Surface Of Monocytes Research Articles

SARS-CoV-2 spike protein induces the cytokine release syndrome by stimulating T cells to produce more IL-2.

Cytokine release syndrome (CRS) is one of the leading causes of mortality in patients with COVID-19 caused by the SARS-CoV-2 coronavirus. However, the mechanism of CRS induced by SARS-CoV-2 is vague. Using spike protein combined with IL-2, IFN-γ, and TNF-α to stimulate human peripheral blood mononuclear cells (PBMCs) to secrete CRS-related cytokines, the content of cytokines in the supernatant was detected, and the effects of NK, T, and monocytes were analyzed. This study shows that dendritic cells loaded with spike protein of SARS-CoV-2 stimulate T cells to release much more interleukin-2 (IL-2,) which subsequently cooperates with spike protein to facilitate PBMCs to release IL-1β, IL-6, and IL-8. These effects are achieved via IL-2 stimulation of NK cells to release tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), as well as T cells to release IFN-γ Mechanistically, IFN-γ and TNF-α enhance the transcription of CD40, and the interaction of CD40 and its ligand stabilizes the membrane expression of toll-like receptor 4 (TLR4) that serves as a receptor of spike protein on the surface of monocytes. As a result, there is a constant interaction between spike protein and TLR4, leading to continuous activation of nuclear factor-κ-gene binding (NF-κB). Furthermore, TNF-α also activates NF-κB signaling in monocytes, which further cooperates with IFN-γ and spike protein to modulate NF-κB-dependent transcription of CRS-related inflammatory cytokines. Targeting TNF-α/IFN-γ in combination with TLR4 may represent a promising therapeutic approach for alleviating CRS in individuals with COVID-19.

Siglec7 functions as an inhibitory receptor of non-specific cytotoxic cells and can regulate the innate immune responses in a primitive vertebrate (Oreochromis niloticus)

In mammals, siglec7, an integral component of the siglecs, is principally found on the surface of natural killer (NK) cells, macrophages, and monocytes, where it interacts with various pathogens to perform immunological regulatory activities. Nonetheless, the immune defense and mechanism of siglec7 in early vertebrates remain unknown. In this study, we identified siglec7 from Oreochromis niloticus (OnSiglec7) and revealed its immune functions. Specifically, OnSiglec7 was abundantly expressed in immune-related tissues of healthy tilapia and its transcription level was strongly activated after being challenged with A. hydrophila, S. agalactiae, and Poly: IC. Meanwhile, OnSiglec7 protein was purified and analyzed, which could recognize multiple pathogens through binding and agglutinating activity. Moreover, OnSiglec7-positive cells were mainly distributed in non-specific cytotoxic cells (NCC) of tilapia HKLs and showed cell membrane localization. Furthermore, OnSiglec7 blockage affected multiple innate immune responses (inflammation, apoptosis, and pyroptosis process) by regulating the activation of MAPK, NF-κB, TLR, and JAK-STAT pathways. Finally, OnSiglec7 blockage also greatly enhanced the cytotoxic effect of tilapia NCC. Summarily, this study uncovers immune functions and mechanisms of siglec7 in primitive vertebrates, thereby enhancing our understanding of the systemic evolution and ancient functions of other siglecs within the host's innate immune system (to our knowledge).

Red wine alleviates atherosclerosis-related inflammatory markers in healthy subjects rather than in high cardiovascular risk subjects: A systematic review and meta-analysis.

Moderate red wine (RW) consumption is associated with a low risk of cardiovascular disease (CVD). However, few studies have evaluated the effects of RW and white wine (WW) on inflammatory markers related to atherosclerosis in healthy individuals and high-risk subjects for CVD. This study aimed to assess the effect of RW on inflammatory markers in healthy individuals and high-risk subjects for CVD compared with moderate alcohol consumption. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA) was followed in this study. The PubMed, Embase, Cochrane, Web of Science, SinoMed, EbscoHost, and ScienceDirect databases were searched. The risk of bias and quality of the included trials were assessed using the Cochrane Handbook. The main results are summarized in Stata 12. Twelve studies were included in the meta-analysis. The results demonstrated that RW significantly decreased circulating intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1 (VCAM-1), tumor necrosis factor-alpha (TNF-α), lymphocyte function-associated antigen-1, and Sialyl-Lewis X expression on the surface of monocytes in healthy subjects, but not in patients with CVD. Additionally, RW significantly decreased Sialyl-Lewis X but increased clusters of differentiation 40 (CD40) expressed on the surface of T lymphocytes and significantly decreased C-C chemokine receptor type 2 (CCR2) and very late activation antigen 4 (VLA-4) expressed on the surface of monocytes. Interestingly, subgroup analysis also found that RW significantly decreased circulating interleukin-6 (IL-6) in Spain but not in other countries, and significantly increased αMβ2 (Mac-1) in the group that had an intervention duration of less than 3 weeks. Moderate consumption of RW is more effective than WW in alleviating atherosclerosis-related inflammatory markers in healthy people rather than high-risk subjects for CVD, but this needs to be further confirmed by studies with larger sample sizes.

