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‐2^k, Thy‐1.1) mice at an early stage after transplantation with bone marrow cells of C3H/HeN (H‐2^k, 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 the thymus.