Thymic nurse cells account for the thymus dependency of preleukemic cells in mice after inoculation of radiation leukemia virus.

Inoculation of Radiation Leukemia Virus (RadLV) into C57BL/Ka mice induces thymic lymphomas after a 3-6 month latent period. The leukemogenic process requires a sequence of events from the productive infection of susceptible target cells and induction of preleukemic cells to irreversible neoplastic transformation. Preleukemic cells were detected in the thymus during the first week following virus injection. The thymus dependency of these cells was shown to depend transiently upon peculiar lymphoepithelial complexes called "Thymic Nurse Cells" (TNCs). Indeed, the first preleukemic cells appearing in the RadLV-inoculated thymuses were observed selectively within TNCs. They remained closely associated with these complexes during the first 2 or 4 weeks. Later on, TNCs disappeared almost completely whereas non-TNCs associated preleukemic cells were found. Lymphoepithelial interactions within TNCs were thus required for the initial events of RadLV-induced lymphomagenesis. The subsequent TNCs depletion expressed a disturbance of thymic lymphopoiesis in relation with the neoplastic process.