Imatinib mesylate down-regulates the expression of nuclear localized RelB protein but not RelA and c-Rel in DCs. Mobilized human CD34⁺ PBPCs were cultured in the presence of GM-CSF, TNF-α, IL-4, and FLT3L with or without imatinib mesylate (3 μM). For activation of DCs, cells were incubated with soluble CD40L and IFN-γ 24 hours before preparing nuclear extracts. Nuclear localized RelB (A), RelA (B), and c-Rel (C) protein were detected by SDS-PAGE and Western blot.