Fig. 2: Dietary fibers and SCFAs alter AID and Blimp1 expression, bacteria-bound/binding antibody responses, and gut bacteria composition.

C57BL/6 mice fed a fiber or no-fiber diet were on SCFAs water (SCFAs) or plain water (nil) and administered OVA together with CT (same as in Fig. 1). a, b AID and Blimp1 expression in spleen B cells of these mice, AID expression in spleen B cells of Aicda^-/- mice, and Blimp1 expression in naive B cells of C57BL/6 mice, as analyzed by intracellular staining followed by fluorescence microscopy (a) and flow cytometry (b). c Quantification of AID⁺ and Blimp1⁺ cells in a and b. n = 3 per group. d Bacteria-bound IgM, IgD, IgG1, and IgA in the feces of fiber diet-fed C57BL/6 mice on SCFAs water or plain water, collected 1 week after the last OVA and CT administration, as well as bacteria-bound IgA in the feces of unimmunized Aicda^–/– mice fed fiber diet and plain water, as analyzed by flow cytometry. e Bacteria-bound IgA in feces of fiber and no-fiber diet-fed mice on SCFAs water or plain water as analyzed by flow cytometry. f Concentration of bacteria-binding IgM and IgA in the serum as measured by ELISA; each symbol represents an individual mouse (n = 5 per group, pooled from two experiments). The bars represent the mean ± SD. g Relative abundance of gut bacteria classes (> 1% in any sample group; fiber, no-fiber, and no-fiber + SCFAs) in the mice (n = 4 per group, pooled from two experiments) as determined by high-throughput 16s rRNA gene miSeq sequencing. h Principal component analysis of gut bacterial composition in these three groups of mice on different diets. Data in a, b, d, and e are representative of three independent experiments. *p < 0.05, ***p < 0.001 values, ns: not significant (unpaired t test). Scale bar = 100 μm. The source data are provided in Source Data file.