Molecular Basis of Gamma Delta TCR Ligand Recognition

描述（由申请人提供）：尽管γ δ（gammadelta）T细胞受体代表了我们在获得性免疫中的第三个抗原受体谱系，沿着抗体和γ δ T细胞受体，但对其结构生物学、配体特异性和功能了解甚少。 然而，新兴的功能研究指出了它在防御癌症和病原体以及维持宿主体内平衡方面的重要作用。 γ δ TCR利用DNA重排产生比抗体或aa TCR潜在更大的组合多样性，但关于这种多样性是否用于特异性抗原识别，或者种系区段是否足以用于γ δ TCR功能的争议仍然存在（2）。此外，与aa TCR不同，γ δ TCR可以在不存在抗原加工的情况下识别MHC样和非MHC配体，类似于抗体/抗原识别。 γ δ TCR是否以会聚的方式识别其配体，使人联想到α TCR与肽-MHC的相互作用，或与抗体/抗原复合物中所见的多种识别溶液的相互作用？ 目前还没有关于γ δ TCR与其配体相互作用的结构信息。 本申请的广泛目标是开始阐明γ δ TCR识别配体的分子和结构原理。 我们的目标是表达，生物化学表征，并确定与蛋白质配体的γ δ TCR复合物的X射线晶体结构，伴随着合作的功能研究，以了解我们的研究结果的免疫学相关性。 我们将我们的结构努力集中在功能良好的γ δ TCR系统上，即G8 γ δ TCR与非经典MHC T22和T10的相互作用。 与Y教授合作，H. Chien，我们还将表达对经典和非经典MHC具有明确特异性的新型γ δ TCR的重组形式，以询问是否存在MHC样配体的普遍收敛的γ δ识别模式。 最后，我们将开始研究γ δ TCR识别非MHC蛋白抗原的结构基础是否与78 TCR识别MHC样抗原有根本不同。

DESCRIPTION (provided by applicant): Although gamma delta (gammadelta) T cell receptors represent our third lineage of antigen receptors in adaptive immunity, along with antibodies and alphgamma T cell receptors, their structural biology, ligand specificity, and function is poorly understood. Yet, emerging functional studies point to important roles in defense against cancers and pathogens, and the maintenance of host homeostasis. Gammadelta TCR use DNA rearrangement to generate potentially greater combinatorial diversity than antibodies or aa TCR, but controversy persists about whether this diversity is used for specific antigen recognition, or whether the germline segments are sufficient for gammadelta TCR function (2). Also, unlike aa TCR, gammadelta TCR can recognize both MHC-like and non-MHC ligands in the absence of antigen processing, similar to antibody/antigen recognition. Do gammadelta TCR recognize their ligands in a convergent manner reminiscent of alphabeta TCR interactions with peptide-MHC, or with a diversity of recognition solutions as seen in antibody/antigen complexes? Currently there is no structural information on the interactions of gammadelta TCR with their ligands. The broad goals of this application are to begin to elucidate the molecular and structural principles of ligand recognition by the gammadelta TCR. We aim to express, biochemically characterize, and determine the x-ray crystal structures of gammadelta TCR complexes with protein ligands, in companion with collaborative functional studies to understand the immunological relevance of our findings. We are focusing our structural efforts on a functionally well-characterized gammadelta TCR system, the interaction of the G8 gammadelta TCR with the non-classical MHC T22 and T10. In collaboration with Prof. Y.-h. Chien, we will also express recombinant forms of new gammadelta TCR with defined specificities for classical and non-classical MHC in order to ask whether there is a universally convergent gammadelta recognition mode of MHC-like ligands. Finally, we will begin to investigate whether the structural basis of gammadelta TCR recognition of non-MHC protein antigens is fundamentally different from 78 TCR recognition of MHC-like antigens.