The regulation of inflammatory mediator production by mast cell products.

Mast cells are prominent in the airways and have been implicated in the pathophysiology of asthma. The ability of mast cells to generate or release the vasoactive/spasmogenic mediators histamine, adenosine, PGD2, sulfidopeptide leukotrienes, and platelet-activating factor is thought relevant to immediate bronchospastic responses in association with mucus secretion and airway edema. Mast cell elaboration of chemotactic factors and release of enzymes with both tryptic and chymotryptic specificity is held responsible for later reactions in which airway inflammation is prominent and nonspecific bronchial hyperreactivity is present. Recent evidence indicates that in addition to direct effect of these mast cell products some mast cell mediators themselves modulate inflammatory mediator production. Thus, adenosine, by interacting with A2 receptors on the surface of mast cells, markedly augments mast cell release of preformed granule associated mediators. Mast cell-derived chemotactic factors, exemplified by low molecular weight eosinophil directed molecules, can induce cell specific synthesis of inflammatory lipids such as platelet-activating factor. These findings only begin to suggest the richness of possibilities for mast cell regulation of the inflammatory response and underline the reality that the inflammatory response in lung as in all tissue is extremely complex and dependent upon cell-to-cell communication for its full expression.