Quantity And Function Of Regulatory B Cells Of The Patients With Immune Thrombocytopenia

Objective Immune thrombocytopenia(ITP) is a disorder caused by autoantibody-mediated platelet destruction and decreased platelet production. B cells play an important role in the immune thrombocytopenia, their major role is to produce antibodies[1]. Regulatory B cells(Bregs) are a distinct B cell subset negatively regulate cellular immune responses through their production of immuno-modulatory cytokines, with interleukin-10(IL-10) being the most studied[2-4]. In human, it has been shown that the frequencies of Bregs are correlated with disease activity in autoimmune disease[5]. In this study, we investigated the the quantity and function of peripheral blood Bregs in newly diagnosed ITP patients、remittion ITP patients and controls, as well as analysed the correlation between Bregs levels and ITP patients’ clinical indicators. Methods There were 67 ITP patients enrolled in this study between November 2013 and October 2014 from hematology department at General Hospital of Tianjin Medical University, including 35 newly diagnosed ITP patients and 32 remittion ITP patients. The healthy control group consisted of 30 adult volunteers. The ITP patients and controls PB Bregs(CD19+CD24hiCD38hicells) and PB IL-10+Bregs were detected by flow cytometry(FCM). Detected the level of ITP patients and controls IL-10 in PB supernatant with Enzyme-linked Immunosorbent assay(ELISA). Correlation between Bregs and clinical parameters of ITP patients were analysed. Results ①Bregs expression of peripheral blood CD19+cells in ITP patients:The percentage of Bregs in CD19+ cells of newly diagnosed ITP patients(3.09%±2.57%)was significantly lower than remittion ITP patients(7.78%±6.59%,p=0.002) and controls(5.42%±3.31%,p=0.003). ②Bregs’ cytoplasmic IL-10 expression in peripheral blood :The percentage of IL-10+ cells in Bregs of newly diagnosed ITP patients( 32.30%±12.71%) was significantly lower than that of remittion ITP patients(71.73%±18.08%,P=0.000)and controls(51.01%±17.08%,P=0.026). And the percentage of IL-10+ cells in Bregs of remittion ITP patients was significantly higher than controls(P=0.026). ③Retrospectively analyzed the newly diagnosed group, the CR patients’ percentage of Bregs in CD19+ cell(4.24%±2.68%)was significantly higher than refractory ITP patients(1.88%±1.16%,p=0.007); According to the thyroid function, the newly diagnosed ITP patients were divided into the normal thyroid function group and hypothyroidism group, the percentage of the normal thyroid function group(4.48%±3.72%)was significantly higher than hypothyroidism group(1.30%±0.88%,p=0.002) ④The level of ITP patients and controls IL-10 in PB supernatant:The newly diagnosed ITP patients [(0.943±0.027)pg/ml ]was significantly lower than that of remittion ITP patients [(0.987±0.039)pg/ml,P=0.002] and controls[(1.125±0.221)pg/ml,P=0.045]. ⑤The correlation between Bregs levels and ITP patients’ clinical indicators:The level of Bregs of newly diagnosed ITP patients had significantly positive correlation with HLA-DR+Lin- CD11c+myeloid dendritic cells(m DC)(r=0.644,P=0.003,n=19)and PB platelet count(r=0.327,P=0.006,n=67),and we didn’t found statistical correlation between Bregs and T-lymphocyte(CD3+CD4+、CD3+CD8+、CD3+CD4+/CD3+CD8+) subsets、CD16+CD56+natural killer cells(NK)、HLADR+Lin-CD123+plasmacytoid dendritic cells(p DC)、the level of platelet antibody(CD41a+Ig G、CD41a+Ig M)、Serum immunoglobulin G、Serum immunoglobulin M、Serum immunoglobulin A、Serum immunoglobulin E. Conclusion The peripheral blood Bregs significant decreased in patients with immune thrombocytopenia. After effective treatment, both quantity and function of Bregs increased. Bregs may play an important role in ITP immune pathological process. By detecting the Bregs level is helpful to diagnose ITP and provide new ideas for further understand the pathogenesis of ITP, promising novel approach in treating human autoimmune disease, potentially without undesirable off-target effects.