Splenic TFH expansion participates in B-cell differentiation and antiplatelet-antibody production during immune thrombocytopenia

Immune thrombocytopenia: Pathophysiology and impacts of Romiplostim treatment

Immune thrombocytopenia (ITP) is an autoimmune bleeding disease caused by immune-mediated platelet destruction and decreased platelet production. ITP is characterized by an isolated thrombocytopenia (<100 × 109/L) and increased risk of bleeding. The disease has a complex pathophysiology wherein immune tolerance breakdown leads to platelet and megakaryocyte destruction. Therapeutics such as corticosteroids, intravenous immunoglobulins (IVIg), rituximab, and thrombopoietin receptor agonists (TPO-RAs) aim to increase platelet counts to prevent hemorrhage and increase quality of life. TPO-RAs act via stimulation of TPO receptors on megakaryocytes to directly stimulate platelet production. Romiplostim is a TPO-RA that has become a mainstay in the treatment of ITP. Treatment significantly increases megakaryocyte maturation and growth leading to improved platelet production and it has recently been shown to have additional immunomodulatory effects in treated patients. This review will highlight the complex pathophysiology of ITP and discuss the usage of Romiplostim in ITP and its ability to potentially immunomodulate autoimmunity.

Efficacy and safety of human umbilical cord-derived mesenchymal stem cells in the treatment of refractory immune thrombocytopenia: a prospective, single arm, phase I trial

Patients with refractory immune thrombocytopenia (ITP) frequently encounter substantial bleeding risks and demonstrate limited responsiveness to existing therapies. Umbilical cord-derived mesenchymal stem cells (UC-MSCs) present a promising alternative, capitalizing on their low immunogenicity and potent immunomodulatory effects for treating diverse autoimmune disorders. This prospective phase I trial enrolled eighteen eligible patients to explore the safety and efficacy of UC-MSCs in treating refractory ITP. The research design included administering UC-MSCs at escalating doses of 0.5 × 106 cells/kg, 1.0 × 106 cells/kg, and 2.0 × 106 cells/kg weekly for four consecutive weeks across three cohorts during the dose-escalation phase, followed by a dose of 2.0 × 106 cells/kg weekly for the dose-expansion phase. Adverse events, platelet counts, and changes in peripheral blood immunity were monitored and recorded throughout the administration and follow-up period. Ultimately, 12 (with an addition of three patients in the 2.0 × 106 cells/kg group due to dose-limiting toxicity) and six patients were enrolled in the dose-escalation and dose-expansion phase, respectively. Thirteen patients (13/18, 72.2%) experienced one or more treatment emergent adverse events. Serious adverse events occurred in four patients (4/18, 22.2%), including gastrointestinal hemorrhage (2/4), profuse menstruation (1/4), and acute myocardial infarction (1/4). The response rates were 41.7% in the dose-escalation phase (5/12, two received 1.0 × 106 cells/kg per week, and three received 2.0 × 106 cells/kg per week) and 50.0% (3/6) in the dose-expansion phase. The overall response rate was 44.4% (8/18) among all enrolled patients. To sum up, UC-MSCs are effective and well tolerated in treating refractory ITP (ClinicalTrials.gov ID: NCT04014166).

The many facets of immune-mediated thrombocytopenia: Principles of immunobiology and immunotherapy

Immune thrombocytopenia (ITP) is a rare autoimmune condition, due to peripheral platelet destruction through antibody-dependent cellular phagocytosis, complement-dependent cytotoxicity, cytotoxic T lymphocyte-mediated cytotoxicity, and megakaryopoiesis alteration. This condition may be idiopathic or triggered by drugs, vaccines, infections, cancers, autoimmune disorders and systemic diseases. Recent advances in our understanding of ITP immunobiology support the idea that other forms of thrombocytopenia, for instance, occurring after immunotherapy or cellular therapies, may share a common pathophysiology with possible therapeutic implications. If a decent pipeline of old and new agents is currently deployed for classical ITP, in other more complex immune-mediated thrombocytopenic disorders, clinical management is less harmonized and would deserve further prospective investigations. Here, we seek to provide a fresh overview of pathophysiology and current therapeutical algorithms for adult patients affected by this disorder with specific insights into poorly codified scenarios, including refractory ITP and post-immunotherapy/cellular therapy immune-mediated thrombocytopenia.

B cells and antibodies in refractory immune thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired bleeding disorder mediated by pathogenic autoantibodies secreted by plasma cells (PCs) in many patients. In refractory ITP patients, the persistence of splenic and bone marrow autoreactive long-lived PCs (LLPCs) may explain primary failure of rituximab and splenectomy respectively. The reactivation of autoreactive memory B cells generating new autoreactive PCs contributes to relapses after initial response to rituximab. Emerging strategies targeting B cells and PCs aim to prevent the settlement of splenic LLPCs with the combination of anti-BAFF and rituximab, to deplete autoreactive PCs with anti-CD38 antibodies, and to induce deeper B-cell depletion in tissues with novel anti-CD20 monoclonal antibodies and anti-CD19 therapies. Alternative strategies, focused on controlling autoantibody mediated effects, have also been developed, including SYK and BTK inhibitors, complement inhibitors, FcRn blockers and inhibitors of platelet desialylation.

The mTORC1 pathway participate in hyper-function of B cells in immune thrombocytopenia

B cell hyper-function plays an important role in the pathogenesis of immune thrombocytopenia (ITP), but the molecular mechanisms underlying such changes remain unclear. We sought to identify regulators of B cell dysfunction in ITP patients through transcriptome sequencing and the use of inhibitors. B cells were isolated from PBMC of 25 ITP patients for B cell function test and transcriptome sequencing. For the potential regulatory factors identified by transcriptome sequencing, the corresponding protein inhibitors were used to explore the regulatory effect of the regulatory factors on B cell dysfunction in vitro. In this study, increased antibody production, enhanced terminal differentiation and highly expressed costimulatory molecules CD80 and CD86 were found in B cells of patients with ITP. In addition, RNA sequencing revealed highly activated mTOR pathway in these pathogenic B cells, indicating that the mTOR pathway may be involved in B cell hyper-function. Furthermore, mTOR inhibitors rapamycin or Torin1 effectively blocked the activation of mTORC1 in B cells, resulting in reduce antibody secretion, impaired differentiation of B cells into plasmablasts and downregulation of costimulatory molecules. Interestingly, as an unspecific inhibitor of mTORC2 besides mTORC1, Torin1 did not show a stronger capacity to modulate B cell function than rapamycin, suggesting that the regulation of B cells by Torin1 may depend on blockade of mTORC1 rather than mTORC2 pathway. These results indicated that the activation of mTORC1 pathway is involved in B cell dysfunction in patients with ITP, and inhibition of mTORC1 pathway might be a potential therapeutic approach for ITP.

