[Histamine receptors in arthritis]

Histamine H1 and H2 receptors in lymphocytes, bone marrow mononuclear cells, synovial fibroblasts and chondrocytes were measured by binding assay and pharmacological study. Histamine suppressed IgG production through H1 and H2 receptors and cytotoxic activity through H2 receptor in lymphocyte. Histamine increased the production of hyaluronic acid in synovial fibroblast through H1 and H2 receptors. In the production of keratan sulfate in the chondrocyte, histamine increased through H1 receptor and decreased through H2 receptor. In arthritis, the functions of H2 receptor in the lymphocyte, bone marrow mononuclear cell and synovial fibroblast were decreased, and the function of H1 receptor in the chondrocyte was decreased. On the other hand, histamine content was reported to increase in synovial fluid with RA. Our data indicate histamine had suppressive effects on IgG production and cytotoxic activity, but the functions of histamine receptors, especially H2 receptor, were decreased in RA. The beneficial effects of histamine in RA synovial fluid might therefore be decreased by hypofunction of the H2 receptor. These data suggest that abnormalities in histamine receptors in arthritis could be involved in perpetuating the inflammatory process in RA.