The expression of IFN-γ, IL-4, Foxp3 and perforin genes are not correlated with DNA methylation status in patients with immune thrombocytopenic purpura

IL-4Rα (rs1801275) A>G polymorphism in Egyptian immune thrombocytopenia (ITP) patients: a single center experience

INTRODUCTION

Chronic immune thrombocytopenia (cITP) is characterized by dysregulation of the immune response. Until recently, the role of Th2-related cytokine gene polymorphisms was unclear. Interleukin 4 (IL-4) exerts its functions by binding to three types of IL-4 receptor (IL-4R) complexes. We aimed to explore the potential association between the gene polymorphism of IL-4Rα and cITP.

METHODS

We investigated the clinical impact of the IL-4Rα (rs1801275) A>G single nucleotide polymorphism (SNP) using the polymerase chain reaction (PCR) followed by the restriction fragment length polymorphism (RFLP) method in 82 cITP patients and 60 healthy controls (HCs).

RESULTS

The IL-4Rα (rs1801275) A>G polymorphism analysis showed the mutant GG genotype was significantly higher in control females (p = 0.033). The wild AA genotype had a higher bleeding score (p = 0.02) in the adulthood onset group. Furthermore, the wild AA genotype in the cITP childhood onset group was significantly associated with the disease severity, as well as the response to treatment (p = 0.040).

CONCLUSION

The mutant G allele is protective against the susceptibility to cITP in the Egyptian females. The IL-4Rα (rs1801275) A>G polymorphism may affect the clinical severity of cITP and treatment response in the Egyptian population.

Scoping Review on Epigenetic Mechanisms in Primary Immune Thrombocytopenia

Immune Thrombocytopenia (ITP) is an autoimmune blood disorder that involves multiple pathways responsible for the homeostasis of the immune system. Numerous pieces of literature have proposed the potential of immune-related genes as diagnostic and prognostic biomarkers, which mostly implicate the role of B cells and T cells in the pathogenesis of ITP. However, a more in-depth understanding is required of how these immune-related genes are regulated. Thus, this scoping review aims to collate evidence and further elucidate each possible epigenetics mechanism in the regulation of immunological pathways pertinent to the pathogenesis of ITP. This encompasses DNA methylation, histone modification, and non-coding RNA. A total of 41 studies were scrutinized to further clarify how each of the epigenetics mechanisms is related to the pathogenesis of ITP. Identifying epigenetics mechanisms will provide a new paradigm that may assist in the diagnosis and treatment of immune thrombocytopenia.

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.

Investigation into imbalance of Th1/Th2 cells in cirrhotic, hypersplenic rats

Objectives

To evaluate the Th1/Th2 cell profile in spleens of cirrhotic and hypersplenic rats by investigating the expression of Th1-associated chemokine receptors CXCR3, CCR5 and Th2-associated chemokine receptor CCR3.

Methods

Experimental liver cirrhosis and hypersplenism were induced in rats by the intragastric administration of carbon tetrachloride (CCl₄; 40% solution [0.3 ml/100g, twice/week for 8 weeks]) and confirmed by pathology and hemogram. Presence of the three chemokine receptors was investigated by real-time polymerase chain reaction (RT-PCR), immunohistochemical staining, and western blot analysis.

Results

By comparison with control animals (n=10), RT-PCR demonstrated that CXCR3 and CCR5-mRNA levels were significantly elevated in the hypersplenic rats (n=26) and CCR3-mRNA levels were lower. Immunohistochemical staining showed that by comparison with controls, the mean density of the Th1-associated CXCR3 and CCR5 receptors was significantly increased but there was no difference between groups in Th2-associated CCR3 receptors. Western blot analysis showed that by comparison with controls, hypersplenic rats had higher levels of CXCR3 and CCR5 protein but lower levels of CCR3 protein.

Conclusions

The abnormal expression of Th1-associated chemokine receptors in spleens of rats with cirrhosis and hypersplenism induced by CCL4 suggests that a functional imbalance between Th1/Th2 cells may play a role in the pathogenesis of hypersplenism.

