Acceleration of leukemogenesis in akr mice by grafts, cell suspensions, and cell‐free centrifugates of thymuses from preleukemic akr donors

AbstractGrafting of 5‐month‐old thymuses of AKR mice into young adult AKR and (AKR x SL)F1 recipients shortened markedly the latent period for leukemia development, but thymus grafts from 3‐ and 1‐month‐old AKR mice had no accelerating effect. Transplantation assay of early lymphomas appearing in (AKR x SL)F1 mice revealed that almost all the neoplasms were derived from F1 host cells. Intraperitoneal injections of thymus cell suspensions made from 5‐month‐old AKR mice also caused acceleration of leukemogenesis. Cell‐free centrifugates prepared from 5‐month‐old AKR mouse thymuses had a striking accelerating activity on early development of leukemia when injected intraperitoneally into isologous newborn mice. The centrifugates from 3‐month‐old thymuses had an intermediate activity but the centrifugates from 1‐month‐old thymuses had no activity. The centrifugates made similarly from AKR mouse spleens at various time points during the preleukemic stage did not show accelerating activity. Intrathymic injection of the centrifugates from 5‐month‐old thymuses was more effective in accelerating leukemia development than intraperitoneal injection of the same material.These results indicate that thymuses of 5‐month‐old AKR mice may contain a large quantity of leukemia viruses and, further, that the latent period may represent the time necessary for the development of an effective concentration of leukemia virus.