Patterns of monocyte subpopulations and their surface expression of HLA-DR during adverse events after hematopoietic stem cell transplantation

Inflammatory Monocyte Subsets Correlation with Iron Levels in Low Vitamin D Pediatric Transfusion-Dependent Thalassemia

Background

Patients with transfusion-dependent thalassemia experience iron dysregulation, which affects the immune response. Surface proteins such as FcγRIII (CD16), lipopolysaccharide receptor (CD14), and human leukocyte antigen (HLA-DR) on monocytes are crucial for innate and adaptive responses. Blood monocytes, identified by their CD14 and CD16 expression, show functional diversity during injury or inflammation. Considering the mechanisms of vitamin D activation and its potential interaction with monocytes, further investigation of its immunomodulatory role in transfusion-dependent thalassemia is essential.

Purpose

This study evaluated monocyte subsets, population, and surface receptor expression (CD14, CD16, and HLA-DR), and their association with iron status and vitamin D levels in patients with transfusion-dependent thalassemia.

Patients and Methods

Fifty lysed erythrocyte-heparinized whole blood samples from transfusion-dependent thalassemia patients were analyzed by flow cytometry and classified into three monocyte subsets: CD14++CD16- (classical), CD14++CD16+ (intermediate), and CD14+CD16++ (non-classical). Cell percentage referred to the monocyte subset population. Median fluorescence intensity (MFI) indicated surface protein expression. The 25(OH)vitamin D level was used to measure vitamin D levels. Iron status was assessed using ferritin and serum iron levels. A correlational study was performed.

Results

We did not find a correlation between low vitamin D levels (22.9 ng/mL ± 3.9) and monocyte characteristics, iron status, or hematology profile. However, we observed a negative correlation between the percentage of intermediate and non-classical monocytes and hemoglobin and ferritin levels (P = 0.02, r = -0.3; P = 0.04, r = -0.3). Additionally, we found a positive correlation between the median fluorescence intensity (MFI) of CD14 in non-classical monocytes and serum iron (P = 0.04, r = 0.3).

Conclusion

Our findings suggest that iron overload and anemia may influence the function of inflammatory monocyte subsets. Considering the immunomodulatory role of vitamin D through monocyte modulation during pathogen insult, further research utilizing a whole-blood stimulation assay is imperative.

Monocytes as an early risk factor for acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and contributes to high morbidity and mortality. However, our current understanding of the development and progression of aGVHD after allo-HSCT remains limited. To identify the potential biomarkers for the prevention and treatment of aGVHD during the early hematopoietic reconstruction after transplantation, we meticulously performed a comparative analysis of single-cell RNA sequencing data from post-transplant patients with or without aGVHD. Prior to the onset of aGVHD, monocytes in the peripheral blood of patients with aGVHD experienced a dramatic rise and activation on day 21 post-transplantation. This phenomenon is closely aligned with clinical cohort results obtained from blood routine examinations. Furthermore, in vitro co-culture experiments showed that peripheral blood monocytes extracted from patients with aGVHD approximately 21 days post-transplantation induced a significantly higher proliferation rate of allogeneic T cells compared to those from patients without aGVHD. Our study indicates that monocytes could be a crucial early clinical risk factor for the development of aGVHD, and this insight could potentially guide the timing of monitoring efforts, recommending assessments at the pivotal juncture of approximately day 21 post-transplantation, shedding fresh light on the significance of early hematopoietic regeneration in relation to the onset of aGVHD.

