Immunological Functions of Inﬂammatory Mediators
Histamine is the classical mediator that has been extensively studied in the context of allergy and asthma.Histamine is stored in granules within mast cells and basophils and can be released under immunological conditions following the cross-linking of antigen to high-a⁄nity IgE receptors present on the surface of mast cells and basophils or by nonimmunological stimuli (e.g., compound 48=80, calcium ionophore, substance P, and hypo-osmolar solutions). Histamine concentrations are elevated in bronchoalveolar lavage (BAL) £uid of asymptomatic mild asthmatics (3) and following antigen challenge (4,5). The acute bronchoconstriction observed following antigen challenge is attenuated by selective H1 receptor antagonists (6). These studies con¢rm that the acute release of histamine following an allergic or nonallergic insult may lead to bronchoconstriction.