Tfh细胞通过分泌IL21激活自身以及B细胞IL21R，促进B细胞向浆细胞转化，是诱导肾移植AMR的重要事件。课题组前期发现肾移植小鼠脾脏中优势Il21r的mRNA亚型发生改变，但机制不明。人IL21R基因3’端外显子与IL21R-AS1基因部分逆向重叠，课题组对Tfh细胞进行外源IL21刺激后发现IL21R-AS1与snRNP70结合度增高，且胞质中信号增强，因此推测IL21R-AS1存在Cis和Trans双重作用，参与IL21R的选择性剪接和IL21应答。本项目将利用离体Tfh/B细胞共培养系统，对IL21R-AS1进行基因过表达或敲除，构建相关功能域上调或缺失的细胞群落；在异种蛋白刺激下，评估IL21R-AS1对IL21R的剪接修饰以及对免疫相关蛋白的调控，探讨其在TD免疫应答中的角色和潜在机制；并在肾移植模型中探究其作为AMR治疗靶点的可行性和有效性。

IL21, secreted by Tfh cells, induces IL21 autocrine itself and germinal center B cells differentiation through Tfh and B cell IL21 receptor (IL21R) binding respectively, and plays an important role in antibody-mediated rejection (AMR) after renal transplantation. It has been revealed in our former work that the predominant subtype of mature IL21r mRNA in murine spleen had switched into UC009JPE.2 after kidney transplantation, whereas the mechanism remains veiled. IL21R-AS1 partly overlaps IL21R by a reverse pattern. After IL21 stimulation, both nuclear and cytosolic IL21R-AS1 signals, and IL21R-AS1 binding snRNP70 increase significantly, therefore IL21R-AS1 is supposed to participate in the IL21 signal response through both Cis and Trans acting mechanisms. To validate the hypothesis, T-cell-dependent antibody (TD) response will be setup on Tfh/B cell co-culture system by keyhole limpet haemocyanin (KLH) administration in vitro. Dual nickase SpCas9 (spCas9n)-induced CRISPR genomic editing and rAAV- or LV-carried CAG-promoted overexpression are induced for IL21R-AS1 functional knock-down and knock-in. The role of IL21R-AS1 in alternative splicing of IL21R mature mRNA and TD response, furthermore in AMR after kidney transplantation will be evaluated by multiple methods.