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.