Alteration in Frequency and Function of CD4+CD25+FOXP3+ Regulatory T cells in Patients with Immune Thrombocytopenic Purpura

Immune thrombocytopenic purpura (ITP) is an autoimmune bleeding disorder characterized by production of auto-antibodies against platelet antigens. It is obvious that regulatory T cells (Tregs) have a major role in controlling immune homeostasis and preventing autoimmunity. To investigate the frequency and functions of Tregs, twenty ITP patients and twenty age- and sexmatched healthy controls were recruited. The peripheral blood mononuclear cells were isolated and the proportion of Tregs was defined by flow cytometry method. The expression of immune-regulatory markers, cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and glucocorticoid induced tumor necrosis factor receptor (GITR) were also assessed by quantitative Real-time polymerase chain reaction TaqMan method. For evaluation of Treg function, Tregs were enriched and their ability to inhibit proliferation of T cells was measured and levels of immune-regulatory cytokines IL-10 and Transforming growth factor beta (TGF-.) were also measured.Results showed that the frequency of Tregs and the mean fluorescence intensity of forkhead box P3 (FOXP3) protein significantly decreased in ITP patients compared to those in healthy controls. In addition, there was a significant reduction in relative expression of both CTLA-4 and GITR mRNA in ITP patients (p=0.02 and p=0.006, respectively). The suppressive function of Tregs also diminished in ITP patients compared to controls. Both IL-10 and TGF-. cytokines were produced in lower amounts in ITP patients than controls. It could be concluded that alteration in Treg frequency and functional characteristics might be responsible for loss of self-tolerance and subsequently destructive immune responses observed in ITP patients.