[Pathophysiology and Diagnostics of Immune Thrombocytopenia]. / Pathophysiologie und Diagnostik der Immunthrombozytopenie.

Immune thrombocytopenia (ITP) is due to autoantibodies against platelet surface antigens. ITP is considered as either primary, with no clear etiology, or as secondary ITP (drug-induced; underlying diseases). Autoantibodies lead both to loss of platelets in the spleen and/or liver but simultaneously reduce their production. Contrary to other disorders with thrombocytopenia, ITP has reduced levels of thrombopoetin. ITP remains a diagnosis of exclusion. A single defining laboratory test does not exist. Glycoprotein-specific antibodies can be detected in only about 50% of cases. Ruling out EDTA-induced pseudo thrombocytopenia is of particular relevance. Secondary causes of thrombocytopenia should be excluded through medical history (especially medication history), physical examination and possibly bone-marrow puncture.

Immune interactions and regulation with CD39+ extracellular vesicles from platelet concentrates.

Introduction: CD39 plays an important role in the immunoregulation and inhibition of effector cells. It is expressed on immune cells, including Tregs, and on extracellular vesicles (EVs) budding from the plasma membrane. Platelet transfusion may induce alloimmunization against HLA-I antigens, leading to refractoriness to platelet transfusion with severe consequences for patients. Tregs may play a key role in determining whether alloimmunization occurs in patients with hematologic disorders. We hypothesized that CD39+ EVs might play an immunoregulatory role, particularly in the context of platelet transfusions in patients with hematologic disorders. Such alloimmunization leads to the production of alloantibodies and is sensitive to the regulatory action of CD39. Methods: We characterized CD39+ EVs in platelet concentrates by flow cytometry. The absolute numbers and cellular origins of CD39+ EVs were evaluated. We also performed functional tests to evaluate interactions with immune cells and their functions. Results: We found that CD39+ EVs from platelet concentrates had an inhibitory phenotype that could be transferred to the immune cells with which they interacted: CD4+ and CD8+ T lymphocytes (TLs), dendritic cells, monocytes, and B lymphocytes (BLs). Moreover, the concentration of CD39+ EVs in platelet concentrates varied and was very high in 10% of concentrates. The number of these EVs present was determinant for EV-cell interactions. Finally, functional interactions were observed with BLs, CD4+ TLs and CD39+ EVs for immunoglobulin production and lymphoproliferation, with potential implications for the immunological management of patients.

Complement-Coagulation Cross-talk: Factor H-mediated regulation of the Complement Classical Pathway activation by fibrin clots.

The classical pathway of the complement system is activated by the binding of C1q in the C1 complex to the target activator, including immune complexes. Factor H is regarded as the key downregulatory protein of the complement alternative pathway. However, both C1q and factor H bind to target surfaces via charge distribution patterns. For a few targets, C1q and factor H compete for binding to common or overlapping sites. Factor H, therefore, can effectively regulate the classical pathway activation through such targets, in addition to its previously characterized role in the alternative pathway. Both C1q and factor H are known to recognize foreign or altered-self materials, e.g., bacteria, viruses, and apoptotic/necrotic cells. Clots, formed by the coagulation system, are an example of altered self. Factor H is present abundantly in platelets and is a well-known substrate for FXIIIa. Here, we investigated whether clots activate the complement classical pathway and whether this is regulated by factor H. We show here that both C1q and factor H bind to the fibrin formed in microtiter plates and the fibrin clots formed under in vitro physiological conditions. Both C1q and factor H become covalently bound to fibrin clots, and this is mediated via FXIIIa. We also show that fibrin clots activate the classical pathway of complement, as demonstrated by C4 consumption and membrane attack complex detection assays. Thus, factor H downregulates the activation of the classical pathway induced by fibrin clots. These results elucidate the intricate molecular mechanisms through which the complement and coagulation pathways intersect and have regulatory consequences.

A Role of Effector CD 8 + T Cells Against Circulating Tumor Cells Cloaked with Platelets: Insights from a Mathematical Model.