#683 Utility of urinary soluble CD163 as a novel biomarker for the detection of IgA nephropathy

Abstract Background and Aims IgA nephropathy (IgAN) is an immune mediated disease and a leading cause of biopsy proven glomerulonephritis (GN) worldwide. CD163 is a membrane protein localised on the surface of monocytes and macrophages. Its soluble form, sCD163, produced by enzymatic splitting of the ectodomain of inflammatory cells when activated, is found in increased concentrations in acute inflammatory diseases such as sepsis and vasculitis. Urinary sCD163 levels have also been reported to be a useful biomarker of glomerular inflammation in lupus nephritis (LN) and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Yet, few studies have evaluated the role of urinary sCD163 as a biomarker in IgAN, and comparing it across different GN subtypes. This study aims to explore the utility of urinary sCD163 as a non-invasive biomarker for IgAN, and across different immune mediated GN types. Method This is a retrospective and prospective cohort study from a single tertiary hospital. Frozen urine samples from patients with GN and healthy controls from the Asian Kidney Disease Study and Singapore Kidney Function Study respectively were utilised for the retrospective cohort. The prospective cohort consists patients with biopsy-proven IgAN recruited from May to December 2023 with informed consent taken. Urinary sCD163 was measured using enzyme-linked immunosorbent assay (ELISA). Univariate analyses were performed and urinary sCD163 values were plotted on receiver-operating characteristic (ROC) curve and the area under the curve (AUC) was calculated. This study obtained Institutional Ethics Board Approval (DSRB 2022/00698). Categorical variables were represented by n (%). Continuous variables with a parametric distribution were represented by their means ± standard deviation, non-parametric variables were expressed as their medians with interquartile ranges. Chi-square test and ANOVA were performed between categorical variables, while a student's t-test was performed for continuous variables. P-value of < 0.05 was taken as statistically significant. A ROC curve was performed for sCD163 values in IgAN and controls, and the AUC calculated. Results In total, urine samples of 59 subjects were analysed (IgAN n = 10; LN n = 5; healthy controls n = 44). There were 30 male subjects (50.8%) and 29 female subjects (49.2%). Median age was 41.0 (IQR 31.0-52.0) years. Median serum creatinine was 78.0 (IQR: 60.0-91.0) µmol/L. Mean urine sCD163 value was 0.32 (±0.19) ng/ml. There were no baseline differences in demographics, comorbidities and medication between groups. Prospective cohort patients with IgAN were more likely to have received steroids (p = 0.03), and there were no patients of the Malay Ethnicity in the prospective cohort (p = 0.05). Median urine protein (g/day) in IgAN was 0.66 (IQR 0.16 to 3.29)¸ 0.159 in LN (IQR 0.09 to 0.26) and 0.12 in controls (IQR 0.07 to 0.20). Using Mann-Whitney U test to compare median proteinuria between IgAN and controls showed significant difference (p = 0.001), whereas median proteinuria between IgAN and LN was not statistically significant (p = 0.08). On univariate analysis compared to healthy controls, IgAN patients had a significantly higher serum creatinine (p = 0.04), compared to LN patients against controls (p = 0.30). Urine sCD163 levels were significantly higher in IgAN patients compared to controls (0.54 ± 0.26, p = 0.02). Patients with LN do not have a significant urinary sCD163 level difference compared to controls (0.21 ± 0.20, p = 0.40), which also correlates with creatinine and degree of proteinuria. There were no other significant baseline differences against controls. On the ROC curve for IgAN patients, urine sCD163 of 0.38 ng/ml has a 70% sensitivity, and 75% specificity in distinguishing IgAN against controls (AUC 0.77; 95% CI: 0.59-0.96, p = 0.008). For LN, urine SCD163 did not distinguish between LN and controls (AUC 0.29; 95% CI: 0.000-0.58, p = 0.12). Conclusion Urine sCD163 is elevated in patients with IgAN compared to controls and LN. Urine sCD163 is useful in the diagnosis of IgAN. A urine sCD163 level of 0.38 ng/ml has a 70% sensitivity and 75% specificity in identifying IgAN against healthy subjects.

