Immune thrombocytopenia: antiplatelet autoantibodies inhibit proplatelet formation by megakaryocytes and impair platelet production in vitro

Thrombopoietin receptor agonists regulate myeloid-derived suppressor cell-mediated immunomodulatory effects in ITP

TPO receptor agonists (TPO-RAs) are a class of clinical second-line regimens for the treatment of primary immune thrombocytopenia (ITP). It can promote megakaryocyte maturation and increase platelet production, but its effect on immunosuppressive cells in patients with ITP has not been explored. Sixty-two ITP patients and 34 healthy controls (HCs) were included in this study. The proportion and functions of myeloid-derived immunosuppressive cells (MDSCs) in ITP patients and HCs were investigated. We found that the proportion and function of MDSCs in ITP patients treated with TPO-RAs were significantly higher than those treated with glucocorticoids (GCs), which was correlated with the clinical efficacy. The proportion and function of cytotoxic Th1 cells and CD8+T cells decreased, while the proportion and immunosuppressive function of Treg cells increased in ITP patients treated with TPO-RAs. We further proved, through MDSC depletion tests, that the inhibitory effect of MDSCs on Th1 cells and the promotion of Treg cells in the original immune micro-environment of GCs-treated ITP patients were impaired; however, these MDSCs' functions were improved in TPO-RAs-treated patients. Finally, we found that the KLF9 gene in MDSCs cells of ITP patients treated with TPO-RAs was down-regulated, which contribute to the higher mRNA expression of GADD34 gene and improved function of MDSCs. These results demonstrate a novel mechanism of TPO-RAs for the treatment of ITP through the assessment of MDSCs and their subsequent impact on T cells, which provides a new basis for TPO-RAs as first-line treatment approach to the treatment of ITP.

A novel scoring model for predicting efficacy and guiding individualised treatment in immune thrombocytopaenia

Despite diverse therapeutic options for immune thrombocytopaenia (ITP), drug efficacy and selection challenges persist. This study systematically identified potential indicators in ITP patients and followed up on subsequent treatment. We initially analysed 61 variables and identified 12, 14, and 10 candidates for discriminating responders from non-responders in glucocorticoid (N = 215), thrombopoietin receptor agonists (TPO-RAs) (N = 224), and rituximab (N = 67) treatments, respectively. Patients were randomly assigned to training or testing datasets and employing five machine learning (ML) models, with eXtreme Gradient Boosting (XGBoost) area under the curve (AUC = 0.89), Decision Tree (DT) (AUC = 0.80) and Artificial Neural Network (ANN) (AUC = 0.79) selected. Cross-validated with logistic regression and ML finalised five variables (baseline platelet, IP-10, TNF-α, Treg, B cell) for glucocorticoid, eight variables (baseline platelet, TGF-β1, MCP-1, IL-21, Th1, Treg, MK number, TPO) for TPO-RAs, and three variables (IL-12, Breg, MAIPA-) for rituximab to establish the predictive model. Spearman correlation and receiver operating characteristic curve analysis in validation datasets demonstrated strong correlations between response fractions and scores in all treatments. Scoring thresholds SGlu ≥ 3 (AUC = 0.911, 95% CI, 0.865-0.956), STPO-RAs ≥ 5 (AUC = 0.964, 95% CI 0.934-0.994), and SRitu = 3 (AUC = 0.964, 95% CI 0.915-1.000) indicated ineffectiveness in glucocorticoid, TPO-RAs, and rituximab therapy, respectively. Regression analysis and ML established a tentative and preliminary predictive scoring model for advancing individualised treatment.

[Pathophysiology and Diagnostics of Immune Thrombocytopenia]

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.

Comprehensive analysis and prediction model of mitophagy and ferroptosis in primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is linked to specific pathogenic mechanisms, yet its relationship with mitophagy and ferroptosis is poorly understood. This study aimed to identify new biomarkers and explore the role of mitophagy and ferroptosis in ITP pathogenesis. Techniques such as differential analysis, Mfuzz expression pattern clustering, machine learning, gene set enrichment analysis, single-cell RNA sequencing (scRNA-seq) and immune infiltration analysis were employed to investigate the molecular pathways of pivotal genes. Two-sample Mendelian randomization (TSMR) assessed the causal effects in ITP. Key genes identified in the training set included GABARAPL1, S100A8, LIN28A, and GDF9, which demonstrated diagnostic potential in validation sets. Functional analysis indicated these genes' involvement in ubiquitin phosphorylation, PPAR signalling pathway and T-cell differentiation. Immune infiltration analysis revealed increased macrophage presence in ITP, related to the critical genes. scRNA-seq indicated reduced GABARAPL1 expression in ITP bone marrow macrophages. TSMR linked S100A8 with ITP diagnosis, presenting an OR of 0.856 (95% CI = 0.736-0.997, p = 0.045). The study pinpointed four central genes, GABARAPL1, S100A8, LIN28A, and GDF9, tied to mitophagy and ferroptosis in ITP. It posits that diminished GABARAPL1 expression may disrupts ubiquitin phosphorylation and PPAR signalling, impairing mitophagy and inhibiting ferroptosis, leading to immune imbalance.

Rituximab alleviates pediatric systemic lupus erythematosus associated refractory immune thrombocytopenia: a case-based review

A complication of pediatric systemic lupus erythematosus (pSLE) is immune thrombocytopenia (ITP). Although corticosteroids and immunoglobulins are frequently used as preliminary treatments, some patients do not respond to them. Rituximab has been reported to be safe and effective in the treatment of pSLE complicated with refractory ITP. Research is currently underway to determine the optimal rituximab dose for these individuals. We report a case of a child with SLE-associated ITP (SLE-ITP) who was successfully treated with rituximab. Rituximab is likely the most viable therapeutic option for refractory SLE-ITP. Furthermore, a comprehensive review of the relevant literature was performed and a concise overview of the pathogenesis and available treatment modalities for pediatric patients diagnosed with SLE and concurrent ITP was provided.

Translating mechanisms into therapeutic strategies for immune thrombocytopenia (ITP): Lessons from clinical trials

Immune thrombocytopenia (ITP) is an autoimmune disorder that causes a significant reduction in peripheral blood platelet count. Fortunately, due to an increased understanding of ITP, there have been significant improvements in the diagnosis and treatment of these patients. Over the past decade, there have been a variety of proven therapeutic options available for ITP patients, including intravenous immunoglobulins (IVIG), Rituximab, corticosteroids, and thrombopoietin receptor agonists (TPO-RAs). Although the effectiveness of current therapies in treating more than two-thirds of patients, still some patients do not respond well to conventional therapies or fail to achieve long-term remission. Recently, a significant advancement has been made in identifying various mechanisms involved in the pathogenesis of ITP, leading to the development of novel treatments targeting these pathways. It seems that new agents that target plasma cells, Bruton tyrosine kinase, FcRn, platelet desialylation, splenic tyrosine kinase, and classical complement pathways are opening new ways to treat ITP. In this study, we reviewed the pathophysiology of ITP and summarized updates in this population's management and treatment options. We also took a closer look at the 315 ongoing trials to investigate their progress status and compare the effectiveness of interventions. May our comprehensive view of ongoing clinical trials serve as a guiding beacon, illuminating the path towards future trials of different drugs in the treatment of ITP patients.

