Thymic nurse cells and radiation leukemia virus induced thymic lymphomas in C57BL mice.

The selective thymotropism of radiation leukemia virus is an interesting example of specific interaction between an oncogenic agent and the differentiation pathway of a well-defined cell lineage. Indeed, the inoculation of RadLV in C57BL/Ka mice leads to the development of thymic lymphomas [4]. Only a few immature thymocytes can act as target cells for productive infection by RadLV [I]. Infection is followed by virus replication which Starts in the outer cortex to spread rapidly to the whole cortical thymocyte population [2]. Thymus-dependent preleukemic cells emerge during the first phase of virus replication, although the thymus is still not tumoral. Finally thymus-independent neoplastic cells appear and give rise to lymphomas (Boniver et al., to be published). The immaturity of target cells and the thymus dependency of the preleukemic process led us to investigate the possible role of thymic nurse cells (TNCs) in thymic lymphomagenesis. These lymphoepithelial cell complexes are indeed at a critical Stage of the early thymic lymphopoiesis [3,5,6].