Regulatory effects of microRNAs on monocytic HLA-DR surface expression.

Decreased monocytic HLA-DR expression is the most studied biomarker of immune competency in critically ill and autoimmune disease patients. However, the underlying regulatory mechanisms remain largely unknown. One probable HLA-DR dysregulation is through microRNAs. The aim of this study was to investigate the effects of specific microRNAs on HLA-DR expression in human monocytic cells. Four up- and four down-HLA-DR-regulating microRNAs were identified, with hsa-miR-let-7f-2-3p showing the most significant upregulation and hsa-miR-567 and hsa-miR-3972 downregulation. Anti-inflammatory glucocorticoid medication Dexamethasone-decreased HLA-DR was significantly restored by hsa-miR-let-7f-2-3p and hsa-miR-5693. Contrarily, proinflammatory cytokines IFN-γ and TNF-α-increased HLA-DR were significantly reversed by hsa-miR-567. Clinically, paired plasma samples from patients before and one day after cardiac surgery revealed up-regulated expression of hsa-miR-5693, hsa-miR-567, and hsa-miR-3972, following the major surgical trauma. In silico approaches were applied for functional microRNA-mRNA interaction prediction and candidate target genes were confirmed by qPCR analysis. In conclusion, novel monocytic HLA-DR microRNA modulators were identified and validated in vitro. Moreover, both the interaction between the microRNAs and anti- and proinflammatory molecules and the up-regulated microRNAs identified in cardiac surgery highlight the potential clinical relevance of our findings.

The monocyte cell surface is a unique site of autoantigen generation in rheumatoid arthritis

Although anti-citrullinated protein autoantibodies (ACPAs) are a hallmark serological feature of rheumatoid arthritis (RA), the mechanisms and cellular sources behind the generation of the RA citrullinome remain incompletely defined. Peptidylarginine deiminase IV (PAD4), one of the key enzymatic drivers of citrullination in the RA joint, is expressed by granulocytes and monocytes; however, the subcellular localization and contribution of monocyte-derived PAD4 to the generation of citrullinated autoantigens remain underexplored. In this study, we demonstrate that PAD4 displays a widespread cellular distribution in monocytes, including expression on the cell surface. Surface PAD4 was enzymatically active and capable of citrullinating extracellular fibrinogen and endogenous surface proteins in a calcium dose-dependent manner. Fibrinogen citrullinated by monocyte-surface PAD4 could be specifically recognized over native fibrinogen by a panel of eight human monoclonal ACPAs. Several unique PAD4 substrates were identified on the monocyte surface via mass spectrometry, with citrullination of the CD11b and CD18 components of the Mac-1 integrin complex being the most abundant. Citrullinated Mac-1 was found to be a target of ACPAs in 25% of RA patients, and Mac-1 ACPAs were significantly associated with HLA-DRB1 shared epitope alleles, higher C-reactive protein and IL-6 levels, and more erosive joint damage. Our findings implicate the monocyte cell surface as a unique and consequential site of extracellular and cell surface autoantigen generation in RA.

Endothelial cell-derived extracellular vesicles expressing surface VCAM1 promote sepsis-related acute lung injury by targeting and reprogramming monocytes.

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a common life-threatening syndrome with no effective pharmacotherapy. Sepsis-related ARDS is the main type of ARDS and is more fatal than other types. Extracellular vesicles (EVs) are considered novel mediators in the development of inflammatory diseases. Our previous research suggested that endothelial cell-derived EVs (EC-EVs) play a crucial role in ALI/ARDS development, but the mechanism remains largely unknown. Here, we demonstrated that the number of circulating EC-EVs was increased in sepsis, exacerbating lung injury by targeting monocytes and reprogramming them towards proinflammatory macrophages. Bioinformatics analysis and further mechanistic studies revealed that vascular cell adhesion molecule 1 (VCAM1), overexpressed on EC-EVs during sepsis, activated the NF-κB pathway by interacting with integrin subunit alpha 4 (ITGA4) on the monocyte surface, rather than the tissue resident macrophage surface, thereby regulating monocyte differentiation. This effect could be attenuated by decreasing VCAM1 levels in EC-EVs or blocking ITGA4 on monocytes. Furthermore, the number of VCAM1+ EC-EVs was significantly increased in patients with sepsis-related ARDS. These findings not only shed light on a previously unidentified mechanism underling sepsis-related ALI/ARDS, but also provide potential novel targets and strategies for its precise treatment.