Effect of recombinant human thrombopoietin on immune thrombocytopenia in pregnancy in a murine model

Primary immune thrombocytopenia (ITP) is a serious medical disorder that has the potential for maternal and fetal mortality. Corticosteroids, intravenous immunoglobulin, or both are the first-line treatments for ITP in pregnancy, but choices are limited if patients fail to respond. Recombinant human thrombopoietin (rhTPO) has been proved effective and safe in management of chronic ITP. However, the efficacy and safety of rhTPO for pregnant ITP patients still need to be explored. Here we developed an ideal murine model that simulated human ITP in pregnancy and evaluated the efficacy and safety of rhTPO in management of ITP in pregnancy. Model mice were subcutaneously administered with 0, 150, 1,500 and 15,000 U/kg rhTPO for 14 days. Significant higher platelet counts were noted in rhTPO-treated groups on Day 7, 10 and 14. On Day 20, half the maternal mice were sacrificed. Frequencies of Tregs in CD4⁺ T cells in rhTPO-treated groups were statistically higher than control. Significant higher plasma levels of TGF-β1 were observed in rhTPO-treated groups than control. There was no significant abnormality in gross or visceral examination of fetuses. The remaining half maternal mice and their pups were observed for at least three weeks to assess vital signs. No abnormal signs were noted. Furthermore, we investigated the underlying mechanisms. Results showed that Tregs were negative for c-Mpl and rhTPO had no direct effect on Tregs. Additionally, the Treg frequency in splenic CD4⁺ T cells in LY2109761-treated model mice was statistically lower than control. Thus, rhTPO may be a safe and effective option for treatment of pregnant ITP patients.

Transplantation of bone-marrow-derived mesenchymal stem cells into a murine model of immune thrombocytopenia

: Several reports have demonstrated T regulatory cells may play an important role in the pathophysiology of immune thrombocytopenia (ITP). As the immunomodulator, bone-marrow-derived mesenchymal stem cells (MSCs) (BM-MSCs) regulate T regulatory cells and show therapeutic effects on autoimmune diseases. However, it is not clear how BM-MSCs affect ITP. In this study, we explored the specific effects of BM-MSCs on ITP in mice. Using a murine model of ITP, mice were randomly divided into three groups: normal control group, ITP control group and ITP and BM-MSCs group. Platelet (PLT) levels were monitored by an automatic blood cell counter, and T regulatory cells were analyzed by flow cytometry. Compared with the untreated ITP mice, the PLT level of the ITP mice was significantly increased after BM-MSCs treatment. In the BM-MSCs group, T regulatory cells were significantly decreased. These findings demonstrate that bone-marrow-derived MSCs are effective in improving PLT levels and reducing the T regulatory cells mediating proinflammatory response in ITP mice.

The cytokine polymorphisms affecting Th1/Th2 increase the susceptibility to, and severity of, chronic ITP

BACKGROUND

T-helper cell type 1 (Th1) polarization in chronic immune thrombocytopenia (cITP) has been reported at the protein and mRNA levels. We evaluated the impact of Th1/Th2 cytokine and cytokine receptor functional polymorphisms on both susceptibility to, and severity of, cITP. We analysed IFN-γ + 874 T/A, IFN-γR -611G/A, IL-4 -590C/T, and IL-4Rα Q576R polymorphisms in 126 cITP patients (male/female: 34/92; median age: 47.7 years) and 202 healthy control donors. Genotyping was determined by PCR and direct sequencing. The Th1/Th2 ratio was detected in peripheral blood mononuclear cells via flow cytometry.

RESULTS

cITP patients had a higher frequency of the IL-4Rα 576 non-QQ genotype compared to healthy subjects (P = 0.04). cITP patients with the IFN-γ +874 non-AA genotype (high expression type) showed more severe thrombocytopenia than those with the AA genotype (P < 0.05). cITP patients had a significantly higher Th1/Th2 ratio than control patients (P < 0.01); this ratio was inversely correlated with platelet counts. Furthermore, patients with both IFN-γ +874 non-AA genotype (high expression type) and IFN-γR -611 non-AA genotype (high-function type) had a significantly higher Th1/Th2 ratio (P < 0.05).

CONCLUSIONS

The cytokine polymorphisms affecting Th1/Th2 increase the susceptibility to, and severity of, chronic ITP.

