THE DIVESITY IN ANTIGEN RECOGNITION AND RESPONSE OF ANTIGEN-SPECIFIC HUMAN CD4^+ T-CELL CLONES

自身免疫性疾病是指免疫系统在健康状态下对自身抗原产生特异性适应性免疫反应。分子模拟模型解释了破坏耐受性的假设机制之一，其中自反应性T细胞由携带与自身抗原肽密切相关的T细胞表位的感染性微生物启动。事实上，越来越多的证据表明，T细胞克隆识别的表位的退化比之前预期的要高。在本研究中，我们分析了受轻微修饰的抗原肽（改变的肽配体；api）刺激的T细胞的信号转导途径，表征了与自身免疫性疾病相关的自反应性T细胞克隆识别的T细胞表位的多样性，并鉴定了可被T细胞克隆识别的微生物来源的非自抗原肽。更多的结果：1)从非自身链球菌肽衍生的部分激动性apl在抗原呈递细胞表面过表达时，可以刺激同源的人CD4^+ t细胞（Th细胞）克隆增殖。然而，增殖性T细胞反应的独特之处在于，它们不伴有可检测的T细胞受体（TCR）近端信号事件，如ZAP-70和LAT的磷酸化以及TCR的下调，所有这些都在原始抗原肽刺激的T细胞中明显观察到。2)利用clip取代不变链建立t细胞表位表达文库，鉴定出多种t细胞表位可被th细胞克隆识别。利用修饰的文库，将随机氨基酸残基缩小为三个连续的氨基酸残基，我们表征了来自IDDM患者的gad65反应性th细胞克隆的表位退化，并鉴定了th细胞克隆与之交叉反应的肺炎链球菌和金黄色葡萄球菌衍生的表位。少

Autoimmune diseases are developed when a specific adaptive immune response is directed against self antigens, to which the immune system is supposed to be tolerated in healthy condition. One of the hypothesized mechanisms that break the tolerance is explained by a molecular mimicry model, where self-reactive T cells were primed by infectious microorganisms carrying T-cell epitopes closely-related to the self-antigenic peptides. Indeed, evidence is accumulating that the degeneracy in epitopes recognized by a T cell clone is higher than that expected before. In the present study, we analyzed the signal transduction pathways of the T cells stimulated with slightly modified antigenic peptides (altered peptide ligands ; APLs), characterized the diversity of the T-cell epitopes recognized by self-reactive T-cell clones associated with an autoimmune disease, and identified microorganism-derived non-self antigenic peptides that were recognized by the T-cell clones. We obtained the following re … More sults :1) Some partially agonistic APLs derived from a non-self streptococcal peptide could stimulate the cognate human CD4^+ T-cell (Th cell) clone to proliferate when they were over-expressed on the surface of antigen presenting cells. However, the proliferative T-cell responses were unique in that they were not accompanied with detectable T-cell receptor (TCR)-proximal signaling events such as phosphorylation of ZAP-70 and LAT and down-regulation of the TCR, all of which were apparently observed in the T cells stimulated with the original antigenic peptide.2) We established a T-cell epitope-expression library using CLIP-substituted invariant chain and identified diverse T-cell epitopes that were recognized by Th-cell clones. Using the modified libraries in which randomized amino acid residues were narrowed down into three successive ones, we characterized the degeneracy in the epitopes of the GAD65-reactive Th-cell clones derived from IDDM patients and identified the Streptcoccus pneumoniae- and Staphylococcus aureus-derived epitopes to which the Th-cell clones cross-reacted. Less