FIG. 2.

Effect of purified rabbit IgG and different preparations of human sIgAs on the adherence of group A streptococci to pharyngeal cells. The M+ strain (10⁶ CFU) was incubated with purified rabbit IgG, purified sIgA, purified sIgA preabsorbed with M protein, or purified M protein-specific sIgA. All were at the final ELISA titer/well shown. Untreated M+ and M− strains were used as controls. Infected monolayers were incubated for 3 h, dispersed by addition of 0.25% trypsin–1 mM EDTA, and lysed with H₂O. Error bars, SD; ∗, P < 0.05 compared to controls.