Díaz Gema, Amicosante Massimo, Jaraquemada Dolores, Butler Richard H, Guillén M Victoria, Sánchez Miguel, Nombela César, Arroyo Javier
Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Int Immunol. 2003 May;15(5):565-76. doi: 10.1093/intimm/dxg057.
The information available on the specific function of HLA-DP and the structure-function relationships is very limited. Here, single amino acid substitutions of HLA-DPB102012 have been used to analyze the role of polymorphic residues of the DPbeta1 domain on DP-mediated T cell allorecognition and peptide binding. Using a panel of specific anti-HLA-DP mAb, we identified the HLA-DP residues involved in the recognition by these mAb, with a crucial role for DPbeta56 for most of the mAb assayed. Individual substitutions at residues 9, 11, 35, 55, 56 and 69 completely abrogated T cell recognition mediated by two different HLA-DPw2-allospecific T cell clones (8.3 and 8.9). Interestingly single changes at positions 9, 11, 35 and 55 of HLA-DPbeta also altered the binding of peptides AAII(12-27) and IIP(53-65), natural ligands of the HLA-DPB102012 molecule. Individual changes at residues located in pocket 1 (84, 85, 86 and 87 from HLA-DPbeta) led to a partial reduction in cytotoxic T lymphocyte-mediated lysis and also partially affected peptide binding. However, the simultaneous substitution of these positions completely abolished both T cell allorecognition and peptide binding, suggesting a major role for polymorphisms at pocket 1 in HLA-DP function. Molecular modeling, used to predict changes induced by amino acid substitutions, supported the functional data. Taken together, these results strongly suggest that polymorphic residues 84, 85, 86 and 87 at pocket 1, residues 9, 35 and 55 at pocket 9, and residues 11 and 69 at pockets 6 and 4 respectively play a key role in HLA-DP function, probably by modifying the way the peptide is bound within the groove of HLA-DP2 and determining changes in the conformation of the MHC-peptide complex recognized by the TCR.
关于HLA - DP的具体功能以及结构 - 功能关系的现有信息非常有限。在此，我们利用HLA - DPB102012的单个氨基酸替换来分析DPβ1结构域多态性残基在DP介导的T细胞同种异体识别和肽结合中的作用。使用一组特异性抗HLA - DP单克隆抗体，我们确定了这些单克隆抗体识别所涉及的HLA - DP残基，对于大多数检测的单克隆抗体而言，DPβ56起着关键作用。在第9、11、35、55、56和69位残基处的单个替换完全消除了由两种不同的HLA - DPw2同种异体特异性T细胞克隆（8.3和8.9）介导的T细胞识别。有趣的是，HLA - DPβ第9、11、35和55位的单个变化也改变了肽AAII(12 - 27)和IIP(53 - 65)（HLA - DPB102012分子的天然配体）的结合。位于口袋1（来自HLA - DPβ的第84、85、86和87位）的残基的单个变化导致细胞毒性T淋巴细胞介导的裂解部分降低，并且也部分影响肽结合。然而，这些位置的同时替换完全消除了T细胞同种异体识别和肽结合，表明口袋1处的多态性在HLA - DP功能中起主要作用。用于预测氨基酸替换诱导变化的分子建模支持了功能数据。综上所述，这些结果强烈表明，口袋1处的多态性残基第84、85、86和87位，口袋9处的第9、35和55位残基，以及口袋6和4处的第11和69位残基分别在HLA - DP功能中起关键作用，可能是通过改变肽在HLA - DP2凹槽内的结合方式并确定TCR识别的MHC - 肽复合物构象的变化来实现的。
