Immunotoxicology studies on lead: Effects of exposure on tumor growth and cell-mediated tumor immunity after syngeneic or allogeneic stimulation

Abstract Chronic exposure of C57Bl/6 mice to lead acetate in the drinking water enhanced the growth of primary Moloney sarcoma virus (MSV)-induced tumors. Regression of MSV-induced tumors was not prevented by lead exposure and lead-treated animals were more resistant to late sarcoma development following primary tumor regression. The primary cell-mediated cytotoxic response in the spleen or lymph nodes of MSV-tumor bearing mice was significantly augmented by lead exposure. This augmentation appeared to reflect the increased antigenic stimulation resulting from the enhanced primary tumor growth in lead-exposed animals. Using an allogeneic tumor model, under conditions of similar antigenic stimulation, little effect of lead on T cell-mediated cytotoxicity was observed. On the other hand, macrophage phagocytic activity was significantly depressed in lead-exposed mice. Coupled with a decrease in the total number of macrophages recovered from lead-exposed mice, the results suggested significant impairment of macrophage function by lead. The influence of lead-induced macrophage dysfunction on tumor growth is discussed.