The thymus and the immune system: layered levels of control.

Control points of normal thymopoiesis may provide insights into strategies for interrupting cell interactions in thymomas which appear to maintain active T cell production. Thymus production of T cells represents one of two pathways by which peripheral T cell populations are maintained or, if lost, regenerated. The production of T cells by the thymus results from a series of thymus epithelial cell (TEC) - thymocyte interactions from entry of thymocyte precursors into the thymus to release of mature naïve single positive T cells into the periphery. Within this series of interactions, certain control points have been identified, all of which act through TEC to modulate thymopoiesis.