Deficiencies of Circulating Mucosal-associated Invariant T Cells and Natural Killer T Cells in Patients with Multiple Trauma

Immunologic response in patients with polytrauma

Purpose

It is now known that traumatic injury initiates a complex and dynamic immune response on the first day. It is believed that in patients with polytrauma, these immune responses contribute to the development of infectious complications. Therefore, understanding the immune response to trauma is critical to improving patient outcomes through the development of new therapies and improved resuscitation strategies. The purpose of this study is to examine the parameters of immunity in patients with severe polytrauma at the stages of surgical treatment (the nearest post-traumatic period and long-term periods) in the absence and presence of purulent-inflammatory complications.

Methods

We retrospectively enrolled 188 patients after severely injured trauma and 210 control group at two Level-1 Trauma Centers. Peripheral blood was collected upon presentation to the hospital and at the following time points: 1, 3, 7, 14, 21, 30, 60 and 90 days, and daily during intensive care unit admission. T-lymphocytes analyses performed using a Beckman Coulter EPICS XL flow cytometer (USA) with monoclonal antibodies (Immunotech, France). Analyses of protein levels of cytokines/chemokines, immunoglobulins, and circulating immune complexes was using ELISA.

Results

Under the influence of trauma, the content of T lymphocytes decreased due to the population of T-helpers. However, the number of B lymphocytes increased. The most pronounced activation of humoral immunity was observed by the 30th day of the post-traumatic period. Concentrations of interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor alpha (TNF-a), interleukin-10 (IL-10) on day 1 after injury were the highest. Later, in the post-traumatic period, a gradual decrease in the initially elevated cytokines was noted.

Conclusions

As we continue to extrapolate new information on immune response factors associated with polytrauma, we will be better equipped to develop new therapeutic strategies to treat this serious clinical and social problem. In addition, individually adjusted immune control is an important interactive concept in polytrauma management.

The Role of the Inflammatory Response in Mediating Functional Recovery Following Composite Tissue Injuries

Composite tissue injuries (CTI) are common among US Military Service members during combat operations, and carry a high potential of morbidity. Furthermore, CTI are often complicated due to an altered wound healing response, resulting in part from a dysregulation of the innate and adaptive immune responses. Unlike normal wound healing, in CTI, disruptions occur in innate immune responses, altering neutrophil functions, macrophage activation and polarization, further impacting the functions of T regulatory cells. Additionally, the biological underpinnings of these unfavorable wound healing conditions are multifactorial, including various processes, such as: ischemia, hypoxia, low nutrient levels, and altered cell metabolic pathways, among others, all of which are thought to trigger anergy in immune cells and destabilize adaptive immune responses. As a result, impaired wound healing is common in CTI. Herein, we review the altered innate and adaptive immune cells and their metabolic status and responses following CTI, and discuss the role a multi-pronged immunomodulatory approach may play in facilitating improved outcomes for afflicted patients.

The Emerging Roles of T Helper Cell Subsets and Cytokines in Severe Neutrophilic Asthma

Neutrophilic asthma (NA) is a severe type of steroid resistant asthma, and so far the immune mechanisms underlying NA are not clear. In this article, we performed a comprehensive assessment of Th-cell subsets and cytokines in severe NA patients. A total of 13 healthy individuals and 31 severe asthma patients were enrolled in this study. Refractory asthma patients were defined as those with eosinophilic asthma (EA, accounted for 32% of asthmatic patients) or NA (68%) according to sputum neutrophil/eosinophil counts or blood eosinophils. Th-cell subsets in peripheral blood mononuclear cells (PBMCs) were analyzed by flow cytometry, and cytokines were detected by cytometric bead array (CBA). The results showed significant differences were observed in Th-cell phenotypes, where the number of Th1 cells were reduced and the numbers of Th2 cells were increased in NA and EA groups, respectively, when compared with healthy controls. Th17 cells were not strongly associated with severe neutrophilic asthma. The frequencies of mucosal-associated invariant T (MAIT) cells were strikingly reduced in severe asthma patients, especially in the NA group. This NA group also showed increased levels of IL-17A, IL-17F, TNF-α, and IL-6 in serum and increased levels of IL-17A, IL-17F, IFN-γ, TNF-α, IL-1β, IL-5, IL-6, and IL-8 in sputum. In addition, sputum IL-6 was positively correlated with TNF-α, IFN-γ, IL-17A, and IL-8. Our results uncovered a controversial role for Th17 cells, which were reduced in severe asthma patients. Severe neutrophilic asthma was associated with a striking deficiency of MAIT cells and high pro-inflammatory cytokine levels.

