Spontaneous and induced lymphomas in mice and rats

have frequently been transplanted to study factors gov erning †̃takes' as well as the possibility of enhancing resist ance in the recipients. It has been learned that trans planted leukemic cells grow in isologous animals, regardless of sex and age, and are rejected in recipients of other strains (3, 5, 6, 8, 16, 22). The data in regard to the effect of the route of trans plantation on the major sites of localization of lymphomas show that I. V. injections elicit generalized lymphomas or leukemias (5, 7), that S. C. grafts produce tumor at the site of injection and generalized disease terminally (3, 5—7,14), and that I. P. inoculation causes lymphomas of the omentum and mesentery, frequently with ascites and widespread metastases (3, 6, 7, 13, 16, 22). Experiments on transplantation in the present study were carried out using leukemic lymphoblasts derived from a virus-induced rat thymoma and grown in tissue culture for18months.