Inflammatory responses to mast cell granules.

Mast cell degranulation leads to classic allergic reactions appearing within minutes and abating in 30-60 min. It is now appreciated that this is but the first stage of a multisequenced reaction that includes late phase allergic reactions that are apparent within 4-8 h and persisting up to 24 h. These late phase reactions (LPR) are clinically experienced as burning, ill-defined erythema, and edema and are thought to participate in airway and nasal hyperreactivity. A rodent model has been developed that permits analyses of the pathogenesis of LPR: LPR may be elicited by isolated inflammatory factors released from mast cell granules, are complement independent, require an influx of neutrophils for full expression, and may be inhibited by combinations of H-1 and H-2 antihistamines as well as corticosteroids. The appreciation of the late phase of allergic reactions broadens our understanding of the pathologic features of immunologically induced inflammation as well as provides new approaches to the treatment of allergy and asthma.