Materials and Methods and Treatment: To clarify the role of NADPH oxidase in the pathophysiology of T cell-initiatedmacrophage-associated allergic asthma, we induced allergen dependent inflammation in a gp91phox−/− SKO (single knockout) and a gp91phox−/− MMP-12−/− DKO (double knockout) mouse and analysed trafficking and functionality of various cell types, the T cell function and T cell-macrophage interaction being given special emphasis. This evidence concerns the gene MMP12 and allergic asthma.