Phagocytosis of Bacteria by Human Leukocytes Measured by Flow Cytometry

Abstract

A new method was developed for the evaluation of the phagocytic activity of human leukoytes using fluorescently labeled bacteria and flow cytometry. By simultaneous measurement of cellular light scatter and fluorescence, extracellular bacteria, phagocytes and nonphagocytes could be discriminated and quantified. All leukocytes assumed to be capable of phagocytosis were phagocytosing; .apprx. 90% of these cells were polymorphonuclear neutrophilic granulocytes. Within 15 min, 85% of the bacteria were phagocytosed and each phagocyte contained an average of 15-20 bacteria. The phagocytic activity of the leukocytes from healthy individuals showed minor interindividual and day-to-day variations. This method facilitates a rapid and accurate in vitro evaluation of the phagocytic activity of human leukocytes.