Thymocyte progenitors and T cell development in aging

Dysfunction of T lymphocytes in aging has been causally related to a gradual loss of the thymic microenvironmental function. However, in view of the fact that T cells are generated from bone marrow-derived stem cells that settle in the thymus, we have investigated the possibility that aging effects on the bone marrow have an impact on T cell development. Our approach was based on seeding of bone marrow cells, from young and old mice, onto lymphoid-depleted fetal thymus explants, and examining the patterns of T lymphocyte development under organ culture conditions. The results indicate multifactorial effects of aging, on pre-thymic and intra-thymic developmental processes, as well as on feedback regulation by mature T cells.