(A–E) GF and ASF mice were colonized with SFB by oral gavage of fecal pellets collected from SFB mono-associated mice. Colonization was confirmed by PCR with recipients’ fecal pellets. Intragastric CT immunization was given 2 weeks after colonization on days 0, 7, and 14. Mice were sacrificed on day 28, when intestinal LPLs were isolated and sera as well as fecal samples were collected. (A) Combined data of IL-17A expression in CD4+ LPLs in GF and ASF mice (n=4 per group; two-way ANOVA), respectively, while absolute numbers of CD4+IL-17A+ cells in the LPLs are shown in (B). (C) Isolated LPLs were cultured with indicated peptides and naïve APCs for 5 days, and IL-17A production in the culture supernatants was measured with multi-plex assay (n=4 per group; Two-way ANOVA). (D) Total IgA level in the feces and sera, (E) CTB- and OVA- specific fecal IgA and serum IgG levels were measured with ELISA (n=5 per group; Student t test and one-way ANOVA).