GPIbα-filamin A interaction regulates megakaryocyte localization and budding during platelet biogenesis

ABSTRACT

Glycoprotein Ibα (GPIbα) is expressed on the surface of platelets and megakaryocytes (MKs) and anchored to the membrane skeleton by filamin A (flnA). Although GPIb and flnA have fundamental roles in platelet biogenesis, the nature of this interaction in megakaryocyte biology remains ill-defined. We generated a mouse model expressing either human wild-type (WT) GPIbα (hGPIbαWT) or a flnA-binding mutant (hGPIbαFW) and lacking endogenous mouse GPIbα. Mice expressing the mutant GPIbα transgene exhibited macrothrombocytopenia with preserved GPIb surface expression. Platelet clearance was normal and differentiation of MKs to proplatelets was unimpaired in hGPIbαFW mice. The most striking abnormalities in hGPIbαFW MKs were the defective formation of the demarcation membrane system (DMS) and the redistribution of flnA from the cytoplasm to the peripheral margin of MKs. These abnormalities led to disorganized internal MK membranes and the generation of enlarged megakaryocyte membrane buds. The defective flnA-GPIbα interaction also resulted in misdirected release of buds away from the vasculature into bone marrow interstitium. Restoring the linkage between flnA and GPIbα corrected the flnA redistribution within MKs and DMS ultrastructural defects as well as restored normal bud size and release into sinusoids. These studies define a new mechanism of macrothrombocytopenia resulting from dysregulated MK budding. The link between flnA and GPIbα is not essential for the MK budding process, however, it plays a major role in regulating the structure of the DMS, bud morphogenesis, and the localized release of buds into the circulation.

Immune attack on megakaryocytes in immune thrombocytopenia

A State of the Art lecture titled "Immune Attack on Megakaryocytes in ITP: The Role of Megakaryocyte Impairment" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. Immune thrombocytopenia (ITP) is an acquired autoimmune disorder caused by autoantibodies against platelet surface glycoproteins that provoke increased clearance of circulating platelets, leading to reduced platelet number. However, there is also evidence of a direct effect of antiplatelet autoantibodies on bone marrow megakaryocytes. Indeed, immunologic cells responsible for autoantibody production reside in the bone marrow; megakaryocytes progressively express during their maturation the same glycoproteins against which ITP autoantibodies are directed, and platelet autoantibodies have been detected in the bone marrow of patients with ITP. In vitro studies using ITP sera or monoclonal antibodies against platelet and megakaryocyte surface glycoproteins have shown an impairment of many steps of megakaryopoiesis and thrombopoiesis, such as megakaryocyte differentiation and maturation, migration from the osteoblastic to the vascular niche, adhesion to extracellular matrix proteins, and proplatelet formation, resulting in impaired and ectopic platelet production in the bone marrow and diminished platelet release in the bloodstream. Moreover, cytotoxic T cells may target bone marrow megakaryocytes, resulting in megakaryocyte destruction. Altogether, these findings suggest that antiplatelet autoantibodies and cellular immunity against bone marrow megakaryocytes may significantly contribute to thrombocytopenia in some patients with ITP. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress. The complete unraveling of the mechanisms of immune attack-induced impairment of megakaryopoiesis and thrombopoiesis may open the way to new therapeutic approaches.

Anti-tubercular therapy (ATT) induced thrombocytopenia: A systematic review

INTRODUCTION

Drug-induced thrombocytopenia is a known adverse event of several drugs. Antitubercular therapy (ATT) is rarely reported but important cause of thrombocytopenia. The present review aimed to understand the profile of thrombocytopenia caused by first-line ATT i.e. isoniazid, rifampicin, pyrazinamide, and ethambutol.

MATERIALS AND METHODS

We screened case reports, case series, and letter-to-editor from databases, like Pubmed/MEDLINE, Ovid, and EMBASE from 1970 to 2021. The PRISMA guidelines were followed in the present systematic review.

RESULTS

Categorical data were expressed as n (%) and quantitative data were expressed as median (IQR). After applying the inclusion/exclusion criteria, 17 case reports and 7 letters to the editor were selected for the present review. Rifampicin was most frequently associated with thrombocytopenia (65%). A median (IQR) drop to 20,000 (49,500) platelets/mm3 was observed. Anti-rifampicin associated antibodies and anti-dsDNA positivity were found in six studies. Except for two, all patients responded to symptomatic treatment.

DISCUSSION

ATT-induced thrombocytopenia can be life-threatening and require hospitalization. Clinicians should be aware of the association of ATT with thrombocytopenia and should take appropriate measures for patient management.

CONCLUSION

This review provides clinicians a comprehensive picture of adverse effects and their management in ATT induced thrombocytopenia.

Rituximab resistance in ITP and beyond

The pathophysiology of immune thrombocytopenia (ITP) is complex and encompasses innate and adaptive immune responses, as well as megakaryocyte dysfunction. Rituximab is administered in relapsed cases and has the added benefit of inducing treatment-free remission in over 50% of patients. Nevertheless, the responses to this therapy are not long-lasting, and resistance development is frequent. B cells, T cells, and plasma cells play a role in developing resistance. To overcome this resistance, targeting these pathways through splenectomy and novel therapies that target FcγR pathway, FcRn, complement, B cells, plasma cells, and T cells can be useful. This review will summarize the pathogenetic mechanisms implicated in rituximab resistance and examine the potential therapeutic interventions to overcome it. This review will explore the efficacy of established therapies, as well as novel therapeutic approaches and agents currently in development.

Role of interleukin 4 (IL4) and interleukin 6 (IL6) in the pathogenesis and prognosis of childhood primary immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by the breakdown of immune tolerance. Impairment of the cellular immunity is primarily evaluated by the levels of the cytokines which can help in predicting the course of ITP. We aimed to assess the levels of IL4 and IL6 in children with ITP and evaluate their role in the pathogenesis and prognosis of this disease. A prospective cohort study was carried on 60 children (15 patients with newly diagnosed ITP, 15 patients with persistent ITP, 15 patients with chronic ITP and 15 healthy children as a control group). Serum IL-4 and serum IL-6 were measured using Human IL-4 and IL-6 ELISA kit in patients and controls. Patients with newly diagnosed and persistent ITP had significantly higher levels of IL4 and IL6 compared to patients with chronic ITP and healthy controls (p < 0.001). The mean serum level of IL4 was 762.0, 741.0, 364.6 and 436.8 pg/ml, and the mean serum level of IL6 was 178.5, 164.4, 57.9 and 88.4 pg/ml for patients with newly diagnosed, persistent, chronic ITP and healthy controls respectively. Serum IL-4 was significantly higher in patients who achieved remission than those who did not improve on first line therapy.

CONCLUSION

Serum IL-4 and IL-6 may have a role in the pathogenesis of primary ITP. IL-4 seems to be a good predictor to treatment response.

WHAT IS KNOWN

• There is a delicate balance of specific cytokine levels in immune thrombocytopenia, which has an important role in the immune system and is known to be deregulated in autoimmune diseases. changes in IL-4 and IL-6 might be involved in the pathogenesis of newly diagnosed ITP in both paediatric and adult patients. • We conducted this research study to measure the serum level of IL-4 and IL-6, in newly diagnosed, persistent and chronic ITP patients and study their relation to disease pathogenesis as well as patient's outcome.

WHAT IS NEW

• We found that IL4 seems to be a good predictor to treatment response and it was a very interesting observation in our study, and to the best of our knowledge, there is no published data about this finding.

A Novel Antithrombocytopenia Agent, Rhizoma cibotii, Promotes Megakaryopoiesis and Thrombopoiesis through the PI3K/AKT, MEK/ERK, and JAK2/STAT3 Signaling Pathways

BACKGROUND

Cibotii rhizoma (CR) is a famous traditional Chinese medicine (TCM) used to treat bleeding, rheumatism, lumbago, etc. However, its therapeutic effects and mechanism against thrombocytopenia are still unknown so far. In the study, we investigated the effects of aqueous extracts of Cibotii rhizoma (AECRs) against thrombocytopenia and its molecular mechanism.

