Differentiation of thymus-derived cells from precursors in mouse bone marrow

An experimental model system was developed to study the differentiation of thymus-derived (T) cells from progenitors in bone marrow. In this system transplantation of bone marrow cells depleted of T cells gave rise to T cells in the spleens of irradiated recipients within 15 days of transplantation. Thus, normal bone marrow contains a class of cells that are progeniotrs of T cells (PT cells). PT cells are different from T cells since PT cells are incapable of responding to alloantigen, are theta resistant, and band in a lighter density region than do T cells. The density profile of PT cells is different from that of hematopoietic stem cells (CFU-S); PT cells band in a denser region of the gradient than do CFU-S.