Fig. 3.

Opsonization enhances uptake but not killing of S. aureus by human PMNs in suspension. a Percentage of PMNs associated with strain LAC was determined by light microscopy as described in the Methods. Phagocytosis (b-d) and bactericidal activity (e) of adherent PMNs (Adh.) or those in suspension (Susp.) were determined for opsonized (Ops.) and unopsonized S. aureus (Unop.). f CD63-enriched S. aureus phagosomes were assessed using fluorescence microscopy. Assays were performed using a CFU:PMN ratio of 1:1. Data represent the mean of 5 or 10 independent experiments ± SEM as indicated. * p < 0.05 for phagocytosis using adherent PMNs vs. those in suspension using either opsonized or unopsonized bacteria. ** p < 0.05 for phagocytosis assays containing opsonized bacteria vs. unopsonized bacteria using either adherent PMNs or those in suspension.