METHODS

Giemsa staining, phalloidin staining, and flow cytometry were performed to measure the effect of AECRs on the megakaryocyte differentiation in K562 and Meg-01 cells. A radiation-induced thrombocytopenia mouse model was constructed to assess the therapeutic actions of AECRs on thrombocytopenia. Network pharmacology and experimental verification were carried out to clarify its mechanism against thrombocytopenia.

RESULTS

AECRs promoted megakaryocyte differentiation in K562 and Meg-01 cells and accelerated platelet recovery and megakaryopoiesis with no systemic toxicity in radiation-induced thrombocytopenia mice. The PI3K/AKT, MEK/ERK, and JAK2/STAT3 signaling pathways contributed to AECR-induced megakaryocyte differentiation. The suppression of the above signaling pathways by their inhibitors blocked AERC-induced megakaryocyte differentiation.

CONCLUSIONS

AECRs can promote megakaryopoiesis and thrombopoiesis through activating PI3K/AKT, MEK/ERK, and JAK2/STAT3 signaling pathways, which has the potential to treat radiation-induced thrombocytopenia in the clinic.

Serum Copper and Zinc Levels in Primary Immune Thrombocytopenia

Although the pathogenesis of immune thrombocytopenia is not fully known, oxidative stress is one of the etiological causes. Copper and zinc are elements in the antioxidant system, and their deficiency causes oxidative stress. We aimed to determine the serum copper and zinc levels and their effects on the response to treatment in patients with immune thrombocytopenia. We analyzed 51 patients with primary immune thrombocytopenia and 33 control cases. Age, gender, and platelet values at the time of diagnosis, drugs used for the treatment of immune thrombocytopenia, remission status, and serum copper and zinc levels were recorded. The primary immune thrombocytopenia and control groups were compared in terms of serum copper and zinc levels. In addition, the relationship between the response status to the treatment of patients with immune thrombocytopenia and serum copper and zinc levels was investigated. The serum zinc level in the immune thrombocytopenia group and control group was 10.35 ± 3.28 µmol/L and 12.82 ± 2.41 µmol/L, respectively (p = 0.01). The serum copper level in patients with immune thrombocytopenia (77.3 ± 22.23 µg/dL) was significantly lower than the control group (99.4 ± 20.82 µg/dL) (p = 0.01). A significant correlation was found between the response to first-line treatment of primary immune thrombocytopenia and serum copper level (p = 0.005). The serum copper level was significantly lower in relapsed cases (p = 0.001). In conclusion, serum copper and zinc levels are lower in patients with primary immune thrombocytopenia than in healthy cases. Patients with relapsed or unresponsive to immune thrombocytopenia treatment have lower serum copper levels than other patients.

Clinical Epidemiology, Treatment Outcome and Mortality Rate of Newly Diagnosed Immune Thrombocytopenia in Adult Multicentre Study in Malaysia

Background

Immune thrombocytopenia (ITP) is well characterized in Western, European and other Asia-Pacific countries. Nevertheless, the clinical epidemiology, treatment pattern and disease outcome of ITP in Malaysia are still limited and not well known.

Objective

This study aimed to describe the clinical epidemiology, treatment outcome and mortality of ITP patients in haematology tertiary multicentre in Malaysia.

Methods

Clinical and laboratory data of newly diagnosed adults with ITP by a platelet count <100 × 10⁹/L from January 2010 to December 2020 were identified and analyzed.

Results

Out of 500 incident ITP, 71.8% were females with a striking age preponderance of both genders among those aged 18–29 years. The median age was 36 years. The median platelet count was 17.5 × 10⁹/L, 23.0% had a secondary ITP, 34.6% had a Charlson’s score ≥1, 53.0% had bleeding symptoms including 2.2% intracranial bleedings (ICB). Helicobacter pylori screening was performed in <5% of cases. Persistency and chronicity rates were 13.6% and 41.8%, respectively. Most (80.6%) were treated at diagnosis onset and 31.2% needed second-line treatment. Throughout the course of ITP, 11.0% of patients died; 3.0% and 8.0% with bleeding and non-bleeding related ITP.

Conclusion

This study confirms the epidemiology of ITP is comparable with worldwide studies. Our incidence is high in the female, Malay ethnicity, primary ITP and events of cutaneous bleeding at ITP onset with 18–29 years predominance age group for both genders. The frequency of persistent and chronic ITP is inconsistent with published literature. Corticosteroids and immunotherapies are the most prescribed first-line and second-line pharmacological treatments. Thrombopoietin receptor agonist medications (TPO-RAs) usage is restricted and splenectomy is uncommon. Our mortality rate is similar but ITP related bleeding death is fourth-fold lower than previous studies. Mortality risks of our ITP patients include age ≥60 years, male, severe bleeding at presentation, CCI≥1 and secondary ITP.

Thrombocytopenia and splenic platelet directed immune responses after intravenous ChAdOx1 nCov-19 administration

Vaccines against SARS-CoV-2 are based on a range of novel platforms, with adenovirus-based approaches (like ChAdOx1 nCov-19) being one of them. Recently a novel complication of SARS-CoV-2 targeted adenovirus vaccines has emerged: immune thrombocytopenia (ITP), either isolated, or accompanied by thrombosis (then termed VITT). This complication is characterized by low platelet counts, and in the case of VITT also by platelet-activating platelet factor 4 (PF4) antibodies reminiscent of heparin-induced thrombocytopenia leading to a prothrombotic state with clot formation at unusual anatomic sites. Here, we detected anti-platelet antibodies targeting platelet glycoprotein receptors in 30% of patients with proven VITT (n=27), as well as 42% of patients with isolated thrombocytopenia after ChAdOx1 nCov-19 vaccination (n=26), indicating broad antiplatelet autoimmunity in these clinical entities. We employ in vitro and in vivo models to characterize possible mechanisms of these platelet-targeted autoimmune responses leading to thrombocytopenia. We show that intravenous but not intramuscular injection of ChAdOx1 nCov-19 triggers platelet-adenovirus aggregate formation and platelet activation. After intravenous injection, these aggregates are phagocytosed by macrophages in the spleen and platelet remnants are found in the marginal zone and follicles. This is followed by a pronounced B-cell response with the emergence of circulating antibodies binding to platelets. Our work contributes to the understanding of platelet associated complications after ChAdOx1 nCov-19 administration and highlights accidental intravenous injection as a potential mechanism of platelet targeted autoimmunity. Hence, preventing intravenous injection when administering adenovirus-based vaccines could be a potential measure against platelet associated pathologies following the vaccination.

Anti-glycoprotein antibodies and sequestration pattern of indium-labeled platelets in immune thrombocytopenia

Antiglycoprotein (anti-GP) antibodies play an important role in the pathophysiology of immune thrombocytopenia (ITP). The sequestration pattern of platelets in the spleen and liver can be studied with 111In-labeled autologous platelet scans. No studies have investigated the role of anti-GP antibodies in sequestration patterns in ITP patients. In this study, we examined the association between antibodies and (1) platelet sequestration site and (2) clearance rate of platelets. All ITP patients receiving an 111In-labeled autologous platelet study between 2014 and 2018 were included. Antibodies were measured using the direct MAIPA method to determine the presence and titer of anti-GPIIb/IIIa, anti-GPIb/IX, and anti-GPV antibodies. Multivariate regression models were used to study the association between anti-GP antibodies, sequestration site, and clearance rate. Seventy-four patients were included, with a mean age of 36 years. Forty-seven percent of the patients showed a predominantly splenic sequestration pattern, 29% mixed, and 25% a hepatic pattern. In 53% of the patients, anti-GP antibodies were detected. Regression models showed a significant association between splenic sequestration and GPV autoantibodies. Furthermore, in patients where antibodies were present, the clearance rate was higher in patients with a splenic sequestration. Anti-GPV antibodies are associated with a splenic sequestration pattern in ITP patients. These associations provide insight into the possible pathophysiological mechanisms of ITP, which may lead to better detection and treatment of this partly idiopathic and prevalent disease.

