A20-deficiency impairs B1 cell generation but enhances GC formation in the GALT. (A) Titers of immunoglobulin isotypes were determined by ELISA; n = 6 to 12 per genotype. (B) Absolute cell numbers of B-cell subsets in the peritoneal cavity: B2 (CD19⁺B220⁺), B1 (CD19^highB220^low), B1a (CD19^highB220^lowCD5⁺), and B1b (CD19^highB220^lowCD5⁻) cell numbers were calculated from 5 to 7 age-matched mice per genotype. Data are mean ± SD. (C) Left panel: Proportions of GC (CD19⁺PNA^hiFas^hiCD38^lo) of total B cells in Peyer patches. Data are mean ± SD of 8 mice per genotype. Right panel: Proportions of GC B cells depicted as individual data points (left chart), absolute cell numbers for naive B cells (mantle zone B cells: CD19⁺PNA⁻ Fas⁻CD38^hi; middle chart), and GC B cells (right chart). Bars represent medians of 8 mice per group (same as in the left panel). *P < .05 (1-way analysis of variance). **P < .001 (1-way analysis of variance).