Opsonophagocytosis mediated by human neutrophils using a flow cytometry assay.

<p>(A) Phagocytosis of D39 strain and <i>lytB</i>, <i>lytC</i> and <i>lytB lytC</i> strains incubated in 20% human serum and expressed as percent fluorescent indices relative to the results for the wild-type D39 strain. (B) Example of a flow cytometry histogram for phagocytosis. (C) Restoration of the levels of phagocytosis of <i>lytB</i>, <i>lytC</i> and <i>lytB lytC</i> mutants in the presence of 2 µ]g of the indicated purified CWHs. Open bars represent phagocytosis without addition of proteins. Grey bar shows phagocytosis of wild-type strain in the presence of LytB and LytC proteins. Striped, blackened, and hatched bars indicate, respectively, phagocytosis of <i>lytB</i>, <i>lytC</i>, or <i>lytB lytC</i> mutants in the presence of LytB, LytC, or a mixture of both proteins, respectively. Error bars represent SDs and asterisks represent statistical significance compared to the wild-type strain (two-tailed Student's <i>t</i> test; *, <i>P</i><0.05; **, <i>P</i><0.01; ***, <i>P</i><0.001). <i>P</i><0.0001 for the overall comparison in phagocytosis (one-way ANOVA with a post hoc Dunnett test). For the comparison of the phagocytosis of the different mutant strains compared to the phagocytosis in the presence of exogenous proteins (<i>P</i><0.05 for <i>lytB</i> and <i>P</i><0.01 for <i>lytC</i> or <i>lytB lytC</i> mutants).