Stromal Derived Factor-1 Gene Polymorphism in Pediatric Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is a multifactorial disease in which both environmental and genetic factors have been implicated. The study aimed to investigate a possible association of single nucleotide polymorphisms (SNPs rs266085 and rs2839693) in the stromal derived factor-1 (SDF-1) gene and its association to ITP and effect on ITP severity and response to treatment. Genomic DNA was extracted from peripheral blood and polymorphism in SDF-1 gene rs266085 and rs2839693 was analyzed using PCR-restriction fragment length polymorphism technique in DNA extracted from 60 children with ITP together with 90 healthy controls. On analysis of SDF-1 rs266085 polymorphism, there was a high frequency of CC genotype in cases than controls and that difference was significant at codominant, overdominant, and dominant models (P<0.05). Furthermore, carriers of the CC genotype were more susceptible to severe ITP at onset, steroid dependency, and chronicity than carriers of other genotypes (P<0.05). Otherwise, no significant differences between ITP patients and controls as regard SDF-1 rs2839693 genotypes and alleles, and we did not find a relation between this polymorphism and ITP severity, steroid dependency, or duration. SDF-1 gene rs266085 SNP C allele is associated with susceptibility to develop ITP as well as increases the risk for severe ITP at onset, chronic ITP and steroid dependency.

Immune Thrombocytopenic Purpura as a Hemorrhagic Versus Thrombotic Disease: An Updated Insight into Pathophysiological Mechanisms

Immune thrombocytopenic purpura (ITP) is a blood disorder characterized by a low platelet count of (less than 100 × 109/L). ITP is an organ-specific autoimmune disease in which the platelets and their precursors become targets of a dysfunctional immune system. This interaction leads to a decrease in platelet number and, subsequently, to a bleeding disorder that can become clinically significant with hemorrhages in skin, on the mucous membrane, or even intracranial hemorrhagic events. If ITP was initially considered a hemorrhagic disease, more recent studies suggest that ITP has an increased risk of thrombosis. In this review, we provide current insights into the primary ITP physiopathology and their consequences, with special consideration on hemorrhagic and thrombotic events. The autoimmune response in ITP involves both the innate and adaptive immune systems, comprising both humoral and cell-mediated immune responses. Thrombosis in ITP is related to the pathophysiology of the disease (young hyperactive platelets, platelets microparticles, rebalanced hemostasis, complement activation, endothelial activation, antiphospholipid antibodies, and inhibition of natural anticoagulants), ITP treatment, and other comorbidities that altogether contribute to the occurrence of thrombosis. Physicians need to be vigilant in the early diagnosis of thrombotic events and then institute proper treatment (antiaggregant, anticoagulant) along with ITP-targeted therapy. In this review, we provide current insights into the primary ITP physiopathology and their consequences, with special consideration on hemorrhagic and thrombotic events. The accumulated evidence has identified multiple pathophysiological mechanisms with specific genetic predispositions, particularly associated with environmental conditions.

Platelets' Role in Dentistry: From Oral Pathology to Regenerative Potential

Platelets are a cellular subgroup of elements circulating in the bloodstream, responsible for the innate immunity and repairing processes. The diseases affecting this cellular population, depending on the degree, can vary from mild to severe conditions, which have to be taken into consideration in cases of minor dental procedures. Their secretion of growth factors made them useful in the regenerative intervention. The aim of this review is to examine the platelets from biological, examining the biogenesis of the platelets and the biological role in the inflammatory and reparative processes and clinical point of view, through the platelets' pathology and their use as platelets concentrates in dental regenerative surgery.

The Extensive Regulation of MicroRNA in Immune Thrombocytopenia

MicroRNA (miRNA) is a small, single-stranded, non-coding RNA molecule that plays a variety of key roles in different biological processes through post-transcriptional regulation of gene expression. MiRNA has been proved to be a variety of cellular processes involved in development, differentiation, signal transduction, and is an important regulator of immune and autoimmune diseases. Therefore, it may act as potent modulators of the immune system and play an important role in the development of several autoimmune diseases. Immune thrombocytopenia (ITP) is an autoimmune systemic disease characterized by a low platelet count. Several studies suggest that like other autoimmune disorders, miRNAs are deeply involved in the pathogenesis of ITP, interacting with the function of innate and adaptive immune responses. In this review, we discuss emerging knowledge about the function of miRNAs in ITP and describe miRNAs in terms of their role in the immune system and autoimmune response. These findings suggest that miRNA may be a useful therapeutic target for ITP by regulating the immune system. In the future, we need to have a more comprehensive understanding of miRNAs and how they regulate the immune system of patients with ITP.

Isolation of megakaryocytes using magnetic cell separation and adverse effects induced by diclofenac toxicity in an experiment

This study investigates the response of bone marrow (particularly megakaryocytes) in mice under the influence of diclofenac sodium for 10 days using intraperitoneal injection at various doses. A fundamentally new immunomagnetic separation method was applied during the experiment, which helped obtain pure lines of bone marrow cells, particularly megakaryocytes (MC), without admixtures of other cells or their particles. The resulting cells completely retain their structure and can be used in further research. The study determined that different doses of diclofenac sodium have different effects on different groups of diabetes mellitus cells CD34-megakaryocytes. The use of 1.0 mg/ml sharply negatively affects the state of early populations of megakaryocytes (decrease by 80%, p=0.05), a dose of 0.025 mg/ml had the least effect on this population of cells (22.8%, p=0.05). The greatest number of average forms of diabetes mellitus 34 was observed when using a dose of 0.95 mg/ml (22.8%, p=0.05), with a gradual decrease in the dose, the indicator of this group of cells decreased. A dose of 0.03 mg/ml did not affect the quantitative state of megakaryocytes, and a dose of 0.025 mg/ml caused a slight decrease (16.6%, p=0.05). Indicators of mature cells of megakaryocytes CD 34- decreased in all studied groups, however, their maximum value reached a maximum decrease by 0.25 mg/ml (55.2%, p=0.05), the dose of diclofenac sodium 0.03 mg/ml, lower (18.4%, p=0.05). Diclofenac sodium in different doses has different effects on the degree of differentiation of CD 34-. Its introduction positively affects the state of intermediate forms of megakaryocytes, except for minimal doses, while the effect on early and mature forms in all cases turned out to be negative.

Platelet Activation Mechanisms and Consequences of Immune Thrombocytopenia

Autoimmune disorders are often associated with low platelet count or thrombocytopenia. In immune-induced thrombocytopenia (IIT), a common mechanism is increased platelet activity, which can have an increased risk of thrombosis. In addition, or alternatively, auto-antibodies suppress platelet formation or augment platelet clearance. Effects of the auto-antibodies are linked to the unique structural and functional characteristics of platelets. Conversely, prior platelet activation may contribute to the innate and adaptive immune responses. Extensive interplay between platelets, coagulation and complement activation processes may aggravate the pathology. Here, we present an overview of the reported molecular causes and consequences of IIT in the most common forms of autoimmune disorders. These include idiopathic thrombocytopenic purpura (ITP), systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), drug-induced thrombocytopenia (DITP), heparin-induced thrombocytopenia (HIT), COVID-19 vaccine-induced thrombosis with thrombocytopenia (VITT), thrombotic thrombocytopenia purpura (TTP), and hemolysis, the elevated liver enzymes and low platelet (HELLP) syndrome. We focus on the platelet receptors that bind auto-antibodies, the immune complexes, damage-associated molecular patterns (DAMPs) and complement factors. In addition, we review how circulating platelets serve as a reservoir of immunomodulatory molecules. By this update on the molecular mechanisms and the roles of platelets in the pathogenesis of autoimmune diseases, we highlight platelet-based pathways that can predispose for thrombocytopenia and are linked thrombotic or bleeding events.

