Dose-dependent macrophage stimulation by Corynebacterium parvum.

Corynebacterium parvum (C. parvum) administered at a dose of either 0.1, 1 or 10 mg/kg intraperitoneally (ip) to BDF1 mice was evaluated for its influence on peritoneal exudate cell differentials, numbers, respiration, phagocytic activity and capacity and intracellular microbicidal activity. The ip administration of 1 mg/kg of C. parvum resulted in a 2-3 fold increase in the yield of peritoneal exudate cells 1-5 days after injection; 0.1 mg/kg was ineffective, while 10 mg/kg of C. parvum manifested an increased cell yield on days 1 and 5 following injection. No alterations in cell differentials were noted at any dose level. A trend toward a dose-related alteration in the respiratory burst, phagocytic activity and capacity was demonstrated. The most dramatic alteration observed was a profound increase in intracellular microbicidal activity in macrophages obtained from mice administered 1 mg/kg of C. parvum. The higher dose of C. parvum was suppressive. It was concluded that a relationship between macrophage microbicidal activity and tumor cell killing exists because the 1 mg/kg, which elicited maximal macrophage microbicidal activity, also induced the greatest increase in protection against two unrelated tumor models as previously reported.