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.

β2-adrenergic receptor agonist corrects immune thrombocytopenia by reestablishing the homeostasis of T cell differentiation

BACKGROUND

The sympathetic nerve is known to regulate immune responses in autoimmunity. Aberrant T cell immunity plays a vital role in immune thrombocytopenia (ITP) pathogenesis. The spleen is the primary site of platelet destruction. However, little is known whether and how splenic sympathetic innervation and neuroimmune modulation contribute to ITP pathogenesis.

OBJECTIVES

To determine the sympathetic distribution in the spleen of ITP mice and the association between splenic sympathetic nerves and T cell immunity in ITP development, and to evaluate the treatment potential of β2-adrenergic receptor (β2-AR) in ITP.

METHODS

Chemical sympathectomy was performed in an ITP mouse model with 6-hydroxydopamine and treated with β2-AR agonists to evaluate the effects of sympathetic denervation and activation.

RESULTS

Decreased sympathetic innervation in the spleen of ITP mice was observed. Significantly increased percentages of Th1 and Tc1 cells and reduced percentages of regulatory T cells (Tregs) were also observed in ITP mice with chemical sympathectomy (ITP-syx mice) relative to mice without sympathectomy (controls). Expression of genes associated with Th1, including IFN-γ and IRF8, was significantly upregulated, whereas genes associated with Tregs, including Foxp3 and CTLA4, were significantly downregulated in ITP-syx mice compared with controls. Furthermore, β2-AR restored the percentage of Tregs and increased platelet counts at days 7 and 14 in ITP mice.

CONCLUSION

Our findings indicate that decreased sympathetic distribution contributes to ITP pathogenesis by disturbing the homeostasis of T cells and that β2-AR agonists have potential as a novel treatment for ITP.

Imbalance of follicular regulatory T (Tfr) cells/follicular helper T (Tfh) cells in adult patients with primary immune thrombocytopenia

This study is to investigate the role of follicular regulatory T (Tfr) cells/follicular helper T (Tfh) cells imbalance in adult patients with primary immune thrombocytopenia (ITP). Totally, 40 cases of primary ITP patients and 30 healthy controls were enrolled. Blood samples were collected from ITP patients (pre- and post-therapy) and controls. Flow cytometry was used to detect the proportion of Tfr and Tfh cells in peripheral blood. Real-time quantitative polymerase chain reaction (PCR) was performed to detect the mRNA expression levels of FOXP3, BCL-6, and BLIMP-1. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect interleukin (IL)-10 and IL-21 levels. Spearman's correlation was used for correlation analysis. Compared with control, Tfr cell proportion, FOXP3 mRNA, and IL-10 were significantly decreased in the pre-therapy ITP group, but were significantly increased post-therapy. Tfh cell proportion, BCL-6 mRNA, and IL-21 were increased, while BLIMP-1 mRNA was decreased, in the pre-therapy ITP group than the control group. These effects were reversed in the post-therapy ITP group. Moreover, the Tfr/Tfh ratio was decreased in the pre-therapy ITP group than control group, whereas was increased in the post-therapy ITP group than the pre-therapy ITP group. Furthermore, Tfr cell proportion, FOXP3 mRNA, IL-10, and Tfr/Tfh ratio were positively correlated with the platelet count (PLT) in the ITP pre-therapy group. In addition, Tfh cell proportion, BCL-6 mRNA, and IL-21 were negatively correlated with the PLT, while BLIMP-1 mRNA was positively correlated with the PLT. Conclusively, Tfr cell proportion in peripheral blood is decreased and Tfh cell proportion is increased, leading to unbalanced Tfr/Tfh ratio in ITP patients pre-therapy. The imbalance of Tfr/Tfh is recovered post-therapy, suggesting that the Tfr and Tfh cells may be involved in ITP pathogenesis. The abnormal expression of FOXP3, BCL-6, and BLIMP-1 mRNA and the changes in IL-10 and IL-21 levels may be related to the imbalance of Tfr/Tfh.

Characterization of immune exhaustion and suppression in the tumor microenvironment of splenic marginal zone lymphoma

The role of the tumor microenvironment (TME) and intratumoral T cells in splenic marginal zone lymphoma (sMZL) is largely unknown. In the present study, we evaluated 36 sMZL spleen specimens by single cell analysis to gain a better understanding of the TME in sMZL. Using mass cytometry (CyTOF), we observed that the TME in sMZL is distinct from that of control non-malignant reactive spleen (rSP). We found that the number of T_FH cells varied greatly in sMZL, ICOS⁺ T_FH cells were more abundant in sMZL than rSP, and T_FH cells positively correlated with increased numbers of memory B cells. T_reg cell analysis revealed that TIGIT⁺ T_reg cells are enriched in sMZL and correlate with suppression of T_H17 and T_H22 cells. Intratumoral CD8⁺ T cells were comprised of subsets of short-lived, exhausted and late-stage differentiated cells, thereby functionally impaired. We observed that T-cell exhaustion was present in sMZL and TIM-3 expression on PD-1^low cells identified cells with severe immune dysfunction. Gene expression profiling by CITE-seq analysis validated this finding. Taken together, our data suggest that the TME as a whole, and T-cell population specifically, are heterogenous in sMZL and immune exhaustion is one of the major factors impairing T-cell function.

How we treat primary immune thrombocytopenia in adults

Primary immune thrombocytopenia (ITP) is an immune-mediated bleeding disorder characterized by decreased platelet counts and an increased risk of bleeding. Multiple humoral and cellular immune abnormalities result in accelerated platelet destruction and suppressed platelet production in ITP. The diagnosis remains a clinical exclusion of other causes of thrombocytopenia. Treatment is not required except for patients with active bleeding, severe thrombocytopenia, or cases in need of invasive procedures. Corticosteroids, intravenous immunoglobulin, and anti-RhD immunoglobulin are the classical initial treatments for newly diagnosed ITP in adults, but these agents generally cannot induce a long-term response in most patients. Subsequent treatments for patients who fail the initial therapy include thrombopoietic agents, rituximab, fostamatinib, splenectomy, and several older immunosuppressive agents. Other potential therapeutic agents, such as inhibitors of Bruton's tyrosine kinase and neonatal Fc receptor, are currently under clinical evaluation. An optimized treatment strategy should aim at elevating the platelet counts to a safety level with minimal toxicity and improving patient health-related quality of life, and always needs to be tailored to the patients and disease phases. In this review, we address the concepts of adult ITP diagnosis and management and provide a comprehensive overview of current therapeutic strategies under general and specific situations.

