Chromosome studies on transplanted and virus-induced lymphoid leukemias in rats.

The i.p. transplantation of viable leukemic cells from AKR mice to newborn W /Fu rats resulted in 2 manifestations of lymphoid leukemia. An early form was characterized by growth of the transplanted leukemic cells in the abdominal cavity. Late leukemias were thymic lymphosarcomas with or without leukemic blood changes (12). Late leukemias were previously considered viral tumors induced by the leukemia virus of Gross (9). To further substantiate this hypothesis, leukemic cells from female AKR mice were transplanted to male and female newborn W /Fu rats, and the chromosomes of early and late leukemias were analyzed. The chromosomes of leukemic cells from the early leukemias had the telocentric configuration and female sex constitution of the transplanted mouse cells. In contrast, the chromosomes of leukemic cells from the late leukemias were morphologically rat chromosomes, and their sex constitution corresponded with the sex of the recipient. These findings indi cated that late, thymic leukemias originated from rat cells probably by virus release from the grafted mouse leukemic cells with infection and malignant transformation of rat thymic cells.