FIG. 4.

Opsonophagocytosis activity of phoP serum. Fluorescently labeled meningococcal cells (H44/76) were incubated with a range of sera, together with complement and either human PBMLs (a) or HL60 cells differentiated with DMF (b). Serum samples included a human serum from a patient with low levels of opsonophagocytic activity (human low control), a human serum from a convalescent patient with high levels of opsonophagocytic activity (human convalescent serum), serum from mice injected with alum adjuvant alone (murine adjuvant only), and phoP serum. A further control was meningococcal cells incubated with complement alone (complement only). Uptake of meningococci was measured by flow cytometry. The phagocytosis product was determined by multiplying the percentage of fluorescent cells by the mean fluorescence of the gated phagocytes. Bars indicate means of duplicate determinations ± SD.