Intestinal IgA antibodies bind diverse groups of gut bacteria. (A) Representative illustration of antibody-positive (mAb pos bac) and antibody-negative bacteria (mAb neg bac) obtained by cell sorting. The diversity and composition of sorted bacteria were characterized by 16S rRNA amplicon sequencing. (B) α-Diversity parameters (richness and Shannon effective count) for sorted antibody-positive (pos) and -negative (neg) bacteria. Two separate experiments, #1 and #2, were performed. Groups were compared by one-way ANOVA and paired Wilcoxon test (*, P < 0.05; ns, not significant). (C) Correlation analysis considering the Shannon effective count as displayed in B and bacteria binding in percent. Symbols represent the mean of two independent experiments. (D) β-Diversity displayed as PCoA of generalized Unifrac distances. The plots depict comparison between antibody-positive samples from HDs and CD patients (left plot) and between antibody-positive and -negative samples from HDs (middle) and CD patients (right). FSC, forward scatter; SSC, side scatter.