FLOW CYTOMETRIC QUANTITATION OF HUMAN OPSONIN-DEPENDENT PHAGOCYTOSIS AND OXIDATIVE BURST RESPONSES TO MENINGOCOCCAL ANTIGENS

A one-step flow cytometric (FCM) assay has been developed to quantify both opsonin- and antigen-dependent phagocytosis and intraphagocyte ox idative burst responses. Meningococcal outer membrane structures (OMV) mere adsorbed to fluorescent polystyrene beads, opsonized with serum, and exposed to leukocytes. FCM parameters of phagocytosis were evalua ted in combinations with oxidative burst indicators. Rhodamine-123 was the most sensitive indicator and was compatible with quantitation of phagocytosis. The phagocytosis and oxidative burst responses induced b y OMV beads were dependent on both antigens and opsonins, Increased hu man opsonic responses against OMV were induced during clinical meningo coccal disease. A dissociation was noted between phagocytosis and oxid ative burst in individual cells, indicating that functional opsonins a gainst OMV components may differ in their ability to stimulate phagocy tosis and oxidative burst responses. The method facilitates evaluation of purified bacterial structures as mediators of opsonin-dependent ph agocytosis and intracellular oxidative microbicidal mechanisms, which is of interest in the complex process of selecting. bacterial antigens as constituents of certain vaccines. (C) 1998 Wiley-Liss, Inc.