Abstract
Previous studies have shown that a macrophage-derived cytotoxin, found in high titre in the serum of BCG-primed rabbits, killed malarial parasites and certain tumour cells. In this study, the macrophage cytotoxin was tested for activity against microorganisms other than protozoa. No activity was seen against a range of gram-negative or gram-positive bacteria or against Candida albicans. It is concluded that the macrophage cytotoxin has limited anti-microbial activity, perhaps restricted to certain intra-cellular parasites.