van Meerwijk J P, Germain R N
Lymphocyte Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Semin Immunol. 1994 Aug;6(4):231-9. doi: 10.1006/smim.1994.1030.
Commitment to the CD4+ or CD8+ T cell lineages and positive selection for full maturation of precursor T cells take place in the thymus. A detailed phenotypic analysis of differentiating thymocytes in normal and MHC-deficient mice has led to the identification of previously unappreciated subpopulations whose characteristics and dependence on major histocompatibility complex (MHC) class I versus class II molecule expression seem incompatible with a CD4/CD8 coreceptor-dependent 'instructional' model of thymocyte development. We suggest here that these and other recent data are most consistent with a model in which the TCR-mediated decision to enter the CD4 versus the CD8 lineage is independent of the class of MHC molecule recognized and is distinct from positive selection. This latter event appears to involve already lineage-committed cells and to require a match of the MHC class specificity of the lineage-defining, highly expressed CD4 or CD8 coreceptor and the TCR.
对CD4+或CD8+ T细胞谱系的定向以及前体T细胞完全成熟的阳性选择在胸腺中发生。对正常和MHC缺陷小鼠中分化的胸腺细胞进行详细的表型分析，已鉴定出先前未被认识的亚群，其特征以及对主要组织相容性复合体（MHC）I类与II类分子表达的依赖性似乎与胸腺细胞发育的CD4/CD8共受体依赖性“指导”模型不相符。我们在此提出，这些以及其他最新数据与这样一种模型最为一致，即TCR介导的进入CD4或CD8谱系的决定独立于所识别的MHC分子类别，并且不同于阳性选择。后一事件似乎涉及已经定向到特定谱系的细胞，并且需要谱系定义的、高表达的CD4或CD8共受体与TCR的MHC类别特异性相匹配。
