CCR6 is required for bacteria-driven IgA GC B cell formation in the NALT. (A) Quantification by flow cytometry of B cell isotypes in NALTs from SPF or GF mice under homeostasis. IgA⁺, IgG2b⁺, and IgG1⁺ populations were gated from Fas⁺CD38⁻B220⁺ GC B cells. n = 8–10; two independent experiments. Unpaired two-tailed Student’s t test; data represent mean ± SEM; **, P < 0.01. (B) Flow cytometry analysis of GC B cells in NALT from CCR6^+/+ or CCR6^−/− SPF mice. n = 6–10; three independent experiments. Unpaired two-tailed Student’s t test; data represent mean ± SEM; *, P < 0.05. (C) Experimental design of mixed BM chimeras generated with CCR6^+/+ and CCR6^−/− donors. (D–G) Flow cytometry analysis of B cell subsets in NALTs from BM chimeras. CCR6^+/+ and CCR6^−/− B cells were gated from B220⁺ B cells (D); GC (Fas⁺CD38⁻) B cell populations were gated from CCR6^+/+ or CCR6^−/− B220⁺ cells in D (E); IgA⁺ and IgG2b⁺ populations were gated from CCR6^+/+ or CCR6^−/− B220⁺ cells (F), or from CCR6^+/+ or CCR6^−/− GC B cells (G). n = 9; two independent experiments. Paired two-tailed Student’s t test; data represent mean ± SEM; *, P < 0.05.