Hepatic graft-versus-host disease: what we know, when to biopsy, and how to diagnose

Graft-versus-host disease (GVHD) is one of the serious complications that may develop after hematopoietic cell transplantation (HCT), for hematologic malignancies, solid organ transplantation, and other hematologic disorders. GVHD develops due to T lymphocytes present in the graft attacking the host antigens, which results in tissue damage. A significant number of HCT patients develop acute or chronic GVHD, which may affect multiple organs including the liver. The diagnosis of hepatic GVHD (hGVHD) is challenging as many other conditions in HCT patients may lead to liver dysfunction. Particularly challenging among the various conditions that give rise to liver dysfunction is differentiating sinusoidal obstruction syndrome and drug-induced liver injury (DILI) from hGVHD on clinical grounds and laboratory tests. Despite the minimal risks involved in performing a liver biopsy, the information gleaned from the histopathologic changes may help in the management of these very complex patients. There is a spectrum of histologic features found in hGVHD, and most involve histopathologic changes affecting the interlobular bile ducts. These include nuclear and cytoplasmic abnormalities including dysmorphic bile ducts, apoptosis, and cholangiocyte necrosis, among others. The hepatitic form of hGVHD typically shows severe acute hepatitis. With chronic hGVHD, there is progressive bile duct loss and eventually fibrosis. Accurate diagnosis of hGVHD is paramount so that timely treatment and management can be initiated. Techniques to prevent and lower the risk of GVHD from developing have recently evolved. If a diagnosis of acute GVHD is made, the first-line of treatment is steroids. Recurrence is common and steroid resistance or dependency is not unusual in this setting. Second-line therapies differ among institutions and have not been uniformly established. The development of GVHD, particularly hGVHD, is associated with increased morbidity and mortality.

The Influence of Permafrost Microorganisms on Monocytes Differentiation In Vitro

Metabolites of fossil microorganisms of dispersed watered rocks that have passed into a frozen state (Bacillus sp. strains 2/09 and 9/08, Bacillus megaterium 8-75) can modulate the differentiation activity of human peripheral blood monocytes into phenotypically different subpopulations when cultured in vitro for 7 days. This effect is largely determined by the type of metabolites that depends on the temperature of their production: cold (collected after bacterium culturing at 5°C), medium (at 22°C), and warm temperature (at 37°C). All three types of metabolites had a weak negative influence on the level of classical (CD14hiCD16-) monocytes and stimulated the differentiation of intermediate (CD14+CD16+) and non-classical (CD14loCD16+) monocytes. The monocytes differentiation into the subpopulation of intermediate (CD14+CD16+) was stimulated to a greater extent by medium-temperature metabolites of the strain 8/75 and into the subpopulation of non-classical (CD14loCD16+) monocytes by warm metabolites of the strains 8/75 and 2/09 throughout culturing of mononuclear cells (days 1, 3, 7). Bearing in mind the anti-infection activity of intermediate and non-classical monocytes, we can consider strains 8/75 Bacillus megaterium and 2/09 Bacillus sp. promising for their in-depth testing.

A unique immune signature in blood separates therapy-refractory from therapy-responsive acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is an immune cell‒driven, potentially lethal complication of allogeneic hematopoietic stem cell transplantation affecting diverse organs, including the skin, liver, and gastrointestinal (GI) tract. We applied mass cytometry (CyTOF) to dissect circulating myeloid and lymphoid cells in children with severe (grade III-IV) aGVHD treated with immune suppressive drugs alone (first-line therapy) or in combination with mesenchymal stromal cells (MSCs; second-line therapy). These results were compared with CyTOF data generated in children who underwent transplantation with no aGVHD or age-matched healthy control participants. Onset of aGVHD was associated with the appearance of CD11b+CD163+ myeloid cells in the blood and accumulation in the skin and GI tract. Distinct T-cell populations, including TCRγδ+ cells, expressing activation markers and chemokine receptors guiding homing to the skin and GI tract were found in the same blood samples. CXCR3+ T cells released inflammation-promoting factors after overnight stimulation. These results indicate that lymphoid and myeloid compartments are triggered at aGVHD onset. Immunoglobulin M (IgM) presumably class switched, plasmablasts, and 2 distinct CD11b- dendritic cell subsets were other prominent immune populations found early during the course of aGVHD in patients refractory to both first- and second-line (MSC-based) therapy. In these nonresponding patients, effector and regulatory T cells with skin- or gut-homing receptors also remained proportionally high over time, whereas their frequencies declined in therapy responders. Our results underscore the additive value of high-dimensional immune cell profiling for clinical response evaluation, which may assist timely decision-making in the management of severe aGVHD.