Platelets in ITP: Victims in Charge of Their Own Fate?

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder. The pathophysiological mechanisms leading to low platelet levels in ITP have not been resolved, but at least involve autoantibody-dependent and/or cytotoxic T cell mediated platelet clearance and impaired megakaryopoiesis. In addition, T cell imbalances involving T regulatory cells (Tregs) also appear to play an important role. Intriguingly, over the past years it has become evident that platelets not only mediate hemostasis, but are able to modulate inflammatory and immunological processes upon activation. Platelets, therefore, might play an immuno-modulatory role in the pathogenesis and pathophysiology of ITP. In this respect, we propose several possible pathways in which platelets themselves may participate in the immune response in ITP. First, we will elaborate on how platelets might directly promote inflammation or stimulate immune responses in ITP. Second, we will discuss two ways in which platelet microparticles (PMPs) might contribute to the disrupted immune balance and impaired thrombopoiesis by megakaryocytes in ITP. Importantly, from these insights, new starting points for further research and for the design of potential future therapies for ITP can be envisioned.

A Case Report of Immune Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination

Immune thrombocytopenia (ITP) is an autoimmune condition characterized by platelet destruction through antibody-mediated mechanism. ITP is one of the manifestations of a coronavirus disease, as well as an adverse event occurring after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several cases of ITP have been described after vaccination with two mRNA-based vaccines-BTN162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna)-against SARS-CoV-2. Herein, we report a case of ITP occurring after vaccination with ChAdOx1 adenovirus vector nCoV-19 (AstraZeneca) vaccine in Korea. A 66-year-old woman presented with multiple ecchymoses on both upper and lower extremities and gingival bleeding, appearing 3 days after receiving the first dose of ChAdOx1 nCoV-19. Her laboratory results showed isolated severe thrombocytopenia without evidence of combined coagulopathy. She was diagnosed with ITP and successfully treated with high-dose dexamethasone and intravenous immunoglobulin. Clinical suspicion to identify vaccine-related ITP is important to promptly initiate appropriate treatment.

Mycophenolate Mofetil for First-Line Treatment of Immune Thrombocytopenia

BACKGROUND

Immune thrombocytopenia is a rare autoimmune disorder with associated bleeding risk and fatigue. Recommended first-line treatment for immune thrombocytopenia is high-dose glucocorticoids, but side effects, variable responses, and high relapse rates are serious drawbacks.

METHODS

In this multicenter, open-label, randomized, controlled trial conducted in the United Kingdom, we assigned adult patients with immune thrombocytopenia, in a 1:1 ratio, to first-line treatment with a glucocorticoid only (standard care) or combined glucocorticoid and mycophenolate mofetil. The primary efficacy outcome was treatment failure, defined as a platelet count of less than 30×10⁹ per liter and initiation of a second-line treatment, assessed in a time-to-event analysis. Secondary outcomes were response rates, side effects, occurrence of bleeding, patient-reported quality-of-life measures, and serious adverse events.

RESULTS

A total of 120 patients with immune thrombocytopenia underwent randomization (52.4% male; mean age, 54 years [range 17 to 87]; mean platelet level, 7×10⁹ per liter) and were followed for up to 2 years after beginning trial treatment. The mycophenolate mofetil group had fewer treatment failures than the glucocorticoid-only group (22% [13 of 59 patients] vs. 44% [27 of 61 patients]; hazard ratio, 0.41; range, 0.21 to 0.80; P = 0.008) and greater response (91.5% of patients having platelet counts greater than 100×10⁹ per liter vs. 63.9%; P<0.001). We found no evidence of a difference between the groups in the occurrence of bleeding, rescue treatments, or treatment side effects, including infection. However, patients in the mycophenolate mofetil group reported worse quality-of-life outcomes regarding physical function and fatigue than those in the glucocorticoid-only group.

CONCLUSIONS

The addition of mycophenolate mofetil to a glucocorticoid for first-line treatment of immune thrombocytopenia resulted in greater response and a lower risk of refractory or relapsed immune thrombocytopenia, but with somewhat decreased quality of life. (Funded by the U.K. National Institute for Health Research; FLIGHT ClinicalTrials.gov number, NCT03156452; EudraCT number, 2017-001171-23.).

A Review of Romiplostim Mechanism of Action and Clinical Applicability

Thrombocytopenia results from a variety of conditions, including radiation, chemotherapy, autoimmune disease, bone marrow disorders, pathologic conditions associated with surgical procedures, hematopoietic stem cell transplant (HSCT), and hematologic disorders associated with severe aplastic anemia. Immune thrombocytopenia (ITP) is caused by immune reactions that accelerate destruction and reduce production of platelets. Thrombopoietin (TPO) is a critical component of platelet production pathways, and TPO receptor agonists (TPO-RAs) are important for the management of ITP by increasing platelet production and reducing the need for other treatments. Romiplostim is a TPO-RA approved for use in patients with ITP in the United States, European Union, Australia, and several countries in Africa and Asia, as well as for use in patients with refractory aplastic anemia in Japan and Korea. Romiplostim binds to and activates the TPO receptor on megakaryocyte precursors, thus promoting cell proliferation and viability, resulting in increased platelet production. Through this mechanism, romiplostim reduces the need for other treatments and decreases bleeding events in patients with thrombocytopenia. In addition to its efficacy in ITP, studies have shown that romiplostim is effective in improving platelet counts in various settings, thereby highlighting the versatility of romiplostim. The efficacy of romiplostim in such disorders is currently under investigation. Here, we review the structure, mechanism, pharmacokinetics, and pharmacodynamics of romiplostim. We also summarize the clinical evidence supporting its use in ITP and other disorders that involve thrombocytopenia, including chemotherapy-induced thrombocytopenia, aplastic anemia, acute radiation syndrome, perisurgical thrombocytopenia, post-HSCT thrombocytopenia, and liver disease.

Platelet number and function in response to a single intravenous dose of vincristine

Background

Vincristine might increase circulating platelet numbers but the functional capacity of these newly released platelets is unknown.

Objective

To evaluate and compare the functionality of mature and immature (reticulated) platelets after a single intravenous dose of vincristine in dogs.

Animals

Ten healthy purpose‐bred dogs.

Methods

Dogs prospectively received a single IV injection of 0.02 mg/kg vincristine or 0.9% saline. Before and after treatment on days 3, 5, and 7, platelets (resting and after thrombin stimulation) were assessed by flow cytometric determination of P‐selectin (CD62P) expression. Reticulated platelets were distinguished using thiazole orange (TO) staining.

Results

Relative to saline, vincristine administration increased platelet count from day 0 to day 7 (225 ± 58 to 273 ± 65 × 10³/μL, vs 299 ± 76.4 to 214 ± 20 × 10³/μL, P = .01) and increased percentage of reticulated platelets from day 0 to day 5 (3.9 ± 1.5% to 6.1 ± 1.6%, P = .02). On all days, reticulated platelets had greater resting expression of CD62P than did mature platelets (49.6 ± 4% vs 10.2 ± 1%, P ≤ .001). Across all days, CD62P expression by reticulated platelets in the vincristine and saline‐treated groups was not different when unstimulated (P = .7) or after thrombin stimulation (P = .33).

Conclusions and Clinical Importance

Reticulated platelets released in response to vincristine administration function similarly to mature platelets.

