Loftus D J, Chen Y, Covell D G, Engelhard V H, Appella E
Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
J Immunol. 1997 Apr 15;158(8):3651-8.
In an effort to better understand functional recognition of structurally dissimilar ligands by a single TCR, a model system for studying cross-recognition of disparate peptide/class I complexes was developed using the murine (H-2b) CTL clone AHIII12.2, which is reactive to a human self-peptide (p1049) bound to an HLA-A2.1 molecule. We identified a second complex comprised of a synthetic peptide, designated p1058, bound to H-2Db that is recognized by clone AHIII12.2. In cytolysis assays, dose-response profiles for peptides p1049 and p1058 pulsed onto the appropriate target cells were comparable, suggesting that p1049/A2.1 and p1058/Db form functionally equivalent epitopes. To probe the interaction between each complex and the TCR of AHIII12.2, singly substituted analogues of each peptide were tested for their activity in lysis assays. Differences were observed between the two epitopes with respect to permissible residue substitutions at each peptide position from P3 to P8; marked differences were evident at P3 and at P8. The results obtained suggest that this TCR forms critical contacts with atoms at peptide positions P3 and P5 of p1049/A2.1 and at P5 and P8 of p1058/Db, and that TCR cross-recognition of these ligands is a function of both shared and complex-specific contacts made with each epitope. These findings further highlight the versatile reactivity that may be shown by a single TCR and suggest a basis for the recognition of peptide ligands sharing only a limited set of structural features.
为了更好地理解单个T细胞受体（TCR）对结构不同的配体的功能识别，利用鼠源（H-2b）细胞毒性T淋巴细胞（CTL）克隆AHIII12.2开发了一个用于研究不同肽段/ I类复合物交叉识别的模型系统，该克隆对与HLA-A2.1分子结合的人源自身肽段（p1049）具有反应性。我们鉴定出了第二种复合物，它由与H-2Db结合的合成肽段（命名为p1058）组成，且能被克隆AHIII12.2识别。在细胞溶解试验中，脉冲到合适靶细胞上的肽段p1049和p1058的剂量反应曲线具有可比性，这表明p1049/A2.1和p1058/Db形成了功能等效的表位。为了探究每种复合物与AHIII12.2的TCR之间的相互作用，对每种肽段的单取代类似物进行了溶解试验活性测试。在从P3到P8的每个肽段位置上，两种表位在允许的残基取代方面存在差异；在P3和P8处差异明显。所得结果表明，该TCR与p1049/A2.1的肽段位置P3和P5以及p1058/Db的P5和P8处的原子形成关键接触，并且这些配体的TCR交叉识别是与每个表位形成的共享接触和复合物特异性接触的函数。这些发现进一步突出了单个TCR可能表现出的多功能反应性，并为识别仅共享有限一组结构特征的肽段配体提供了基础。