Pro-inflammatory monocytes are increased in Duchenne muscular dystrophy and suppressed with omega-3 fatty acids: A double-blind, randomized, placebo-controlled pilot study

BACKGROUND

Omega-3 long chain polyunsaturated fatty acids (LCPUFA) reduce circulating cytokines produced by monocytes. Nevertheless, whether the omega-3 LCPUFA regulate the monocytes and their cytokines in Duchenne muscular dystrophy (DMD) is unknown. The aim of this study was to evaluate whether circulating pro-inflammatory monocytes are increased and whether omega-3 LCPUFA selectively suppress these monocytes and their cytokines in patients with DMD.

METHODS

This was a double-blind, randomized, placebo-controlled pilot study carried out in patients with DMD supplemented with omega-3 LCPUFA (n = 6) or sunflower oils (placebo, n = 6) for 6 months. Monocytes and their cytokines were measured at baseline and after 1, 2, 3, and 6 months of supplementation.

RESULTS

The anti-inflammatory monocytes (median, [95% CI]) are increased at month 3 (-0.46 [-13.5-9.5] vs. 8.4 [5.5-12.5], p = 0.05) in the omega-3 LCPUFA group compared with the placebo group. The pro-inflammatory monocytes (-5.7 [-63.8-114.1] vs. -51.9 [-91.2 to -25.4], p = 0.026 and -16.4 [-50.8-50.6] vs. -57.9 [-86.9 to -18.5], p = 0.045 at months 3 and 6, respectively) and their cytokine interleukin 6 (-11.9 [-93.5-148.9] vs. -64.7 [-77.8 to -42.6], p = 0.019 at month 6) decreased in the omega-3 LCPUFA group compared with the placebo group. Pro-inflammatory monocytes decreased and anti-inflammatory monocytes were augmented (p < 0.05) during the 6 months of supplementation with omega-3 LCPUFA.

CONCLUSIONS

This pilot study suggests that supplementation with omega-3 LCPUFA could have a selective reductive effect on pro-inflammatory monocytes and their cytokines in patients with DMD. These findings also support the performance of studies in a significant population to explore the role of omega-3 LCPUFA on monocyte populations and their cytokines in patients with DMD. This research was registered at clinicaltrials.gov (NCT018264229).

Pattern of human monocyte subpopulations in health and disease

Monocytes are important cells of the innate system. They are a heterogeneous type of cells consisting of phenotypically and functionally distinct subpopulations, which play a specific role in the control, development and escalation of the immunological processes. Based on the expression of superficial CD14 and CD16 in flow cytometry, they can be divided into three subsets: classical, intermediate and non-classical. Variation in the levels of human monocyte subsets in the blood can be observed in patients in numerous pathological states, such as infections, cardiovascular and inflammatory diseases, cancer and autoimmune diseases. The aim of this review is to summarize current knowledge of human monocyte subsets and their significance in homeostasis and in pathological conditions.

Monocyte Subpopulation Recovery as Predictors of Hematopoietic Cell Transplantation Outcomes