A modern reassessment of glycoprotein-specific direct platelet autoantibody testing in immune thrombocytopenia

Platelet autoantibody (PA) testing has previously shown poor sensitivity for immune thrombocytopenia (ITP) diagnosis, but no previous study used both 2011 American Society of Hematology (ASH) guidelines for ITP diagnosis and 2012 International Society on Thrombosis and Haemostasis (ISTH) PA testing recommendations. We therefore performed a comprehensive retrospective study of PA testing in adult patients with ITP strictly applying these criteria. Of 986 PA assays performed, 485 assays in 368 patients met criteria and were included. Sensitivity and specificity of a positive test result for diagnosis of active ITP (n = 228 patients) were 90% and 78%, respectively. Sensitivity and specificity of a negative test result for clinical remission (n = 61 assays) were 87% and 91%. Antibodies against both glycoprotein IIb (GPIIb)/IIIa and GPIb/IX were required for the presence of antibodies against GPIa/IIa in patients with ITP. Logistic regression analysis revealed that more positive autoantibodies predicted more severe disease (relative to nonsevere ITP, relative risk ratio for severe ITP and refractory ITP was 2.27 [P < .001] and 3.09 [P < .001], respectively, per additional autoantibody); however, serologic testing did not meaningfully predict treatment response to glucocorticoids, intravenous immunoglobulin, or thrombopoietin receptor agonists. Sixty-four patients with ITP had multiple PA assays performed longitudinally: all 10 patients achieving remission converted from positive to negative serologic results, and evidence for epitope spreading was observed in 35% of patients with ongoing active disease. In conclusion, glycoprotein-specific direct PA testing performed using ISTH recommendations in patients meeting ASH diagnostic criteria is sensitive and specific for ITP diagnosis and reliably confirms clinical remission. More glycoproteins targeted by autoantibodies predicts for more severe disease.

Phase 2 multiple-dose study of an FcRn inhibitor, rozanolixizumab, in patients with primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is a predominantly immunoglobulin G (IgG)-autoantibody-mediated disease characterized by isolated thrombocytopenia. Rozanolixizumab, a subcutaneously infused humanized monoclonal anti-neonatal Fc receptor (FcRn) antibody, reduced serum IgG in healthy volunteers. In this phase 2, multicenter, open-label study, patients with persistent/chronic primary ITP received 1 to 5 once-weekly subcutaneous infusions of rozanolixizumab (cumulative doses, 15-21 mg/kg). Primary objectives were safety and tolerability, and secondary objectives were clinical efficacy (change in platelet count) and pharmacodynamic effect (change in IgG). In all, 51 (77.3%) of 66 patients reported 1 or more adverse events (AEs), all mild-to-moderate, most commonly headaches (26 [39.4%] of 66), of which 15 were treatment related. Four patients had serious AEs, but none were treatment related. No AEs resulted in discontinuation of the study drug. No serious infections occurred. Platelet counts of ≥50 × 109/L were achieved at least once at any time after multiple infusions (5 × 4, 3 × 7, or 2 × 10 mg/kg: 35.7%, 35.7%, and 45.5% of patients, respectively) or single infusions (15 or 20 mg/kg: 66.7% and 54.5% patients, respectively). Minimum mean IgG levels and maximum mean platelet counts both occurred by day 8 in the higher (15 and 20 mg/kg) single-dose cohorts and maximum platelet count occurred by day 11 onward in the multiple-dose cohorts. No clinically meaningful changes occurred in IgA, IgM, IgE, or albumin levels. In patients with persistent/chronic primary ITP, rozanolixizumab demonstrated a favorable safety profile and rapid, substantial platelet increases concordant with substantial IgG reductions, especially with single doses. By day 8, in the 15 and 20 mg/kg single-dose cohorts, >50% patients achieved clinically relevant platelet responses (≥50 × 109/L), coinciding with the lowest mean IgG levels. These data support phase 3 development of rozanolixizumab in persistent/chronic primary ITP. This trial was registered at www.clinicaltrials.gov as #NCT02718716.

Comparative study of IgG binding to megakaryocytes in immune and myelodysplastic thrombocytopenic patients

Immune thrombocytopenia (ITP) is a disorder in which autoantibodies are responsible for destruction and decreased production of platelets. In the meantime, thrombocytopenia is frequent in patients with myelodysplastic syndromes (MDS) and immune clearance of megakaryocytes could be a reason. The aim of the present study is to evaluate and compare IgG binding to megakaryocytes in bone marrow of ITP and MDS patients to determine megakaryocytes targeting by autoantibodies in vivo as a mechanism of platelet underproduction in these disorders. The study was carried out on 20 ITP (group I) patients, 20 thrombocytopenic patients with (MDS) (group II), and 20 non-ITP patients as a control (group III) who were admitted to Minia University Hospital. Serial histological sections from bone marrow biopsies were stained for IgG. All patients in group I and 50% of group II patients showed bleeding tendency and the difference was significant (p < 0.001). No patient experienced fatigue in group I while 35% of patients in group II complained of easy fatigability, and the difference was significant (p < 0.008). High IgG antibody binding was found in ITP and MDS compared to the control group but no significant difference between ITP and MDS patients (14/20 (70%) vs. 13/20 (65%)) (p value = 0.736). Antibody binding to megakaryocytes in a proportion of MDS patients suggests that immune-mediated mechanism underlies platelet underproduction in those patients.

Immune Thrombocytopenia Plasma-Derived Exosomes Impaired Megakaryocyte and Platelet Production through an Apoptosis Pathway

Reduced megakaryocyte (MK) apoptosis and insufficient platelet production play important roles in the pathogenesis of immune thrombocytopenia (ITP). The contribution of plasma-derived exosomes to the decreased platelet count in ITP has not been entirely understood. Here, we found the percentage of apoptotic MKs in patients with ITP was significantly lower than those in healthy volunteers. In the presence of ITP plasma-derived exosomes (ITP-Exo), the apoptosis of MKs was reduced during the process of MK differentiation in vitro, which contributed to the reduced platelet production by Bcl-xL/caspase signaling. Furthermore, in vivo study demonstrated that ITP-Exo administration led to significantly delayed platelet recovery in mice after 3.5 Gy of irradiation. All these findings indicated that ITP-Exo, as a regulator of platelet production, impaired MK apoptosis and platelet production through Bcl-xL/caspase signaling, unveiling new mechanisms for reduced platelet count in ITP.

The molecular basis of immune-based platelet disorders

Platelets have a predominant role in haemostasis, the maintenance of blood volume and emerging roles as innate immune cells, in wound healing and in inflammatory responses. Platelets express receptors that are important for platelet adhesion, aggregation, participation in inflammatory responses, and for triggering degranulation and enhancing thrombin generation. They carry a cargo of granules bearing enzymes, adhesion molecules, growth factors and cytokines, and have the ability to generate reactive oxygen species. The platelet is at the frontline of a host of cellular responses to invading pathogens, injury, and infection. Perhaps because of this intrinsic responsibility of a platelet to rapidly respond to thrombotic, pathological and immunological factors as part of their infantry role; platelets are susceptible to targeted attack by the adaptive immune system. Such attacks are often transitory but result in aberrant platelet activation as well as significant loss of platelet numbers and platelet function, paradoxically leading to elevated risks of both thrombosis and bleeding. Here, we discuss the main molecular events underlying immune-based platelet disorders with specific focus on events occurring at the platelet surface leading to activation and clearance.

