Natural macrophage cytotoxicity against Trichomonas vaginalis is mediated by soluble lytic factors

A cytochemical study of the interaction between Tritrichomonas foetus and mouse macrophages

Light and electron microscopy were used to analyse the process of interaction of normal and antibody-coated Tritrichomonas foetus with resident and activated mouse peritoneal macrophages. Activated macrophages ingest more parasites than do resident macrophages. Previous incubation of the parasites in the presence of sub-agglutinating concentrations of a polyclonal anti-T. foetus antibody significantly increased their ingestion by the macrophages. Adherence of the parasites to the surface of activated macrophages triggers the respiratory oxidative burst as revealed by reduction of nitroblue tetrazolium. This process was more evident in antibody-coated parasites. Transmission electron microscopy showed the presence of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-oxidase in the portions of the macrophage plasma membrane that were in contact with the parasites as well as in the phagocytic vacuoles. Fusion of macrophage lysosomes with parasite-containing phagocytic vacuoles was observed in macrophages labeled with Lucifer yellow and gold-labeled peroxidase as well as by localisation of acid phosphatase.

Cytotoxic activity of stimulated mouse macrophages exposed to various inhibitors

Mouse peritoneal macrophages were cultured for 3 days with or without zymosan and at the same time exposed to various inhibitors of cellular metabolism. The cells were assayed for selective release of a lysosomal enzyme, and for cytotoxic activity against a tumor cell line, L-929-cells. Selective release of beta-glucuronidase was demonstrated in the supernatants from zymosan-stimulated macrophages. The stimulated macrophages were cytotoxic for the tumors cells, evaluated by measuring release of radioactivity during subsequent 4 days' co-culture of macrophages and 14C-thymidine-labelled tumor cells, and by counting cells per culture. Colchicine caused a slight, variable reduction in enzyme release and no change in cytotoxic effect from stimulated macrophages. Monensin decreased extracellular enzyme secretion and reduced the cytotoxicity in stimulated macrophages to control levels. Chloroquine caused a similar reduction in lysosomal enzyme release and cytotoxic activity in zymosan-stimulated cells. This inhibitor increased the enzyme release from control cells and induced a small, variable cytotoxic effect from these cells. The data indicate co-variation between macrophage-mediated cytotoxicity and a secretory process which can be blocked by monensin. The need for intact lysosomal function was also demonstrated.