Phenotypic analysis of mouse thymus development

In this review, we have presented some of our data on the developing mouse thymus studied using mAbs to cell surface determinants and FMF. In the past, numerous parameters have been used in an attempt to describe the differentiation of T cells in the thymus. These parameters have included relative cell size, anatomical location, enzyme activity (TdT), expression of surface molecules such as Thy-1, Lyt-1, H-2, PNA, T200, TL, and CD4/CD8, and the ability to express IL-2R [45, 46]. None of these parameters has been adequate to describe how the thymus generates functional ‘mature’ T cells, which now include CD4/CD8 single-positive and double-negative cells, from its small numbers of elusive precursors [17, 45, 47]. However, given the irrefutable evidence that the thymus does influence the repertoire of TcR expressed by cells generated therein [48], analysis of gene regulation and surface expression of TcR molecules by thymocytes is certainly the most promising approach for the elucidation of the mysterious nature of intrathymic T cell differentiation.