Hematologic cytopenia post CAR T cell therapy: Etiology, potential mechanisms and perspective

Chimeric Antigen-Receptor (CAR) T-cell therapies have shown dramatic efficacy in treating relapsed and refractory cancers, especially B cell malignancies. However, these innovative therapies cause adverse toxicities that limit the broad application in clinical settings. Hematologic cytopenias, one frequently reported adverse event following CAR T cell treatment, are manifested as a disorder of hematopoiesis with decreased number of mature blood cells and subdivided into anemia, thrombocytopenia, leukopenia, and neutropenia, which increase the risk of infections, fatigue, bleeding, fever, and even fatality. Herein, we initially summarized the symptoms, etiology, risk factors and management of cytopenias. Further, we elaborated the cellular and molecular mechanisms underlying the initiation and progression of cytopenias following CAR T cell therapy based on previous studies about acquired cytopenias. Overall, this review will facilitate our understanding of the etiology of cytopenias and shed lights into developing new therapies against CAR T cell-induced cytopenias.

Systemic lupus erythematosus-complicating immune thrombocytopenia: From pathogenesis to treatment

Immune thrombocytopenia (ITP) is a common hematological manifestation of systemic lupus erythematosus (SLE). The heterogeneity of its clinical characteristics and therapeutic responses reflects a complex pathogenesis. A better understanding of its pathophysiological mechanisms and employing an optimal treatment regimen is therefore important to improve the response rate and prognosis, and avoid unwanted outcomes. Besides glucocorticoids, traditional immunosuppressants (i.e. cyclosporine, mycophenolate mofetil) and intravenous immunoglobulins, new therapies are emerging and promising for the treatment of intractable SLE-ITP, such as thrombopoietin receptor agonists (TPO-RAs), platelet desialylation inhibitors(i.e. oseltamivir), B-cell targeting therapy(i.e. rituximab, belimumab), neonatal Fc receptor(FcRn) inhibitor, spleen tyrosine kinase(Syk) inhibitor and Bruton tyrosine kinase(BTK) inhibitor et al., although more rigorous randomized controlled trials are needed to substantiate their efficacy. In this review, we update our current knowledge on the pathogenesis and treatment of SLE-ITP.

High-affinity autoreactive plasma cells disseminate through multiple organs in patients with immune thrombocytopenic purpura

The major therapeutic goal for immune thrombocytopenic purpura (ITP) is to restore normal platelet counts using drugs to promote platelet production or by interfering with mechanisms responsible for platelet destruction. Eighty percent of patients with ITP possess anti–integrin αIIbβ3 IgG autoantibodies that cause platelet opsonization and phagocytosis. The spleen is considered the primary site of autoantibody production by autoreactive B cells and platelet destruction. The immediate failure in approximately 50% of patients to recover a normal platelet count after anti-CD20 rituximab-mediated B cell depletion and splenectomy suggests that autoreactive, rituximab-resistant, IgG-secreting B cells (IgG-SCs) reside in other anatomical compartments. We analyzed more than 3,300 single IgG-SCs from spleen, bone marrow, and/or blood of 27 patients with ITP, revealing high interindividual variability in affinity for αIIbβ3, with variations over 3 logs. IgG-SC dissemination and range of affinities were, however, similar for each patient. Longitudinal analysis of autoreactive IgG-SCs upon treatment with the anti-CD38 mAb daratumumab demonstrated variable outcomes, from complete remission to failure with persistence of high-affinity anti–αIIbβ3 IgG-SCs in the bone marrow. This study demonstrates the existence and dissemination of high-affinity autoreactive plasma cells in multiple anatomical compartments of patients with ITP that may cause the failure of current therapies.

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.

Dysregulated expression of miRNAs in immune thrombocytopenia

In recent years the critical role of miRNAs has been established in many diseases, including autoimmune disorders. Immune thrombocytopenia purpura (ITP) is a predominant autoimmune disease, in which aberrant expression of miRNAs has been observed, suggesting that miRNAs are involved in its development. miRNAs could induce an imbalance in the T helper (Th)1/Th2 cell and Th17/Treg cell-related responses. Moreover, they could also cause alterations in Th9 and Th22 cell responses, and activate Tfh (T follicular helper) cell-dependent auto-reactive B cells, thus influencing megakaryogenesis. Herein, we summarize the role of immune-related miRNAs in ITP pathogenesis, and look forward to clinical applications.

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.).

Efficacy, safety and immunological profile of combining rituximab with belimumab for adults with persistent or chronic immune thrombocytopenia: results from a prospective phase 2b trial

B-cell activating factor may be involved in the failure of B-cell depleting therapy with rituximab in immune thrombocytopenia (ITP) by promoting the emergence of splenic long-lived plasma cells. From results obtained in mouse models, we hypothesized that combining rituximab with sequential injections of belimumab could increase the rate of response at one year in patients with persistent or chronic ITP by preventing the emergence of these long-lived plasma cells. The study was a single-center, single arm, prospective phase 2b trial (RITUX-PLUS, NCT03154385) investigating the safety and efficacy of rituximab given at a fixed dose of 1,000 mg, two weeks apart, combined with five infusions of belimumab, 10 mg/kg at week 0 (W0)+2 days, W2+2 days, W4, W8 and W12 for adults with primary persistent or chronic ITP. The primary endpoint was the total number of patients achieving an overall response (complete response + response) at W52 according to a standard definition. In total, 15 non-splenectomized adults, nine (60%) with persistent IPT and six (40%) with chronic ITP, were included. No severe adverse event, infection, or severe hypogammaglobulinemia was observed. Thirteen patients achieved an initial overall response. At W52, 12 (80%) patients achieved an overall response, including ten (66.7%) with complete response. When compared with a cohort of patients receiving rituximab alone, the kinetics of B-cell repopulation appeared similar, but the number of circulating T follicular helper cells was significantly decreased with belimumab combination therapy. Combining rituximab and belimumab seems a promising strategy in ITP, with high efficacy and acceptable safety.

