Preliminary Study On The Expression And Role Of CD4~+ CD25~+ Regulatory T Cells In Uveitis

Objective:Uveitis is a clinically common heterogenous group of diseases in which intraocular inflammation leads to reduced vision, retinal destruction, and blindness. Because its cause and pathogenesis are very complicated, there are still no satisfactory therapy methods to cure uveitis. In recent years, with the development of molecular biology and immunology, uveitis were more and more considered as organ-specific antoimmune disease and T-cell-dependent immunological events are increasingly being regarded as centrally important in the pathogenesis of uveitis. Moreover, many cytokines such as IFN-γ, TNF-α, IL-10, IL-1, TGF-βand many chemokines also were found to play important roles in the pathogenesis of uveitis. However, most of the exact pathogenesis of uveitis was still not very clear and further research on it is very necessary.CD4+CD25+ Regulatory T cells (Treg) are one of many subpopulations of T cells with regulatory properties. CD4+CD25+Treg cells representing about 5–10% of both the mouse and human peripheral CD4+T cells have been well demonstrated to play a crucial role in keeping immune homeostasis, which can prevent the development of autoimmune diseases and keeping self-tolerance. Until now the researches on the role of CD4+CD25+Treg cells in the pathogenesis of uveitis were mostly focused on the study of IRBP-induced experimental autoimmune uveoretinitis (EAU). Many findings showed that natural CD4+CD25+ Treg cells possess the ability to inhibit activation of IRBP-reactive T cells, and adoptive transfer of these cells ameliorates EAU. Supplementation of natural CD4+CD25+ Treg cells may have therapeutic potential for effective treatment of uveitis. But the study on the expression and role of CD4+CD25+ Treg cells in uveitis patients were relatively very few.We aimed to: 1. To examine the expression of CD4+CD25high regulatory T cells in peripheral blood of patients of uveitis with different disease activity and to explore its roles in the disease development of uveitis.2. To detect the expression of cytokines IFN-γ, TNF-α, IL-10 in the CD4+ cells of uveitis patients, and also analyze the relationship between cytokines expression and CD4+CD25high expression for further understand the immune pathogenesis of uveitis.Methods:1. Thirty patients with active uveitis and sixteen normal healthy subjects as controls were selected. The disease activity and inflammatory index such ESR were graded.2. Peripheral blood lymphocytes were obtained from these patients and controls. The frequencies of CD4+CD25high T cells and CD4+CD25high CTLA-4+ cells were detected by immunoflurescence method and analyzed by flow cytometry (FCM). Moreover, their correlation with disease typy and disease activity were studied.3. The levels of IFN-γ, TNF-αand IL-10 in peripheral blood CD4+ T cell of uveitis patients and controls were examined by intra-cellular immunoflurescence method and analyzed by flow cytometry. ELISA method also was used to study the expression of these cytokines in cell culture of peripheral blood mononuclear cells. Their correlation with disease activity and CD4+CD25high expression were also studied.Results:1. The percentage of CD4+CD25high T cells in peripheral blood of patients with uveitis was higher than that of the healthy controls (8.56±4.22% vs. 5.72±3.11%, P = 0.022), and it correlated very well with the disease severity of uveitis. And the percentage of CD4+CD25high CTLA4+ T cells in uveitis was also higher than that of the healthy controls (P=0.012).2. The expression of IFN-γand TNF-αin peripheral blood CD4+ cells of uveitis were both higher than that of normal healthy controls(P<0.05). As for IL-10, its expression in peripheral blood CD4+ cells of uveitis was little higher than controls with no statistical significance.3. IFN-γ, TNF-αand IL-10 expression in peripheral blood CD4+ cells of uveitis were all well correlated with disease activity of uveitis and they correlated with each other. Meanwhile, TNF-αand IL-10 expression were well correlated with the percentage of CD4+CD25high T cells in peripheral blood of uveitis patients (P <0.05).4. ELISA results showed that the levels of IFN-γand TNF-αin the culture of peripheral blood mononuclear cells of uveitis were high than that of normal control. IL-10 expression in that of uveitis was little higher than controls with no statistical significance.Conclusions:1. The higher expression of CD4+CD25+ regulatory T cells in peripheral blood of patients with uveitis suggest that CD4+CD25+ regulatory T cells may play important roles in the pathogenesis of uveitis.2. We have established the detection system of intra cellular cytokines and our results confirmed that the elevated cytokines including IFN-γ, TNF-αand IL-10 secreted by CD4+ cells play important roles in uveitis. Moreover, the increased secretion of TNF-αand IL-10 by CD4+cells correlated with CD4+CD25high T cells expression implied that CD4+CD25+ Treg cells perhaps have considerable regulatory roles in cytokines expression.3. The experimental systems we have established provide a good foundation for the further research on the roles of CD4+CD25+ regulatory T cells and cytokines in pathogenesis of SpA, and also find important clues of the new immune therapy method of uveitis.