Autoantibodies directed to islet cell surface antigens and their pathologic roles in type-1 diabetes

胰岛自身抗体（AAs）是胰腺自身免疫的可靠生物标志物。针对四种主要 生物化学抗原（胰岛素、GAD、IA-2和ZnT 8）常规用于临床研究中作为用于检测胰岛素水平的关键指标。 1型糖尿病（T1 D）患者的诊断和治疗，以及高危人群的疾病预测 在T1 D发病前。已经开发了稳健的生物化学测定来检测识别AAs 可溶性抗原或膜结合抗原的可溶性结构域。对膜结合的AA的检测 然而，抗原在其不溶性跨膜结构域的适应中受到技术困难的挑战， (TMD)到基于溶液的测定平台。目前，我们还不知道这种疾病的流行情况， 出现靶向任何TMD抗原的AA。在四种主要的生化抗原中，胰岛特异性 ZnT 8的独特之处在于具有包含全长ZnT 8中三分之二蛋白质序列的主要TMD。我们 最近的工作表明，ZnT 8在胰岛素分泌后被运输到胰腺β细胞的表面， 表面TMD具有高度抗原性，可被T1 D患者的血清ZnT 8 AA识别。这些发现 表明ZnT 8中的TMD是表面靶向AA的新免疫原性结构域，并且其在表面上的展示是一种新的免疫原性结构域。 细胞表面的抗体可促进抗体介导的细胞毒性，直接导致β细胞自身免疫破坏。 为了检验这些假设，我们将（i）在进展中的患者中验证针对ZnT 8的TMD的AA（TMDAs）， （ii）建立TMDA作为直接靶向AA，因此，直接结合活胰腺β细胞， 调节它们的功能和生存。这项研究有望验证一种全新的 AAs靶向最近发现的胰岛细胞表面抗原，阐明了TMDA在自然史中的作用 T1 D（目标1）和疾病发病机制（目标2）。所获得的知识将被转化为新的诊断 工具和潜在的治疗干预。

Islet autoantibodies (AAs) are reliable biomarkers of pancreatic autoimmunity. Serum AAs against four major biochemical antigens (insulin, GAD, IA-2, and ZnT8) are routinely used in clinical research as key metrics for diagnostics and prognostics in patients with type-1 diabetes (T1D), and for disease prediction in at-risk individuals before T1D onset. Robust biochemical assays have been developed to detect AAs recognizing soluble antigens or soluble domains of membrane-bound antigens. Detection of AAs to membrane-bound antigens, however, is challenged by technical difficulties in adaption of their insoluble transmembrane domains (TMD) to solution-based assay platforms. At present, we have no knowledge of the prevalence and first appearance of AAs targeting any TMD antigens. Among the four major biochemical antigens, the islet-specific ZnT8 is unique in having a major TMD that encompasses two thirds protein sequence in a full-length ZnT8. Our recent works showed that ZnT8 is trafficked to the surface of pancreatic β-cells following insulin secretion, and the surfaced TMD is highly antigenic, recognized by serum ZnT8 AAs in patients with T1D. These findings suggest that the TMD in ZnT8 is a novel immunogenic domain for surfaced-targeted AAs, and its display on the cell surface may promote antibody-mediated cytotoxicity contributing directly to β-cell autoimmune destruction. To test these hypotheses, we will (i) validate AAs directed to the TMD of ZnT8 (TMDAs) in patients progressing to T1D, and (ii) establish TMDAs as direct-targeting AAs, as such, bind directly to live pancreatic β cells to modulate their functions and survival. The proposed research is expected to validate a completely new class of AAs targeting a recently identified islet cell surface antigen, illuminating the roles of TMDAs in the natural history of T1D (Aim 1) and disease pathogenesis (Aim 2). The knowledge gained will be translated to novel diagnostic tools and potential therapeutic interventions.