Expression And Clinical Significance Of CD8~+CD28~-regulation T Cell And Platelet-specific Autoantibodies In Patients With Immune Thrombocytopenia

Background Immune thrombocytopenia is a complex autoimmune disease involving multiple mechanisms.The main clinical features were the decrease of platelet count,the increase of megakaryocytes with maturation disorder,the hemorrhage of the skin and mucosa^[1,2].Previous studies have suggested that platelet-specific autoantibody mediated platelet destruction is one of the pathophysiological mechanisms of ITP.Common antibody types include GPIIb/IIIa antibodies and GPIb antibodies^[3].Recently,with the indepth study of ITP diseases,Studies have found that abnormal expressions of regulatory T cells（Treg）and related cytokines also play an important role in the pathogenesis of ITP^[4,5].CD8⁺CD28^-Treg refers to the heterogeneous T lymphocyte subsets with immunomodulatory functions produced in the process of in vivo and in vitro immunity.They belong to CD8⁺Treg,CD8⁺CD28^-Treg,which regulate the immune response of the body through a variety of complex mechanisms and play an important role in maintaining the immune balance and immune homeostasis of the body.We detected the expression level of platelet specific autoantibody and CD8⁺CD28^-Treg and related cytokines in peripheral blood of ITP patients.To explore their significance in the pathogenesis and clinical treatment of ITPObjective To detect the expression levels of CD8⁺CD28^-Treg,platelet-specific autoantibodies and cytokines in peripheral blood of patients with immune thrombocytopenia（ITP）,and to discuss the significance of the three indexes in the pathogenesis and treatment of ITP.Methods Seventy-three patients with ITP were divided into the hormone-treated group（n=42）and the recombinant human thrombopoietin（rhTPO）-treated group（n=31）,and were divided into effective group and ineffective group according to the therapeutic effect.Flow cytometry was used to detect the expression of CD8⁺CD28^-Treg in peripheral blood of patients before and after treatment,and the expression of platelet-specific autoantibodies in peripheral blood was detected by cytometric bead array.Serum levels of transforming growth factor（TGF）-β1,interleukin（IL）-10 and interferon-γ（IFN-γ）were measured by ELISA before and after treatment.30 healthy subjects in the same period were used as normal control group.Results（1）The expressions of CD8⁺CD28^-Treg Treg and cytokines IL-10 and TGF-β1in 73 patients with ITP were lower than those in the normal control group,and the expression of IFN-γwas higher than that in the normal control group（P<0.05）.The expressions of CD8⁺CD28^-Treg Treg,IL-10 and TGF-β1 in the hormone-treated and rhTPO-treated groups were significantly higher than those before treatment,and the expression of IFN-γwas significantly decreased（P<0.05）.The expression of CD8⁺CD28^-Treg,IFN-γ,IL-10 and TGF-β1 in the ineffective group showed no significant change compared with that before treatment;（2）According to the receiver operating characteristic curve（ROC curve）,the threshold value of CD8⁺CD28^-Treg before treatment in the hormone group was 14.35.The sensitivity and specificity of this value in predicting the efficacy of patients were 66.7%and 73.3%.Of the 27 patients who were hormonally effective,18（66.7%）had CD8⁺CD28^-Treg less than 14.35,and11（73.3%）of the 15 patients with treatment failure greater than 14.35.The threshold value of CD8⁺CD28^-Treg before treatment in the rhTPO group was 15.45.The sensitivity and specificity of this value in predicting the efficacy of patients were 63.6%and 88.9%,Among the 22 patients who were effective after rhTPO therapy,14 cases（63.6%）had CD8⁺CD28^-Treg greater than 15.45,and 8 cases（88.9%）had less than15.45 in 9 patients who were ineffective after treatment;（3）hormone group anti-GPIb antibody positive in 18 cases,the effective rate was 44.4%,anti-GPIb antibody negative in 24 cases,the effective rate was 79.1%,the difference was significant（P<0.05）.Conclusion CD8⁺CD28^-Treg and related cytokine expression abnormalities are involved in the pathogenesis of ITP.Hormones and rhTPO may play a role in changing this abnormality.Detection of CD8⁺CD28^-Treg before treatment can help predict the efficacy of hormones and rhTPO.Anti-GPIb antibody positive may be one of the influencing factors of hormone therapy insensitivity.