Tissue-resident regulatory T cells accumulate at human barrier lymphoid organs

Regulatory T cells (Tregs) play a critical role in immune regulation and peripheral tolerance. While different types of Tregs have been identified in both mice and humans, much of our understanding about how these cells maintain immune homeostasis is derived from animal models. In this study, we examined two distinct human lymphoid organs to understand how repeated exposure to infections at the mucosal surface influences the phenotype and tissue localization of Tregs. We show that while Tregs in both tonsils and spleen express a tissue-resident phenotype, they accumulate in greater numbers in tonsils. Tonsillar-resident Tregs exhibit a highly suppressive phenotype with significantly increased expression of CD39, ICOS and CTLA-4 compared with their counterparts in circulation or in the spleen. Functionally, resident Tregs are able effectively to suppress T cell proliferation. We further demonstrate that tonsillar-resident Tregs share key features of T follicular helper cells. Spatial analysis reveals that the vast majority of resident Tregs are localized at the border of the T-zone and B cell follicle, as well as within the lymphocyte pockets enriched with resident memory T cells. Together our findings suggest that resident Tregs are strategically co-localized to maintain immune homeostasis at sites of recurrent inflammation.

Increasing numbers of CD19 + CD24highCD38high regulatory B cells and pre-germinal center B cells reflect activated autoimmunity and predict future treatment response in patients with untreated immune thrombocytopenia

The pathophysiology of immune thrombocytopenia (ITP) is poorly understood, particularly aspects regarding abnormal homeostasis and dysregulation of B cells. In this study, we analyzed peripheral lymphocyte subsets in patients with untreated ITP and healthy controls, and examined correlations between cell percentages/counts and titers of serum cytokines and antibodies. We also compared ITP patients who later required second-line therapies and those who did not. The percentages of CD19 + CD24^highCD38^high regulatory B cells, pre-germinal center (GC) B cells, and plasmablast-like B cells were significantly higher in ITP patients than in healthy controls. Absolute counts of regulatory B cells and pre-GC B cells were significantly higher in those who needed second-line therapies. In addition, serum B cell-activating factor belonging to the tumor necrosis factor family (BAFF) levels and platelet-associated immune globulin G antibody titers correlated positively with regulatory B cell, pre-GC B cell, and auto-reactive B cell counts. Serum interferon-α (IFN-α) levels were elevated in four ITP patients with high auto-reactive B cell counts. These results indicate that increases in regulatory B cells and pre-GC B cells may reflect activated autoimmunity induced by BAFF and/or IFN-α. Consequently, evaluation of B cell subsets in untreated ITP patients may predict treatment response.

Rituximab-resistant splenic memory B cells and newly engaged naive B cells fuel relapses in patients with immune thrombocytopenia

Rituximab (RTX), an antibody targeting CD20, is widely used as a first-line therapeutic strategy in B cell-mediated autoimmune diseases. However, a large proportion of patients either do not respond to the treatment or relapse during B cell reconstitution. Here, we characterize the cellular basis responsible for disease relapse in secondary lymphoid organs in humans, taking advantage of the opportunity offered by therapeutic splenectomy in patients with relapsing immune thrombocytopenia. By analyzing the B and plasma cell immunoglobulin gene repertoire at bulk and antigen-specific single-cell level, we demonstrate that relapses are associated with two responses coexisting in germinal centers and involving preexisting mutated memory B cells that survived RTX treatment and naive B cells generated upon reconstitution of the B cell compartment. To identify distinctive characteristics of the memory B cells that escaped RTX-mediated depletion, we analyzed RTX refractory patients who did not respond to treatment at the time of B cell depletion. We identified, by single-cell RNA sequencing (scRNA-seq) analysis, a population of quiescent splenic memory B cells that present a unique, yet reversible, RTX-shaped phenotype characterized by down-modulation of B cell-specific factors and expression of prosurvival genes. Our results clearly demonstrate that these RTX-resistant autoreactive memory B cells reactivate as RTX is cleared and give rise to plasma cells and further germinal center reactions. Their continued surface expression of CD19 makes them efficient targets for current anti-CD19 therapies. This study thus identifies a pathogenic contributor to autoimmune diseases that can be targeted by available therapeutic agents.

Immune Thrombocytopenia Revealing Enriched IgG-4 Peri-Renal Rosai-Dorfman Disease Successfully Treated with Rituximab: A Case Report and Literature Review

Immune thrombocytopenia (ITP) is a rare autoimmune-mediated condition characterized by isolated thrombocytopenia (<100 G/L) after exclusion of other causes. Mostly primary, it is associated with hematological malignancy, autoimmune disorders, or infection in 20% of patients. It is exceptionally described in patients with histiocytosis, mostly in children (seven patients in literature). We report a case of a 69-year-old man with ITP leading to the diagnosis of histiocytosis. At ITP's diagnosis, the patient had elevated gamma-globulins leading to computed tomography showing bilateral peri-renal infiltration. The biopsy showed enriched IgG-4 peri-renal Rosai Dorfman disease with MAP2K1 mutation, although peri-renal infiltration is highly suggestive of Erdheim-Chester disease. This overlapping association was described in men with mutation in MAP2K1 gene. Macrophages are implicated in the pathophysiology of ITP in multiple ways, notably by the phagocytosis of opsonized platelets and their function of antigen-presenting cells able to stimulate autoreactive T cells. Histiocytic cells derivate from monocyte-macrophage lineage. Activation of macrophages in active histiocytosis is responsible for consequential platelet destruction in ITP associated histiocytosis. Finally, this case highlights a rare presentation of ITP revealing histiocytosis, both being efficiently treated with rituximab.

