Distinct signalling pathways of murine histamine H1- and H4-receptors expressed at comparable levels in HEK293 cells.

Histamine (HA) is recognized by its target cells via four G-protein-coupled receptors, referred to as histamine H1-receptor (H1R), H2R, H3R, and H4R. Both H1R and H4R exert pro-inflammatory functions. However, their signal transduction pathways have never been analyzed in a directly comparable manner side by side.

Histamine via the histamine H₂-receptor reduces α-CD3-induced interferon-γ synthesis in murine CD4+ T cells in an indirect manner.

Histamine is involved in the execution of an immune reaction. Receptors for histamine, of which four different subtypes are known so far, are found on dendritic cells and on T cells. Via these receptors, histamine either indirectly or directly affects the activation of T cells.