I-EP BOUND SELF-PEPTIDES: IDENTIFICATION AND CHARACTERIZATION

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。T细胞对多肽/同种异体MHC复合体的识别是引起移植排斥反应的主要原因。目前提出的自体肽和MHC分子都参与其中；然而，同种异体反应性的分子基础和自体肽的贡献仍然不清楚。小鼠2.102 T细胞对Hb(-76)/I-Ek具有特异性，对I-EP具有同种反应性。2.102识别的天然自体多肽/i-EP复合体仍不清楚。在本研究中，我们对I-EP自然加工和呈递的多肽进行了表征，并利用这些信息定义了小鼠I-EP II类分子的结合基序。有趣的是，我们发现I-EP偏好的P9锚残基与其他I-E分子偏好的残基截然不同，尽管P1锚残基是保守的。19种不同的自体多肽缺乏对2.102个T细胞的刺激，显示出一定程度的同种异体反应的特异性。该结合基序被用来搜索小鼠基因组中含有强P1和P9锚定残基并具有先前已确定的允许TCR接触残基的2.102个反应性同源多肽。鉴定出两个潜在的同源多肽，但其中只有一个，G蛋白偶联受体128，能够刺激2.102个T细胞。因此，G蛋白偶联受体128肽代表了一种候选的同源多肽，它被2.102个与I-EP结合的T细胞特异性识别，并通过生物信息学进行了鉴定。这些研究强调了自体多肽在同种异体反应中的具体参与。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. T cell recognition of peptide/allogeneic MHC complexes is a major cause of transplant rejection. Both the presented self-peptides and the MHC molecules are involved; however, the molecular basis for alloreactivity and the contribution of self-peptides are still poorly defined. The murine 2.102 T cell is specific for Hb(64-76)/I-Ek and is alloreactive to I-Ep. The natural self-peptide/I-Ep complex recognized by 2.102 remains unknown. In this study, we characterized the peptides which are naturally processed and presented by I-Ep, and used this information to define the binding motif for the murine I-Ep class II molecule. Interestingly, wefound that the P9 anchor residue preferred by I-Ep is quite distinct from the residues preferred by other I-E molecules, although the P1 anchor residue is conserved. A degree of specificity for the alloresponse was shown by the lack of stimulation of 2.102 T cells by 19 different identified selfpeptides. The binding motif was used to search the mouse genome for candidate 2.102 reactive allo-peptides that contain strong P1 and P9 anchor residues and possess previously identified allowable TCR contact residues. Two potential allo-peptides were identified, but only one of these peptides, G protein-coupled receptor 128, was able to stimulate 2.102 T cells. The G protein-coupled receptor 128 peptide, thus, represents a candidate allo-peptide that is specifically recognized by 2.102 T cells bound to I-Ep and was identified using bioinformatics. These studies highlight the specific involvement of self-peptides in alloreactivity.