IL4 and allergic disease: In conclusion, siRNAs of PAR-1, PAR-2, PAR-4 not only block their corresponding PAR expression, inhibit IL-12 induced alteration of expression of PARs, but also reduce tryptase and trypsin provoked IL-4 release from P815 cells, confirming that mast cell PARs are likely to be involved in the pathogenesis of allergic reactions.