Effect of radiation on normal hematopoiesis and on viral induced cancers of the hematopoietic system. Three-year technical progress report, August 1, 1973--April 30, 1976

In studies conducted during the first three-year segment of this contract, it was observed that in the process of viral leukemogenesis the affected animals became more radioresistant than normal. Initial studies into the reason for the enhanced radioresistance implicated an increase in the number of pluripotent stem cells as one possible cause. During the current period, studies were carried out to further define the effect of the virus on stem cells and their kinetics using exposure to tritiated thymidine (3HTdR) in vivo and in vitro. In addition, separate studies were initiated in an attempt to determine if the immune system played a part in the radioresistance, as well as what the effects might be of immune manipulations on the disease during the oncogenic period. Finally, studies were also undertaken to assess the sensitivity of the virus itself to radiation in vitro and in vivo to radiation and treatment with cells transplanted from viral resistant mice