Reduced numbers of steady-state IgG1- and IgG2c-producing AFCs and total serum IgG1 and IgG2c titers in the absence of IRF7. (A and B) (A) Numbers of splenic and (B) BM AFCs were enumerated by ELISpot assay. (C) Total serum titers of IgG and IgG subclasses (IgG1, IgG2c, and IgG3) in 4-mo-old FcγRIIB^−/− and FcγRIIB^−/−IRF7^−/− mice. Each symbol represents an individual mouse, and data are presented as means ± SEM. P values were calculated via an unpaired Student’s t test or Mann–Whitney test (ns, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001).