An ultrastructural examination of the interaction between macrophages andCryptococcus neoformans

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Abstract
The interaction of [guinea pig] mononuclear phagocytes with C. neoformans was examined in vitro and in vivo using ultrastructural techniques. Immune serum roughens the surface of the yeast and in the 1st 2 h, increases the number of organisms attaching to the macrophage surface, and the number of contacts between individual yeasts and the phagocyte. Contact is established by means of thin filopodia and cytoplasmic flaps. During the next few days the macrophages increase in size, and, by intimate apposition of their contiguous cell surfaces, a cellular barrier surrounds the now enclosed yeast. These events are accompanied by thinning of fungal capsule, degradation of the enclosed cryptococcus and the formation of macrophage polykaryons. Electron cytochemical techniques for peroxidase reveal that these multinucleated cells are formed predominantly by the fusion of stimulated macrophages. Destruction of the enclosed yeast probably results from the secretion of various agents by the surrounding cells.