Mast Cell
An immune cell found in tissues throughout the body that releases histamine, heparin, and other mediators during allergic and inflammatory reactions. Mast cell degranulation causes the symptoms of allergic reactions. Peptide-induced hypersensitivity reactions may involve mast cell activation.
Technical Context
Mast cells originate from CD34+ bone marrow progenitors, mature in tissues under the influence of stem cell factor (SCF/c-Kit ligand). Tissue distribution: connective tissue (skin, peritoneum, perivascular), mucosal surfaces (respiratory, GI tract). Mast cell granules contain: histamine, heparin, tryptase, chymase, and TNF-α (pre-formed mediators released within seconds of activation). De novo synthesised mediators (produced over minutes-hours): prostaglandin D2, leukotriene C4, and cytokines (IL-4, IL-5, IL-6, TNF-α). Activation triggers: IgE crosslinking on FcεRI (classical allergic reaction), complement fragments C3a and C5a (anaphylatoxins), substance P, and physical stimuli (cold, pressure). For peptide drugs, mast cell activation is relevant to: injection site reactions (local mast cell degranulation from needle trauma and foreign substance deposition), hypersensitivity reactions (IgE-mediated or direct mast cell activation), and anaphylaxis (systemic mast cell degranulation).