Exploratory Evaluation of the Relationship Between iNKT Cells and Systemic Cytokine Profiles of Critically Ill Patients with Neurological Injury

BACKGROUND

Neurological injury can alter the systemic immune system, modifying the functional capacity of immune cells and causing a dysfunctional balance of cytokines, although mechanisms remain incompletely understood. The objective of this study was to assess the temporal relationship between changes in the activation status of circulating invariant natural killer T (iNKT) cells and the balance of plasma cytokines among critically ill patients with neurological injury.

METHODS

We conducted an exploratory prospective observational study of adult (18 years or older) intensive care unit (ICU) patients with acute neurological injury (n = 20) compared with ICU patients without neurological injury (n = 22) and healthy controls (n = 10). Blood samples were collected on days 1, 2, 4, 7, 14, and 28 following ICU admission to analyze the activation status of circulating iNKT cells by flow cytometry and the plasma concentration of inflammation-relevant immune mediators, including T helper 1 (T_H1) and T helper 2 (T_H2) cytokines, by multiplex bead-based assay.

RESULTS

Invariant natural killer T cells were activated in both ICU patient groups compared with healthy controls. Neurological patients had decreased levels of multiple immune mediators, including T_H1 cytokines (interferon-γ, tumor necrosis factor-α, and interleukin-12p70), indicative of immunosuppression. This led to a greater than twofold increase in the ratio of T_H2/T_H1 cytokines early after injury (days 1 - 2) compared with healthy controls, a shift that was also observed for ICU controls. Systemic T_H2/T_H1 cytokine ratios were positively associated with iNKT cell activation in the neurological patients and negatively associated in ICU controls. These relationships were strongest for the CD4⁺ iNKT cell subset compared with the CD4^- iNKT cell subset. The relationships to individual cytokines similarly differed between patient groups. Forty percent of the neurological patients developed an infection; however, differences for the infection subgroup were not identified.

CONCLUSIONS

Critically ill patients with neurological injury demonstrated altered systemic immune profiles early after injury, with an association between activated peripheral iNKT cells and elevated systemic T_H2/T_H1 cytokine ratios. This work provides further support for a brain-immune axis and the ability of neurological injury to have far-reaching effects on the body's immune system.

The Trajectory of Alterations in Immune-Cell Counts in Severe-Trauma Patients Is Related to the Later Occurrence of Sepsis and Mortality: Retrospective Study of 917 Cases

Background

Severe trauma is believed to disrupt the homeostasis of the immune system, and lead to dramatic changes in the circulating immune-cell count (ICC). The latter fluctuates widely over time. Knowledge about the relationship between these dramatic changes and dynamic fluctuations and the late prognosis of trauma patients is sparse. We investigated the relationship between the trajectory of alterations in the circulating ICC within 7 days in severe-trauma patients and subsequent sepsis and mortality.

Methods

A retrospective analysis of 917 patients with an Injury Severity Score ≥16 was undertaken. The absolute neutrophil, lymphocyte, and monocyte counts (ANC, ALC, and AMC, respectively) on days 1, 3, and 7 (D1, D3, and D7, respectively) after trauma, and whether sepsis or death occurred within 60 days, were recorded. As the disordered circulating ICCs fluctuated widely, their time-varying slopes (D3/D1 and D7/D3) were calculated. Patients were divided into “sepsis” and “non-sepsis” groups, as well as “alive” and “death” groups. Comparative studies were conducted between every two groups. Univariate and multivariate logistic regression analyses were used to identify variables related to the risk of sepsis and mortality. Receiver operating characteristic curves were plotted to assess the predictive value of various risk factors.