Cancer metastasis accounts for a majority of cancer-related deaths worldwide. Metastasis occurs when the primary tumor sheds cells into the blood and lymphatic circulation, thereby becoming circulating tumor cells (CTCs) that transverse through the circulatory system, extravasate the circulation and establish a secondary distant tumor. Accumulating evidence suggests that circulating effector CD 8 + T cells are able to recognize and attack arrested or extravasating CTCs, but this important antitumoral effect remains largely undefined. Recent studies highlighted the supporting role of activated platelets in CTCs's extravasation from the bloodstream, contributing to metastatic progression. In this work, a simple mathematical model describes how the primary tumor, CTCs, activated platelets and effector CD 8 + T cells participate in metastasis. The stability analysis reveals that for early dissemination of CTCs, effector CD 8 + T cells can present or keep secondary metastatic tumor burden at low equilibrium state. In contrast, for late dissemination of CTCs, effector CD 8 + T cells are unlikely to inhibit secondary tumor growth. Moreover, global sensitivity analysis demonstrates that the rate of the primary tumor growth, intravascular CTC proliferation, as well as the CD 8 + T cell proliferation, strongly affects the number of the secondary tumor cells. Additionally, model simulations indicate that an increase in CTC proliferation greatly contributes to tumor metastasis. Our simulations further illustrate that the higher the number of activated platelets on CTCs, the higher the probability of secondary tumor establishment. Intriguingly, from a mathematical immunology perspective, our simulations indicate that if the rate of effector CD 8 + T cell proliferation is high, then the secondary tumor formation can be considerably delayed, providing a window for adjuvant tumor control strategies. Collectively, our results suggest that the earlier the effector CD 8 + T cell response is enhanced the higher is the probability of preventing or delaying secondary tumor metastases.

Peripheral blood immune cell parameters in patients with high-grade squamous intraepithelial lesion (HSIL) and cervical cancer and their clinical value: a retrospective study.

Objective: The objective of this study was to delineate the profile of peripheral blood lymphocytic indices in patients afflicted with high-grade squamous intraepithelial lesions (HSIL) and cervical neoplasms, and to elucidate the correlation of these hematologic markers with the clinicopathological spectra in individuals diagnosed with cervical carcinoma. Methods: We adopted a retrospective case-control modality for this investigation. An aggregate of 39 HSIL patients and 42 cervical carcinoma patients, who were treated in our facility from July 2020 to September 2023, were meticulously selected. Each case of cervical malignancy was confirmed through rigorous histopathological scrutiny. Concomitantly, 31 healthy female individuals, who underwent prophylactic health evaluations during the corresponding timeframe, were enlisted as the baseline control group. We systematically gathered and analyzed clinical demographics, as well as the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR), from peripheral blood samples. Pearson's correlation coefficient was deployed to dissect the interrelation between peripheral NLR and PLR concentrations and the clinicopathological features in the cervical cancer group. Results: Inter-group comparative analysis unveiled statistically substantial variances in the PLR and NLR values among the tripartite clusters (F = 36.941, 14.998, P < 0.001, respectively). Although discrepancy in NLR (P = 0.061) and PLR (P = 0.759) measures between the groups of cervical carcinoma and HSIL was not statistically appreciable, these indices were markedly elevated in the cervical carcinoma faction as juxtaposed with the normative control group (t = 5.094, 5.927; P < 0.001 for both parameters). A discernible gradation in peripheral blood PLR and NLR concentrations was noted when stratified by clinical stage and the profundity of myometrial invasion in cervical cancer subjects (P < 0.001). The correlation matrix demonstrated a positive liaison between peripheral blood PLR and the clinical gradation, as well as the invasiveness of the neoplastic cells into the muscularis propria (P < 0.05); a similar trend was observed with the NLR values (P < 0.05). Conclusion: Augmented NLR and PLR levels in peripheral blood specimens are indicative of HSIL and cervical malignancy. These hematological parameters exhibit a pronounced interconnection with clinical staging and muscular wall penetration depth, serving as potential discriminative biomarkers for the diagnosis and prognosis of cervical cancer.

