Hemopoietic stem cells in mice with virus-induced leukemia. II. Studies in C3H mice after Rauscher virus infection

Susceptibility of mice reconstituted with trisomy 19 hematopoietic cells to infection with Rauscher leukemia virus

Radiation chimeras with trisomy 19 hematopoietic cells were constructed to test the sensitivity of the trisomic hematopoietic system to infection with Rauscher leukemia virus: Hematopoietic cells from livers of trisomic fetuses were rescued by transplantation into lethally irradiated adult mice. These Ts 19 radiation chimeras show a stable and sufficiently long-lived trisomic hematopoiesis to allow experimental induction of Rauscher leukemia. Rauscher leukemia virus (RLV) induced a marked proliferation of erythroblasts in the spleens of Ts 19 mice and control chimeras within 3 weeks. The onset of erythroblast proliferation was significantly delayed in the Ts 19 mice, suggesting a smaller number of target cells for the RLV and/or reduced susceptibility of the target cells to RLV. Both Ts 19 and control chimeras developed nonlymphocytic leukemia 2-4 months after RLV injection. The course of leukemogenesis was similar in the two experimental groups. No numerical chromosome abnormalities associated with leukemogenesis were detectable in Ts 19 or control cells. The numbers of chromosomal sister chromatid exchanges 2 weeks after RLV injection were elevated to the same degree in both Ts 19 and control cells. Thus, cells with constitutional trisomy do not show increased chromosomal instability due to leukemogenesis.

Effect of antiserum on transplantable hematopoietic colony-forming units during Rauscher leukemia development

Studies have been carried out to determine the sensitivity of hematopoietic CFU-S from Rauscher leukemic mice to an antiserum against the disease prepared in syngeneic mice. Test of this antiserum against Rauscher virus prior to injection showed it to be effective both in vitro and in vivo. At the same time, normal serum was shown to be without effect either against the CFU-S or against the virus. Spleen CFU-S were obtained from control and leukemic mice over a sequence of days following Rauscher virus injection and assayed by transplantation technique. Prior to transplantation these were incubated in vitro in either normal syngeneic serum or syngeneic antiserum. Incubation with antiserum had no effect on CFU-S obtained from the spleens of normal mice. However, incubation in this antiserum of spleen CFU-S from Rauscher leukemic mice resulted in a reduction of up to 50% in their colony-forming ability. Additional tests with guinea pig complement suggested that the levels of inactivation seen are not complement limited. This antiserum-induced reduction in colony formation was first evident in the second week after the injection of virus, coincident with the onset of splenomegaly in the leukemic mice. Thereafter, sensitivity of CFU-S to the antiserlm could be detected up to the terminal point of the leukemia (44 days).