The Effect of Cytokine Adsorption on Leukocyte and Platelet Activation after Extracorporeal Cardiopulmonary Resuscitation.

Post-cardiac arrest syndrome (PCAS) is a frequent complication following successful cardiopulmonary resuscitation and correlates with poor outcome. PCAS is characterized by an excessive inflammatory response to whole-body ischemia and reperfusion. Cytokine adsorption was suggested as an adjunctive treatment option for the removal of cytokines from the patients' blood to restore the physiological equilibrium of pro- and anti-inflammatory activity and thus mitigate hemodynamic instability and end-organ complications. To better understand the cellular effects of cytokine adsorption in patients receiving extracorporeal cardiopulmonary resuscitation (ECPR) after in- and out-of-hospital cardiac arrest, we compared the activation status of neutrophils, monocytes, and platelets as well as the formation of platelet-leukocyte complexes in intravenous whole blood samples from an exploratory subgroup (n = 24) from the randomized CYTER study. At 48 hours after initiation of ECPR, flow cytometry analyses did neither reveal significant differences in neutrophil (CD11b, CD66b, L-selectin, and PSGL-1) and monocyte (CD11b, L-selectin, and PSGL-1) surface molecule expression nor in circulating platelet-monocyte complexes between patients receiving cytokine adsorption and those without. Data did not show a relevant effect of cytokine adsorption on neutrophil and monocyte activation during the first 48 hours after initiation of ECPR.

The selection of animal models influences the assessment of anti-tumor efficacy: promising sialic acid-conjugate modified liposomes demonstrate remarkable therapeutic effects in diverse mouse strains.

Mice as a crucial tool for preclinical assessment of antineoplastic agents. The impact of physiological differences among mouse strains on the in vivo efficacy of antitumor drugs, however, has been significantly overlooked. Mononuclear phagocyte system (MPS) is the major player in clearance in vivo, and differences in MPS among different strains may potentially impact the effectiveness of antitumor preparations. Therefore, in this study, we employed conventional liposomes (CL-EPI) and SA-ODA modified liposomes (SAL-EPI) as model preparations to investigate the comprehensive tumor therapeutic effects of CL-EPI and SAL-EPI in KM, BALB/c, and C57BL/6 tumor-bearing mice. The results demonstrated significant variability in the efficacy of CL-EPI for tumor treatment across different mouse strains. Therefore, we should pay attention to the selection of animal models in the study of antitumor agents. SAL-EPI effectively targeted tumor sites by binding to Siglec-1 on the surface of peripheral blood monocytes (PBMs), and achieved good therapeutic effect in different mouse strains with little difference in treatment. The SA modified preparation is therefore expected to achieve a favorable therapeutic effect in tumor patients with different immune states through PBMs delivery (Siglec-1 was expressed in both mice and humans), thereby possessing clinical translational value and promising development prospects.

IL-1 alpha is myristoylated for monocyte surface translocation and promotes atherosclerosclerosis in mice