Evaluation of the inflammatory parameters as potential biomarkers of systemic inflammation extent and the disease severity in psoriasis patients.

The disease severity of psoriasis is mainly assessed subjectively via  psoriasis area and severity index (PASI) and body surface area (BSA), while an optimal measure of cutaneous response, may overlook systemic inflammation in psoriasis patients. The neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), monocyte to lymphocyte ratio (MLR), monocyte to high density lipoprotein ratio (MHR), and systemic immune-inflammation index (SII) exhibit notable associations with the inflammation severity in multiple diseases. The aim of this retrospective study was to explore the associations between inflammatory parameters and the skin lesions' severity of psoriasis. After analysis, we found that patients with psoriasis had higher NLR, MLR, PLR, MHR, and SII levels compared to the control group. At baseline, the parameters of NLR (r = 0.124, P = 0.003), MLR (r = 0.153, P < 0.001), MHR (r = 0.217, P < 0.001) and SII (r = 0.141, P = 0.001) had a positive correlation with PASI in psoriasis patients. At the same time, we analyzed the patients who received different systemic therapy. We observed a significant decrease in NLR, PLR, MLR, and SII in psoriasis patients after treatment. Notably, TNF-α inhibitors and IL-17A inhibitors subgroups showed a more significant reduction than IL-23/IL-12/23 inhibitors and MTX medication. Additionally, we found the change of NLR (r = 0.194, P < 0.001), PLR (r = 0.104, P = 0.014), MLR (r = 0.191, P < 0.001), MHR (r = 0.106, P = 0.012), and SII (r = 0.228, P < 0.001) had a positive correlation with the change of PASI in psoriasis patients. In conclusion, this study suggests that NLR, MLR, and SII may serve as useful biomarkers for assessing systemic inflammation extent and disease severity in psoriasis patients.

Interactions between platelets and the cancer immune microenvironment.

Cancer is a leading cause of death in both China and developed countries due to its high incidence and low cure rate. Immune function is closely linked to the development and progression of tumors. Platelets, which are primarily known for their role in hemostasis, also play a crucial part in the spread and progression of tumors through their interaction with the immune microenvironment. The impact of platelets on tumor growth and metastasis depends on the type of cancer and treatment method used. This article provides an overview of the relationship between platelets and the immune microenvironment, highlighting how platelets can either protect or harm the immune response and cancer immune escape. We also explore the potential of available platelet-targeting strategies for tumor immunotherapy, as well as the promise of new platelet-targeted tumor therapy methods through further research.

The role of platelets in central hubs of inflammation: A literature review.

Platelets are increasingly recognized for their multifaceted roles in inflammation beyond their traditional involvement in haemostasis. This review consolidates knowledge on platelets as critical players in inflammatory responses. This study did an extensive search of electronic databases and identified studies on platelets in inflammation, focusing on molecular mechanisms, cell interactions, and clinical implications, emphasizing recent publications. Platelets contribute to inflammation via surface receptors, release of mediators, and participation in neutrophil extracellular trap formation. They are implicated in diseases like atherosclerosis, rheumatoid arthritis, and sepsis, highlighting their interaction with immune cells as pivotal in the onset and resolution of inflammation. Platelets are central to regulating inflammation, offering new therapeutic targets for inflammatory diseases. Future research should explore specific molecular pathways of platelets in inflammation for therapeutic intervention.

Alternative platelet differentiation pathways initiated by nonhierarchically related hematopoietic stem cells.

Rare multipotent stem cells replenish millions of blood cells per second through a time-consuming process, passing through multiple stages of increasingly lineage-restricted progenitors. Although insults to the blood-forming system highlight the need for more rapid blood replenishment from stem cells, established models of hematopoiesis implicate only one mandatory differentiation pathway for each blood cell lineage. Here, we establish a nonhierarchical relationship between distinct stem cells that replenish all blood cell lineages and stem cells that replenish almost exclusively platelets, a lineage essential for hemostasis and with important roles in both the innate and adaptive immune systems. These distinct stem cells use cellularly, molecularly and functionally separate pathways for the replenishment of molecularly distinct megakaryocyte-restricted progenitors: a slower steady-state multipotent pathway and a fast-track emergency-activated platelet-restricted pathway. These findings provide a framework for enhancing platelet replenishment in settings in which slow recovery of platelets remains a major clinical challenge.

