| Receptor | Expression | Intracellular signaling | Immunological activity |
| H1R | Endothelial cells, nerve cells, epithelial cells, neutrophils, eosinophils, monocytes, macrophages, DCs, and T and B cells | PLC, PIP2, DAG, IP3, Ca2+, and PKC | Allergic reactions and inflammation, histamine release, eosinophil and neutrophil chemotaxis, antigen presentation ability, Th1/IFN-γ activity, and recruitment of Th2 cells; decreases humoral immunity and IgE production |
| H2R | Endothelial cells, nerve, epithelial, neutrophils, eosinophils, monocytes, macrophages, DCs, and T cells and B | Adenyl cyclase, cAMP, PKA, CREB, and EPAC | Increases IL-10 production and humoral immunity; decreases cellular immunity; inhibits Th2 cells and cytokines, chemotaxis of eosinophils, and neutrophils; suppresses IL-12p70 of MoDCs |
| H3R | Histaminergic neurons, monocytes, eosinophils | Inhibitor of adenyl cyclase and cAMP; increases levels of Ca2+ | Control of neurogenic inflammation, increased proinflammatory activity, and antigen presentation capacity |
| H4R | Eosinophils, DCs, Langerhans cells, neutrophils, T cells, basophils, and mast cells | Inhibitor of adenyl cyclase and cAMP; increases levels of Ca2+ | Affects pDC and mDC functions, Th1/Th2 differentiation, eosinophil and mast cell chemotaxis, IL-6 production, leukotriene B4, and migration of Tγ/δ cells; increases IL-17 secretion by Th17 cells, and regulatory T recruitment; suppresses IL-12p70 of MoDCs |
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