Stromal cells in the mouse thymus : an immunocytochemical characterization of the thymic microenvironment

This thesis deals with the differentiation and maturation ofT (thymusderived) lymphocytes. The development of mature immunocompetent T lymphocytes requires 3 steps. Firstly, HSC differentiate to prothymocytes, precursors committed to the T cell lineage. These cells leave the BM and settle in the thymus. Secondly, upon entry into the thymus, these prothymocytes proliferate and give rise to a population of immature thymocytes (thymic lymphocytes). Thirdly, thymocytes differentiate into mature T eel ls that emigrate from the thymus to peripheral lymphoid organs. After activation by antigen these mature T ~ells function as effector eel ls in the cellular immune response, and as regulatory cells in both the humoral and the cellular immune response (Cantor and Weissman, 1976; Stutman, 1978). This thesis deals mainly with intrathymic events in T eel l differentiation. A summary of current knowledge ofT eel 1 differentiation is given in Chapter 2.