Stimulation of Histamine Receptors of Human Monocytoid and Hepatoma-Derived Cell Lines and Mouse Hepatocytes Modulates the Production of the Complement Components C3, C4, Factor B, and C2

The influence of histamine (and the related agonists and antagonists) alone or in the presence of recombinant human interleukin 1α (IL-1α) and gamma interferon (IFN-γ) was studied on the production of complement components C3, C2, factor B, and C4 in vitro with human monocytoid cell line U937, hepatoma-derived cell line HepG2, and mouse hepatocytes. Both U937 and HepG2 cells responded to histamine through H1 and H2 histamine receptors. The effect of histamine on the biosynthesis and gene expression of complement proteins was predominantly enhancing via the H1 histamine receptors and inhibitory through the H2 receptors. The actual predominance of the histamine receptor involved (and the outcome of the ligand interaction) seemed to be greatly affected by the simultaneous activation of the cells by IL-1 or IFN-γ.