Immune Thrombocytopenia: Recent Advances in Pathogenesis and Treatments

Immune thrombocytopenia (ITP) is a rare autoimmune disease due to both a peripheral destruction of platelets and an inappropriate bone marrow production. Although the primary triggering factors of ITP remain unknown, a loss of immune tolerance-mostly represented by a regulatory T-cell defect-allows T follicular helper cells to stimulate autoreactive splenic B cells that differentiate into antiplatelet antibody-producing plasma cells. Glycoprotein IIb/IIIa is the main target of antiplatelet antibodies leading to platelet phagocytosis by splenic macrophages, through interactions with Fc gamma receptors (FcγRs) and complement receptors. This allows macrophages to activate autoreactive T cells by their antigen-presenting functions. Moreover, the activation of the classical complement pathway participates to platelet opsonization and also to their destruction by complement-dependent cytotoxicity. Platelet destruction is also mediated by a FcγR-independent pathway, involving platelet desialylation that favors their binding to the Ashwell-Morell receptor and their clearance in the liver. Cytotoxic T cells also contribute to ITP pathogenesis by mediating cytotoxicity against megakaryocytes and peripheral platelets. The deficient megakaryopoiesis resulting from both the humoral and the cytotoxic immune responses is sustained by inappropriate levels of thrombopoietin, the major growth factor of megakaryocytes. The better understanding of ITP pathogenesis has provided important therapeutic advances. B cell-targeting therapies and thrombopoietin-receptor agonists (TPO-RAs) have been used for years. New emerging therapeutic strategies that inhibit FcγR signaling, the neonatal Fc receptor or the classical complement pathway, will deeply modify the management of ITP in the near future.

Emerging Therapies in Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is a rare autoimmune disorder caused by peripheral platelet destruction and inappropriate bone marrow production. The management of ITP is based on the utilization of steroids, intravenous immunoglobulins, rituximab, thrombopoietin receptor agonists (TPO-RAs), immunosuppressants and splenectomy. Recent advances in the understanding of its pathogenesis have opened new fields of therapeutic interventions. The phagocytosis of platelets by splenic macrophages could be inhibited by spleen tyrosine kinase (Syk) or Bruton tyrosine kinase (BTK) inhibitors. The clearance of antiplatelet antibodies could be accelerated by blocking the neonatal Fc receptor (FcRn), while new strategies targeting B cells and/or plasma cells could improve the reduction of pathogenic autoantibodies. The inhibition of the classical complement pathway that participates in platelet destruction also represents a new target. Platelet desialylation has emerged as a new mechanism of platelet destruction in ITP, and the inhibition of neuraminidase could dampen this phenomenon. T cells that support the autoimmune B cell response also represent an interesting target. Beyond the inhibition of the autoimmune response, new TPO-RAs that stimulate platelet production have been developed. The upcoming challenges will be the determination of predictive factors of response to treatments at a patient scale to optimize their management.

Histology of the spleen in immune thrombocytopenia: clinical-pathological characterization and prognostic implications

OBJECTIVE

Immune thrombocytopenia (ITP) is an acquired disorder, characterized by immune-mediated platelet destruction. The spleen plays a key pathogenic role in ITP and splenectomy is a valuable second-line therapy for this disease. Little is known on ITP spleen histology and response to splenectomy is unpredictable. This study aims to characterize ITP spleen histology and assess possible predictors of splenectomy outcome.

METHODS

A series of 23 ITP spleens were retrospectively assessed for the following histological parameters: density of lymphoid follicles (LFs), marginal zones (MZs), T helper and cytotoxic T cells; presence of reactive germinal centers (GCs); width of perivascular T cell sheaths; and red pulp features. Clinical and histological data were matched with postsplenectomy platelet counts to assess their prognostic relevance.

RESULTS

Three histological patterns were documented: a hyperplastic white pulp pattern, a non-activated white pulp pattern (lacking GCs), and a white pulp-depleted pattern. Poor surgical responses were associated with presplenectomy high-dose steroid administration, autoimmune comorbidities and low T follicular helper cell density. The combination of such parameters stratified patients into different splenectomy response groups. The removal of accessory spleens was also associated with better outcome.

CONCLUSION

ITP spleens are histologically heterogeneous and clinical-pathological parameters may help predict the splenectomy outcome.

Tacrolimus ameliorates thrombocytopenia in an ITP mouse model

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by lower platelet count resulting from immune cells-mediated platelet clearance. Tacrolimus is an immunosuppressive agent which selectively inhibits T cell activation. Whether tacrolimus plays a role in ITP remains unclear. This study aimed to investigate the effect of tacrolimus on ITP in mice. An ITP mouse model was established by injection of rat anti-mouse integrin GPIIb/CD41 immunoglobulin and treated with tacrolimus followed by isolation of peripheral blood mononuclear cells and plasma. The mRNA expression of T-bet, GATA3, and Foxp3 was measured by RT-PCR, and level of IFN-γ, IL-12p70, IL-4, IL-13, and TGF-β in plasma was measured by ELISA. Tacrolimus inhibited antiplatelet antibody-mediated platelet clearance in ITP mouse model. Meanwhile, tacrolimus-treated ITP mice displayed a significant decrease in the mRNA expression of T-bet and plasma level of IFN-γ and IL-12p70 compared with ITP mice but without differences when compared with normal mice. Furthermore, the expression of GATA3, Foxp3, and plasma level of IL-4 and TGF-β were upregulated in tacrolimus-treated ITP mice without significant differences to normal mice (except TGF-β). Tacrolimus prevents antiplatelet antibody-mediated thrombocytopenia in ITP mice possibly through regulating T cell differentiations, suggesting it might be a novel approach for preventing ITP.

[Immune thrombocytopenia: From pathogenesis to treatment]

Immune thrombocytopenia (ITP) is a rare autoimmune disease due to an immune peripheral destruction of platelets and an inappropriate platelet production. The pathogenesis of ITP is now better understood: it involves a humoral immune response which dependents on the stimulation of B cells by specific T cells called T follicular helper cells, leading to their differentiation into plasma cells that produce antiplatelet antibodies thus promoting the phagocytosis of platelets mainly by splenic macrophages. The deciphering of ITP pathogenesis has led to a better understanding of the inefficiency of treatments such as rituximab, although it has not provided yet the determination of biological predictive factor of response to treatments. Moreover, new therapeutic perspectives have been opened in the last few years with the development of molecules targeting Fcγ receptor signalling such as Syk inhibitor, or molecules increasing the clearance of pathogenic autoantibodies such as inhibitors of the neonatal Fc receptor (FcRn).

Fostamatinib is an effective second-line therapy in patients with immune thrombocytopenia

Fostamatinib demonstrated efficacy in phase 3 trials of adults with immune thrombocytopenia (ITP). Post hoc analysis compared patients who received fostamatinib as second‐line therapy (after steroids ± immunoglobulins) versus third‐or‐later‐line therapy (after ≥2 prior lines of therapy including a second‐line agent). Platelet responses ≥50 000/µl were observed in 25/32 (78%) second‐line and 54/113 (48%) third‐or‐later‐line patients. Bleeding events were less frequent in second‐line (28%) versus third‐or‐later‐line (45%) patients. Responses once achieved tended to be durable in both groups. The safety profile was similar in both groups. In this post hoc analysis, fostamatinib was more effective as second‐line than third‐or‐later‐line therapy for ITP.