Insights on chronic immune thrombocytopenia pathogenesis: A bench to bedside update

Immune thrombocytopenia (ITP) is a heterogeneous disease with an unpredictable course. Chronicity can develop in up to two-thirds of adults and 20-25% of children, representing a significant burden on patients' quality of life. Despite acceptable responses to treatment, precise etiology and pathophysiology phenomena driving evolution to chronicity remain undefined. We analyzed reported risk factors for chronic ITP and associated them with proposed underlying mechanisms in its pathogenesis, including bone marrow (BM) microenvironment disturbances, clinical features, and immunological markers. Their understanding has diagnostic implications, such as screening for the presence of specific antibodies or BM examination employing molecular tools, which could help predict prognosis and recognize main pathogenic pathways in each patient. Identifying these underlying mechanisms could guide the use of personalized therapies such as all-trans retinoic acid, mTor inhibitors, FcRn inhibitors, oseltamivir, and others. Further research should lead to tailored treatments and chronic course prevention, improving patients' quality of life.

Platelet desialylation and TFH cells-the novel pathway of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by immune-mediated destruction of one's own platelets. The progression of thrombocytopenia involves an imbalance of platelet production and clearance. B cells can induce autoantibodies, and T cells contribute to the pathological progression as well. Some patients with ITP have a poor response to common first-line therapies. Recent studies have shown that a novel Fc-independent platelet clearance pathway is associated with poor prognosis in these patients. By this pathway, desialylated platelets can be cleared by Ashwell-Morell receptor (AMR) on hepatocytes. Research has demonstrated that patients with refractory ITP usually have a high level of desialylation, indicating the important role of sialylation on platelet membrane glycoprotein (GP) in patients with primary immune thrombocytopenia, and neuraminidase 1(NEU1) translocation might be involved in this process. Patients with ITP who are positive for anti-GPIbα antibodies have a poor prognosis, which indicates that anti-GPIbα antibodies are associated with this Fc-independent platelet clearance pathway. Experiments have proven that these antibodies could lead to the desialylation of GPs on platelets. The T follicular helper (TFH) cell level is related to the expression of the anti-GPIbα antibody, which indicates its role in the progression of desialylation. This review will discuss platelet clearance and production, especially the role of the anti-GPIbα antibody and desialylation in the pathophysiology of ITP and therapy for this disease.

Primary Immune Thrombocytopenia: Novel Insights into Pathophysiology and Disease Management

Immune thrombocytopenia (ITP) is an autoimmune disorder defined by a significantly reduced number of platelets in blood circulation. Due to low levels of platelets, ITP is associated with frequent bruising and bleeding. Current evidence suggests that low platelet counts in ITP are the result of multiple factors, including impaired thrombopoiesis and variations in immune response leading to platelet destruction during pathological conditions. Patient outcomes as well as clinic presentation of the disease have largely been shown to be case-specific, hinting towards ITP rather being a group of clinical conditions sharing common symptoms. The most frequent characteristics include dysfunction in primary haemostasis and loss of immune tolerance towards platelet as well as megakaryocyte antigens. This heterogeneity in patient population and characteristics make it challenging for the clinicians to choose appropriate therapeutic regimen. Therefore, it is vital to understand the pathomechanisms behind the disease and to consider various factors including patient age, platelet count levels, co-morbidities and patient preferences before initiating therapy. This review summarizes recent developments in the pathophysiology of ITP and provides a comprehensive overview of current therapeutic strategies as well as potential future drugs for the management of ITP.

Primary Immunodeficiency and Thrombocytopenia

Primary immunodeficiency (PID) or Inborn errors of immunity (IEI) refers to a heterogeneous group of disorders characterized by immune system impairment. Although patients with IEI manifest highly variable symptoms, the most common clinical manifestations are recurrent infections, autoimmunity and malignancies. Some patients present hematological abnormality including thrombocytopenia due to different pathogenic mechanisms. This review focuses on primary and secondary thrombocytopenia as a complication, which can occur in IEI. Based on the International Union of Immunological Societies phenotypic classification for IEI, the several innate and adaptive immunodeficiency disorders can lead to thrombocytopenia. This review, for the first time, describes manifestation, mechanism and therapeutic modalities for thrombocytopenia in different classes of IEI.

Autoantibody-mediated desialylation impairs human thrombopoiesis and platelet lifespan

Immune thrombocytopenia is a common bleeding disease caused by autoantibody-mediated accelerated platelet clearance and impaired thrombopoiesis. Accumulating evidence suggests that desialylation affects platelet life span in immune thrombocytopenia. Herein, we report on novel effector functions of autoantibodies from immune thrombocytopenic patients which might interfere with the clinical picture of the disease. Data from our study show that a subgroup of autoantibodies is able to induce cleave of sialic acid residues from the surface of human platelets and megakaryocytes. Moreover, autoantibody-mediated desialylation interferes with the interaction between cells and extracellular matrix proteins leading to impaired platelet adhesion and megakaryocyte differentiation. Using a combination of ex vivo model of thrombopoiesis, a humanized animal model, and a clinical cohort study, we demonstrate that cleavage of sialic acid induces significant impairment in production, survival as well as function of human platelets. These data may indicate that prevention of desialylation should be investigated in the future in clinical studies as a potential therapeutic approach to treat bleeding in immune thrombocytopenia.

New Developments in the Pathophysiology and Management of Primary Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease that is characterized by a significant reduction in the number of circulating platelets and frequently associated with bleeding. Although the pathogenesis of ITP is still not completely elucidated, it is largely recognized that the low platelet count observed in ITP patients is due to multiple alterations of the immune system leading to increased platelet destruction as well as impaired thrombopoiesis. The clinical manifestations and patients' response to different treatments are very heterogeneous suggesting that ITP is a group of disorders sharing common characteristics, namely, loss of immune tolerance toward platelet (and megakaryocyte) antigens and dysfunctional primary hemostasis. Management of ITP is challenging and requires intensive communication between patients and caregivers. The decision to initiate treatment should be based on the platelet count level, age of the patient, bleeding manifestation, and other factors that influence the bleeding risk in individual patients. In this review, we present recent data on the mechanisms that lead to platelet destruction in ITP with a particular focus on current findings concerning alterations of thrombopoiesis. In addition, we give an insight into the efficacy and safety of current therapies and management of ITP bleeding emergencies.

Significant reductions in apoptosis-related proteins (HSPA6, HSPA8, ITGB3, YWHAH, and PRDX6) are involved in immune thrombocytopenia

To investigate differences in the expression of plasma proteins in immune thrombocytopenia (ITP) and normal control groups, bone marrow samples were collected from 20 active ITP patients and 20 healthy controls. Quantitative proteomics analysis based on mass spectrometry was used to measure the protein levels and understand the protein networks. We found differentially expressed proteins in ITP patients and healthy controls. Parallel reaction monitoring (PRM), a targeted proteome quantification technique, was used to quantitatively confirm the identified target proteins and verify the proteomics data. In this study, a total of 829 proteins were identified, and the fold-change cut-off was set at 1.5 (patients vs controls); a total of 26 proteins were upregulated, and 69 proteins were downregulated. The bioinformatics analysis indicated that some differentially expressed proteins were associated with apoptosis. KEGG enrichment analysis showed that the apoptosis-related proteins were closely related to the PI3K-Akt signalling pathway. PRM demonstrated that apoptosis-related proteins were significantly decreased in ITP patients, which further confirmed the important effect of apoptosis on ITP pathogenesis. We hypothesised that apoptosis may be closely related to ITP pathogenesis through the PI3K-Akt signalling pathway.

Copy-number variations in adult patients with chronic immune thrombocytopenia

OBJECTIVES

Immune thrombocytopenia (ITP) is an autoimmune disease with heterogeneous background. FCGR2C mutations were defined in one third of the patients but genetic players have not been fully elucidated yet. Although childhood ITP present as benign, ITP in adulthood is chronic disease with treatment challenges. This study aimed to focus on adult ITP patients using a whole genome genotyping that is valuable approach to identify the responsible genomic regions for the disease.

