Serum autoantibodies and mechanisms of altered B-cell tolerance in Rag1-mutant mice. (A) Anti-PC IgM measured by enzyme-linked immunosorbent assay (ELISA). (B) Peritoneal lavage was analyzed by flow cytometry for B1 (CD19⁺CD11b⁺) and B2 (CD19⁺CD11b⁻) cells and B1a (CD19⁺CD11b⁺CD5⁺) and B1b (CD19⁺CD11b⁺CD5⁻) cells. (C) Heat map of serum IgM binding to a protein autoantigen microarray (n = 7-8 mice per strain), normalized to WT reactivity. (D) Percentage of IgM⁺ B cells in spleen expressing Igλ (n = 4-7 per group). (E) BAFF serum concentrations measured by ELISA (n = 4 per group). (F) Age-associated B cells (ABCs) (Tbet⁺CD11c⁺) as percentage of CD19⁺ cells in spleen (n = 7-8 per group). Error bars represent standard error of the mean. One-way analysis of variance (A-B,D-E) and Mann-Whitney U test (F): *P ≤ .05, **P ≤ .01, ***P ≤ .001, ****P ≤ .0001.