Monocyte recovery after hematopoietic cell transplantation (HCT) has been correlated with overall survival (OS). However, monocytes are heterogeneous and consist of classic (CD14⁺⁺CD16^-), intermediate (CD14⁺CD16⁺), and nonclassic (CD14⁺CD16⁺⁺) subpopulations, with unique functional properties. We hypothesized that monocyte subpopulation reconstitution would vary based on allogeneic stem cell source and would be associated with outcomes. We studied monocyte subpopulation recovery at days 28, 60, 100, 180, and 365 post-HCT among 202 patients with hematologic malignancy. Significant differences in absolute monocyte count (AMC) and monocyte subpopulation counts at days 60 and 100 were identified based on stem cell source (all P < .01), with more robust recovery in umbilical cord blood (UCB) recipients. Using 2-fold cross-validation, optimal cutpoints were calculated for day 28 AMC and monocyte subpopulations based on OS. These were used to calculate hazard ratios for OS, disease-free survival (DFS), relapse, transplant-related mortality (TRM), and acute and chronic graft-versus-host disease. OS and DFS were superior when AMC and classic monocyte recovery were above optimal cutpoints (all P < .03). Relapse was reduced for those with AMC (P < .01) and classic (P = .05) monocyte counts above optimal cutpoints. TRM was also reduced when classic (P = .02) monocyte count exceeded optimal cutpoints. Intermediate and nonclassic monocyte recovery were not associated with outcomes. In summary, hematopoietic cell source is associated with monocyte subpopulation recovery, with the early robust recovery in UCB recipients. Recovery of AMC and classic monocytes were prognostic for survival, relapse, and TRM. These indicators may identify patients at increased risk for post-HCT failure and guide therapeutic interventions.

HLA-DR Expression on Monocyte Subsets in Critically Ill Children

BACKGROUND

To longitudinally study blood monocyte subset distribution and human leukocyte antigen-DR (HLA-DR) expression on monocyte subsets in children with sepsis, post-surgery and trauma in relation to nosocomial infections and mortality.

METHODS

In 37 healthy children and 37 critically ill children (12 sepsis, 11 post-surgery, 10 trauma and 4 admitted for other reasons)-participating in a randomized controlled trial on early versus late initiation of parenteral nutrition-monocyte subset distribution and HLA-DR expression on monocyte subsets were measured by flow cytometry upon admission and on days 2, 3 and 4 of pediatric intensive care unit (PICU) stay.

RESULTS

Upon PICU admission, critically ill children had a higher proportion of classical monocytes (CD14++CD16-) than healthy children [PICU 95% (interquartile range [IQR] 88%-98%); controls, 87% (IQR 85%-90%), P < 0.001]. HLA-DR expression was significantly decreased within all monocyte subsets and at all time points, being most manifest on classical monocytes and in patients with sepsis. Percentage of HLA-DR expressing classical monocytes [upon PICU admission 67% (IQR 44%-88%); controls 95% (IQR 92%-98%), P < 0.001], as well as the HLA-DR mean fluorescence intensity [upon PICU admission 3219 (IQR 2650-4211); controls 6545 (IQR 5558-7647), P < 0.001], decreased during PICU stay. Patients who developed nosocomial infections (n = 13) or who died (n = 6) had lower HLA-DR expression on classical monocytes at day 2 (P = 0.002) and day 3 (P = 0.04), respectively.

CONCLUSIONS

Monocytic HLA-DR expression decreased during PICU stay and was lower compared with controls on all examined time points, especially on classical monocytes and in children admitted for sepsis. Low HLA-DR expression on classical monocytes was associated with nosocomial infections and death.

Characterization of monocyte subtypes regarding their phenotype and development in the context of graft-versus-host disease

Graft-versus-host disease (GvHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). In this study, monocyte subtypes were characterized regarding cytokine expression pattern and development in the context of GvHD. Using inflammatory S100 proteins for monocyte stimulation, it could be demonstrated that intermediate monocytes are the main producers of inflammatory cytokines such as IL-6 and TNFα known to be involved in the development of Th17 cells pointing towards an inflammatory phenotype of this monocyte subtype. Furthermore, novel aspects regarding monocyte subtype development were found. Our data reveal that prednisolone promotes the induction of intermediate monocytes from classical monocytes which correlates with HSP70 expression levels. However, 1α,25-Dihydroxyvitamin D3 treatment results in the abrogation of the prednisolone-mediated induction of this inflammatory monocyte subset and low HSP70 expression levels. Treatment of classical monocytes with pifithrin-μ, a specific HSP70 inhibitor, also leads to an inhibited induction of intermediate monocytes in the presence of prednisolone. These data point towards a predominant role of HSP70 in the development of intermediate monocytes. Thus, HSP70 might be a promising target for GvHD therapy, especially in combination with glucocorticoids, in order to decrease intermediate monocyte subset levels.

