Age, Strain and Species Factors in Post-Irradiation Protection by Spleen Homogenates

Abstract

The phenomenon of post-irradiation protection against mortality by spleen homogenates is modified by age, strain and species factors. A single intraperitoneal injn. of as little as 28 mg. of spleen-tissue homogenate from 1 week old LAf1 mice protected adult mice against otherwise lethal, whole body X-ray exposure; at least 100 mg. of adult spleen-tissue homogenate was required for comparable protection. A converse age-effect was observed in recipient irradiated mice: aliquots from the same spleen homogenate prepn. which gave protection against radiation mortality when administered to adult mice (10-11 weeks old) exposed to 750 r, failed to protect irradiated 5 week old mice. Spleen homogenate was effective in decreasing mortality in irradiated splenectomized mice; in intact irradiated mice it induced a marked spleen hypertrophy. Homogenates of spleens from LAf2 mice afforded little or no protection when injd. into irradiated LAf1 mice. A small but consistent degree of protection was observed in whole body irradiated Sprague-Dawley rats (700 r) receiving rat spleen homogenate injn. It is suggested that radiation injury to rat intestine may be a limiting factor which masks the hemopoietic recovery effect of spleen homogenate in this sp.