Extracellular endogenous proteases, as well as exogenous proteases from mites and molds,
react with cell-surface receptors in the airways to generate leukocyte infiltration and to
amplify the response to allergens. Stimulation leads to increased intracellular Ca++ and
gene transcription. The most thoroughly investigated receptors, protease-activated receptors
(PARs), are 7-transmembrane proteins coupled to G proteins. PARs are widely distributed
on the cells of the airways, where they contribute to the inflammation characteristic of allergic …