Cellular immune dysregulation in the pathogenesis of immune thrombocytopenia

: Immune thrombocytopenia (ITP) is an acquired autoimmune hemorrhagic disease characterized by immune-mediated increased platelet destruction and decreased platelet production, resulting from immune intolerance to autoantigen. The pathogenesis of ITP remains unclear, although dysfunction of T and B lymphocytes has been shown to be involved in the pathogenesis of ITP. More recently, it is found that dendritic cells, natural killer, and myeloid-derived suppressor cells also play an important role in ITP. Elucidating its pathogenesis is expected to provide novel channels for the targeted therapy of ITP. This article will review the role of different immune cells in ITP.

Phenotypic and Functional Analysis of T Follicular Cells in Common Variable Immunodeficiency

INTRODUCTION

One of the most frequent abnormalities of B cells in common variable immunodeficiency (CVID) is reduced number of class-switched memory B cells, suggesting an impaired germinal center response. Therefore, due to its pivotal role in regulating the development of humoral immunity, the objective of this study was to evaluate the role of circulating T follicular helper (cTFH) and circulating T follicular regulatory (cTFR) cells in the pathogenesis of CVID.

METHODS

cTFH and cTFR cells from CVID patients and healthy subjects were phenotypically characterized by flow cytometry. cTFH and memory B cells from CVID patients and healthy subjects were isolated and cocultured.

RESULTS

Our results showed a reduced proportion of cTFH17 cells in patients with CVID and an increased ratio of cTFH/cTFR cells in CVID patients with autoimmune diseases. Furthermore, the proportion of IL-21-producing cTFH cells was directly related to the proportion of CD27+ IgD- B cells. Interestingly, coculture assay showed that CVID-derived cTFH cells are able to help memory B cells from healthy controls to produce immunoglobulins.

CONCLUSIONS

The proportions of cTFH17 and cTFR cells are altered in CVID patients; however, the cTFH function in assisting B cells to produce antibodies in vitro is preserved.

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.

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.

The Role of T Follicular Helper Cells and T Follicular Regulatory Cells in the Pathogenesis of Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is an acquired autoimmune disease mediated by antibodies against the patient’s red blood cells. However, the underlying mechanisms for antibody production are not fully understood. Previous studies of etiology and pathogenesis of AIHA mainly focus on autoreactive B cells that have escaped tolerance mechanisms. Few studies have reported the function of T_FH and T_FR cells in the process of AIHA. The present study aimed to explore the potential mechanism of T_FH and T_FR cells in the pathogenesis of AIHA. With the model of murine AIHA, increased ratios of T_FH:T_FR, elevated serum IL-21 and IL-6 levels, and upregulated Bcl-6 and c-Maf expression were reported. Also, adoptive transfer of purified CD4⁺CXCR5⁺CD25^- T cells from immunized mice promoted the induction of autoantibody in the AIHA mouse model. Altogether, our data demonstrate the important role of T_FH cells for control and induction of AIHA. In the light of the key contributions of T_FH cells to the immune response in AIHA, strategies aimed at inhibiting the T_FH development or function should be emphasized.

Research Progress on Chinese Medicine Immunomodulatory Intervention for Chronic Primary Immune Thrombocytopenia: Targeting Cellular Immunity

Chronic primary immune thrombocytopenia (CITP) is the most common acquired autoimmune disease that seriously threaten the physical and mental health of patients. Compared with Western medicine treatment, the intervention and treatment of Chinese medicine (CM) has shown certain therapeutic advantages. This paper reviewed the new pathogenesis progress on T cell immune abnormality in CITP, and CM studies on interferes effects of cellular immune regulation of CITP in recent years. Qi deficiency failing to control blood and internal obstruction of blood stasis are the two common types of CM syndromes in CITP patients, the corresponding treatments include invigorating Pi (Spleen), supplementing qi, activating blood, as well as tonifying qi and activating yang, regulating Gan (Liver) to invigorate Pi. The authors also mentioned the problems in the research field of CM for CTIP treatment, and put forward new ideas for the research in the future.

Trial protocol: a multicentre randomised trial of first-line treatment pathways for newly diagnosed immune thrombocytopenia: standard steroid treatment versus combined steroid and mycophenolate. The FLIGHT trial

INTRODUCTION

Immune thrombocytopenia (ITP) is an autoimmune condition that may cause thrombocytopenia-related bleeding. Current first-line ITP treatment is with high-dose corticosteroids but frequent side effects, heterogeneous responses and high relapse rates are significant problems with only 20% remaining in sustained remission with this approach. Mycophenolate mofetil (MMF) is often used as the next treatment with efficacy in 50%-80% of patients and good tolerability but can take up to 2 months to work.

OBJECTIVE

To test the hypothesis that MMF combined with corticosteroid is a more effective first-line treatment for immune thrombocytopenia (ITP) than current standard of corticosteroid alone.

METHODS AND ANALYSIS

DesignMulticentre, UK-based, open-label, randomised controlled trial.

SETTING

Haematology departments in secondary care.

PARTICIPANTS

We plan to recruit 120 patients >16 years old with a diagnosis of ITP and a platelet count <30x10⁹/L who require first-line treatment. Patients will be followed up for a minimum of 12 months following randomisation.

PRIMARY OUTCOME

Time from randomisation to treatment failure defined as platelets <30x10⁹/L and a need for second-line treatment.

SECONDARY OUTCOMES

Side effects, bleeding events, remission rates, time to relapse, time to next therapy, cumulative corticosteroid dose, rescue therapy, splenectomy, socioeconomic costs, patient-reported outcomes (quality of life, fatigue, impact of bleeding, care costs).

ANALYSIS

The sample size of 120 achieves a 91.5% power to detect a doubling of the median time to treatment failure from 5 to 10 months. This will be expressed as an HR with 95% CI, median time to event if more than 50% have had an event and illustrated with Kaplan-Meier curves. Cost-effectiveness will be based on the first 12 months from diagnosis.

ETHICS AND DISSEMINATION

Ethical approval from NRES Committee South West (IRAS number 225959). EudraCT Number: 2017-001171-23. Results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03156452.