Abstract Background The role of Interleukin-1 alpha (IL-1α) and beta (IL-1β) in the pathogenesis of atherosclerosis in vivo has been controversial for years. In contrast to IL-1β, which is dependent on the NLR family pyrin domain containing 3 (NLRP3) inflammasome, IL-1α can be tethered to the plasma membrane (csIL-1α) where it exerts pro-inflammatory effects. We characterised the role of IL-1α and the Nlrp3 inflammasome in a nongenetic hyperlipidemic mouse model and examined the function of csIL-1α in human monocytes. Methods Atherosclerosis was induced by a single injection of mutant PCSK9-AAV8 virus in wild-type (WT, referred to as PCSK9-AAV), Il1a-/-, Nlrp3-/-, and Il1b-/- mice, in combination with high-fat western diet (21% fat, 0.2% cholesterol) for 12 weeks. Plaque size and lipid content, were histologically analysed. The serum proteome was studied using a targeted multiplex PEA (Olink Proteomics). Human primary monocytes and human umbilical vein endothelial cells (HUVECs) were used to examine csIL-1α-IL1R interaction by analyzing VCAM1 expression and monocyte adhesion. LPS was used to induce IL-1α protein synthesis and membrane translocation in vitro. Myristoylation was measured via flow cytometry. Results Il1a-/- animals showed significantly reduced atherosclerotic lesion size (-62% vs. PCSK9-AAV) and fat accumulation within the plaque (-64% vs. PCSK9-AAV). Knockout of Nlrp3 and IL-1β did not reduce plaque size or lipid content, indicating an Nlrp3-independent mechanism of the protective effect of Il1a-/-. Circulating pro-inflammatory cytokines such as IL-1α, IL-1β, and IL-6 were downregulated in serum of Il1a-/-, Nlrp3-/-, and Il1b-/- mice compared to PCSK9-AAV mice suggesting that the development of atherosclerotic plaques is independent of circulating inflammatory cytokines at an early stage. Therefore, we investigated the role of csIL-1α on human monocytes. Stimulation with LPS showed enrichment of csIL-1α by 13.2% (p<0.05) on monocytes without releasing IL-1α. Treatment of HUVECs with LPS-stimulated monocytes resulted in increased VCAM1 expression (+22.2%, p<0.05) and monocyte adhesion (1.9 fold, p<0.05) through a csIL-1α-IL1R interaction which was abolished by the addition of neutralising antibodies for IL1R1 and IL-1α (p<0.05, vs. LPS-treated monocytes). To investigate whether the IL-1α translocation is mediated by protein myristoylation, human monocytes were pre-incubated with the n-myristoyl-transferase inhibitor IMP-1088 before LPS stimulation, resulting in a reduction of csIL-1α expression (p<0.05, vs. LPS-treated monocytes). Conclusion This study demonstrated a protective effect of Il1a deficiency on the development of atherosclerosis. CsIL-1α mediates monocyte-to-endothelial adhesion by increasing VCAM1 expression through endothelial IL1R1 signaling. The data underscore the importance of the juxtacrine signaling of IL-1α and its role in the development of atherosclerosis independent of circulating cytokine levels.

SIRPα: A key player in innate immunity.

Signal regulatory protein alpha (SIRPα) is a crucial inhibitory regulator expressed on the surface of myeloid cells, including macrophages, dendritic cells, monocytes, neutrophils, and microglia. SIRPα plays an indispensable role in innate immune and adoptive immune responses in cancer immunology, tissue homeostasis, and other physiological or phycological conditions. This review provides an overview of the research history, ligands, signal transduction pathways, and functional mechanisms associated with SIRPα. Additionally, we summarize the therapeutic implications of targeting SIRPα as a promising novel strategy in immuno-oncology.

Neutrophil extracellular trap formation during surgical procedures: a pilot study

Neutrophils can release neutrophil extracellular traps (NETs) containing DNA fibres and antimicrobial peptides to immobilize invading pathogens. NET formation (NETosis) plays a vital role in inflammation and immune responses. In this study we investigated the impact of surgical trauma on NETosis of neutrophils. Nine patients undergoing “Transcatheter/percutaneous aortic valve implantation” (TAVI/PAVI, mild surgical trauma), and ten undergoing “Aortocoronary bypass” (ACB, severe surgical trauma) were included in our pilot study. Peripheral blood was collected before, end of, and after surgery (24 h and 48 h). Neutrophilic granulocytes were isolated and stimulated in vitro with Phorbol-12-myristate-13-acetate (PMA). NETosis rate was examined by microscopy. In addition, HLA-DR surface expression on circulating monocytes was analysed by flow-cytometry as a prognostic marker of the immune status. Both surgical procedures led to significant down regulation of monocytic HLA-DR surface expression, albeit more pronounced in ACB patients, and there was a similar trend in NETosis regulation over the surgical 24H course. Upon PMA stimulation, no significant difference in NETosis was observed over time in TAVI/PAVI group; however, a decreasing NETosis trend with a significant drop upon ACB surgery was evident. The reduced PMA-induced NETosis in ACB group suggests that the inducibility of neutrophils to form NETs following severe surgical trauma may be compromised. Moreover, the decreased monocytic HLA-DR expression suggests a post-operative immunosuppressed status in all patients, with a bigger impact by ACB, which might be attributed to the extracorporeal circulation or tissue damage occurring during surgery.

