of cellular cytotoxicity suggesting such mechanisms may actually help to resolve neuropathic pain. Thus while the immune response to peripheral nerve injury is a major driver of maladaptive pain, it is simultaneously capable of directing resolution of injury in part through the pathways of cellular cytotoxicity. Our growing knowledge in tuning immune function away from inflammation toward recovery from nerve injury therefore holds promise for interventions aimed at preventing the transition from acute to chronic pain.

Altered monocyte and NK cell phenotypes correlate with posttrauma infection

BACKGROUND

Trauma induces a complex immune response, requiring a systems biology approach to capture multicellular changes. Using mass cytometry by time-of-flight (CyTOF), we evaluated time-dependent changes in peripheral blood in trauma patients to identify changes correlated with infection.

METHODS

Total leukocytes were prepared via red blood cell lysis using peripheral blood samples from trauma patients with an Injury Severity Score greater than 20 at Days 1, 3, and 5 after injury, and from age- and sex-matched uninjured controls. Cells were stained using a 33-marker immunophenotyping CyTOF panel. Statistics were calculated using one-way analysis of variance with multiple comparisons.

RESULTS

The CyTOF staining demonstrated changes in many cell subsets. The mean expression intensity of CD86 on monocytes decreased significantly at all time points after injury. When the patients were stratified based on development of infection, there was a trend to decreased CD86 expression on monocytes of those patients that developed subsequent infection. Based on stratification, we identified significantly increased expression of CD39 on NK cells only in patients that developed an infection.

CONCLUSION

This study used a systems biology approach to identify novel changes in circulating immune cell subsets in trauma patients correlating with post-traumatic infection. Decreased expression of CD86, a costimulatory molecule, on monocytes demonstrates that trauma affects the innate system's ability to control T-cell immunity. We also found that CD39 expression on NK cells increased significantly in patients with subsequent infection. CD39 is a protein that generates adenosine, which has immunosuppressive effects on several immune cell types including NK cells. In summary, our results point to pathways that may be central to second-hit infections and further study to delineate these pathways could be key to generating clinical biomarkers or targeted immune therapies for trauma patients.

LEVEL OF EVIDENCE

Prognostic study, level II.

New considerations on pathways involved in acute traumatic coagulopathy: the thrombin generation paradox

Abstract

Background

An acute traumatic coagulopathy (ATC) is observed in about one third of severely traumatized patients. This early, specific, and endogenous disorder is triggered by the association of trauma and hemorrhage. The early phase of this condition is characterized by the expression of a bleeding phenotype leading to hemorrhagic shock and the late phase by a prothrombotic profile leading to multiple organ failure. The physiopathology of this phenomenon is still poorly understood. Hypotheses of disseminated intravascular coagulation, activated protein C-mediated fibrinolysis, fibrinogen consumption, and platelet functional impairment were developed by previous authors and continue to be debated. The objective of this study was to observe general hemostasis disorders in case of ATC to confront these hypotheses.

Method

Four groups of 15 rats were compared: C, control; T, trauma; H, hemorrhage; and TH, trauma and hemorrhage. Blood samples were drawn at baseline and 90 min. Thrombin generation tests, platelet aggregometry, and standard hemostasis tests were performed.

Results

Significant differences were observed between the baseline and TH groups for aPTT (17.9 ± 0.8 s vs 24.3 ± 1.4 s, p < 0.001, mean ± SEM), MAP (79.7 ± 1.3 mmHg vs 43.8 ± 1.3 mmHg, p < 0.001, mean ± SEM), and hemoglobin (16.5 ± 0.1 g/dL vs 14.1 ± 0.3 g/dL, p < 0.001, mean ± SEM), indicating the presence of an hemorrhagic shock due to ATC. Compared to all other groups, coagulation factor activities were decreased in the TH group, but endogenous thrombin potential was (paradoxically) higher than in group C (312 ± 17 nM/min vs. 228 ± 23 nM/min; p = 0.016; mean ± SEM). We also observed a subtle decrease in platelet count and function in case of ATC and retrieved an inversed linear relationship between fibrinogen concentration and aPTT (intercept, 26.53 ± 3.16; coefficient, − 3.40 ± 1.26; adjusted R²: 0.1878; p = 0.0123).

