A rapid, inexpensive and easily quantified assay for phagocytosis and microbicidal activity of macrophages and neutrophils

Abstract

The objective of the present study was to develop a technique to quantitate the phagocytic and intracellular microbicidal activity in different populations of phagocytes, i.e. neutrophils and macrophages. Elicited peritoneal neutrophils and macrophages as well as alveolar macrophages and adherent splenic macrophages were used as representative cell types. The method to assess intracellular killing was based upon dye uptake and concentration by a dead micro-organism; methylene blue was used as the indicator dye and the test organism was Saccharomyces cerevisiae. Phagocytosis was measured by counting, microscopically, the number of ingested yeast (Saccharomyces cerevisiae) within the neutrophils or macrophages. A number of killed yeast, i.e., those which took up the dye, were readily visualized. The temporal pattern of phagocytosis and killing was determined concurrently. Splenic macrophages demonstrated the slowest phagocytic activity whereas neutrophils and alveolar macrophages manifested a similar phagocytic activity. Peritoneal macrophages exhibited a continuous increase in activity throughout the test period. Microbicidal activity was similar for all 4 cells types. The new technique for measuring phagocytosis and killing provides a rapid, inexpensive and easily quantified assay for assessing discrete phagocytic cell functions.