Sprent J, Gao E K, Webb S R
Department of Immunology, Research Institute of Scripps Clinic, La Jolla, CA 92037.
Science. 1990 Jun 15;248(4961):1357-63. doi: 10.1126/science.1694041.
The specificity of mature CD8+ and CD4+ T lymphocytes is controlled by major histocompatibility complex (MHC) class I and class II molecules, respectively. The MHC class specificity of T cells is stringent in many assays, but is less evident when cells are supplemented with exogenous lymphokines. The repertoire of T cells is shaped through contact with MHC molecules in the thymus and involves a complex process of positive selection and negative selection (tolerance). Tolerance of immature T cells to MHC molecules can reflect either clonal deletion or anergy and results from intrathymic contact with several cell types, including epithelial cells and cells with antigen-presenting function. Unlike immature T cells, mature T cells are relatively resistant to tolerance induction. In certain situations partial unresponsiveness of mature T cells can be achieved by exposing T cells to foreign MHC molecules expressed on atypical antigen-presenting cells. Tolerance is rarely complete, however, and the precise requirements for tolerizing mature T cells are still unclear.
成熟的CD8⁺和CD4⁺T淋巴细胞的特异性分别由主要组织相容性复合体（MHC）I类和II类分子控制。在许多检测中，T细胞的MHC类特异性很严格，但当细胞补充外源性淋巴因子时则不太明显。T细胞库是通过在胸腺中与MHC分子接触而形成的，涉及一个复杂的阳性选择和阴性选择（耐受）过程。未成熟T细胞对MHC分子的耐受可反映克隆清除或无反应性，这是胸腺内与几种细胞类型（包括上皮细胞和具有抗原呈递功能的细胞）接触的结果。与未成熟T细胞不同，成熟T细胞对耐受诱导相对有抵抗力。在某些情况下，通过将T细胞暴露于非典型抗原呈递细胞上表达的外来MHC分子，可以使成熟T细胞产生部分无反应性。然而，耐受很少是完全的，使成熟T细胞耐受的确切要求仍不清楚。