Altered circulating T follicular helper cells in patients with chronic immune thrombocytopenia

The present study aimed to illuminate the role of circulating T follicular helper (TFH) cells in patients diagnosed with chronic immune thrombocytopenia (cITP). Fifty-four patients with cITP and 30 age-matched healthy control subjects were enrolled in the present study. TFH cell frequencies, expression of CD4⁺ TFH cell-associated cytokines, including interleukin (IL)-2, IL-4, IL-10 and IL-21 and associated regulatory mRNA expression levels including Bcl-6, c-Maf, Blimp-1 and PD-1 pre- and post-treatment with intravenous immunoglobulin and corticosteroids, were detected by flow cytometry, ELISA and reverse transcription-quantitative polymerase chain reaction, respectively. TFH cell frequencies of patients were significantly higher compared with healthy controls pre-treatment (P<0.05). Following treatment, significantly decreased percentages of TFH cells were present in cITP responders (P<0.05). Correlation analysis revealed that the number of TFH cells was negatively correlated with the platelet count in the peripheral blood. Furthermore, analysis of inflammatory cytokines indicated significant differences in serum interleukin (IL)-21 and IL-10 between pretreated patients and healthy controls (P<0.05). Additionally, transcription factor B-cell lymphoma (Bcl)-6, c-Maf and programmed death-ligand (PD)-1 mRNA expression levels were significantly different between cITP patients prior to treatment and the healthy controls (P<0.05). However, the expression levels of Bcl-6, C-Maf and PD-1 mRNA were significantly changed post-treatment (P<0.05). These data demonstrated that circulating TFH cells and CD4⁺ TFH cell-associated cytokines may serve a role in cITP. The findings suggest that the overactivation of TFH cells may contribute to the immunopathogenesis of cITP, thus blocking the pathway of TFH cells may be reasonable for therapeutic intervention.

Altered distribution and function of splenic innate lymphoid cells in adult chronic immune thrombocytopenia

Innate lymphoid cells (ILCs) have been characterized as innate immune cells capable to modulate the immune response in the mucosae. Human ILCs have been rarely described in secondary lymphoid organs except in tonsils. Moreover, their function and phenotype in human secondary lymphoid organs during autoimmune diseases have never been studied. We took advantage of splenectomy as a treatment of immune thrombocytopenia (ITP) to describe and compare splenic ILC from 18 ITP patients to 11 controls. We first confirmed that ILC3 represented the most abundant ILC subset in human non-inflamed spleens, accounting for 90% of total ILC, and that they were mostly constituted of NKp44^- cells. On the contrary, proportions of ILC1 and ILC2 in spleens were lower than in blood. Splenic IL-2- and IFN-γ-producing ILC1 were increased in ITP. While the frequencies of total splenic ILC3 were similar in the two groups, splenic GM-CSF-producing ILC3 were increased in ITP. This is the first description of human ILC in a major secondary lymphoid organ during an autoimmune disease, ITP. We observed an expansion of splenic ILC1 that could participate to the Th1 skewing, while the increased production of GM-CSF by splenic ILC3 could stimulate splenic macrophages which play a key role in ITP pathophysiology.

T Follicular Helper Cells in Autoimmune Disorders

T follicular helper (Tfh) cells are a distinct subset of CD4⁺ T lymphocytes, specialized in B cell help and in regulation of antibody responses. They are required for the generation of germinal center reactions, where selection of high affinity antibody producing B cells and development of memory B cells occur. Owing to the fundamental role of Tfh cells in adaptive immunity, the stringent control of their production and function is critically important, both for the induction of an optimal humoral response against thymus-dependent antigens but also for the prevention of self-reactivity. Indeed, deregulation of Tfh activities can contribute to a pathogenic autoantibody production and can play an important role in the promotion of autoimmune diseases. In the present review, we briefly introduce the molecular factors involved in Tfh cell formation in the context of a normal immune response, as well as markers associated with their identification (transcription factor, surface marker expression, and cytokine production). We then consider in detail the role of Tfh cells in the pathogenesis of a broad range of autoimmune diseases, with a special focus on systemic lupus erythematosus and rheumatoid arthritis, as well as on the other autoimmune/inflammatory disorders. We summarize the observed alterations in Tfh numbers, activation state, and circulating subset distribution during autoimmune and some other inflammatory disorders. In addition, central role of interleukin-21, major cytokine produced by Tfh cells, is discussed, as well as the involvement of follicular regulatory T cells, which share characteristics with both Tfh and regulatory T cells.

Emerging Concepts in Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease defined by low platelet counts which presents with an increased bleeding risk. Several genetic risk factors (e.g., polymorphisms in immunity-related genes) predispose to ITP. Autoantibodies and cytotoxic CD8⁺ T cells (Tc) mediate the anti-platelet response leading to thrombocytopenia. Both effector arms enhance platelet clearance through phagocytosis by splenic macrophages or dendritic cells and by induction of apoptosis. Meanwhile, platelet production is inhibited by CD8⁺ Tc targeting megakaryocytes in the bone marrow. CD4⁺ T helper cells are important for B cell differentiation into autoantibody secreting plasma cells. Regulatory Tc are essential to secure immune tolerance, and reduced levels have been implicated in the development of ITP. Both Fcγ-receptor-dependent and -independent pathways are involved in the etiology of ITP. In this review, we present a simplified model for the pathogenesis of ITP, in which exposure of platelet surface antigens and a loss of tolerance are required for development of chronic anti-platelet responses. We also suggest that infections may comprise an important trigger for the development of auto-immunity against platelets in ITP. Post-translational modification of autoantigens has been firmly implicated in the development of autoimmune disorders like rheumatoid arthritis and type 1 diabetes. Based on these findings, we propose that post-translational modifications of platelet antigens may also contribute to the pathogenesis of ITP.

