Histamine Release

Basophils and mast cells play an important role in allergic disorders. Both of these cell types produce and secrete many mediators that play an obligatory role in immediate hypersensitivity reactions. Some of the mediators are preformed and stored in granules. An example is histamine. Other mediators are generated de novo , e.g., eicosanoids. Mast cells and basophils produce some important cytokines, e.g., IL-4, IL-13, TNF-α (1 –5 ) and the chemokines MlP-1α and RANTES (6 ) upon activation. The cells are typically activated by cross-linking the high affinity IgE receptors. In addition to this classical activation mechanism basophils respond to a wide variety of stimuli. They include C5a, C3a, FMLP, hyperosmolar solutions, neuropeptides, histamine releasing factor, and CC chemokines (7 ). The most potent basophil-activating CC chemokines are MCP-1, MCP-3, MCP-4, eotaxin, RANTES, and MlP-lα (7 ).