Tcf4 haplodeficiency ameliorates immune activation in B6.Sle1.Sle3 mice. 30-wk-old B6.Sle1.Sle3 mice (Sle) or their Tcf4 haplodeficient littermates (Sle/het) were analyzed along with WT controls. (A) Splenic weights were determined in individual indicated animals. (B) Peripheral blood cells from the indicated mice were analyzed by flow cytometry, gated on CD4⁺ T cells, and the frequencies of activated CD44⁺ CD45RB⁻ cells among CD4⁺ T cells were determined. Data were pooled from 3 independent experiments. (C) Sca-1 expression on gated B and T cells (left) and mean fluorescent intensities (MFIs) of Sca-1 on these cells from individual mice was determined by flow cytometry. Data were pooled from 3 independent experiments (right). (D and E) Levels of total IgM, IgG, and IgG subclasses (mean ± SD; D), anti-dsDNA, and anti-RNA IgG (E) in the sera of indicated experimental groups were measured by ELISA. Data were pooled from 2 independent experiments. (F) Fixed Hep2 cells were incubated with sera from Sle mice, stained for IgG (red) alone or with DNA (blue), and analyzed by fluorescence microscopy (bars, 20 µm). Images are representative of 2 independent staining experiments. (G) Kidney cryosections were stained for IgG (red) and DNA (blue) and analyzed by florescence microscopy (bars, 100 µm). Arrows show kidney glomeruli. Images are representative of 9 animals in each group from 3 independent experiments. Horizontal bars indicate mean. *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001.