Increase of Intermediate Monocytes in Graft-versus-Host Disease: Correlation with MDR1+Th17.1 Levels and the Effect of Prednisolone and 1α,25-Dihydroxyvitamin D3

Graft-versus-host disease (GVHD) remains one of the major complications after allogeneic hematopoietic stem cell transplantation that is mainly treated with glucocorticoids such as prednisolone. In this study the influence of monocyte subpopulations, prednisolone, and 1α,25-dihydroxyvitamin D3 (1α,25-(OH)₂D3) on the induction of a proinflammatory subset of Th17 cells (MDR⁺Th17.1) characterized by CCR6⁺CXCR3^hiCCR4^loCCR10^-CD161⁺ and stable expression of the multidrug resistance protein type 1 (MDR1) was investigated. Our results demonstrate that intermediate monocytes are increased in patients with acute GVHD, promoting the induction of proinflammatory MDR1⁺Th17.1 cells. Furthermore, prednisolone induces the development of MDR1⁺Th17.1 cells, whereas 1α,25-(OH)₂D3 acts as an anti-inflammatory, leading to diminished percentages of proinflammatory MDR1⁺Th17.1 cells in the presence of prednisolone after stimulation with the TLR4-ligand S100A8/S100A9. Moreover, 1α,25-(OH)₂D3 decreased the expression level of the targets JAK2 and CD74, both associated with T cell activation, in monocytes. Thus, in steroid-resistant GVHD, 1α,25-(OH)₂D3 could be an important regulator in monocyte-induced development of proinflammatory MDR1⁺Th17.1 cells and might therefore be a potential therapeutic agent in combination with glucocorticoids for GVHD treatment.

Challenges in the harmonization of immune monitoring studies and trial design for cell-based therapies in the context of hematopoietic cell transplantation for pediatric cancer patients

Clinical trials aimed at improving results of hematopoietic cell transplantation (HCT) by adjuvant cell-based interventions in children have been limited by small numbers and pediatric-specific features. The need for a larger number of pediatric HCT centers to participate in trials has resulted in a demand for harmonization of disease-specific clinical trials and immune-monitoring. Thus far, most phase I/II trials select different end points evaluated at disparate time points, making inter-study comparisons difficult and, sometimes, impossible. In this review, we discuss the various aspects that are important to consider for harmonizing clinical trial design as well as the critical elements for standardized (immune)-monitoring protocols in cell-based intervention trials in the context of HCT. Comparison data from trials applying harmonized trial design will lead to optimized immunotherapeutic treatment protocols to maximize clinical efficacy while minimizing toxicity.

Phagocyte function decreases after high-dose treatment with melphalan and autologous stem cell transplantation in patients with multiple myeloma

High-dose melphalan with autologous hematopoietic stem cell transplantation (ASCT) is the standard of care for younger patients with newly diagnosed multiple myeloma and is aimed at achieving as deep and complete a response as possible after various combinations of induction therapy. However, it is frequently associated with infectious complications. This study investigated the effects of high-dose treatment with autologous stem cell support on patients' innate immunity, with a focus on subpopulations and functioning of recently released polymorphonuclear leukocytes (PMNs) and monocytes in peripheral blood. Flow cytometry-based analysis was used to measure the degree of PMN maturation and activation, before and after ASCT and compared with healthy controls. After high-dose treatment and ASCT, a smaller proportion of patients' PMNs had the capacity for oxidative burst. Moreover, patients' PMNs, both before and after ASCT, had a reduced capacity for phagocytosis. Eosinophils, which recently have been suggested to play a role in promoting malignant plasma cell proliferation, were markedly reduced after ASCT, with slow regeneration. HLA-DR expression by monocytes was significantly depressed after ASCT, a characteristic often attributed to monocytic myeloid-derived suppressor cells. Our results suggest that several aspects of phagocytic function are impaired for at least 20 days after ASCT.

