FIG. 3.
Effect of rabbit anti-FBP54 serum on opsonization and killing of S. pyogenes. (A) Heparinized whole blood (80 μl) was mixed with bacteria (10 μl, ∼5 × 106 CFU) and with rabbit anti-FBP54 serum (20 μl) or nonimmunized serum and incubated for 5 to 10 min at 37°C. The sample fixed on a glass slide was stained with Giemsa stain, and the percentage of phagocytosed leukocytes was determined by counting 100 cells per slide under a microscope. (B) Heparinized whole blood (80 μl) was mixed with bacteria (10 μl, ∼30 CFU) and with rabbit anti-FBP54 serum (20 μl) or nonimmunized serum and then gently shaken for 3 h at 37°C. The mixture was serially diluted and plated on THY agar. Following incubation, the number of CFU was determined. Data are expressed as the mean ± the SEM of four independent determinations with a total of three wells.