Role and immunomodulatory profile of histamine receptors by H1 and H2 antagonists

Abstract

The present study was designed to delineate the immunomodulatory role of histamine receptors (H1- and H2-) on induction of antibody response to sheep red blood cells (SRBC), as well as the antibody generation profile, in rabbit system, systemically. The rabbits in two groups received pheniramine (H1-receptor antagonist) and ranitidine (H2-receptor antagonist), respectively, via intramuscular route and were immunized with SRBC intravenously to evaluate suppression or enhancement of antibody responses in sem. A third, control group, received vehicle and were immunized in a similar manner. Histamine released from effector cells (mast cells and basophils) in vivo during inflammatory reactions could influence a detectable antibody response to SRBC as early as day 7-postimmunization (post-I), which lasted until day 28- post-I. Pheniramine-treated rabbits had significantly (&42;Pa ≤ 0.05 and &42;&42;Pa ≤ 0.01) more suppressed total serum antibody (IgM + IgG) to SRBC as compared to ranitidine-treated ad cotrol rabbits, while ranitidine-treated rabbits showed different pattern (suppressed or enhanced) during the whole study period. Ranitidine suppressed total antibody level at days 7- and 14- post-I, and enhanced at days 21- and 28- post-I. IgM suppression at day 7- and enhancement at days 14-, 21- and 28- post-I, while IgG suppression during whole study period, as compared to control group was significant (&42;Pa ≤ 0.05 and &42;&42;Pa ≤ 0.01) as assessed by direct hemagglutination assay&42; ad whole SBC-ELISA method&42;&42;. Here we report that histamine receptor type 2 (H2R)-antagonists have a dominant role on immunosuppression and in immunoregulation of humoral immune responses. Histamine receptor type 2 (H2R)-antagonists are mainly involved in B cell differentiation and proliferation over histamine receptor type 1 (H1R)-antagonists.