Early and Late Leukemias in Rats after Transplantation of Leukemic Cells from Akr Mice.

mouse leukemia to rats ( 12). Cell suspensions from the leukemic tissues of AKR mice were injected by the sub cutaneous, intraperitoneal, or intravenous route into non inbred, newborn Wistar rats. A second inoculation of leukernic cells was given to some groups of rats 7—10days later. Single subcutaneous or intraperitoneal injections did not establish progressively growing, fatal leukemic grafts. Two consecutive intraperitoneal or intravenous injections produced death from leukemia in 39—48per cent of the recipients at the age of 3—5weeks. More than half of the rats apparently rejected the leukemic hetero grafts. However, after an interval of 12—16 weeks lymph oid leukernias were noted in some of these initially “nega tive― rats. The two leukemic manifestations were referred to as “early― and “late― leukemias because of the differences in latent periods. Further experiments revealed that cells from early leukemias were readily back-transplantable into young, adult, AKR mice. In contrast, cellular grafts from late leukernias were rejected by AKR mice. These findings pointed to differences in the antigenicity and etiology be