Trembleau S, Giacomini P, Guéry J C, Setini A, Hammer J, Sette A, Appella E, Adorini L
Roche Milano Ricerche, Milano, Italy.
Int Immunol. 1995 Dec;7(12):1927-38. doi: 10.1093/intimm/7.12.1927.
HLA-DRA transgenic (tg) mice on H-2d background were constructed to study assembly, expression and function of DR alpha: E beta class II heterodimers when an alternate E alpha chain is available. Cytofluorimetric analysis and immunoprecipitation studies demonstrate that the majority (90%) of E beta d molecules on class II-positive splenocytes from DRA-tg mice are associated with DR alpha rather than E alpha chains. To characterize the functional role of the interspecies as compared with the wild-type I-E molecules, MHC restriction and T cell epitope immunodominance of synthetic peptides spanning the entire sequence of 65 kDa heat shock protein (hsp) from Mycobacterium tuberculosis were determined in hsp-primed DRA-tg and DBA/2 mice. A similar pattern of responsiveness was observed in both strains, but hsp epitopes recalled a higher response in DRA-tg as compared with DBA/2 mice. A panel of T cell hybridomas specific for two hsp peptides or a hen egg white lysozyme peptide presented by both DR alpha: E beta d and E alpha d: E beta d was studied in detail. Surprisingly, DR alpha: E beta d dimers present these peptides more efficiently than E alpha d: E beta d, even when the TCR was selected in mice expressing only E alpha d: E beta d molecules. The higher efficiency of antigen presentation by DR alpha: E beta d dimers does not appear to depend on increased binding affinity for peptides, as demonstrated by competition for antigen presentation, nor on increased efficiency in the interaction with CD4 molecules. Rather, the higher efficiency of antigen presentation could be explained by a more effective ligand-TCR interaction. This is consistent with molecular modeling based on the class II structure, indicating that 16 out of 17 substitutions between the first domain of E alpha d and DR alpha chains ile outside the peptide binding groove and are potentially available for interaction with the TCR.
构建了H-2d背景下的HLA-DRA转基因（tg）小鼠，以研究当存在替代的Eα链时DRα:Eβ II类异二聚体的组装、表达和功能。细胞荧光分析和免疫沉淀研究表明，来自DRA-tg小鼠的II类阳性脾细胞上的大多数（90%）Eβd分子与DRα而非Eα链相关。为了表征与野生型I-E分子相比种间分子的功能作用，在经热休克蛋白（hsp）致敏的DRA-tg小鼠和DBA/2小鼠中测定了跨越结核分枝杆菌65 kDa热休克蛋白（hsp）全序列的合成肽的MHC限制性和T细胞表位免疫显性。在两个品系中观察到了相似的反应模式，但与DBA/2小鼠相比，hsp表位在DRA-tg小鼠中引发了更高的反应。对由DRα:Eβd和Eαd:Eβd呈递的两种hsp肽或一种鸡蛋清溶菌酶肽特异性的一组T细胞杂交瘤进行了详细研究。令人惊讶的是，即使TCR是在仅表达Eαd:Eβd分子的小鼠中选择的，DRα:Eβd二聚体呈递这些肽的效率也比Eαd:Eβd更高。DRα:Eβd二聚体抗原呈递效率更高似乎不取决于对肽的结合亲和力增加，抗原呈递竞争证明了这一点，也不取决于与CD4分子相互作用的效率提高。相反，抗原呈递效率更高可以用更有效的配体-TCR相互作用来解释。这与基于II类结构的分子建模一致，表明Eαd的第一个结构域和DRα链之间的17个取代中有16个位于肽结合槽之外，可能可用于与TCR相互作用。
