Microenvironmental regulation of T cell development in the thymus

T cell development in the thymus occurs through a series of events beginnin g with thymic colonization by migrant precursors and ending with the emigra tion of functionally competent CD4(+) and CD8(+) T cells to the periphery. It is well accepted that signals through the pre-T cell receptor (pre-TCR) and alpha-beta TCR (alpha beta TCR) complex play pivotal roles in the matur ation of CD4(-) 8(-) and CD4(+) 8(+) thymocytes, respectively. It is clear that stromal cells constituting the thymic microenvironment provide non-TCR -mediated interactions which are essential for several developmental events . Examples of such will be discussed here in relation to early and late eve nts in T cell development.