Radioprotective Effect of Rauscher Leukemia Virus in the SJL/J Mouse: III. Relationship of Hematologic Factors and Splenomegaly to the Development of Radioresistance

A study of splenomegaly and of changes in numbers of nucleated cell types circulating in the blood of Rauscher leukemia virus (RLV)-infected mice has been performed and related to the recently reported pattern of development of radioresistance in these animals. Splenomegaly was first apparent as a 2-fold increase in spleen weight 10 days after RLV infection, with spleen weights increasing rapidly thereafter. The total number of circulating lymphocytes or granulocytes did not change until 18 days after infection, after which time there was a marked rise in the number of cells in both populations reaching maximum numbers that were 5-fold normal. Increased numbers of circulating nucleated erythroid cells and "smudge" cells were seen by the 14th day of infection. "Smudge" cell numbers increased by 100-fold over the next 2 weeks and nucleated erythroid cell numbers increased by 1000-fold during the same period. Thus, the Rauscher disease-induced changes in the mature blood cell population do not appear to be responsible for the early (10 day) appearance of radioresistance after RLV infection but may contribute to the maintenance of radioresistance at later times. In contrast, development of splenomegaly correlates well with the initial appearance of radioresistance, and increasing spleen size thereafter appears to be related to increasing radioresistance as the infection progresses.