['Histamine exerts diverse effects on immune regulation through four types of histamine receptors (HRs). Among them, type 1 receptor (H1R) plays an important role in allergic inflammation. Dendritic cells (DCs), which express at least three types of HRs, are professional antigen-presenting cells controlling the development of allergic inflammation. However, the molecular mechanisms involved in H1R-mediated NF-ĸB signaling of DCs remain poorly defined.', 'Bone-marrow (BM)-derived DCs (BM-DCs) were treated with H1R inverse agonists to interrupt basal H1R-mediated signaling. The crosstalk of H1R-mediated signaling and the NF-ĸB pathway was examined by NF-ĸB cellular activity using a luciferase reporter assay, NF-ĸB subunit analysis using Western blotting and TNF-α promoter activity using chromatin immunoprecipitation.', 'Blockage of H1R signaling by inverse agonists significantly inhibited TNF-α and IL-6 production of BM-DCs. H1R-specific agonists were able to enhance TNF-α production, but this overexpression was significantly inhibited by NF-ĸB inhibitor. The H1R inverse agonist ketotifen also suppressed cellular NF-ĸB activity, suggesting crosstalk between H1R and NF-ĸB signaling in DCs. After comprehensive analysis of NF-ĸB subunits, c-Rel protein expression was significantly down-regulated in ketotifen-treated BM-DCs, which led to inhibition of the promoter activity of TNF-α. Finally, adoptive transfer of the ketotifen-treated BM-DCs did not induce significant allergic airway inflammation compared to that of control cells in vivo.'] Does inhibition of histamine H1 receptor activity modulate proinflammatory cytokine production of dendritic cells through c-Rel activity?