Platelets: Orchestrators of immunity in host defense and beyond.

Platelets prevent blood loss during vascular injury and contribute to thrombus formation in cardiovascular disease. Beyond these classical roles, platelets are critical for the host immune response. They guard the vasculature against pathogens via specialized receptors, intracellular signaling cascades, and effector functions. Platelets also skew inflammatory responses by instructing innate immune cells, support adaptive immunosurveillance, and influence antibody production and T cell polarization. Concomitantly, platelets contribute to tissue reconstitution and maintain vascular function after inflammatory challenges. However, dysregulated activation of these multitalented cells exacerbates immunopathology with ensuing microvascular clotting, excessive inflammation, and elevated risk of macrovascular thrombosis. This dichotomy underscores the critical importance of precisely defining and potentially modulating platelet function in immunity.

Platelet-derived major histocompatibility complex class I coating on Treponema pallidum attenuates natural killer cell lethality.

The evasive tactics of Treponema pallidum pose a major challenge in combating and eradicating syphilis. Natural killer (NK) cells mediate important effector functions in the control of pathogenic infection, preferentially eliminating targets with low or no expression of major histocompatibility complex (MHC) class I. To clarify T. pallidum's mechanisms in evading NK-mediated immunosurveillance, experiments were performed to explore the cross-talk relations among T. pallidum, NK cells, and platelets. T. pallidum adhered to, activated, and promoted particle secretion of platelets. After preincubation with T. pallidum, platelets expressed and secreted high levels of MHC class I, subsequently transferring them to the surface of T. pallidum, potentially inducing an immune phenotype characterized by the "pseudo-expression" of MHC class I on the surface of T. pallidum (hereafter referred to a "pseudo-expression" of MHC class I). The polA mRNA assay showed that platelet-preincubated T. pallidum group exhibited a significantly higher copy number of polA transcript than the T. pallidum group. The survival rate of T. pallidum mirrored that of polA mRNA, indicating that preincubation of T. pallidum with platelets attenuated NK cell lethality. Platelets pseudo-expressed the MHC class I ligand on the T. pallidum surface, facilitating binding to killer cell immunoglobulin-like receptors with two immunoglobulin domains and long cytoplasmic tail 3 (KIR2DL3) on NK cells and initiating dephosphorylation of Vav1 and phosphorylation of Crk, ultimately attenuating NK cell lethality. Our findings elucidate the mechanism by which platelets transfer MHC class I to the T. pallidum surface to evade NK cell immune clearance.

Platelets and inter-cellular communication in immune responses: Dialogue with both professional and non-professional immune cells.

Platelets, derived from bone marrow megakaryocytes, are essential for vascular integrity and play multifaceted roles in both physiological and pathological processes within the vasculature. Despite their small size and absence of a nucleus, platelets are increasingly recognized for their diverse immune functions. Recent research highlights their pivotal role in interactions with various immune cells, including professional cells like macrophages, dendritic cells, natural killer cells, T cells, and B cells, influencing host immune responses. Platelets also engage with non-professional immune cells, contributing to immune responses and structural maintenance, particularly in conditions like inflammation and atherosclerosis. This review underscores the emerging significance of platelets as potent immune cells, elucidating their interactions with the immune system. We explore the mechanisms of platelet activation, leading to diverse functions, such as aggregation, immunity, activation of other immune cells, and pathogen clearance. Platelets have become the predominant immune cells in circulation, involved in chronic inflammation, responses to infections, and autoimmune disorders. Their immunological attributes, including bioactive granule molecules and immune receptors, contribute to their role in immune responses. Unlike professional antigen-presenting cells, platelets process and present antigens through an MHC-I-dependent pathway, initiating T-cell immune responses. This review illuminates the unique features of platelets and their central role in modulating host immune responses in health and disease.