Immune Reconstitution after Allogeneic Hematopoietic Cell Transplantation in Children

Allogeneic (allo) hematopoietic cell transplantation (HCT) has evolved into a potent curative treatment option for a variety of malignant and nonmalignant diseases. The occurrence of complications and mortality after allo-HCT is, however, still high and is strongly associated with immune reconstitution (IR). Therefore, detailed information on IR through immunomonitoring is crucial to improve survival chances after HCT. To date, information about the reconstituting immune system after allo-HCT in pediatric patients is mostly derived from routine standard-of-care measurements. More profound knowledge on IR may provide tools to better predict and modulate adverse reactions and, subsequently, improve survival chances. Here, we provide an overview of IR (eg, immune cell subsets and circulating chemokines/cytokines) after allo-HCT in children, taking into account different cell sources and serotherapy, and discuss strategies to enhance immunomonitoring. We conclude that available IR data after allo-HCT contain limited information on immune cell families (mostly only generic T, B, and NK cells), which would improve with more detailed information on reconstituting cell subsets or effector cell functionality at earlier time points (<1 month). In addition, secretome data (eg, multiplex cytokine/chemokine profiles) could add to the understanding of IR mechanisms and cell functionality and may even provide (early) biomarkers for individual disease outcome, such as viral reactivity, graft-versus-host disease, or graft-versus-leukemia. The present data and suggestions for more detailed, standardized, and harmonized immunomonitoring in future (pediatric) allo-HCT studies will pave the path to "precision transplantation:" an individualized HCT approach (including conditioning), based on detailed information on IR and biomarkers, aiming to reduce transplantation related mortality and relapse, and subsequently improve survival chances.

Sepsis-induced immune alterations monitoring by flow cytometry as a promising tool for individualized therapy

Septic syndromes remain a major although largely under-recognized health care problem and represent the first cause of mortality in intensive care units. While sepsis has, for long, been solely described as inducing a tremendous systemic inflammatory response, novel findings indicate that sepsis indeed initiates a more complex immunologic response that varies over time, with the concomitant occurrence of both pro- and anti-inflammatory mechanisms. As a resultant, after a short proinflammatory phase, septic patients enter a stage of protracted immunosuppression. This is illustrated in those patients by reactivation of dormant viruses (CMV or HSV) or infections due to pathogens, including fungi, which are normally pathogenic solely in immunocompromised hosts. Although mechanisms are not totally understood, these alterations might be directly responsible for worsening outcome in patients who survived initial resuscitation as nearly all immune functions are deeply compromised. Indeed, the magnitude and persistence over time of these dysfunctions have been associated with increased mortality and health-care associated infection rate. Consequently, new promising therapeutic avenues are currently emerging from those recent findings such as adjunctive immunostimulation (IFN-γ, GM-CSF, IL-7, anti-PD1/L1 antibodies) for the most immunosuppressed patients. Nevertheless, as there is no clinical sign of immune dysfunctions, the prerequisite for such therapeutic intervention relies on our capacity in identifying the patients who could benefit from immunostimulation. To date, the most robust biomarkers of sepsis-induced immunosuppression are measured by flow cytometry. Of them, the decreased expression of monocyte HLA-DR appears as a "gold standard." This review reports on the mechanisms sustaining sepsis-induced immunosuppression and its related biomarkers measurable by flow cytometry. The objective is to integrate the most recent facts in an up-to-date account of clinical results, flow cytometry aspects as well as issues in results standardization for multicenter studies. © 2015 International Clinical Cytometry Society.