A sensitive and reproducible assay for the quantitation of erythrophagocytosis and its correlation with reduction in tritiated thymidine uptake in a tumor target cell system modified by immunoenhancing or immunosuppressive agents.

A new and sensitive assay procedure for studying erythrophagocytosis is described. The assay technique permits quantitation of the in vivo and in vitro effects of chemicals, hormones, and cell, or microbrial products, on the level of phagocytic activation of glass-adherent cells. The effect of intraperitoneal injection of BCG, Zymosan, Vitamin A, B. pertussis, cortisone, estrone, and thioglycollate on phagocytic activation of peritoneal exudate cells harvested from two days up to 28 days following drug injection was examined by this assay. Erythrophagocytosis was compared to the effect of "activated" spleen cells on tritiated thymidine uptake of a tumor target cell suspension.