Auphan N, Jézo-Brémond A, Schönrich G, Hämmerling G, Arnold B, Malissen B, Schmitt-Verhulst A M
Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, France.
Int Immunol. 1992 Dec;4(12):1419-28. doi: 10.1093/intimm/4.12.1419.
To evaluate the role of the structure of the class I molecule and associated peptide(s) in intrathymic selection and tolerance, mice expressing as a transgene (tg) a TCR specific for the H-2Kb alloantigen were crossed with mice expressing the mutant class I molecule H-2Kbm1 or H-2Kbm8. In H-2k/k TCR tg mice (in a situation of exclusive positive selection), peripheral tg TCR expressing (Ti+) CD8+ T cells showed high, suboptimal, and an absence of reactivity for H-2Kb, H-2Kbm1, and H-2Kbm8, respectively. In the peripheral lymphoid organs of TCR tg H-2k/k, H-2k/bm8, H-2k/bm1, and H-2k/b mice respectively, the tg TCR was expressed on T cells with decreasing intensity of surface CD8. Thymic subpopulations of TCR tg mice presented a pattern of negative selection with decreasing intensity from H-2k/b to H-2k/bm1 and H-2k/bm8. This suggests that a weak interaction between the TCR and H-2Kbm8 exists which partially results in negative, but not in positive, intrathymic selection. Results further indicate that expression of H-2Kbm8 does not induce tolerance to H-2Kb. In H-2k/bm1 mice, the peripheral Ti+ CD8lo cells express two distinct types of 'threshold' tolerance in vitro: (i) they generate cytotoxic T lymphocytes (CTL), in the presence of exogenous IL-2, which fail to respond to H-2Kbm1 but remain reactive to H-2Kb; and (ii) they do not make significant titers of IL-2 and do not significantly proliferate in response to H-2Kb, unlike the Ti+ CD8+ T cells from H-2k/k TCR tg mice which respond efficiently. These results show that tolerance is induced up to a level of non-reactivity within a given MHC environment: for the same TCR, CTL reactivity to H-2Kbm1 is totally lost, whereas CTL reactivity to H-2Kb is only slightly reduced. Additionally, proliferation and IL-2 production by Ti+ CD8+ cells in response to H-2Kb were strongly affected in H-2k/bm1 mice. Thus, in H-2k/k mice the Ti+ CD8+ cells behave as helper-independent, whereas in H-2k/bm1 mice CD8+ cells expressing the same TCR behave as helper-dependent CTL.
为了评估I类分子结构及相关肽段在胸腺内选择和耐受性中的作用，将作为转基因（tg）表达对H-2Kb同种抗原具有特异性的TCR的小鼠，与表达突变I类分子H-2Kbm1或H-2Kbm8的小鼠进行杂交。在H-2k/k TCR tg小鼠（处于排他性阳性选择的情况下），外周表达tg TCR的（Ti+）CD8+ T细胞对H-2Kb、H-2Kbm1和H-2Kbm8分别表现出高反应性、次优反应性和无反应性。在TCR tg H-2k/k、H-2k/bm8、H-2k/bm1和H-2k/b小鼠的外周淋巴器官中，tg TCR在T细胞上的表达强度随着表面CD8强度的降低而降低。TCR tg小鼠的胸腺亚群呈现出从H-2k/b到H-2k/bm1和H-2k/bm8强度逐渐降低的阴性选择模式。这表明TCR与H-2Kbm8之间存在弱相互作用，这部分导致了胸腺内的阴性选择，但不是阳性选择。结果进一步表明，H-2Kbm8的表达不会诱导对H-2Kb的耐受性。在H-2k/bm1小鼠中，外周Ti+ CD8lo细胞在体外表现出两种不同类型的“阈值”耐受性：（i）在存在外源性IL-2的情况下，它们产生细胞毒性T淋巴细胞（CTL），这些CTL对H-2Kbm1无反应，但对H-2Kb仍有反应；（ii）与来自H-2k/k TCR tg小鼠的能有效反应的Ti+ CD8+ T细胞不同，它们不产生显著滴度的IL-2，并且对H-2Kb不显著增殖。这些结果表明，在给定的MHC环境中，耐受性被诱导至无反应水平：对于相同的TCR，对H-2Kbm1的CTL反应性完全丧失，而对H-2Kb的CTL反应性仅略有降低。此外，在H-2k/bm1小鼠中，Ti+ CD8+细胞对H-2Kb的增殖和IL-2产生受到强烈影响。因此，在H-2k/k小鼠中，Ti+ CD8+细胞表现为不依赖辅助细胞，而在H-2k/bm1小鼠中，表达相同TCR的CD8+细胞表现为依赖辅助细胞的CTL。
