Regnase-1 controls immunopathology after B cell differentiation. (A) Representative immunofluorescence images of spleens from 44-wk-old mice of indicated genotypes, Regnase-1^f/f Cγ1^Cre/+ mice with less severe disease (middle), Regnase-1^f/f Cγ1^Cre/+ mice with more severe disease (right). Cryosections stained for follicular B cells (IgD in blue), GC B cells (PNA in green), and T cells (CD3e in red). Scale bars = 100 µM (n = 2 or 3 mice; two independent experiments). (B) H&E staining of livers collected from 44-wk-old mice of indicated genotypes. Scale bars = 100 µM (n = 3 mice; two independent experiments). (C) Representative flow cytometry plots (left) and plotted frequencies (right) from spleens of mice of indicated genotypes analyzed at 44 wk of age, splenic lymphocytes probed for CD138⁺B220⁻ B cells (top), and for IgG1⁺B220⁻ B cells. Each circle represents an animal, solid circles = Regnase-1^+/+ Cγ1^Cre/+, clear circles = Regnase-1^f/f Cγ1^Cre/+. (D) Mean and standard deviation of relative titers of total IgM and IgG in the sera collected at the indicated time points from mice of indicated genotype (n = 5 or 6), measured by sandwich ELISA. (C and D) n = 4–6 mice; two independent experiments. Horizontal lines in the graphs indicate means with SD shown by error bars. Statistical significance calculated by unpaired Student’s t test (*, P < 0.05; **, P < 0.01).