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Another important site of histamine storage and release is the enterochromaffin-like (ECL) cell of the stomach. The most important pathophysiologic mechanism of mast cell and basophil histamine release is immunologic. These cells, if sensitized by IgE antibodies attached to their membranes, degranulate when exposed to the appropriate antigen.
The C3a, C4a and C5a components are referred to as anaphylatoxins: [4] [5] they cause smooth muscle contraction, vasodilation, histamine release from mast cells, and enhanced vascular permeability. [5] They also mediate chemotaxis, inflammation, and generation of cytotoxic oxygen radicals. [5]
Histamine is a weak base (a compound able to react with a hydrogen ion to form an acid) that can link with acid groups within the granules of the mast cells. [8] The mechanism of the displacement theory. The crux of this theory lies in the assumption that histamine liberators release histamine by displacing it from cells.
Inflammation is a generic response, and therefore is considered a mechanism of innate immunity, whereas adaptive immunity is specific to each pathogen. [2] Inflammation is a protective response involving immune cells, blood vessels, and molecular mediators. The function of inflammation is to eliminate the initial cause of cell injury, clear out ...
Basophils appear in many specific kinds of inflammatory reactions, particularly those that cause allergic symptoms. Basophils contain anticoagulant heparin, [8] which prevents blood from clotting too quickly. They also contain the vasodilator histamine, which promotes blood flow to tissues.
When activated, mast cells rapidly release characteristic granules, rich in histamine and heparin, along with various hormonal mediators and chemokines, or chemotactic cytokines into the environment. Histamine dilates blood vessels, causing the characteristic signs of inflammation, and recruits neutrophils and macrophages. [5]
Degranulation in mast cells is part of an inflammatory response, and substances such as histamine are released. Granules from mast cells mediate processes such as "vasodilation, vascular homeostasis, innate and adaptive immune responses, angiogenesis, and venom detoxification."
The histamine H 4 receptor, like the other three histamine receptors, is a member of the G protein-coupled receptor superfamily that in humans is encoded by the HRH4 gene. [ 5 ] [ 6 ] [ 7 ] Discovery