METHODS

Herein 24 adult primary-refractory for ITP patients were evaluated using HumanCytoSNP12BeadChip,Illumina. Forty-six age and sex matched healthy individuals, and ptients awith nonhematological conditions were analyzed as controls. Identified CNV regions were verified by qRTPCR. T-cell receptor beta and delta (TCRB/TCRG) clonality were assessed by heteroduplex analysis in mosaic cases.

RESULTS

Several CNV losses and gains were defined (losses:2q,7q,17q,19p, and gains: 1q,2p,3q,4q,7q,10q,12p,13q,14q,15q,17p,20q,21p,22q,Xp). Mosaic changes of different sizes (0.2-17.77Mb) were identified in five patients and three of them showed clonality. CNV regions that were unique to ITP patients were identified for the first time and among these genes, those related to immune regulation, and cellular trafficking were noteworthy. Conclusion: Identified CNV regions harbor several candidate genes, the functions of which might shed light on the pathogenesis of chronic ITP.

CD4+ T cell phenotypes in the pathogenesis of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by low platelet counts due to enhanced platelet clearance and compromised production. Traditionally, ITP was regarded a B cell mediated disorder as anti-platelet antibodies are detected in most patients. The very nature of self-antigens, evident processes of isotype switching and the affinity maturation of anti-platelet antibodies indicate that B cells in order to mount anti-platelet immune response require assistance of auto-reactive CD4⁺ T cells. For a long time, ITP pathogenesis has been exclusively reviewed through the prism of the disturbed balance between Th1 and Th2 subsets of CD4⁺ T cells, however, more recently new subsets of these cells have been described including Th17, Th9, Th22, T follicular helper and regulatory T cells. In this paper, we review the current understanding of the role and immunological mechanisms by which CD4⁺ T cells contribute to the pathogenesis of ITP.

Acquired Glanzmann thrombasthenia associated with platelet desialylation

BACKGROUND

The notable discrepancy between platelet count and bleeding manifestations in immune thrombocytopenia (ITP) patients with acquired Glanzmann thrombasthenia (GT) has been described.

OBJECTIVES

We aimed to examine the mechanisms responsible for thrombocytopenia and the bleeding phenotype in a patient with acquired GT.

PATIENT, METHODS, AND RESULTS

A patient with primary ITP underwent splenectomy due to steroid intolerance. Despite platelet count normalization, bleeding continued. Platelet aggregometry was abnormal with all agonists except for ristocetin. Flow cytometry demonstrated the presence of antiplatelet antibody, which caused dose-dependent inhibition of fibrinogen and PAC-1 binding, induction of neuraminidase-1 expression as well as platelet desialylation in donor platelets. Indirect monoclonal antibody immobilization of platelet specific antigen assay (MAIPA) confirmed specificity to αIIb β3 only, corroborated by binding on Chinese hamster ovary (CHO) cells expressing human glycoprotein αIIb β3 but not GP Ib/IX. Both desialylation and neuraminidase expression were observed with plasma adsorbed on Ib/IX CHO cells and with the immunoglobulin G (IgG) fraction. Desialylation was inhibited in the presence of anti-Fc-gamma receptor IIa (FcγRIIa) antibody. A nonobese diabetic/severe combined immunodeficient ITP murine model was established, which showed rapid hepatic donor platelet clearance in the presence of patient IgG. Treatment of mice with the neuraminidase inhibitor oseltamivir significantly reduced antibody-induced platelet destruction.

CONCLUSIONS

We report the first case of a patient with acquired GT due to ITP with FcγRIIa mediated platelet desialylation, independent of platelet activation. Treatment with neuraminidase inhibitor may prevent platelet clearance by anti-αIIb β3 antibodies.

Novel scientific approaches and future research directions in understanding ITP

Diagnosis of immune thrombocytopenia (ITP) and prediction of response to therapy remain significant and constant challenges in hematology. In patients who present with ITP, the platelet count is frequently used as a surrogate marker for disease severity, and so often determines the need for therapy. Although there is a clear link between thrombocytopenia and hemostasis, a direct correlation between the extent of thrombocytopenia and bleeding symptoms, especially at lower platelet counts is lacking. Thus, bleeding in ITP is heterogeneous, unpredictable, and nearly always based on a multitude of risk factors, beyond the platelet count. The development of an evidence-based, validated risk stratification model for ITP treatment is a major goal in the ITP community and this review discusses new laboratory approaches to evaluate the various pathobiologies of ITP that may inform such a model.

Disrupted balance of CD4+ T-cell subsets in bone marrow of patients with primary immune thrombocytopenia

Disequilibrium of CD4⁺ T-cell subpopulations in peripheral blood (PB) of patients with primary immune thrombocytopenia (ITP) has been well established, whereas the profile of CD4⁺ T-cell subpopulations in bone marrow (BM) remains elusive. In the present study, the frequencies of T helper 22 (Th22), Th17, Th1, Th2, follicular T helper (Tfh) cells and regulatory T cells (Tregs) as well as their effector cytokines in BM and PB from active ITP patients and healthy controls (HCs) were determined. Results showed that the frequencies of Th22, Th17, Th1, and Tfh cells were significantly higher, but Treg number was remarkably lower in BM from ITP patients than from HCs. In the ITP group, it was notable that the numbers of BM Th22, Th17, Th1, Th2, and Tfh cells were significantly elevated compared with the matched PB counterparts, while Treg number in BM was considerably reduced compared with that in PB. In consistence with the BM Th subset pattern, plasma levels of interleukin (IL)-22, IL-17A, and interferon (INF)-γ in BM from ITP patients were significantly increased compared with that from HCs. Therefore, the balance of CD4⁺ T-cell subsets was disrupted in both BM and PB of ITP patients, suggesting that this might play important roles in the pathophysiological process of ITP.

Mechanisms and therapeutic prospects of thrombopoietin receptor agonists

The second-generation thrombopoietin (TPO) receptor agonists eltrombopag and romiplostim are potent activators of megakaryopoiesis and represent a growing treatment option for patients with thrombocytopenic hematological disorders. Both TPO receptor agonists have been approved worldwide for the treatment of children and adults with chronic immune thrombocytopenia. In the EU and USA, eltrombopag is approved for the treatment of patients with severe aplastic anemia who have had an insufficient response to immunosuppressive therapy and in the USA for the first-line treatment of severe aplastic anemia in combination with immunosuppressive therapy. Eltrombopag has also shown efficacy in several other disease settings, for example, chemotherapy-induced thrombocytopenia, selected inherited thrombocytopenias, and myelodysplastic syndromes. While both TPO receptor agonists stimulate TPO receptor signaling and enhance megakaryopoiesis, their vastly different biochemical structures bestow upon them markedly different molecular and functional properties. Here, we review and discuss results from preclinical and clinical studies on the functional and molecular mechanisms of action of this new class of drug.

Immune thrombocytopenia (ITP): Pathophysiology update and diagnostic dilemmas

Immune thrombocytopenia (ITP) is a common autoimmune bleeding disorder. The understanding of ITP pathogenesis is rapidly evolving. We now recognize ITP as a complex and heterogeneous syndrome that results from a combination of humoral and cell-mediated attacks on platelets peripherally and megakaryocytes in the bone marrow. Autoantibody-mediated ITP also varies in the pathway used to clear platelets, which depends on the platelet glycoprotein being targeted. Moreover, ITP patients present with variable bleeding severities and treatment responses that do not closely correlate with platelet count. A gold standard diagnostic test for ITP is lacking, and biomarkers to assess disease severity are in their infancy. This review provides an update on the immunopathogenesis of ITP and summarizes currently available tests for ITP diagnosis, prediction of disease severity, and treatment responses. Given the heterogeneous pathogenesis and clinical presentation of ITP, we highlight the need for the development of diagnostic and prognostic tests that would allow for the individualized management of a complex disease.