CD8+CD122+PD1+ 调节性T细胞诱导免疫耐受及其免疫调节机制

A patient with a transplanted oragn or autoimmune disease needs continuous immunosuppressive treaments , which cause serious side effects including infections and tumors. Induction of immune tolerance to an allograft or autoantigen without continuous immunosuppression is a highly desired goal in the field of transplantation and immunology. CD4+CD25+ Tregs have been extensively studied and utilized to promote allograft survival, inhibit autoimmune diseases and induce immune tolerance. However, their potential applications in clinical transplantation are limited due to their inability to prolong allograft survival in normal wide-type animals after their adoptive transfer. Hence it is compelling to search for more effective Tregs. Our recent studies have shown that CD8+CD122+ Tregs are more potent in suppression of conventional T cell proliferation in vitro and inhibition of allograft rejection in Rag1-/- mouse models than their CD4+CD25+ counterparts. We also found that CD8+CD122+ Tregs underwent faster homeostatic proliferation in vivo than CD4+CD25+ Tregs. Moreover, our preliminary data have demonstrated that in vitro-expanded CD8+CD122+PD1+ Tregs by donor antigens are even capable of delaying allograft rejection in wide-type mice. These findings suggest that CD8+CD122+ Tregs may be more valuable in clinical applications than their CD4+CD25+ counterparts. Based on these novel findings, we therefore propose to explore the new strategies of inducing long-term allograft survival or tolerance by adoptive transfer of the CD8+CD122+PD1+ Tregs. We will seek to significantly enhance their efficacy in suppression in normal recipient mice using apoptosis-resistant CD8+CD122+PD1+ Tregs or via combining the Treg transfers with low doses of immunosuppressive agents for short-term. Both measures are designed to promote the Treg strength for the induction of long-term allograft survival or tolerance in wild-type mice. Finally, we will propose to study the mechanisms by which these Tregs exert their suppression. Understanding their mechanisms of action would provide new insight into designing highly effective approaches to enhancing their suppression of allograft rejection. In these studies, neutralizing antibodies and gene-deficient mice will be utilized to study their mechanisms of action. Murine skin and islet transplant models will be employed to study Treg suppression of allograft rejection. Completion of the proposed studies, therefore, has important clinical implications.

器官移植和自身免疫疾病病人需要持续使用免疫抑制剂治疗，但是长期治疗易引起严重的副作用。短期使用免疫调节性T细胞（CD4+CD25+Treg)诱导免疫耐受以抑制移植排斥或自身免疫是最理想治疗方案，但其在正常动物受体的抑制效果有限。我们的最新研究表明CD8+CD122+Treg比CD4+CD25+Treg能更有效地抑制传统T淋巴细胞的增殖, 并能在免疫缺陷小鼠模型更显著地推迟同种异体移植物的排斥，提示前者更有潜在的应用价值。此外,我们的初步研究首次显示经体外抗原特异性扩容后的CD8+CD122+PD1+Treg还能推迟正常小鼠受体对移植物的排斥。因此，我们将在本项目中进一步采用能抵制自身细胞凋亡的Treg（内因）和联合使用小剂量免疫抑制剂（外因）的新策略,以提高该Treg的抑制效果和诱导免疫耐受，并进一步研究该Treg的免疫调节作用机制,为设计更有效的抑制移植排斥的临床试验方案提供理论依据。

器官移植和自身免疫疾病病人需要持续使用传统免疫抑制剂治疗，但是长期治疗易引起严重的副作用。该项目探索短期使用免疫抑制剂并联合调节性T细胞（CD8+CD122+PD1+Treg)诱导免疫耐受以抑制器官移植排斥 以便将来建立副作用小的理想治疗方案。我们的前期研究发现CD8+CD122+Treg比传统的CD4+CD25+Treg细胞能更有效地抑制免疫排斥反应。因此，我们在该项目研究中进一步采用能抵制自身细胞凋亡的Treg（内因）和联合使用小剂量免疫抑制剂（外因）的新策略,以提高CD8+CD122+PD-1+Treg的抑制免疫排斥的效果和诱导免疫耐受能力，并进一步研究了该Treg的免疫调节作用机制。在本研究中，我们发现CD8+CD122+PD-1+Treg细胞与免疫抑制剂Rapamycin或MR1（CD40/CD154共刺激阻断）联合使用对同种异体移植排斥的抑制具有协调作用，而且使用能抵制自身细胞凋亡的Treg细胞（Fas-/-或Bcl-2+）抑制效果更好。其主要抑制作用机制是抑制效应T细胞增殖，以及由其FasL配体启动的对效应T细胞的杀伤与效应T细胞本身Fas介导的自身凋亡决定，而且CD8+CD122+PD-1+ Tregs 也能下调辅助性T细胞Th1/Th17。此外，在基本完成项目原计划研究内容的基础上，延伸的研究进一步发现银屑灵方或大黄素对移植排斥反应的抑制作用，其作用机制正是通过诱导CD8+CD122+Treg细胞。于是，该项目使用短期免疫抑制剂联合调节性T细胞（Treg) 治疗以抑制器官移植排斥的研究成果具有潜在的临床应用价值。该项目有关Treg细胞免疫调节新机制的研究也具有重大的学术与科学价值，为理解细胞免疫调节机制并指导细胞免疫治疗提供了新的科学依据。研究成果已发表SCI论文4篇 （其中5分以上3篇），另外还有1篇已投稿的论文也正在准备修回。