E2/ERα signaling acts in a cell-autonomous manner to increase expression of IRF4. (A-D) WT or ERα^−/− BM cells were incubated with GM-CSF in standard medium for 7 days. (A) The percentage of CD11c⁺ CD11b⁺ DCs was determined. (B) WT CD11c⁺ cells harbor both CD11b^hi Ly6C⁺ and CD11b^int Ly6C⁻ subsets, whereas ERα^−/− CD11c⁺ cells primarily harbor the CD11b^hi Ly6C⁺ subset. (C) Binding of anti-IRF4 Ab to WT (solid line) or ERα^−/− (dotted line) cells. The binding of isotype control IgG on WT cells is indicated (shaded gray). MFI values for anti-IRF4 binding to cells are indicated (with value for isotype control IgG subtracted). (D) The average fold change in IRF4 expression (anti-IRF4 Ab MFI) due to ERα in CD11c⁻ and CD11c⁺ is plotted; error bars represent the standard error in 5 independent experiments. (E-F) BM from ERα⁺/ERα^−/− BM chimeric mice was incubated with GM-CSF in standard medium for 7 days. (E) The percentage of CD11c⁺ DCs in the WT/CD45.1 and ERα^−/−/CD45.2 cell fractions was determined. (F) The bar graph shows MFI values of anti-IRF4 Ab binding to CD11c⁻ and CD11c⁺ cells, averaged (mean ± SEM) from 4 BM chimeric mice generated from the same BM transfer. Identical results were obtained upon analyses of 4 mice from a second BM chimera experiment. ***P < .001; *P < .05, n = 4.