CD86 expression is regulated by PU.1 and to a lesser extent by C/EBPα and C/EBPβ. (A) PU.1^fl/fl × Mx Cre F1 mice, C/EBPα^fl/fl × MxCre F1 mice were injected with poly IC intraperitoneally. Four days after the last injection, CD150⁺ CD48⁻ LSK cells in the BM were analyzed by flow cytometry. HSC-rich LSK cells from BM of global C/EBPβ KO mice were similarly analyzed. (B) shRNA knockdown of PU.1 in a Pax5^−/− pre-pro-B cell line reduces CD86 expression. The Pax5^−/− cell line³¹  was transduced with lentiviral supernatant fluids containing either a no-template control (NT-shRNA) or PU.1-targeted shRNA as previously described.³²  Puromycin-resistant cells were harvested and analyzed for surface expression of the indicated markers by flow cytometry. The black lines indicate background fluorescence of unstained cells, the hatched lines reflect staining of cells transduced with the NT-shRNA, and the filled histograms show staining of cells transduced with the PU.1-shRNA.