B cell–intrinsic and –extrinsic roles of IRF7 in breaking tolerance and autoimmune PC and GC responses. (A) Gating strategy of B220⁺CD19⁺GL-7⁻CD95⁻ non-GC B cells (non-GCB), B220⁺CD19⁺GL-7⁻CD95⁺ pre-GC B cells (pre-GCB), and B220⁺CD19⁺GL-7⁺CD95⁺ GC B cells (GCB). (B) IRF7 expression in geometric mean fluorescent intensity (gMFI) in non-GCB, pre-GCB, and GCB cells in B6 and FcγRIIB^−/− mice. (C and D) Our analysis of published RNAseq data of healthy control (HC) and SLE patients showing IRF7 RNA expression in total (C) and various subsets of B cells (D), such as transitional 3 (T3), resting naïve (rN), activated naïve (aN), double negative (DN2) B cells, switched memory (SM), and plasmablast/PCs (ASCs). (E)IRF7 expression was measured in B cells from healthy PBMCs following activation for 24 h with a TLR7 agonist. (F) Schematic of B cell–specific mixed BM chimeric mice generation. (G–I) (G) Immunofluorescent staining of Hep-2 slides for serum ANA seropositivity (Scale bars, 100 μm) and (H and I) serum anti-dsDNA and anti-SmRNP antibody titers in μMT recipient mice with FcγRIIB^−/− B cells sufficient and deficient IRF7. RNA expression in HC and SLE patient B cells. (J–L) Spleen weight and frequencies of B220⁺ total and FO B cells, GC B cells, splenic plasma, and bone PCs of B220⁺ total B cells. (M) Flow cytometry analysis of frequencies of CD4⁺ total T cells, CD4⁺ Teffs, and Tfh cells of total CD4⁺ T cells. (N) Flow cytometry analysis of frequencies of splenic myeloid cells in these mice. Each symbol represents an individual mouse (n = 9–10 mice per group), and data are presented as means ± SEM. Data in each panel represent two independent experiments. P values were calculated via two-way ANOVA with Dunn–Sidak correction (B) or an unpaired Student’s t test (C–E and G–N) (NS, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001).