I型主要组织相容性复合体参与1型糖尿病异常自身抗原呈递的机制研究

1型糖尿病（T1DM）由CD8+T细胞对胰腺β细胞破坏引起，表现为胰岛素绝对缺乏，血糖水平增高。基于MHC I类分子稳定性决定T1DM易感性的假说，我们前期在分子伴侣tapasin敲除及抗原呈递抑制细胞系中，配对比较易感（HLA-B*44:05）和保护型（HLA-B*44:02）MHC I类分子的差异，发现前者稳定较好，无需tapasin帮助即可实现胞内运输和抗原递呈，而后者相反。此外，MHC I类分子的稳定性由其羧基端决定，诱导Y84F突变可降低其稳定性。在此基础上本项目在tapasin敲除的胰岛β细胞系中研究T1DM相关的8种MHC I类分子的稳定性，识别其致病抗原肽，同时提出治疗该病的两种新策略：诱导Y84F突变降低易感型MHC I类分子稳定性；肽治疗－置换致病抗原肽而诱导免疫耐受。我们将开展离体实验验证上述，并为T1DM的临床治疗提供新思路。

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease, in which auto-reactive CD8+ T cells de-stroy pancreatic β cells. Diagnosed with which, patients cannot produce insulin and eventually cannot control blood glucose levels. Managing auto-reactivity of CD8+ T cells at the early stage of pancreas destruction could be a viable therapeutic strategy. In T1DM CD8+ T cells auto-reactivity is caused by a self-antigen presentation by certain MHC class I molecules. MHC class I molecules are hyper-expressed at the surface of pancreatic β cells, and there is a genetic correlation of MHC class I polymorphism to T1DM. .We hypothesized that the stability of MHC class I molecules determines susceptibility to T1DM. We compared two closely-related MHC class I molecules - one T1DM-predisposing - HLA-B*44:05, the other T1D-protective - HLA-B*44:02 in a cell line lacking MHC I chaperone protein tapasin and/or with inhibited antigen delivery. We found that B*44:05 is stable and does not require tapasin for its intracellular transport nor antigen presentation, while B*44:02 is unable to bind and present antigen without tapasin. We observed that MHC I stability is confined to the region where C-terminus of antigen binds and designed a novel mutant Y84F that indeed showed reduced stability. .We will study the stability of eight other MHC class I molecules associated with T1DM in pancreatic β cell lines with knockout of TAPASIN gene by CRISPR/Cas9. We will identify possible diabetogenic antigens pre-sented by these MHC I molecules. This will allow us to develop two strategies to modify MHC class I antigen presentation in T1DM - first one by reducing the stability of T1DM-predisposing molecules (Y84F mutation) and the second by peptide therapy - exchanging diabetogenic peptides for an antigen that may confer tolerance. These are two strategies when proven effective ex vivo could be further developed into treatment options for T1D patients.