Histamine, Histamine Receptors, and their Role in Immunomodulation: An Updated Systematic Review

Histamine, a biological amine, is considered as a principle mediator of many pathological processes regulating several essential events in allergies and autoimmune diseases. It stimulates different biological activities through differential expression of four types of histamine receptors (H1R, H2R, H3R and H4R) on secretion by effector cells (mast cells and basophils) through various immunological or non-immunological stimuli. Since H4R has been discovered very recently and there is paucity of comprehensive literature covering new histamine receptors, their antagonists/agonists, and role in immune regulation and immunomodulation, we tried to update the current aspects and fill the gap in existing literature. This review will highlight the biological and pharmacological characterization of histamine, histamine receptors, their antagonists/agonists, and implications in immune regulation and immunomodulation.