Although the cleavage site differs from one enzyme to another, in the end, each of the proteases plays a similar role with respect to IL-33 but under different physiological conditions: indeed, it is likely that neutrophil proteases activate IL-33 in virus-induced asthma exacerbations and other inflammatory or infectious conditions, whereas mast cell proteases may be essential for IL-33 activation in allergic asthma and allergic inflammation. This evidence concerns the gene IL33 and asthma.