Measurement of rates of phagocytosis . The use of cellular monolayers

A method has been developed for measuring the rate of phagocytosis rather than the quantity of particles ingested per cell when the process is virtually complete. The method, which is simpler and more rapid than those described previously, utilizes cellular monolayers, radioactive particles, and short incubation times. Under the conditions described, the rate of uptake of particles by either guinea-pig peritoneal or human blood leukocytes was proportional to both cell concentration and the time of incubation, and was independent of changes in the concentration of particles during the measurement. The particles were retained by the cells for at least 90 min. The most suitable particles so far used have been (32)P-labeled Salmonella typhimurium, and acetyl-(14)C- or methyl-(14)C-labeled starch particles. The oxidation of (14)C-labeled glucose has been studied under the same conditions that were used for the assays of phagocytosis: the greatest increase in formation of (14)CO(2) from glucose-1-(14)C occurred a few minutes after the most rapid period of phagocytosis