Is a major component of the late phase response. Produced by platelets, macrophages, lymphocytes. B. Generates a signal through the cross-linking of Fce IgE receptors. C. Membrane lipid and adenine metabolism is initiated. D. Granule solubilization and release of preformed amines, proteins, peptides and proteoglycans from granules occurs.
Histamine is primary preformed vasoactive mediator in basophils and mast cells.
Acts on H1 to contact smooth muscles, increase vascular permeability, and generate prostaglandins. Acts on H2 to increase vascular permeability, gastric acid secretion, stimulate suppressor lymphocytes, decrease PMN enzyme release, chemotaxis mast cell and basophil histamine release. Acts on H3 receptors to inhibit neurotransmitter and histamine release. Tryptase in the mucosal mast cell is a preformed enzyme which cleaves C3. Kallikrein similar to plasma kallikrein cleaves bradykinin from HMW Kininogenase and activated Hageman factor.