FIG. 2.

Mean percent inhibition of adherence (± standard error [error bars]) to Detroit 562 cell monolayers by normal human donor sera (n = 22). Inhibition assays were performed in duplicate with either Pnc serotype 19F or 18C. Symbols indicate the concentration of anti-PsaA IgG in serum. There was a significant increase (P < 0.05, t test) in the percent inhibition observed with sera containing anti-PsaA IgG antibody anti-PsaA IgG antibody at ≥12 μg/ml when compared to the percent inhibition of sera containing anti-PsaA IgG antibody at <5 μg/ml.