MUC16 stimulates neutrophils to an inflammatory and immunosuppressive phenotype in ovarian cancer

BackgroundMUC16 (CA125) is a commonly used tumor marker for ovarian cancer screening and reported to be an immunosuppressive factor by acting on the sialic acid-binding immunoglobulin-like lectin-9 (Siglec-9) on the surface of natural killer cells (NK cells), B cells, and monocytes. However, the role of MUC16 on neutrophils in the tumor microenvironment remains to be further explored.MethodsThe correlation between the proportion and count of peripheral blood cells, serum inflammatory-related factors and serum MUC16 (CA125) level in patients was constructed based on clinical samples. RNAseq data was obtained from TCGA and sequencing of ovarian cancer tissues, followed by TIMER immune cell infiltration and correlation analysis. Ovarian cancer organoid was constructed to stimulate neutrophils with immunophenotype identification by qPCR and flow cytometry. MUC16 protein stimulation to neutrophils validated the role of MUC16 under the analysis of RNA sequencing and inhibition of NK cytotoxicity in vitro.ResultsThe serum MUC16 level was positively correlated with the proportion and count of peripheral blood neutrophils, neutrophil-to-lymphocyte ratio (NLR) and inflammatory factors IL-6, IL-8, IL-10 and IL-2R. Siglec-9, the receptor of MUC16, was expressed on neutrophils and was positively correlated to neutrophil infiltration in ovarian cancer. After the stimulation of ovarian cancer organoids and MUC16 respectively, the proportions of CD11b+, CD66b+, and ICAM-1+ neutrophils were significantly increased, while the proportion of CXCR4+ neutrophils was slightly decreased, with increasing of of inflammatory factors MMP9, IL-8, OSM, IL-1β, TNF-α, CXCL3, and ROS. RNA-sequencing analysis revealed that inflammatory response, TNFA signaling pathway, and IL6-related pathway were upregulated in MUC16-stimulated neutrophils, accompanied by high expression of immunosuppression-related factors HHLA2, IL-6, TNFRSF9, ADORA2A, CD274 (PD-L1), and IDO1. NK cytotoxicity was decreased when treated by supernanant of MUC16-stimulated neutrophils in vitro.ConclusionMUC16 acted on neutrophils by Siglec-9 leading to an inflammatory and immunosuppressive phenotype in ovarian cancer.

A mAb to SIRPα downregulates the priming of naive CD4 + T cell in Primary immune thrombocytopenia

SIRPα is a transmembrane protein that binds the protein tyrosine phosphatases SHP-1 and SHP-2 through its cytoplasmic region and is abundantly expressed on monocytes, dendritic cells, and macrophages. Studies recently showed that SIRPα is essential for priming of CD4 + T cells by DCs and for development of Th17 cell-mediated autoimmune diseases. We have now further evaluated the importance of SIRPα and that of its ligand CD47 in primary immune thrombocytopenia (ITP). In this study, we show that there was a low expression state of SIRPα on the surface of monocytes. Treatment of cells culture from ITP patients with a mAb to SIRPα that blocks the binding of SIRPα to CD47 downregulated the ITP response. The abilities of monocytes from ITP patients to stimulate an allogenic MLR were reduced. The proliferation of, and production of IL-2, by CD4 + T cells from ITP patients were inhibited, the Treg cell numbers and the production of IL-10 pairs were upregulated, and the production of TGF-β not was inhibited, by a mAb to SIRPα. Moreover, a mAb to SIRPα, the expression of HLA-DR and CD86 were markedly inhibited and the expression of CD80 was slightly upregulated, on the surface of CD14 + monocytes from ITP patients as compared with healthy subjects. However, blockade of SIRPα increased the secretion of TLR-dependent cytokines TNF-α, IL-6 and IL-1β by PBMCs, which may be considered as a reserve in response to danger signals. These results suggest that SIRPα on monocytes is essential for the priming of naive T cells and the development of ITP. Therefore, SIRPα is a potential therapeutic target for ITP and other autoimmune diseases.

