Flow cytometry staining of IgA₁ and IgA₂ on (A) intestinal PCs from a representative HD and patient CD068 and (B) memory B (B_mem) cells in colon and circulation from CD068. (C) Frequency of intestinal PCs from HDs (n = 19), patients with IBD (n = 15), and CD068. Each point represents a sample. Mean ± SD, and interval estimate are shown. (D) Immunofluorescence staining of IgA₁ and IgA₂ from a representative HD and CD068. Scale bar: 80 μm. (E) Secreted IgA₂ levels in the serum and ileal tissue culture supernatant of HDs and CD068. (F) Plasma IgA₂ in HDs (n = 18), patients with CD (n = 15), and CD068. (G) Total serum immunoglobulins from HDs (gray) and CD068. (H) Representative flow cytometry plots and quantification of IgA⁺ and IgA₂⁺ microbiota in HDs (n = 3), patients with CD (n = 4), and CD068. (I) Metagenomic sequencing analysis from fecal samples, including α diversity and relative abundance (HD, n = 10; CD, n = 7). (J) Circulating zonulin and ASCA IgG and IgA in HDs (n = 367), patients with CD (n = 806), and CD068. All comparisons were done with Mann-Whitney test, except in C, where Kruskal-Wallis test and Dunn’s test was used. P values are shown.