FIGURE 5.

The anti‐αGal antibody contains antibody subsets of distinct polyreactivity. Flow cytometry analyses of anti‐αGal reactivity with target cells in the presence of soluble polysaccharides. (A) Heatmap showing results for various cells. Anti‐αGal was added at 5 mg/L and polysaccharides at 125 mg/L. Target cells were ten different serotypes of pneumococci, C‐mutant, EcO86 and pig erythrocytes (carries surface terminal Galα3Gal). The level of inhibition was determined as the mean of two separate experiments. The left downward diagonal of red squares shows that the homologous polysaccharide inhibited reactivity better than the heterologous polysaccharides. (B) Reactivity of anti‐αGal with each of three encapsulated pneumococcal strains in the presence of increasing concentration of either CW polysaccharide or homologous capsular polysaccharide. Anti‐αGal was added at 2·0 mg/L (serotypes 9V and 12F) or 10 mg/L (serotype 15B). Mean and standard deviation of two separate experiments. Centre (serotype 12F): vertical arrows indicate half‐maximal inhibitory concentration of each polysaccharide. The panel shows that CW polysaccharide was a more potent inhibitor than the homologous capsular polysaccharide for this serotype 12F strain. Also, neither substance alone caused complete inhibition. Bottom (serotype 15B): CW polysaccharide inhibited at most half of the reactivity, indicating that only a subset of the anti‐αGal antibodies that reacted with this strain possessed specificity for CW polysaccharide. (C) Residual reactivity of anti‐αGal at 2·0 mg/L with the strain of serotype 12F in the presence of soluble polysaccharides, each added at 125 mg/L. Mean with 95% confidence intervals of three separate experiments. (D) As in the previous panel, but with the strain of serotype 15B as target cells and anti‐αGal at 10 mg/L