Safety and efficacy of romiplostim in splenectomized and nonsplenectomized patients with primary immune thrombocytopenia

Primary immune thrombocytopenia is an autoimmune disorder characterized by increased platelet destruction and insufficient platelet production without another identified underlying disorder. Splenectomy may alter responsiveness to treatment and/or increase the risk of thrombosis, infection, and pulmonary hypertension. The analysis herein evaluated the safety and efficacy of the thrombopoietin receptor agonist romiplostim in splenectomized and nonsplenectomized adults with primary immune thrombocytopenia. Data were pooled across 13 completed clinical studies in adults with immune thrombocytopenia from 2002-2014. Adverse event rates were adjusted for time of exposure. Results were considered different when 95% confidence intervals were non-overlapping. Safety was analyzed for 1111 patients (395 splenectomized; 716 nonsplenectomized) who received romiplostim or control (placebo or standard of care). At baseline, splenectomized patients had a longer median duration of immune thrombocytopenia and a lower median platelet count, as well as a higher proportion with >3 prior immune thrombocytopenia treatments versus nonsplenectomized patients. In each treatment group, splenectomized patients used rescue medications more often than nonsplenectomized patients. Platelet response rates (≥50×10⁹/L) for romiplostim were 82% (310/376) for splenectomized and 91% (592/648) for nonsplenectomized patients (P<0.001 by Cochran-Mantel-Haenszel test). Platelet responses were stable over time in both subgroups. Exposure-adjusted adverse event rates were higher for control versus romiplostim for both splenectomized (1857 versus 1226 per 100 patient-years) and nonsplenectomized patients (1052 versus 852 per 100 patient-years). In conclusion, responses to romiplostim were seen in both splenectomized and nonsplenectomized patients, and romiplostim was not associated with an increase in the risk of adverse events in splenectomized patients. clinicaltrials.gov Identifier: 00111475(A)(B), 00117143, 00305435, 01143038, 00102323, 00102336, 00415532, 00603642, 00508820, 00907478, 00116688, and 00440037.

B cell depleting therapy regulates splenic and circulating T follicular helper cells in immune thrombocytopenia

B cells are involved in immune thrombocytopenia (ITP) pathophysiology by producing antiplatelet auto-antibodies. However more than a half of ITP patients do not respond to B cell depletion induced by rituximab (RTX). The persistence of splenic T follicular helper cells (TFH) that we demonstrated to be expanded during ITP and to support B cell differentiation and antiplatelet antibody-production may participate to RTX inefficiency. Whereas it is well established that the survival of TFH depends on B cells in animal models, nothing is known in humans yet. To determine the effect of B cell depletion on human TFH, we quantified B cells and TFH in the spleen and in the blood from ITP patients treated or not with RTX. We showed that B cell depletion led to a dramatic decrease in splenic TFH and in CXCL13 and IL-21, two cytokines predominantly produced by TFH. The absolute count of circulating TFH and serum CXCL13 also decreased after RTX treatment, whatever the therapeutic response. Therefore, we showed that the maintenance of TFH required B cells and that TFH are not involved in the inefficiency of RTX in ITP.

Advances in Diagnosis and Treatments for Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is an acquired hemorrhagic condition characterized by the accelerated clearance of platelets caused by antiplatelet autoantibodies. A platelet count in peripheral blood <100 × 10⁹/L is the most important criterion for the diagnosis of ITP. However, the platelet count is not the sole diagnostic criterion, and the diagnosis of ITP is dependent on additional findings. ITP can be classified into three types, namely, acute, subchronic, and persistent, based on disease duration. Conventional therapy includes corticosteroids, intravenous immunoglobulin, splenectomy, and watch-and-wait. Second-line treatments for ITP include immunosuppressive therapy [eg, anti-CD20 (rituximab)], with international guidelines, including rituximab as a second-line option. The most recently licensed drugs for ITP are the thrombopoietin receptor agonists (TRAs), such as romiplostim and eltrombopag. TRAs are associated with increased platelet counts and reductions in the number of bleeding events. TRAs are usually considered safe, effective treatments for patients with chronic ITP at risk of bleeding after failure of first-line therapies. Due to the high costs of TRAs, however, it is unclear if patients prefer these agents. In addition, some new agents are under development now. This manuscript summarizes the pathophysiology, diagnosis, and treatment of ITP. The goal of all treatment strategies for ITP is to achieve a platelet count that is associated with adequate hemostasis, rather than a normal platelet count. The decision to treat should be based on the bleeding severity, bleeding risk, activity level, likely side effects of treatment, and patient preferences.

Imbalanced immune homeostasis in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder resulting from low platelet counts caused by inadequate production as well as increased destruction by autoimmune mechanisms. As with other autoimmune disorders, chronic ITP is characterized by perturbations of immune homeostasis with hyperactivated effector cells as well as defective regulatory arm of the adaptive immune system, which will be reviewed here. Interestingly, some ITP treatments are associated with restoring the regulatory imbalance, although it remains unclear whether the immune system is redirected to a state of tolerance once treatment is discontinued. Understanding the mechanisms that result in breakdown of immune homeostasis in ITP will help to identify novel pathways for restoring tolerance and inhibiting effector cell responses. This information can then be translated into developing therapies for averting autoimmunity not only in ITP but also many autoimmune disorders.

A distinct plasmablast and naïve B-cell phenotype in primary immune thrombocytopenia

Primary immune thrombocytopenia is an autoimmune disorder in which platelet destruction is a consequence of both B- and T-cell dysregulation. Flow cytometry was used to further characterize the B- and T-cell compartments in a cross-sectional cohort of 26 immune thrombocytopenia patients including antiplatelet antibody positive (n=14) and negative (n=12) patients exposed to a range of therapies, and a cohort of matched healthy volunteers. Markers for B-cell activating factor and its receptors, relevant B-cell activation markers (CD95 and CD21) and markers for CD4(+) T-cell subsets, including circulating T-follicular helper-like cells, were included. Our results indicate that an expanded population of CD95(+) naïve B cells correlated with disease activity in immune thrombocytopenia patients regardless of treatment status. A population of CD21-naïve B cells was specifically expanded in autoantibody-positive immune thrombocytopenia patients. Furthermore, the B-cell maturation antigen, a receptor for B-cell activating factor, was consistently and strongly up-regulated on plasmablasts from immune thrombocytopenia patients. These observations have parallels in other autoantibody-mediated diseases and suggest that loss of peripheral tolerance in naïve B cells may be an important component of immune thrombocytopenia pathogenesis. Moreover, the B-cell maturation antigen represents a potential target for plasma cell directed therapies in immune thrombocytopenia.

The Centenary of Immune Thrombocytopenia - Part 1: Revising Nomenclature and Pathogenesis

The natural history of the immune thrombocytopenia (ITP) is interesting and intriguing because it traces different steps underlying autoimmune diseases. The review points out the main steps that have accompanied the stages of its history and the consequential changes related to its terminology. ITP is an autoimmune disease resulting from platelet antibody-mediated destruction and impaired megakaryocyte and platelet production. However, research advances highlight that a complex dysregulation of the immune system is involved in the pathogenesis of this condition. The review examines the role of the multiple immune components involved in the autoimmunity process, focusing on the more recent mechanisms, which could be new promising therapeutic targets for ITP patients.