Mast cells newly generated mediators

Both immediate and late-phase reactions are observed after allergen exposure. The immediate reaction occurs within minutes, resulting in the rapid release of preformed mediators and newly generated mediators from the arachidonic acid cascade as the mast cell membrane is disturbed (Table 93-1). These mediators of immediate hypersensitivity include histamine, leukotrienes (LTs) C4, LTD4, LTE4, prostaglandin D2, tryptase, and kinins. In addition, the mast... 

Mast cells, positioned in the asthmatic airways, also play a major role in the maintenance of the condition. During the active disease, these cells are primed to secrete preformed and newly generated inflammatory mediators, neutral proteases, cysteinyl leukotrienes, cytokines, and chemokines [73]. The local delivery of glucocorticoids to the affected tissues has been found to reduce significantly the number of mast cells present. In one study in which glucocorticoids were directly applied to mouse dermis, the number of mast cells decreased. No direct effect of the glucocorticoids on the mast cells themselves was observed thus, the decrease was probably the result of increased apoptosis [74]. 

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