Radiation and the phagocytic function of the reticuloendothelial system. II. Mechanism of RES stimulation after irradiation.

Treatment of mice with bone marrow or lymph-node cells or with antibiotics partially reversed the stimulating effect of irradiation on the phagocytic activity of the reticuloendothelial system (RES) as measured by the clearance of colloidal carbon from the blood. Irradiation of the rear part of the body, including the whole abdomen, resulted in a faster clearance of carbon, but irradiation of the front part of the body failed to do so. The phagocytic activity was not altered in irradiated germ-free mice, but was markedly enhanced in irradiated conventional and SPF animals. It was concluded that irradiation facilitates bacterial invasion which causes the stimulation of the RES.