Efferocytosis of viable versus heat-inactivated MSC induces human monocytes to distinct immunosuppressive phenotypes

BackgroundImmunomodulation by mesenchymal stromal cells (MSCs) can occur through trophic factor mechanisms, however, intravenously infused MSCs are rapidly cleared from the body yet a potent immunotherapeutic response is still observed. Recent work suggests that monocytes contribute to the clearance of MSCs via efferocytosis, the body’s natural mechanism for clearing dead and dying cells in a non-inflammatory manner. This begs the questions of how variations in MSC quality affect monocyte phenotype and if viable MSCs are even needed to elicit an immunosuppressive response.MethodsHerein, we sought to dissect MSC’s trophic mechanism from their efferocytic mechanisms and determine if the viability of MSCs prior to efferocytosis influences the resultant phenotype of monocytes. We cultured viable or heat-inactivated human umbilical cord MSCs with human peripheral blood mononuclear cells for 24 h and observed changes in monocyte surface marker expression and secretion profile. To isolate the effect of efferocytosis from MSC trophic factors, we used cell separation techniques to remove non-efferocytosed MSCs before challenging monocytes to suppress T-cells or respond to inflammatory stimuli. For all experiments, viable and heat-inactivated efferocytic-licensing of monocytes were compared to non-efferocytic-licensing control.ResultsWe found that monocytes efferocytose viable and heat-inactivated MSCs equally, but only viable MSC-licensed monocytes suppress activated T-cells and suppression occurred even after depletion of residual MSCs. This provides direct evidence that monocytes that efferocytose viable MSCs are immunosuppressive. Further characterization of monocytes after efferocytosis showed that uptake of viable-but not heat inactivated-MSC resulted in monocytes secreting IL-10 and producing kynurenine. When monocytes were challenged with LPS, IL-2, and IFN-γ to simulate sepsis, monocytes that had efferocytosed viable MSC had higher levels of IDO while monocytes that efferocytosed heat inactivated-MSCs produced the lowest levels of TNF-α.ConclusionCollectively, these studies show that the quality of MSCs efferocytosed by monocytes polarize monocytes toward distinctive immunosuppressive phenotypes and highlights the need to tailor MSC therapies for specific indications.

CD44‑hyaluronan axis plays a role in the interactions between colon cancer‑derived extracellular vesicles and human monocytes.

During tumor progression, monocytes circulating in the blood or infiltrating tissue may be exposed to tumor-derived extracellular vesicles (TEVs). The first stage of such interactions involves binding of TEVs to the surface of monocytes, followed by their internalization. The present study examines the role of CD44 molecules in the interactions between monocytes and EVs derived from colon cancer cell lines (HCT116 and SW1116). The efficiency of the attachment and engulfment of TEVs by monocytes is linked to the number of TEVs and time of exposure/interaction. The two investigated TEVs, TEVsHCT116 and TEVsSW1116, originating from HCT116 and SW1116 cells, respectively, differ in hyaluronan (HA) cargo, which reflects HA secretion by parental cancer cells. HA-rich TEVsHCT116 are internalized more effectively in comparison with HA-low TEVsSW1116. Blocking of CD44 molecules on monocytes by anti-CD44 monoclonal antibody significantly decreased the engulfment of TEVsHCT116 but not that of TEVsSW1116 after 30 min contact, suggesting the involvement of the HA-CD44 axis. The three subsets of monocytes, classical, intermediate and non-classical, characterized by gradual changes in the expression of CD14 and CD16 markers, also differ in the expression of CD44. The highest expression of CD44 molecules was observed in the intermediate monocyte subset. Blocking of CD44 molecules decreased the internalization of HA-rich TEVs in all three subsets, which is associated with CD44 expression level. It was hypothesized that HA carried by TEVs, potentially as a component of the 'corona' coating, may facilitate the interaction between subsets of monocytes and TEVs, which may influence the fate of TEVs (such as the rate of TEVs adhesion and engulfment) and change monocyte activity.

Heparin Induced Thrombocytopenia - Pathophysiology, Diagnosis and Treatment: A Narrative Review.

Heparin-induced thrombocytopenia (HIT) is a life-threatening, immune-mediated complication following heparin exposure and is considered to be the most severe adverse reaction to heparin treatment that is not associated with bleeding. Development of autoantibodies against platelet factor 4 (PF4) - heparin complex constitutes the basis of the pathophysiological changes in patients suffering from HIT, which then binds to the surface of platelets and monocytes, thus provoking their activation and subsequent aggregation, ultimately leading to the formation of thrombosis. Formation of arterial and venous thrombosis is aggravated by the simultaneous activation of platelets and monocytes with a substantial mortality rate. The incidence of HIT is reported to be significantly lower in pediatric patients compared with adults. Diagnosis of HIT in pediatric population remains a clinical entity supplemented by laboratory evaluation. The positive predictive value of laboratory evaluation is further elevated by the use of scoring systems and predictive models used for hastening the diagnosis of HIT. Use of alternative anticoagulants like direct thrombin inhibitors and factor Xa inhibitors form the mainstay of treatment in cases of HIT, however, more prospective studies would be required in the pediatric population to delineate definitive guidelines for proper management of patients in this age-group. This article delivers diagnostic and treatment approach in case of patients with HIT, wherein the pathophysiology, clinical manifestations, diagnostic approach and the management of patients with HIT has been described.

