FIG 7 .

EVs bind complement proteins in human serum, thereby impairing the phagocytic activity of host cells. (A) Adhesion and phagocytosis assay of THP-1 cells incubated with pneumococcal strain T4 pretreated with human serum only (-EVs) or with human serum and EVs (+ EVs) for 30 min at 37°C. (B) Opsonophagocytosis killing assay of differentiated HL-60 cells incubated with strain T4 pretreated with human serum or heat-inactivated human serum, alone or in combination with EVs. Data are represented as means ± SEM of results from three independent experiments. *, P < 0.05; **, P < 0.01.