Conclusions

The clinical-biological profile that we observed, combining normal thrombin generation, fibrinogen depletion, and a hemorrhagic phenotype, reinforced the hypothesis of activated protein C mediated-fibrinolysis. The key role of fibrinogen, but not of the platelets, was confirmed in this study. The paradoxical preservation of thrombin generation suggests a protective mechanism mediated by rhabdomyolysis in case of major trauma. Based on these results, we propose a new conception concerning the pathophysiology of ATC.

Functional immune monitoring in severely injured patients-A pilot study

After severe trauma, the resulting excessive inflammatory response is countered by compensatory anti-inflammatory mechanisms. The systemic inflammatory response to trauma enhanced by inappropriately timed surgical second hits may be detrimental for the patient. On the other hand, overwhelming anti-inflammatory mechanisms may put patients at increased risk from secondary local and systemic infections. The ensuing sepsis and organ dysfunction due to immune dysregulation remain the leading causes of death after injury. To date, there are no clinically applicable techniques to monitor the pro-/anti-inflammatory immune status of the patients and the remaining ability to react to microbial stimuli. Therefore, in the present study, we used a highly standardized and easy-to-use system to draw peripheral whole blood from polytraumatized patients (ISS ≥ 32, n = 7) and to challenge it with bacterial lipopolysaccharide. Secreted cytokines were compared with those in samples from healthy volunteers. We observed a significant decrease in the release of monocyte-derived mediators. Surprisingly, we detected stable or even increased concentrations of cytokines related to T cell maturation and function. For clinical practicability, we reduced the incubation time before supernatants were collected. Even after an abbreviated stimulation period, a stable release of almost all analysed parameters in patient blood could be detected. In conclusion, the data are indicative of a clinically well-applicable approach to monitor the immune status in severely injured patients in a short time. This may be used to optimize the timing of necessary surgical interventions to avoid a boost of proinflammation and reduce risk of secondary infections.

Early increase in anti-inflammatory biomarkers is associated with the development of multiple organ dysfunction syndrome in severely injured trauma patients

Background

As a result of improvements in the early resuscitation phase of trauma, mortality is largely driven by later mortality due to multiple organ dysfunction syndrome (MODS), which may be mediated by an early overdrive in the host immune response. If patients at risk for MODS could be identified early, preventive treatment measures could be taken. The aim of this study is to investigate whether specific biomarkers are associated with MODS.

Methods

Multiple trauma patients presenting to the Amsterdam University Medical Centers, location Academic Medical Center, between 2012 and 2018 with an Injury Severity Score of 16 or higher were sampled on arrival at the emergency department. A wide variety of inflammatory cytokines, endothelial and lung-specific markers were determined. Comparisons were made between patients with and without MODS. Univariate and multivariate logistic regression was used to determine associations between specific biomarkers and MODS. A p value of 0.05 was considered to be statistically significant.

Results

In total, 147 multiple trauma patients were included. Of these, 32 patients developed MODS (21.7%). Patients who developed MODS were more severely injured, had more traumatic brain injury and showed more deranged markers of coagulation when compared with patients without MODS. Overall, both proinflammatory and anti-inflammatory cytokines were higher in patients with MODS, indicative of a host immune reaction. In the multivariate analysis, the combination of anti-inflammatory proteins interleukin 1 receptor antagonist (IL-1RA) (OR 1.27 (1.07–1.51), p=0.002) and Clara cell protein 16 (CC-16) (1.06 (1.01–1.05), p=0.031) was most strongly associated with the development MODS.

Conclusions

In trauma, anti-inflammatory proteins IL-1RA and CC-16 have the potential to early identify patients at risk for development of MODS. Further research is warranted to prospectively validate these results.

Level of evidence

Prognostic study, level III.

A conceptual time window-based model for the early stratification of trauma patients

Progress in the testing of therapies targeting the immune response following trauma, a leading cause of morbidity and mortality worldwide, has been slow. We propose that the design of interventional trials in trauma would benefit from a scheme or platform that could support the identification and implementation of prognostic strategies for patient stratification. Here, we propose a stratification scheme based on defined time periods or windows following the traumatic event. This 'time-window' model allows for the incorporation of prognostic variables ranging from circulating biomarkers and clinical data to patient-specific information such as gene variants to predict adverse short- or long-term outcomes. A number of circulating biomarkers, including cell injury markers and damage-associated molecular patterns (DAMPs), and inflammatory mediators have been shown to correlate with adverse outcomes after trauma. Likewise, several single nucleotide polymorphisms (SNPs) associate with complications or death in trauma patients. This review summarizes the status of our understanding of the prognostic value of these classes of variables in predicting outcomes in trauma patients. Strategies for the incorporation of these prognostic variables into schemes designed to stratify trauma patients, such as our time-window model, are also discussed.

