7-6IgA binds LPS on metabolically active bacteria. (A and B) Representative flow cytometry of cultured B. theta incubated with 7-6IgA and stained with anti-IgA (A) and quantification of the percent of metabolically active bacteria with high nucleic acid content (SybrGreenhi) of the indicated cultured Bacteroidales within both the 7-6IgA–/+ populations (B). Data are cumulative from four independent experiments per group. (C) Representative flow cytometry plots showing 7-6IgA binding to cultured B. theta treated with 70% ethanol (upper panels) or heat killed (70°C, 30 min; lower panels). Numbers in plots represent the mean frequency of gated cells, ±SEM of the gated fraction pooled from four independent experiments. (D) ELISA OD measurements of the capacity of the indicated monoclonal IgA clones to bind B. theta–derived LPS. Representative plot showing the mean of triplicate measurements from two similar experiments. The total amounts of carbohydrate indicated under each purified IgA clone was measured by total carbohydrate colorimetric assay. Statistical analyses were performed with unpaired Student’s t test (B) and with two-way ANOVA with Tukey’s multiple comparison test (D). **P < 0.01 and ****P < 0.0001. Error bars represent SEM.
