A novel CD3-J11d+ subset of CD4+CD8- cells repopulating thymus in radiation bone marrow chimeras.

Sequential appearance of T cell subpopulations occurs in the thymus of irradiated AKR (H-2k, Thy-1.1) mice at an early stage after transplantation with bone marrow cells of C3H/HeN (H-2k, Thy-1.2) mice. The donor-derived thymocytes were first detected on day 8 after bone marrow reconstitution. Although most of the thymocytes were CD4-CD8- cells, an appreciable level of CD4+CD8- cells was detected in the thymus at this stage. The early appearing CD4+CD8- cells were a novel subset of thymocytes that were J11d+CD3-. From day 10 to day 21 the proportion of CD4+CD8-CD3-J11d+ cells decreased while the proportion of CD4+CD8+ cells and CD4+CD8-CD3+J11d- cells increased. The CD4+CD8-CD3- cells seem to diversify to form CD4+CD8+ thymocytes after short-term culture in vitro. These results suggested the existence of a differential pathway from CD4-CD8- cells to CD4+CD8+ cells via CD4+CD8- cells in thymus.