Characteristics of the phagocytic process assessed by Coulter Counter

The phagocytosis in suspensions of heat-killed yeast cells, Saccharomyces cerevisiae, by human polymorphonuclear leucocytes was studied in vitro by means of an electronic particle counter, the Coulter Counter, and a 100-channel pulse-height analyzer, the Channelyzer. The two cell populations were separated from each other electronically by the Channelyzer. Phagocytosis was recorded as disappearence of yeast cells. Concomitantly, aggregation and swelling of the PMN-cells were observed, which increased with the concentration of the prey. The process could be inhibited by cytochalasin B and iodoacetamide. With the latter inhibitor, the analysis of the kinetics showed that ingestion, but not adhesion, was affected. The ingestion of yeast cells was augmented on increase of the initial ratio between the number of yeast and PMN cells to around 5:1, but was then reduced on further increase. A ratio of 2:1 and a reaction time of 30 min seemed suitable for studying the phagocytic process. First-order kinetics were obeyed under these circumstances.