The serum levels of the cytokines involved in the Th17 and Th1 cell commitment are increased in individuals with borderline thrombocytopenia

IL-23/Th17 pathway and IL-17A gene polymorphism in Egyptian children with immune thrombocbytopenic purpura

Background

Immune thrombocytopenic purpura (ITP) is an acquired complex autoimmune thrombocytopenia. Uncontrolled cellular immune response is one of the key triggers for the loss of immune tolerance in ITP patients. The purpose of this study was to investigate the association of IL-23/Th17, IL-17A and IL-17A rs2275913 gene polymorphism with ITP in Egyptian children.

Methods

60 patients with ITP and 50 healthy control children from Minia city- Egypt were involved. Serum levels of IL-23 and IL-17A were determined by enzyme-linked immunosorbent assay. The frequency of Th17 cells was measured using flow cytometer. Genotyping for IL-17A was performed via polymerase chain reaction-restriction fragment length polymorphism.

Results

Comparing children with ITP to controls, serum levels of IL-23 and IL-17A as well as Th17 cells percentage were significantly increased (p <  0.001). Also, higher levels of these ILs and Th17 cells percentage were associated with decreased platelet count within ITP patients (p <  0.001). Analysis of genotype frequencies for IL-17A rs2275913 polymorphism and its alleles (A, G) showed no significant difference between cases and controls. Likewise, no significant differences were demonstrated between acute and chronic ITP regarding both IL-17A rs2275913 polymorphism prevalence and levels of IL-23, IL-17A plus Th17 cells percentage. The frequency of A alleles was 85 and 86% within patients and controls, respectively.

Conclusions

Elevated levels of IL-23, IL-17A and Th17 cells may be involved in ITP pathogenesis while IL-17A polymorphism rs2275913 is not prevalent in Egyptian children with ITP.

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.

Human leukocyte antigen-G upregulates immunoglobulin-like transcripts and corrects dysfunction of immune cells in immune thrombocytopenia

Human leukocyte antigen-G (HLA-G) is a non-classical major histocompatibility complex class I antigen with potent immune-inhibitory function. HLA-G benefit patients in allotransplantation and autoimmune diseases by interacting with its receptors, immunoglobulinlike transcripts. Here we observed significantly less HLA-G in plasma from immune thrombocytopenia (ITP) patients positive for anti-platelet autoantibodies compared with autoantibodies-negative patients or healthy controls, while we found that HLA-G is positively correlated with platelet counts in both patients and healthy controls. We also found less membranebound HLA-G and immunoglobulin-like transcripts on CD4⁺ and CD14⁺ cells in patients. Recombinant HLA-G upregulated immunoglobulin-like transcript 2 expression on CD4⁺ and immunoglobulin-like transcript 4 on CD14⁺ cells. HLA-G upregulated IL-4 and IL-10, and downregulated tumor necrosis factor-a, IL-12 and IL-17 secreted by patient peripheral blood mononuclear cells, suggesting a stimulation of Th2 differentiation and downregulation of Th1 and Th17 immune response. HLA-G-modulated dendritic cells from ITP patients showed decreased expression of CD80 and CD86, and suppressed CD4⁺ T-cell proliferation compared to unmodulated cells. Moreover, HLA-G-modulated cells from patients induced less platelet apoptosis. HLA-G administration also significantly alleviated thrombocytopenia in a murine model of ITP. In conclusion, our data demonstrated that impaired expression of HLA-G and immunoglobulin-like transcripts is involved in the pathogenesis of ITP; recombinant HLA-G can correct this abnormality via upregulation of immunoglobulin-like transcripts, indicating that HLA-G can be a diagnostic marker and a therapeutic option for ITP.

