[Studies of comparison with fluorescent bioparticles and microspheres for phagocytosis by flow cytometric assay in...

We have determined the conditions for quantitative phagocytosis assay in human polymorphonuclear leukocytes by flow cytometry using fluorescent bioparticles (Zymosan A, S. aureus, E. coli). The changes in the phagocytic index after an exogenous stimulation and after addition of monoclonal antibodies against receptor antigens on polymorphonuclear leukocytes were examined by using fluorescent microspheres (FM particles) and bioparticles. When bioparticles were used, the phagocytic index decreased after an exogenous stimulation with phorbol myristate acetate (PMA). The phagocytic index obtained with the FM particles increased by the addition of PMA and the supernatant of E. coli, but decreased by the addition of the supernatant of S. aureus. After the addition of the monoclonal antibodies the phagocytosis for the S. aureus and E. coli particles was blocked by anti-CR3, that for the Zymosan A particles was blocked by anti-CR3 and IgGFcR2, and that for the PM particles was blocked by anti-CR1, CR3, and LFA-1 beta, partially. These findings implied the involvement of a complement receptor. However, the degree of its involvement varied with the target particle.