Interleukin-18 gene promoter--607 A/C polymorphism and the risk of immune thrombocytopenia

Interleukin-18 (IL-18) is a T helper 1 cytokine, which is postulated to play a role in immune thrombocytopenia (ITP). The aim of this study was to determine whether IL-18 promoter gene -607 A/C polymorphism was associated with ITP. Three-hundred and fifty-four Chinese ITP patients and 300 Chinese healthy individuals were enrolled. Genomic DNA was extracted from the peripheral blood. Polymerase chain reaction-restriction fragment length polymorphism (RFLP) was used to genotype the DNA samples for single nucleotide polymorphism (SNP)-607. Allelic and genotypic frequencies were compared between the case-control groups by the chi-square test. The results showed that the frequencies of the CC, CA and AA genotypes and C and A allele were 32.4, 47.8, 19.8, 56.4 and 43.6% in ITP patients and 32.3, 50.4, 17.3, 57.5 and 42.5% in the controls, respectively. There was no significant difference in either genotypes or allelic distribution between ITP patients and the controls. Furthermore, stratified analysis by the platelet count, age and disease course including ITP with severe thrombocytopenia (sITP), non-sITP, acute adult, chronic adult, acute childhood and chronic childhood revealed no significant difference in genotype and alleles distribution. In conclusion, this polymorphism was almost equally distributed between ITP patients and the controls. These data showed that this SNP may not be used as a stratification marker to predict the susceptibility to Chinese ITP.

DNA methylation and primary immune thrombocytopenia

DNA methylation is a heritable, stable, and also reversible way of DNA modification; it can regulate gene expression without changing the nucleotide sequences. Because it takes part in regulation of immune responses, the loss of methylation homeostasis in immune cells will result in autoimmune disease by inducing aberrant gene expression. Primary immune thrombocytopenia (ITP) is an acquired autoimmune disease with many immune deficiencies. Recently, it was well documented that abnormal DNA methylation is also involved in the etiology of ITP. In this review, we elucidate the role of DNA methylation in autoimmune diseases by summarizing the DNA methylation-sensitive genes and the relationship between DNA methylation and ITP.

Interleukin-27 rs153109 polymorphism and the risk for immune thrombocytopenia

The aim of the present study was to investigate the association of single nucleotide polymorphisms (SNP) of the interleukin-27 (IL-27) genes with the risk for immune thrombocytopenia (ITP). In this case-control study, the genotyping of IL-27 rs153109 polymorphism was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In ITP patients, the frequencies of GG, GA and AA genotypes, and G and A alleles were 9.7%, 58.5%, 31.8%, 38.9% and 61.1%, respectively. There was no significant difference in genotype and alleles distribution between the ITP patient and the healthy controls (p = 0.68 and 0.80, respectively). Similar results were found between the two groups when stratified by the age and disease course including non-chronic adult, chronic adult, non-chronic childhood, and chronic childhood. In conclusion, the IL-27 polymorphism may not be involved in susceptibility to ITP in a Chinese population.

Acute psychosocial stress-mediated changes in the expression and methylation of perforin in chronic fatigue syndrome

Perforin (PRF1) is essential for immune surveillance and studies report decreased perforin in chronic fatigue syndrome (CFS), an illness potentially associated with stress and/or infection. We hypothesize that stress can influence regulation of PRF1 expression, and that this regulation will differ between CFS and non-fatigued (NF) controls. We used the Trier Social Stress Test (TSST) as a standardized acute psychosocial stress, and evaluated its effect on PRF1 expression and methylation in CFS (n = 34) compared with NF (n = 47) participants. During the TSST, natural killer (NK) cells increased significantly in both CFS (P = <0.0001) and NF subjects (P = <0.0001). Unlike previous reports, there was no significant difference in PRF1 expression at baseline or during TSST between CFS and NF. However, whole blood PRF1 expression increased 1.6 fold during the TSST in both CFS (P = 0.0003) and NF (P = <0.0001). Further, the peak response immediately following the TSST was lower in CFS compared with NF (P = 0.04). In addition, at 1.5 hours post TSST, PRF1 expression was elevated in CFS compared with NF (whole blood, P = 0.06; PBMC, P = 0.02). Methylation of seven CpG sites in the methylation sensitive region of the PRF1 promoter ranged from 38%–79% with no significant differences between CFS and NF. Although, the average baseline methylation of all seven CpG sites did not differ between CFS and NF groups, it showed a significant negative correlation with PRF1 expression at all TSST time points in both CFS (r = −0.56, P = <0.0001) and NF (r = −0.38, P = <0.0001). Among participants with high average methylation (≥65%), PRF1 expression was significantly lower in CFS than NF subjects immediately following TSST. These findings suggest methylation could be an important epigenetic determinant of inter-individual differences in PRF1 expression and that the differences in PRF1 expression and methylation between CFS and NF in the acute stress response require further investigation.