Results

More severe trauma caused more pronounced increases in the ANC and slower recovery of the ALC within 7 days. The ALC (D3), ANC (D7), ALC (D3/D1), and ANC (D7/D3) were independent risk factors for sepsis. The ALC (D3), ALC (D7), AMC (D7), and ALC (D3/D1) were independent risk factors for mortality. A combination of the ALC (D3) and ALC (D3/D1) exerted a good predictive value for sepsis and death.

Conclusions

The trajectory of alterations in the circulating ICC in the early stage after trauma is related to subsequent sepsis and mortality.

Clinical predictors of prognosis in patients with traumatic brain injury combined with extracranial trauma

Objective: The purpose of this study was to investigate whether routine blood tests on admission and clinical characteristics can predict prognosis in patients with traumatic brain injury (TBI) combined with extracranial trauma. Methods: Clinical data of 182 patients with TBI combined with extracranial trauma from April 2018 to December 2019 were retrospectively collected and analyzed. Based on GOSE score one month after discharge, the patients were divided into a favorable group (GOSE 1-4) and unfavorable group (GOSE 5-8). Routine blood tests on admission and clinical characteristics were recorded. Results: Overall, there were 48 (26.4%) patients with unfavorable outcome and 134 (73.6%) patients with favorable outcome. Based on multivariate analysis, independent risk factors associated with unfavorable outcome were age (odds ratio [OR], 1.070; 95% confidence interval [CI], 1.018-1.124; p<0.01), admission Glasgow Coma Scale (GCS) score (OR, 0.807; 95% CI, 0.675-0.965; p<0.05), heart rate (OR, 1.035; 95% CI, 1.004-1.067; p<0.05), platelets count (OR, 0.982; 95% CI, 0.967-0.997; p<0.05), and tracheotomy (OR, 15.201; 95% CI, 4.121-56.078; p<0.001). Areas under the curve (AUC) of age, admission GCS, heart rate, tracheotomy, and platelets count were 0.678 (95% CI, 0.584-0.771), 0.799 (95% CI, 0.723-0.875), 0.652 (95% CI, 0.553-0.751), 0.776 (95% CI, 0.692-0.859), and 0.688 (95% CI, 0.606-0.770), respectively. Conclusions: Age, admission GCS score, heart rate, tracheotomy, and platelets count can be recognized as independent predictors of clinical prognosis in patients with severe TBI combined with extracranial trauma.

Activation, Deficiency, and Reduced IFN-γ Production of Mucosal-Associated Invariant T Cells in Patients with Inflammatory Bowel Disease

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that can activate either in response to T-cell receptor (TCR) engagement or through activating cytokines and play an important role in autoimmune disorders. The study examined the level and function of MAIT cells in patients with inflammatory bowel disease (IBD). Circulating MAIT cell levels were significantly reduced in IBD patients. This MAIT cell deficiency was correlated with IBD disease activity grades, hemoglobin, and CRP. IFN-γ production of circulating MAIT cells in response to both MHC class 1b-like related protein (MR1)-dependent and -independent stimulations was decreased in IBD patients, which was partially associated with reduced activation of nuclear factor of activated T cells 1 (NFAT1) transcription factor, a main regulator of IFN-γ production. Expression levels of CD69, programmed death-1 (PD-1), and annexin V in MAIT cells were elevated in IBD patients. CCL20, CXCL10, CXCL16, and CCL25 were expressed higher in inflamed intestinal tissues than in noninflamed tissues. This study demonstrates that circulating MAIT cells are activated and numerically and functionally deficient in IBD patients. Furthermore, activated MAIT cells have the potential to migrate to inflamed tissues. These findings suggest an important role of MAIT cells in mucosal immunity in IBD.