Triglyceride-inflammation score established on account of random survival forest for predicting survival in patients with nasopharyngeal carcinoma: a retrospective study.

Objective: This study aimed to establish an effective prognostic model based on triglyceride and inflammatory markers, including neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR), to predict overall survival (OS) in patients with nasopharyngeal carcinoma (NPC). Additionally, we aimed to explore the interaction and mediation between these biomarkers in their association with OS. Methods: A retrospective review was conducted on 259 NPC patients who had blood lipid markers, including triglyceride and total cholesterol, as well as parameters of peripheral blood cells measured before treatment. These patients were followed up for over 5 years, and randomly divided into a training set (n=155) and a validation set (n=104). The triglyceride-inflammation (TI) score was developed using the random survival forest (RSF) algorithm. Subsequently, a nomogram was created. The performance of the prognostic model was measured by the concordance index (C-index), time-dependent receiver operating characteristic (ROC) curve, and decision curve analysis (DCA). The interaction and mediation between the biomarkers were further analyzed. Bioinformatics analysis based on the GEO dataset was used to investigate the association between triglyceride metabolism and immune cell infiltration. Results: The C-index of the TI score was 0.806 in the training set, 0.759 in the validation set, and 0.808 in the entire set. The area under the curve of time-dependent ROC of TI score in predicting survival at 1, 3, and 5 years were 0.741, 0.847, and 0.871 respectively in the training set, and 0.811, 0.837, and 0.758 in the validation set, then 0.771, 0.848, and 0.862 in the entire set, suggesting that TI score had excellent performance in predicting OS in NPC patients. Patients with stage T1-T2 or M0 had significantly lower TI scores, NLR, and PLR, and higher LMR compared to those with stage T3-T3 or M1, respectively. The nomogram, which integrated age, sex, clinical stage, and TI score, demonstrated good clinical usefulness and predictive ability, as evaluated by the DCA. Significant interactions were found between triglyceride and NLR and platelet, but triglyceride did not exhibit any medicating effects in the inflammatory markers. Additionally, NPC tissues with active triglyceride synthesis exhibited high immune cell infiltration. Conclusion: The TI score based on RSF represents a potential prognostic factor for NPC patients, offering convenience and economic advantages. The interaction between triglyceride and NLR may be attributed to the effect of triglyceride metabolism on immune response.

The prognostic value of platelet aggregation in patients with sepsis.

BACKGROUND: This study aims to investigate the relevance of platelet aggregation markers, specifically arachidonic acid (AA) and adenosine diphosphate (ADP), in relation to the prognosis of sepsis patients. METHODS: A cohort of 40 sepsis patients was included and stratified, based on their 28-day post-treatment prognosis, into two groups: a survival group (n = 31) and a severe sepsis group (n = 9. Then, their various clinical parameters, including patient demographics, platelet counts (PLT), inflammatory markers, and platelet aggregation rates (PAR) induced by AA and ADP between the two groups, were compared. Long-term health implications of sepsis were assessed using the Acute Physiologic Assessment and Chronic Health Evaluation II (APACHE II) score, and logistic regression analysis was conducted to evaluate the prognostic significance of PAR in sepsis patients. RESULTS: Patients with severe sepsis exhibited significantly elevated levels of procalcitonin (PCT), platelet adhesion rates, and PAR induced by ADP (P < 0.05), but having lower PLT (P < 0.05), compared to those in the survival group. Logistic regression analysis demonstrated that PAR induced by ADP was a protective factor in predicting prognosis in sepsis patients (P < 0.01). CONCLUSIONS: Activation of platelets in sepsis intensifies inflammatory response. Patients with sepsis whose ADP-induced PAR was < 60% displayed significant impairment in platelet aggregation function, and had higher mortality rate. Monitoring ADP-induced PAR is crucial for management of sepsis.

