Spontaneous Hematopoietic Recovery of Friend Virus-Infected Mice After Heavy X Irradiation

Abstract

Endogenous hematopoietic recovery, after exposure to 950 R of whole-body X radiation, was obtained in Swiss mice made splenomegalic (800–2000 mg) by inoculation of anemia-producing Friend virus (FVA) 15 days prior to irradiation. Mice infected 6 days before, whose spleen weight did not exceed 300 mg, showed no hematopoietic recovery and died within the same interval as their controls. This finding seems to indicate that the stem-cell pool still available after exposure to 950 R was considerably increased in splenomegalic, FVA-infected mice. Clusters of precursors of granulocytes, platelets, and sometimes erythrocytes were observed in spleen sections as early as 3 days after irradiation. No strict correlation was found between presence of surface spleen nodules and survival, which did not exceed 40%. Unrestrained proliferation of reticulum cells was resumed the 2d week after irradiation. Survivors demonstrated an increased lifespan as compared with un irradiated mice that had been virus-inoculated at the same time.