Development of a Comprehensive Antibody Staining Database Using a Standardized Analytics Pipeline

Large-scale immune monitoring experiments (such as clinical trials) are a promising direction for biomarker discovery and responder stratification in immunotherapy. Mass cytometry is one of the tools in the immune monitoring arsenal. We propose a standardized workflow for the acquisition and analysis of large-scale mass cytometry experiments. The workflow includes two-tiered barcoding, a broad lyophilized panel, and the incorporation of a fully automated, cloud-based analysis platform. We applied the workflow to a large antibody staining screen using the LEGENDScreen kit, resulting in single-cell data for 350 antibodies over 71 profiling subsets. The screen recapitulates many known trends in the immune system and reveals potential markers for delineating MAIT cells. Additionally, we examine the effect of fixation on staining intensity and identify several markers where fixation leads to either gain or loss of signal. The standardized workflow can be seamlessly integrated into existing trials. Finally, the antibody staining data set is available as an online resource for researchers who are designing mass cytometry experiments in suspension and tissue.

Early Immunologic Response in Multiply Injured Patients With Orthopaedic Injuries Is Associated With Organ Dysfunction

OBJECTIVES

To quantify the acute immunologic biomarker response in multiply injured patients with axial and lower extremity fractures and to explore associations with adverse short-term outcomes including organ dysfunction and nosocomial infection (NI).

DESIGN

Prospective cohort study.

SETTING

Level 1 academic trauma center.

PATIENTS

Consecutive multiply injured patients, 18-55 years of age, with major pelvic and lower extremity orthopaedic injuries (all pelvic/acetabular fractures, operative femur and tibia fractures) that presented as a trauma activation and admitted to the intensive care unit from April 2015 through October 2016. Sixty-one patients met inclusion criteria.

INTERVENTION

Blood was collected upon presentation to the hospital and at the following time points: 8, 24, 48 hours, and daily during intensive care unit admission. Blood was processed by centrifugation, separation into 1.0-mL plasma aliquots, and cryopreserved within 2 hours of collection.

MAIN OUTCOME MEASUREMENTS

Plasma analyses of protein levels of cytokines/chemokines were performed using a Luminex panel Bioassay of 20 immunologic mediators. Organ dysfunction was measured by the Marshall Multiple Organ Dysfunction score (MODScore) and nosocomial infection (NI) was recorded. Patients were stratified into low (MODS ≤ 4; n = 34) and high (MODS > 4; n = 27) organ dysfunction groups.

RESULTS

The MODS >4 group had higher circulating levels of interleukin (IL)-6, IL-8, IL-10, monocyte chemoattractant protein-1 (MCP-1), IL-1 receptor antagonist (IL-1RA), and monokine induced by interferon gamma (MIG) compared with the MODS ≤4 group at nearly all time points. MODS >4 exhibited lower levels of IL-21 and IL-22 compared with MODS ≤4. Patients who developed NI (n = 24) had higher circulating concentrations of IL-10, MIG, and high mobility group box 1 (HMGB1) compared with patients who did not develop NI (n = 37).

CONCLUSIONS

Temporal quantification of immune mediators identified 8 biomarkers associated with greater levels of organ dysfunction in polytrauma patients with major orthopaedic injuries.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Circulating growth/differentiation factor 15 is associated with human CD56bright natural killer cell dysfunction and nosocomial infection in severe systemic inflammation

Background

Systemic inflammation induced by sterile or infectious insults is associated with an enhanced susceptibility to life-threatening opportunistic, mostly bacterial, infections due to unknown pathogenesis. Natural killer (NK) cells contribute to the defence against bacterial infections through the release of Interferon (IFN) γ in response to Interleukin (IL) 12. Considering the relevance of NK cells in the immune defence we investigated whether the function of NK cells is disturbed in patients suffering from serious systemic inflammation.

