IRF7 promotes autoimmunity in the FcγRIIB ^−/− mouse model of SLE. (A–H) B and T cell responses were evaluated in the spleens of FcγRIIB^−/− and FcγRIIB^−/−IRF7^−/− mice at 2, 4, and 6 mo time points. (A) Frequency and number of B220⁺GL-7⁺CD95⁺ GC B cells of total B220⁺ B cells. (B) Representative flow plots showing the gating strategy of GC B cells. (C) Representative images showing IgD⁻GL-7⁺ GC B cells and CD4⁺ Tfh cells within the GC by staining splenic sections with anti-IgD (blue), GL-7 (green), and anti-CD4 (red). Scale bars, 100 μm. (D) Frequency and number of CD4⁺CD44⁺CD62L⁻ Teffs of total CD4⁺ cells. (E and F) (E) Flow cytometry gating strategy and (F) frequency and number of CD4⁺CD44⁺CD62L⁻CXCR5⁺PD-1⁺ Tfh of total CD4⁺ cells. (G and H) (G) Number and (H) flow cytometry gating strategy of CD138⁺TACI⁺ total PCs gated on IgD⁻ cells from lymphocyte gated populations, followed by gating on CD138⁺TACI⁺ total PCs for B220 and CD19 expression to identify B220⁺CD19⁺ plasmablast (PB), B220^-CD19⁺ immature (iPC), and B220⁻CD19⁻ mature (mPC) PCs based on B220 and CD19 expression. (I and J) ELISpot assay quantifying the number of dsDNA-, nucleosome-, and SmRNP-specific (I) splenic and (J) BM AFCs from 4-mo-old mice. (K) Hep-2 immunofluorescent (IF) images showing ANA seropositivity in 4-mo-old mice. Scale bars, 100 μm. (L–N) (L) Nucleosome-, (M) dsDNA-, and (N) SmRNP-specific serum IgG and IgG2c titers. (O) IF images of kidney sections showing C3⁺ (green) and IgG⁺ (red) IC deposition. Scale bars, 100 μm. (P) Flow cytometry plots showing the gating strategy and frequency of CD45⁺ immune cells in the kidney. (Q and R) (Q) Representative images of kidney sections from 6-mo-old mice were stained with periodic acid–Schiff and (R) the pathology score for glomerulonephritis (GN), interstitial nephritis (IN), and vessels. Scale bars, 50 μm. Each symbol (panels A–P and R) represents an individual mouse (n = 7–22 mice per group), and data are presented as means ± SEM. Data in panels A to R represent two to four experiments per time point. P values were calculated via two-way ANOVA with Sidak multiple comparisons test (A–G) or an unpaired Student’s t test (I–R) (*, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001). ns, not significant.