Identification and characterization of T cell epitope in primary biliary cirrhosis

在原发性胆汁性肝硬化（PBC）患者中，抗线粒体抗体反应主要针对丙酮酸脱氢酶复合物（PDC-E2）、2-氧戊二酸脱氢酶复合物（OGDC-E2）、支链2氧酸脱氢酶复合物（BCOADC-E2）和PDC的E3结合蛋白（E3BP）的E2组分。我们之前已经证明PDC-E2 163-176肽（GDLLAEIETDKATI）是受HLA DR53 （DRA1^*0101/DRB4^*0101）限制的免疫显性自身反应性T细胞表位。为了解决线粒体抗原之间的分子模仿和交叉识别问题，我们分析了来自健康受试者和PBC患者的10个克隆T细胞系对一系列单氨基酸取代肽的反应性，这些T细胞系识别单一T细胞受体（TCR）配体PDC-E2 163-176肽/HLA DR53。此外，我们使用类似肽进行拮抗和激动试验，以确定最关键的TCR接触阻抗。我们的数据表明，每个T细胞克隆的整体精细特异性都是独特的，但这些T细胞克隆根据其TCR配体的识别基序大致分为两个不同的组；^<170>ExDK^<173> （A组）和^<168>EIExD^<172> （B组）。^<170>E是两组克隆T细胞系最关键的TCR接触残基，而^<173>K和^<168>E分别是A组和B组克隆T细胞系最关键的TCR接触残基。重要的是，A组和B组T细胞克隆都是从PBC患者和健康受试者的外周血中建立的。最重要的是，一些A组克隆的T细胞系与人E3BP 34-47、人OGDC-E2 100-113以及多种携带ExDK基序的微生物蛋白衍生的多肽发生交叉反应，而B组克隆的T细胞系仅与携带EIExD基序的E3BP 34-47发生反应。此外，在B组克隆的T细胞系中，RGxG基序只存在于TCR Vβ的互补决定区（CDR3），而在A组克隆的T细胞系中，G、S和/或R基序经常出现在TCR Vβ的互补决定区（CDR3）。这些数据可能为了解PBC线粒体抗原的分子模仿和交叉识别提供分子基础。少

In patients with primary biliary cirrhosis (PBC), the anti-mitochondrial antibody response is primarily directed against E2 components of the pyruvate dehydrogenase complex (PDC-E2), 2-oxoglutarate dehydrogenase complex (OGDC-E2), the branched chain 2 oxo-acid dehydrogenase complex (BCOADC-E2), and the E3 binding protein (E3BP) of PDC. We have previously demonstrated that the PDC-E2 163-176 peptide (GDLLAEIETDKATI) is the immunodominant autoreactive T cell epitope which is restricted by HLA DR53 (DRA1^*0101/DRB4^*0101). To address the issue of molecular mimicry and cross-recognition among mitochondrial antigens, we analyzed the reactivity to a series of single amino acid substituted peptides of ten cloned T cell lines derived from both healthy subjects and patients with PBC which recognize a single T cell receptor (TCR) ligand, PDC-E2 163-176 peptide/HLA DR53. In addition, we performed antagonism and agonism assays using analogue peptides to determine the most critical TCR contact resi … More due(s). Our data demonstrate that the overall fine specificities are unique for every single T cell clone but that these T cell clones are roughly categorized into two distinct groups based on their recognition motifs of TCR ligand ; the ^<170>ExDK^<173> (group A) and the ^<168>EIExD^<172> (group B). ^<170>E is the most critical TCR contact residue for both groups of cloned T cell lines whereas ^<173>K and ^<168>E are critical TCR contact residues for group A and group B cloned T cell lines, respectively. Importantly, both group A and group B T cell clones were established from the peripheral blood of both patients with PBC and healthy subjects. Most importantly, some of the group A cloned T cell lines cross-react to human E3BP 34-47, human OGDC-E2 100-113, and several peptides derived from various microbial proteins carrying an ExDK motif, while group B cloned T cell lines react only to E3BP 34-47 carrying an EIExD motif. Furthermore, an RGxG motif was exclusively found in the complementarity determining region (CDR3) of the TCR Vβ in the group B cloned T cell lines, while G, S, and/or R were frequently found in the CDR3 of the TCR Vβ in the group A cloned T cell lines. These data may provide a molecular basis for understanding molecular mimicry and cross-recognition among mitochondrial antigens in PBC. Less