The association between the neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and monocyte-to-lymphocyte ratio and systemic sclerosis and its complications: a systematic review and meta-analysis.

Introduction: The identification of new, easily measurable biomarkers might assist clinicians in diagnosing and managing systemic sclerosis (SSc). Although the full blood count is routinely assessed in the evaluation of SSc, the diagnostic utility of specific cell-derived inflammatory indices, i.e., neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR), has not been critically appraised in this patient group. Methods: We conducted a systematic review and meta-analysis of studies investigating the NLR, PLR, and MLR, in SSc patients and healthy controls and in SSc patients with and without relevant complications. PubMed, Scopus, and Web of Science were searched from inception to 23 February 2024. Risk of bias and certainty of evidence were assessed using validated tools. Results: In 10 eligible studies, compared to controls, patients with SSc had significantly higher NLR (standard mean difference, SMD=0.68, 95% CI 0.46 to 0.91, p<0.001; I2 = 74.5%, p<0.001), and PLR values (SMD=0.52, 95% CI 0.21 to 0.83, p=0.001; I2 = 77.0%, p=0.005), and a trend towards higher MLR values (SMD=0.60, 95% CI -0.04 to 1.23, p=0.066; I2 = 94.1%, p<0.001). When compared to SSc patients without complications, the NLR was significantly higher in SSc with interstitial lung disease (ILD, SMD=0.31, 95% CI 0.15 to 0.46, p<0.001; I2 = 43.9%, p=0.11), pulmonary arterial hypertension (PAH, SMD=1.59, 95% CI 0.04 to 3.1, p=0.045; I2 = 87.6%, p<0.001), and digital ulcers (DU, SMD=0.43, 95% CI 0.13 to 0.74, p=0.006; I2 = 0.0%, p=0.49). The PLR was significantly higher in SSc patients with ILD (SMD=0.42, 95% CI 0.25 to 0.59, p<0.001; I2 = 24.8%, p=0.26). The MLR was significantly higher in SSc patients with PAH (SMD=0.63, 95% CI 0.17 to 1.08, p=0.007; I2 = 66.0%, p=0.086), and there was a trend towards a higher MLR in SSc patients with ILD (SMD=0.60, 95% CI -0.04 to 1.23, p=0.066; I2 = 94.1%, p<0.001). Discussion: Pending the results of appropriately designed prospective studies, the results of this systematic review and meta-analysis suggest that blood cell-derived indices of inflammation, particularly the NLR and PLR, may be useful in the diagnosis of SSc and specific complications. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024520040.

Platelet-derived TGF-ß1 induces functional reprogramming of myeloid-derived suppressor cells in immune thrombocytopenia.

ABSTRACT: Platelet α-granules are rich in transforming growth factor ß1 (TGF-ß1), which is associated with myeloid-derived suppressor cell (MDSC) biology. Responders to thrombopoietin receptor agonists (TPO-RAs) revealed a parallel increase in the number of both platelets and MDSCs. Here, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient mice to establish an active murine model of immune thrombocytopenia (ITP). Subsequently, we demonstrated that TPO-RAs augmented the inhibitory activities of MDSCs by arresting plasma cells differentiation, reducing Fas ligand expression on cytotoxic T cells, and rebalancing T-cell subsets. Mechanistically, transcriptome analysis confirmed the participation of TGF-ß/Smad pathways in TPO-RA-corrected MDSCs, which was offset by Smad2/3 knockdown. In platelet TGF-ß1-deficient mice, TPO-RA-induced amplification and enhanced suppressive capacity of MDSCs was waived. Furthermore, our retrospective data revealed that patients with ITP achieving complete platelet response showed superior long-term outcomes compared with those who only reach partial response. In conclusion, we demonstrate that platelet TGF-ß1 induces the expansion and functional reprogramming of MDSCs via the TGF-ß/Smad pathway. These data indicate that platelet recovery not only serves as an end point of treatment response but also paves the way for immune homeostasis in immune-mediated thrombocytopenia.