Uncontrolled microbiota drives the GC but not the MZ and B1-cell phenotypes in AID^−/−µS^−/− mice. FACS analysis of splenic, mLN, and peritoneal cavity B cells from AID^−/−µS^−/− and WT mice maintained in SPF or GF conditions. (A) Total numbers of CD19⁺IgM⁺ B cells per spleen. (B) Absolute numbers of follicular (FO), MZ, and CD21^loCD23^lo in the spleen (left) and B1 in the peritoneal cavity (right) are shown. (C) Representative dot plots showing the percentages of GL7⁺FAS⁺ GC B cells in mLNs. (D) Total numbers of CD19⁺IgM⁺ B cells and GC B cells per mLN (right) and of GC B cells per spleen (left) are shown. Results are representative of 3 independent experiments; each dot represents one animal. Statistical analyses are shown only to compare groups that have the same genotype but were kept in different housing conditions (GF vs SPF); *P ≤ .05; **P ≤ .01; ***P ≤ .005.