Changes in Reticuloendothelial Phagocytosis in Mice With Spontaneous Tumors2

Abstract

Reticuloendothelial (RE) phagocytosis was investigated in mice with spontaneous mammary carcinomas of strains C3H/S, DBA/S, BALB/cf/S, and A/Sn/S, and mice with lymphomas of strains AKR/S and SJL. Tumor-bearing mice and their tumor-free litter mates were tested simultaneously. Twenty-four hours after intraperitoneal injection of ⁵¹Cr-labeled sheep red cells, the mice were killed and the radioactivity in liver and spleen was determined, which permitted calculation of phagocytic uptake (percentage of injected radioactivity) in these organs. When data obtained for animals grouped according to strain, sex, and presence or absence of tumors were compared, mice with spontaneous tumors were found to have significantly lower splenic uptakes than did comparable tumor-free animals. Hepatic uptake was less regularly decreased in the presence of tumor. Lower levels of splenic and hepatic phagocytosis than in tumor-free mice were also observed in C3H/S and BALB/cf/S mice with spontaneous mammary carcinomas, when tested by means of radioassay of liver and spleen 2 hours after intravenous injection of suspensions of chromic radio-phosphate. The rate of blood clearance of the radioisotope was slower in tumor-bearing than in tumor-free mice. Evaluation of these findings included discussion of their relationship to previously reported changes in RE phagocytosis in mice and rats with transplanted tumors. Depression of splenic phagocytosis was common to all experimental models studied, whereas hepatic phagocytosis was affected variably. Reference was made to results of other recent studies of RE functions in experimental cancer. A working hypothesis was proposed concerning the interrelation between RE functions and development and progression of cancer.