A NEW METHOD FOR STUDYING THE BINDING AND INGESTION OF ZYMOSAN PARTICLES BY MACROPHAGES

One of the major problems encountered during quantitative studies of p hagocytosis is the discrimination without ambiguity between intracellu lar and extracellular particles. This difficulty is especially acute w hen zymosan particles are used because of their poor affinity for dyes . We show in this paper that zymosan particles may be stained by a mix ture of a basic dye and tannic acid in water (or in an isotonic non sa line solution). Crystal violet is one of the most suitable dyes and by combining this staining step with May-Grunwald Giemsa staining, it wa s possible to observe two populations of macrophage-associated particl es. One comprises blue violet particles (BVP), and the second consists of particles with a purple-stained core (PPC). Treating macrophages i n culture with various concentrations of cytochalasin B decreases the number of PPC and increases the number of BVP, in a dose dependant man ner. Moreover, treatment with alpha-mannan or laminarin decreases the number of cell-associated particles, especially that of PPC. From thes e observations we concludes that BVP are extracellularly located and P PC are ingested.