IL13 and asthma: Consistent with the observation of elevated serum IL-4 and IL-13 in patients experiencing asthma, the ITGB4−/− mice showed significantly enhanced IL-4 levels (Fig. 6c, BALF p < 0.05; serum p < 0.01) and IL-13 levels (Fig. 6d, BALF p < 0.05; serum p < 0.01) measured by ELISA.