Methods

NK cells from severely injured patients were analysed from the first day after the initial inflammatory insult until the day of discharge in terms of IL-12 receptor signalling and IFN-γ synthesis.

Findings

During systemic inflammation, the expression of the IL-12 receptor β2 chain, phosphorylation of signal transducer and activation 4, and IFN-γ production on/in NK cells was impaired upon exposure to Staphylococcus aureus. The profound suppression of NK cells developed within 24 h after the initial insult and persisted for several weeks. NK cells displayed signs of exhaustion. Extrinsic changes were mediated by the early and long-lasting presence of growth/differentiation factor (GDF) 15 in the circulation that signalled through the transforming growth factor β receptor I and activated Smad1/5. Moreover, the concentration of GDF-15 in the serum inversely correlated with the IL-12 receptor β2 expression on NK cells and was enhanced in patients who later acquired septic complications.

Interpretation

GDF-15 is associated with the development of NK cell dysfunction during systemic inflammation and might represent a novel target to prevent nosocomial infections.

Fund

The study was supported by the Department of Orthopaedics and Trauma Surgery, University Hospital Essen.

How Clinical Flow Cytometry Rebooted Sepsis Immunology

On May 2017, the World Health Organization (WHO) recognized sepsis as a global health priority by adopting a resolution to improve the prevention, diagnosis, and management of this deadly disease. While it has long been known that sepsis deeply perturbs immune homeostasis by inducing a tremendous systemic inflammatory response, pivotal observations based on clinical flow cytometry indicate that sepsis indeed initiates a more complex immune response that varies over time, with the concomitant occurrence of both pro- and anti-inflammatory mechanisms. As a resultant, some septic patients enter a stage of protracted immunosuppression. This paved the way for immunostimulation approaches in sepsis. Clinical flow cytometry permitted this evolution by drawing a new picture of pathophysiology and reshaping immune trajectories in patients. Additional information from cytometry by time of flight mass cytometry and other high-dimensional flow cytometry platform should rapidly enrich our understanding of this complex disease. This review reports on landmarks of clinical flow cytometry in sepsis and how this single-cell analysis technique permitted to breach the wall of decades of unfruitful anti-inflammatory-based clinical trials in sepsis. © 2019 International Society for Advancement of Cytometry.

Beyond the message: advantages of snapshot proteomics with single-cell mass cytometry in solid tumors

Single-cell technologies that can quantify features of individual cells within a tumor are critical for treatment strategies aiming to target cancer cells while sparing or activating beneficial cells. Given that key players in protein networks are often the primary targets of precision oncology strategies, it is imperative to transcend the nucleic acid message and read cellular actions in human solid tumors. Here, we review the advantages of multiplex, single-cell mass cytometry in tissue and solid tumor investigations. Mass cytometry can quantitatively probe nearly any cellular feature or target. In discussing the ability of mass cytometry to reveal and characterize a broad spectrum of cell types, identify rare cells, and study functional behavior through protein signaling networks in millions of individual cells from a tumor, this review surveys publications of scientific advances in solid tumor biology made with the aid of mass cytometry. Advances discussed include functional identification of rare tumor and tumor-infiltrating immune cells and dissection of cellular mechanisms of immunotherapy in solid tumors and the periphery. The review concludes by highlighting ways to incorporate single-cell mass cytometry in solid tumor precision oncology efforts and rapidly developing cytometry techniques for quantifying cell location and sequenced nucleic acids.

Inflammation and Disease: Modelling and Modulation of the Inflammatory Response to Alleviate Critical Illness

Critical illness, a constellation of interrelated inflammatory and physiological derangements occurring subsequent to severe infection or injury, affects a large number of individuals in both developed and developing countries. The prototypical complex system embodied in critical illness has largely defied therapy beyond supportive care. We have focused on the utility of data-driven and mechanistic computational modelling to help address the complexity of critical illness and provide pathways towards discovering potential therapeutic options and combinations. Herein, we review recent progress in this field, with a focus on both animal and computational models of critical illness. We suggest that therapy for critical illness can be posed as a model-based dynamic control problem, and discuss novel theoretical and experimental approaches involving biohybrid devices aimed at reprogramming inflammation dynamically. Together, these advances offer the potential for Model-based Precision Medicine for critical illness.