Natural Killer T Cells Are Numerically and Functionally Deficient in Patients with Trauma

Natural killer T (NKT) cells rapidly produce Th1 and Th2 cytokines such as interferon-γ (IFN-γ) and interleukin (IL)-4. This study examined the frequency and function of NKT cells in trauma patients. Frequencies, proliferative responses to α-galactosylceramide (α-GalCer), and Th1/Th2 cytokine secretion levels of NKT cells in peripheral blood mononuclear cells from trauma patients and healthy controls (HC) were measured by flow cytometry. Circulating NKT cell levels were significantly reduced in trauma patients. Proliferation and IFN-γ production of circulating NKT cells in response to α-GalCer were markedly decreased in trauma patients. CD69 expression levels produced by NKT cells were significantly upregulated in trauma patients compared to those in HC. In addition, annexin V+ NKT cells were profoundly increased in trauma patients after α-GalCer stimulation. Trauma patients had higher plasma levels of IL-6, IL-8, and TNF-α compared to HC. In particular, the proliferative response of NKT cells to α-GalCer was significantly decreased in the presence of these cytokines. Such decrease was partially recovered after treatment with blocking antibodies against these cytokines. This study demonstrates that circulating NKT cells are numerically deficient and functionally impaired in IFN-γ production in trauma patients. These findings provide an important insight into the trauma-related innate immune response.

Activation and Impaired Tumor Necrosis Factor-α Production of Circulating Mucosal-Associated Invariant T Cells in Patients with Trauma

Mucosal-associated invariant T (MAIT) cells rapidly produce proinflammatory cytokines in an innate-like manner and play an important role in controlling the host immune response. This study examined the function of MAIT cells in trauma patients. The expression of cytokines in peripheral blood MAIT cells was measured by flow cytometry. MAIT cells in trauma patients displayed impaired tumor necrosis factor (TNF)-α production, together with elevated CD69 expression. The expression of CD69 was negatively correlated with MAIT cell frequency. These patients had higher plasma levels of interleukin (IL)-12 and IL-18. In particular, CD69 expression of MAIT cells was increased by stimulation with IL-18 in synergy with other proinflammatory cytokines or plasma of trauma patients. The production of TNF-α by MAIT cells was characterized by an initial burst and rapid decline, in contrast to delayed and sustained production of interferon (IFN)-γ. Activated MAIT cells showed a functional defect in the production of TNF-α upon restimulation. This study demonstrates that circulating MAIT cells are activated and functionally impaired in TNF-α production in patients with trauma. The activation and dysfunction of MAIT cells was mediated by proinflammatory cytokines. These findings provide important information underlying the innate immune response of patients with trauma.

Role of MAIT cells in the immunopathogenesis of inflammatory diseases: New players in old game

Current advances in immunology have led to the identification of a population of novel innate immune T cells, called mucosa-associated invariant T (MAIT) cells. The cells in humans express an invariant TCRα chain (Vα7.2-Jα33) paired with a limited subset of TCRβ chains (Vβ2, 13 and 22), are restricted by the MHC class I (MH1)-related (MR)-1, and recognize molecules that are produced in the bacterial riboflavin (vitamin B2) biosynthetic pathway. They are present in the circulation, liver and at various mucosal sites (i.e. intestine, lungs and female reproductive tract, etc.). They kill host cells infected with bacteria and yeast, and secrete soluble mediators such as TNF-α, IFN-γ, IL-17, etc. The cells regulate immune responses and inflammation associated with a wide spectrum of acute and chronic diseases in humans. Since their discovery in 1993, significant advances have been made in understanding biology of MAIT cells and the potential role of these cells in the pathogenesis of autoimmune, inflammatory and infectious diseases as well as cancer in humans. The purpose of this review is to provide a current state of our knowledge about MAIT cell biology and delineate their role in autoimmune and inflammatory diseases (sterile or caused by infectious agents) and cancer in humans. A better understanding of the role of MAIT cells in human diseases may lead to novel ways of immunotherapies.