Gyotoku T, Fukui Y, Sasazuki T
Department of Genetics, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
Eur J Immunol. 1998 Dec;28(12):4050-61. doi: 10.1002/(SICI)1521-4141(199812)28:12<4050::AID-IMMU4050>3.0.CO;2-Y.
Immunization with self peptides often elicits activation of CD4+ T cells in vivo. Although such peptides have been suggested to be derived from minor self determinants or self antigens sequestered from the immune system, we found that immunization with Ealpha peptide (Ealpha52-68), a major self determinant bound to I-Ab molecules, elicits an immune response in Ealpha-transgenic C57BL/6 (Ealpha-B6) mice where Ealpha52-68 is endogenously processed and presented by I-Ab molecules in the thymus and periphery. To better understand this response, a panel of T cell hybridomas raised against exogenous Ealpha52-68 were analyzed for their reactivity to spleen cells from Ealpha-B6 mice. Some hybridomas were stimulated with Ealpha-B6 spleen cells in the absence of exogenous Ealpha52-68, whereas others were not stimulated with them. The Ealpha52-68/I-Ab complex recognized by the TCR that is expressed on the hybridoma with reactivity to Ealpha-B6 spleen cells was found to be quite stable, whereas the complex recognized by the TCR on the hybridoma specific for the exogenous Ealpha52-68 lost the stimulation activity by incubation the complex at 37 degrees C for 10 min. Stimulation experiments using extensively substituted Ealpha analogue peptides suggested that amino acid residues at positions 57, 58, 60 and 62 of Ealpha52-68 are involved in the interaction with TCR recognizing the Ealpha52-68/I-Ab complex expressed on Ealpha-B6 spleen cells. While amino acid substitutions at positions 60 and 62 also affected the recognition of TCR specific for exogenous Ealpha52-68, all or many amino acid substitutions were allowed at position 58 or 57, respectively, without impairing the TCR recognition. Taken together, these results suggest that endogenously processed self peptide and the corresponding exogenous peptide bound to the same MHC class II molecule could be distinct TCR ligands with different kinetic stability and probably with different configuration.
用自身肽进行免疫通常会在体内引发CD4+ T细胞的激活。尽管有人提出此类肽源自次要自身决定簇或与免疫系统隔离的自身抗原，但我们发现，用Eα肽（Eα52-68）进行免疫，Eα52-68是与I-Ab分子结合的主要自身决定簇，在Eα转基因C57BL/6（Eα-B6）小鼠中引发了免疫反应，在该小鼠中，Eα52-68在胸腺和外周由I-Ab分子进行内源性加工和呈递。为了更好地理解这种反应，分析了一组针对外源性Eα52-68产生的T细胞杂交瘤对Eα-B6小鼠脾细胞的反应性。一些杂交瘤在没有外源性Eα52-68的情况下被Eα-B6脾细胞刺激，而其他杂交瘤则未被其刺激。发现杂交瘤上表达的与Eα-B6脾细胞有反应性的TCR所识别的Eα52-68/I-Ab复合物相当稳定，而特异性针对外源性Eα52-68的杂交瘤上的TCR所识别的复合物在37℃孵育10分钟后失去了刺激活性。使用广泛取代的Eα类似肽进行的刺激实验表明，Eα52-68第57、58、60和62位的氨基酸残基参与了与识别Eα-B6脾细胞上表达的Eα52-68/I-Ab复合物的TCR的相互作用。虽然第60和62位的氨基酸取代也影响了特异性针对外源性Eα52-68的TCR的识别，但分别在第58或57位允许所有或许多氨基酸取代，而不损害TCR的识别。综上所述，这些结果表明，内源性加工的自身肽和与同一II类MHC分子结合的相应外源性肽可能是具有不同动力学稳定性且可能具有不同构象的不同TCR配体。
