AP BIOLOGY

Detailed explanation-1: -Histamine is the most important mediator released from the mast cell involved with an allergic response. Histamine is derived from the amino acid histidine and works through three different receptors (H1, H2, H3). Stimulation of H1 receptors by the binding of histamine induces the classic allergic reaction.

Detailed explanation-2: -Mast cells and basophils are the major source of granule-stored histamine, where it is closely associated with the anionic proteoglycans and chondroitin-4-sulfate. Histamine is released when these cells degranulate in response to various immunologic and nonimmunologic stimuli.

Detailed explanation-3: -Once activated, mast cells secrete numerous vasoactive and pro-inflammatory mediators [37-42]. These include pre-formed molecules such as histamine, serotonin, TNF, kinins and proteases stored in secretory granules.

Detailed explanation-4: -Mast cells are key players in the inflammatory response as they can be activated to release a wide variety of inflammatory mediators, by many different antigens including allergens, pathogens and physiological mediators.

Detailed explanation-5: -Mast cells and basophils represent the most relevant source of histamine in the immune system. Histamine is stored in cytoplasmic granules along with other amines (e.g., serotonin), proteases, proteoglycans, cytokines/chemokines, and angiogenic factors and rapidly released upon triggering with a variety of stimuli.