Identification and characterization of T cell epitope in primary biliary cirrhosis

在原发性胆汁性肝硬变(PBC)患者中，抗线粒体抗体主要针对PDC的丙酮酸脱氢酶复合体(PDC-E2)、2-氧戊二酸脱氢酶复合体(OGDC-E2)、支链2氧酸脱氢酶复合体(BCOADC-E2)和PDC的E3结合蛋白(E3BP)的E2组分。我们先前已经证明PDC-E2 163-176肽(GDLLAEIETDKATI)是受HLADR53(DRA1^*0101/DRB4^*0101)限制的免疫优势的自身反应性T细胞表位。为了解决线粒体抗原之间的分子模拟和交叉识别问题，我们分析了来自正常人和PBC患者的10个克隆的T细胞株对识别单个T细胞受体(TCR)配体PDC-E2 163-176肽/HLADR53的一系列单一氨基酸取代肽的反应性。此外，我们还使用类似肽进行了拮抗和激动性分析，以确定最关键的tcr接触因子…。更多到期(S)。我们的数据表明，每个T细胞克隆的总体精细特异性是独一无二的，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：^&lt；170&gt；ExDK^&lt；173&gt；(A组)和^&lt；168&gt；EIExd^&lt；172&gt；(B组)。^&lt；170&gt；E是两组克隆T细胞系最关键的TCR接触残基，而^&lt；173&gt；K和^&lt；168&gt；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患者和健康人的外周血中建立的。最重要的是，一些A组克隆的T细胞株与人E3BP 34-47、人OGDC-E2 100-113以及几种携带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细胞株仅与携带EIExD基序的E3BP 34-47发生反应。在B组克隆的T细胞株TCRVβ的互补决定区(CDR3)中仅发现RGxG基序，而在A组克隆的T细胞系中TCRVβ的CDR3中经常发现G、S和/或R。这些数据可能为理解PBC中线粒体抗原之间的分子模拟和交叉识别提供分子基础。较少

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