HLA-DR Expression on Monocytes and Sepsis Index Are Useful in Predicting Sepsis.

The reduction of mortality in patients with sepsis depends on the early identification and treatment of at-risk patients. The aim was to evaluate the HLA-DR expression on the surface of monocytes (MHLA-DR ratio), the sepsis index (CD64 expression on neutrophils/MHLA-DR ratio), and C-reactive protein (CRP) with the development of sepsis. We prospectively enrolled 77 critically ill patients, 59 with stroke and 18 with traumatic brain injuries. The biomarkers were tested at the baseline and 3, 6, 9, 12, and 15 days later. Most patients (71%) developed sepsis (4.2 ± 1.3 days after admission). On day 3, those subsequently developing sepsis had lower levels of MHLA-DR+ (81.7 ± 16.2% vs. 88.5 ± 12.1%, p < 0.05) and higher sepsis indexes (0.19 ± 0.19 vs. 0.08 ± 0.08, p < 0.01) than those not developing sepsis. The MHLA-DR ratio slowly recovered before day 6, while the sepsis index remained raised in septic patients up to day 9 (p < 0.05). To predict the development of sepsis, optimal cut-offs were CRP levels > 106.90 mg/mL (74.19% sensitivity, 69.49 specificity) and MHLA-DR expression rate < 72.80% (45.31% sensitivity, 89.47% specificity). The periodic monitoring of the MHLA-DR expression together with CRP and sepsis index may help to identify patients in the ICU at increased risk of developing sepsis.

Association of serum CD14 level and functional polymorphism C-159T in the promoter region of CD14 gene with allergic rhinitis

Allergic rhinitis (AR) is an inflammatory disease of the upper respiratory tract affecting a significant number of the world’s population. It occurs as an IgE-mediated immune response of the nasal mucosa to inhaled allergens. The human Cluster of Differentiation 14 (CD14) is a glycosyl-phosphatidylinositol-anchored molecule expressed on the surface of monocytes and macrophages and functions as a receptor to lipopolysaccharides and inhaled endotoxins that may stimulate interleukins production by antigen-presenting cells. Consequently, CD14 plays a substantial role in allergic diseases and may become one of their etiological causes. This study aimed to determine the association between C-159T polymorphism in the CD14 gene promoter region and serum CD14 levels and the risk of Allergic rhinitis Egyptian patients and to test the validity of serum CD14 level measurement in predicting AR. This case–control study included 45 patients with AR referred to Allergy and Immunology Unit, Zagazig University Hospital, Zagazig, Egypt, and 45 healthy subjects as controls. Serum CD14 levels were measured by ELISA. The polymerase chain reaction-restriction fragment length polymorphism technique was used to detect C-159T gene polymorphism in the CD14 promoter region. There was a significant association between CD14 serum levels and AR incidence (P < 0.001), with patients having higher serum CD14 levels than controls. In addition, a significant association (P < 0.001) was detected between serum CD14 levels and the severity of AR, as well as elevated serum CD14 levels in severe and the most severe cases. On the molecular level, there was a statistically significant relationship between patients and the control group regarding the CD14 genotype (P < 0.001), where CT and TT genotypes and T allele were primarily associated with the cases group, indicating that the risk of AR was significantly associated with the inheritance of the TT genotype. Additionally, a statistically significant association was found between the severity of AR and CD14 genotype (P < 0.001), where TT genotypes were mainly associated with severe and the most severe cases. In the studied groups, there was a statistically significant difference (P < 0.05) between the CD14 genotype and serum CD14 levels, with TT genotypes being associated with higher CD14 levels. The results obtained in this study revealed that serum CD14 level is a potential biomarker for the diagnosis of AR and, at the genetic level, a potential predictor of disease.

TOP-093 - Soluble and monocyte surface CD206 is a promising indicator of sepsis in patients with acute liver failure

TOP-093 - Soluble and monocyte surface CD206 is a promising indicator of sepsis in patients with acute liver failure