Thymic retention of CD4+CD25+FoxP3+ T regulatory cells is associated with their peripheral deficiency and thrombocytopenia in a murine model of immune thrombocytopenia

Immune thrombocytopenia (ITP) is a bleeding disorder in which antibodies and/or T cells lead to enhanced peripheral platelet destruction and reduced bone marrow platelet production. Several reports have observed that ITP is associated with a peripheral deficiency of tolerance-inducing CD4+CD25+FoxP3+ T regulatory cells (Tregs). Using a murine model of ITP, we analyzed Tregs in the spleen and thymus. CD61 knockout mice were immunized against wild-type (CD61+) platelets, and their splenocytes were transferred into severe combined immunodeficient (SCID) mice. Compared with SCID mice receiving naive splenocytes, within 2 weeks after transfer, the ITP SCID mice became thrombocytopenic (< 200 × 109 platelets/L) and had increased serum anti-CD61 antibodies. The quantity of thymic Tregs by 2 weeks after transfer was significantly elevated, whereas Tregs in the spleens were significantly reduced. Treatment of the ITP mice with 2 g/kg intravenous immunoglobulin raised the platelet counts, reduced antibody production, and normalized the thymic and splenic Treg populations. Compared with thymocytes from ITP mice treated with intravenous immunoglobulin, thymocytes from untreated ITP mice delayed the onset of ITP when administered before engraftment with immune splenocytes. These results suggest that ITP in mice is associated with a peripheral Treg deficiency because of thymic retention and therapy normalizes the Tregs.

Abnormal DNA methylation in CD4+ T cells from people with latent autoimmune diabetes in adults

Aberrant DNA methylation in T cells has been linked to pathogenesis of autoimmune diseases. To investigate genomic and gene-specific DNA methylation levels in CD4(+) T cells from patients with latent autoimmune diabetes in adults (LADA), and to investigate changes in the expression of genes that regulate methylation as well as the autoimmune-related gene FOXP3 in these patients. Global CD4(+) T cell DNA methylation was measured in 15 LADA patients and 11 healthy controls using a methylation quantification kit. mRNA levels of DNA methytransferases (DNMTs), methyl-DNA binding domain proteins (MBDs) and FOXP3 were measured by real time PCR. Methylation of a FOXP3 regulatory element region was determined by bisulphite genomic sequencing. Genomic DNA methylation in CD4(+) T cells from LADA patients was significantly increased compared to controls. DNMT3b mRNA levels were higher in CD4(+) T cells from LADA patients than in controls. DNMT3b expression positively correlated with global DNA methylation in LADA CD4(+) T cells. FOXP3 expression was decreased, and the FOXP3 promoter region was hypermethylated in CD4(+) T cells from LADA patients compared with controls. DNA methylation levels are altered in CD4(+) T cells from LADA patients, which may contribute to disease onset and progression by affecting the expression of autoimmune-related genes.

Recent progress in understanding the pathogenesis of immune thrombocytopenia

PURPOSE OF REVIEW

Immune thrombocytopenia (ITP) is a bleeding disorder in which both antibody and cell-mediated autoimmune responses are directed against an individual's own platelets and/or megakaryocytes, leading to either enhanced platelet destruction and/or reduced platelet production, respectively. The cause of this platelet-specific autoimmunity remains unknown, but there has been a constant stream of recent publications that suggest ITP is the result of T-cell dysregulation.

RECENT FINDINGS

In the last 18 months, a rich tapestry of studies has emerged that seems to clarify some immunopathologic issues in ITP while raising new questions related to ITP pathogenesis. The current view on the immunopathogenic mechanisms associated with ITP appears to particularly concentrate on how incompetent CD4+ T-regulatory cells (Tregs) allow autoimmune effector mechanisms to proceed and cause thrombocytopenia. There is a parallel body of recent literature focusing on molecular mimicry mechanisms, B-cell abnormalities, abnormal cytokine patterns and genetic studies in ITP. Of interest, one can recognize inter-relationships between these immune dysregulations.

SUMMARY

This article will discuss the literature from the past 18 months pertaining to these observations and will show that whereas many of the T-cell defects have been clarified, new questions have also come to light and more immunopathological research is warranted.