New method for estimating digestion of Paracoccidioides brasiliensis by phagocytic cells in vitro

We describe a method by which phagocytosis and digestion of Paracoccidioides brasiliensis yeast cells by polymorphonuclear leukocytes or other phagocytic cells may be estimated. Suspensions of P. brasiliensis in its yeastlike phase were sonicated, counted, and incubated with known numbers of peripheral blood polymorphonuclear leukocytes. At given intervals, cytocentrifuge droplets were stained by a variation of Papanicolaou's method. Stained preparations were examined with phase-contrast optics. Digested organisms showed total or partial disappearance of protoplasm. Green-stained cell walls resisted digestion. The proportion of digested cells as a function of time was estimated.