Autoreactive T cell receptors with shared germline-like α chains in type 1 diabetes.

Human islet antigen reactive CD4+ memory T cells (IAR T cells) play a key role in the pathogenesis of autoimmune type 1 diabetes (T1D). Using single-cell RNA sequencing (scRNA-Seq) to identify T cell receptors (TCRs) in IAR T cells, we have identified a class of TCRs that share TCRα chains between individuals (“public” chains). We isolated IAR T cells from blood of healthy, new-onset T1D and established T1D donors using multiplexed CD154 enrichment and identified paired TCRαβ sequences from 2767 individual cells. More than a quarter of cells shared TCR junctions between 2 or more cells (“expanded”), and 29/47 (~62%) of expanded TCRs tested showed specificity for islet antigen epitopes. Public TCRs sharing TCRα junctions were most prominent in new-onset T1D. Public TCR sequences were more germline like than expanded unique, or “private,” TCRs, and had shorter junction sequences, suggestive of fewer random nucleotide insertions. Public TCRα junctions were often paired with mismatched TCRβ junctions in TCRs; remarkably, a subset of these TCRs exhibited cross-reactivity toward distinct islet antigen peptides. Our findings demonstrate a prevalent population of IAR T cells with diverse specificities determined by TCRs with restricted TCRα junctions and germline-constrained antigen recognition properties. Since these “innate-like” TCRs differ from previously described immunodominant TCRβ chains in autoimmunity, they have implications for fundamental studies of disease mechanisms. Self-reactive restricted TCRα chains and their associated epitopes should be considered in fundamental and translational investigations of TCRs in T1D.

人胰岛抗原反应性CD4 + 记忆性T细胞（IAR T细胞）在自身免疫性1型糖尿病（T1D）的发病机制中起关键作用。利用单细胞RNA测序（scRNA - Seq）来鉴定IAR T细胞中的T细胞受体（TCR），我们已经鉴定出一类在个体之间共享TCRα链（“公共”链）的TCR。我们使用多重CD154富集方法从健康人、新发T1D患者和确诊的T1D供体的血液中分离出IAR T细胞，并从2767个单个细胞中鉴定出成对的TCRαβ序列。超过四分之一的细胞在2个或更多细胞之间共享TCR连接区（“扩增”），并且所测试的扩增TCR中有29/47（约62%）对胰岛抗原表位具有特异性。共享TCRα连接区的公共TCR在新发T1D中最为显著。公共TCR序列比扩增的独特或“私有”TCR更类似于胚系，并且具有更短的连接区序列，这表明随机核苷酸插入更少。公共TCRα连接区在TCR中经常与不匹配的TCRβ连接区配对；值得注意的是，这些TCR的一个子集对不同的胰岛抗原肽表现出交叉反应性。我们的研究结果表明，存在大量具有不同特异性的IAR T细胞，这些特异性由具有受限的TCRα连接区和胚系限制的抗原识别特性的TCR所决定。由于这些“先天性样”TCR不同于先前在自身免疫中描述的免疫优势TCRβ链，它们对疾病机制的基础研究具有重要意义。在T1D中TCR的基础和转化研究中，应考虑自身反应性受限的TCRα链及其相关表位。