Studies With Transplantable AK4 Mouse Leukemia. III. Effect of Spleen and Marrow Shielding on AK4 Leukemic Implants in Homologous Strains of Irradiated Mice

Alterations in the susceptibility of homologous strains of X-irradiated mice to AK4 leukemic implants by spleen and femur shielding at the time of whole-body irradiation was determined in the A/St and C57BL strains of mice. The protective effect of spleen or femur shielding in irradiated animals that did not receive leukemia was also evaluated in these strains. The results of the experiments with irradiated animals that did not receive leukemia indicated that, although a protective effect was produced by either spleen or femur shielding in both strains, there were no significant quantitative differences afforded by the tissue shielded in either strain. Resistance to transplantable leukemia was partially protected by femur shielding in the irradiated A/St and C57BL mice and by spleen shielding in the irradiated A/St mice. However, in the irradiated C57BL animals that received leukemia, there was no significant difference between the spleen-shielded and nonshielded groups. The differences in the spleen-shielding results between the A/St and C57BL mice tend to indicate that greater protection was associated with myelopoietic tissue than with lymphoid tissue.