Effect of pH on IgG1-mediated phagocytosis. (A) The V-ATPase inhibitor chloroquine and the weak base NH₄Cl inhibit phagocytosis but have no effect on association of IgG1-osonized pneumococci to PMNs. (B) Phagocytosis is increased in medium of pH 6.0 but has no effect on association of IgG1-opsonized pneumococci. ^**P < .01 when compared with WT by ANOVA. Data represent means plus standard deviations and are representative of at least 3 individual experiments.