Prediction of response to first-line therapy with ITP by flow cytometric analysis of bone marrow lymphocyte phenotypes

In the present study, we analyzed phenotypes of cells in the lymphocyte region of bone marrow in 68 patients with primary immune thrombocytopenia (ITP) to determine whether cellular phenotype predicts response to first-line therapy (corticosteroids or corticosteroids plus intravenous immunoglobulin). In 52 newly diagnosed ITP patients, an abnormal CD4:CD8 ratio (CD4/CD8 ratio < 0.4 and 2.3 < CD4/CD8 ratio) was noted in 22 patients in the responder group, whereas all non-responder and control individuals showed normal CD4:CD8 ratio (p < 0.001). The absolute number of CD19+ cells in patients with 0.4 ≤ CD4/CD8 ratio ≤ 2.3 or 2.3 < CD4/CD8 ratio was higher than that in other groups. (p = 0.016). In 16 chronic ITP patients, the absolute number of NK cells in the responder group was lower than those in the non-responder and control groups (p = 0.032). An abnormal CD4:CD8 ratio was noted in all patients in the responder group, whereas all patients in non-responder and control groups showed normal CD4:CD8 ratio (p < 0.001). The present results indicate that CD4:CD8 ratio, B cells, and NK cells contribute to the prediction of therapeutic outcomes of ITP patients.

A CARD9 single-nucleotide polymorphism rs4077515 is associated with reduced susceptibility to and severity of primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disease characterized by a low platelet count and consequent increased risk of bleeding. The etiology underlying this condition remains poorly understood. The aim of this study is to evaluate the association of a single nucleotide polymorphism (SNP) rs4077515 in the caspase recruitment domain-containing protein 9 (CARD9) gene with the pathogenesis and therapy of ITP. Two hundred ninety-four patients with ITP and 324 age-matched healthy participants were recruited in this case-control study. Genotyping of CARD9 rs4077515 polymorphism was performed by Sanger sequencing. Our results revealed that a polymorphism rs4077515 in CARD9 gene is associated with decreased risk of susceptibility to and severity of ITP (susceptibility: codominant, AA vs. GG, OR = 0.175, 95% CI = 0.054-0.776, p = 0.001; recessive, GG + AG vs. AA, OR = 6.183, 95% CI = 2.287-16.715, p < 0.001; severity: allele, A vs. G, OR = 0.685, 95% CI = 0.476-0.985, p = 0.041; codominant, AG vs. GG, OR = 0.571, 95% CI = 0.350-0.931, p = 0.025; dominant, AA + AG vs. GG, OR = 0.558, 95% CI = 0.343-0.907, p = 0.019). The existence of the allele A, the mutant AA genotype and the heterozygous AG genotype of CARD9 rs4077515, plays a protective role in ITP. However, CARD9 rs4077515 polymorphism had no effect on corticosteroid sensitivity or refractoriness of ITP.

Circulating level of Th17 cells is associated with sensitivity to glucocorticoids in patients with immune thrombocytopenia

Glucocorticoids are a widely recognized first-line therapy for immune thrombocytopenia (ITP). However, some patients are unresponsive to glucocorticoid therapy for reasons that remain unclear. Accumulating evidence suggests that CD4⁺ T-cell abnormalities play a crucial role in the development of ITP. In the present study, we investigated peripheral blood CD4⁺ T cells, Th17-associated cytokines, and the mRNA expression level of Th17 transcription factor-RORγt-in patients with newly-diagnosed ITP before glucocorticoid therapy. The study involved 27 newly-diagnosed patients. Th17-cell levels in the peripheral blood of newly-diagnosed ITP patients were associated with responsiveness to glucocorticoid therapy. Newly-diagnosed ITP patients who were not sensitive to glucocorticoid treatment were found to have lower levels of Th17 cells. Quantifying Th17 cells may allow physicians to predict prognosis of glucocorticoid treatment and stratify therapy for those with ITP. This strategy may provide a new approach to the treatment of glucocorticoid-insensitive patients.

Babesiosis-associated immune thrombocytopenia

Thrombocytopenia is a common feature of babesiosis. The mechanism for thrombocytopenia in babesiosis remains elusive. We report a case of babesiosis with severe new onset immune thrombocytopenia (ITP). In addition to antibiotics treatment for babesiosis, ITP therapy was administered. ITP in the present case was most likely triggered by the babesia infection. The severity of ITP in this case was not proportional to the severity of parasitemia. The neoantigen triggering the autoimmune response in babesiosis requires further characterization.

