Tumoricidal macrophages isolated from liver granulomas of Schistosoma mansoni-infected mice.

In murine schistosomiasis, inflammatory macrophages (M phi) are a major cell type of the granulomata that encase eggs of the tropical helminth Schistosoma mansoni as they are deposited in the liver by adult worm pairs. The granulomatous response is vigorous during acute infection (8 wk) and spontaneously undergoes immunomodulation during chronic infection (20 wk). Inflammatory M phi isolated from liver granulomas of 8 and 20-wk schistosome-infected CBA/J mice were assessed for their cytolytic potential. Macrophages from vigorous liver granulomas displayed significant cytolytic activity against 3 mammary tumor lines of strain BALB/cfC3H origin, while leaving untransformed embryo fibroblasts relatively unharmed. The cytolytic activity of inflammatory M phi from immunomodulated lesions was markedly less than that of cells from vigorous lesions at equivalent effector to target (E:T) cell ratios. Granuloma cell preparations depleted of the inflammatory macrophage component were marginally cytolytic at the higher E:T cell ratio; supernatant fluids from cultured inflammatory M phi-enriched cell preparations possessed no tumoricidal activity. The cytolytic potential of the vigorous granuloma M phi was lost subsequent to prolonged in vitro culture. We conclude that inflammatory M phi in S. mansoni egg-elicited granulomas are sufficiently activated to lyse allogeneic tumor cells. The degree of activation appears to correlate directly with the intensity of the granulomatous response.