Opsonophagocytic effector function activities of human MAb SS269 and murine MAbs 207,B-4, 208,D-5, and MN14C11.6. Phagocytic activity was tested against log-phase-growth strain 44/76-SL bacteria by using human serum as a complement source, human PMNs as effector cells, and increasing concentrations of each MAb as the opsonin. The test was performed by using flow cytometry to measure the respiratory burst induced in the effector cells following phagocytosis of the test strain.