Contributions of T lymphocyte abnormalities to therapeutic outcomes in newly diagnosed patients with immune thrombocytopenia

T cell abnormalities have been reported to play an important role in pathogenesis of immune thrombocytopenia (ITP) besides specific autoantibodies towards platelet. The aim of this study was to explore the clinical importance of T lymphocyte subsets in adult patients with newly diagnosed ITP before and after first-line treatment. Elderly ITP patients were also studied and we tried to analyze the relationships between these items and therapeutic outcomes. The patients were treated with intravenous immunoglobulin (IVIG) plus corticosteroids and therapeutic responses were evaluated. As a result, compared with the controls, absolute lymphocyte counts in ITP patients decreased significantly before treatment. After treatment, lymphocyte counts restored to control level regardless of their treatment outcomes. In addition, we observed increased IgG and CD19+ cell expression and decreased CD4+/CD8+ cell ratio in both whole ITP group and elderly group before treatment. After treatment, the increased IgG and CD19+ cell expression could be reduced in both respond and non-respond group regardless of patient age, while CD4+/CD8+ cell ratio could not be corrected in non-respond ITP patients. In non-respond ITP patients, increased CD8+ cell expression was noticed and could not be corrected by first-line treatment. Furthermore, even lower NK cell expression was found in non-respond elderly patients after treatment when compared with that in controls. Our findings suggest that ITP patients usually had less numbers of peripheral lymphocytes and patients with higher levels of CD8+ cells or lower levels of CD4+/CD8+ cell ratio were less likely to respond to first-line treatment. Lower levels of NK cells made therapies in elderly ITP patients even more difficult.

T cell immune abnormalities in immune thrombocytopenia

Immune thrombocytopenia is an autoimmune disease with abnormal T cell immunity. Cytotoxic T cells, abnormal T regulatory cells, helper T cell imbalance, megakaryocyte maturation abnormalities and abnormal T cell anergy are involved in the pathogenesis of this condition. The loss of T cell-mediated immune tolerance to platelet auto-antigens plays a crucial role in immune thrombocytopenia. The induction of T cell tolerance is an important mechanism by which the pathogenesis and treatment of immune thrombocytopenia can be studied. Studies regarding the roles of the new inducible costimulator signal transduction pathway, the ubiquitin proteasome pathway, and the nuclear factor kappa B signal transduction pathway in the induction of T cell tolerance can help improve our understanding of immune theory and may provide a new theoretical basis for studying the pathogenesis and treatment of immune thrombocytopenia.

The role of T cell immunoglobulin and mucin domain-3 in immune thrombocytopenia

T cell immunoglobulin and mucin domain-3 (TIM-3), originally identified as a T helper (Th) 1-specific type I membrane protein, plays a vital role in Th1 immunity and tolerance induction through interaction with its ligand, galectin-9. The binding of TIM-3 by galectin-9 serves to downregulate Th1 responses. Moreover, the regulatory function of TIM-3 has been extended to other cells, such as Th17 cells, CD4(+) CD25(+) regulatory T cells (Tregs), CD8(+) T cells and certain innate immune cells. Previous studies have acknowledged that the TIM-3 pathway is involved in the pathogenesis of several human autoimmune diseases, such as systemic lupus erythematous, rheumatoid arthritis and aplastic anaemia. Moreover, genetic data suggest a role for TIM-3 in human autoimmune diseases. However, in immune thrombocytopenia (ITP), a common Th1- and possibly Th17-biased autoimmune disorder, the role of TIM-3 has not been explored. Recently, our data have demonstrated that TIM-3 expression is reduced in ITP patients, and we have found a potential link between ITP and the TIM-3 pathway. In this article, we discuss and speculate on the role of the TIM-3 pathway in ITP.