Dendritic cells prevent radiation-induced thymic lymphoma.

Thymic lymphomas develop in C57BL/Ka mice within 36 weeks after split-dose X-irradiation. Lymphoma development can be abrogated in such mice by the injection of syngeneic bone marrow from healthy donors. The abrogation mechanism is unknown, but since bone marrow supplies the thymus with precursors of thymocytes and of dendritic cells, we tested the ability of early thymocytes and of immortalized thymic dendritic cells to abrogate lymphomagenesis. Fifteen weeks after irradiation, mice which had received bone marrow or dendritic cells had an equally low incidence of lymphoma, whereas mice which had received thymocytes or which had been only irradiated developed equally high levels of lymphomas, indicating that thymic dendritic cells played a key role in the prevention of lymphoma development. When thymuses from 15-week survivors were tested for pre-lymphoma cells, those from dendritic cell-treated mice proved to be endowed with a level of lymphomagenic potential intermediate between that from bone marrow-treated mice (nonlymphomagenic) and that from untreated or thymocyte-treated mice (highly lymphomagenic). These data indicate that lymphoma abrogation by bone marrow cells involves the participation of marrow-derived thymic dendritic cells.