In asthma pathogenesis, a number of inflammatory mediators of the T helper 2-dependent reaction play a pivotal role in a complex signaling environment that contributes to AHR: several experimental studies on isolated airway preparations and in vivo animal models have demonstrated an association between enhanced ASM hyperreactivity and overexpression of IgE [16], IL-4 [17,18], IL-5 [19], IL-13 [18,20,21], and TSLP [22,23]. This evidence concerns the gene IL13 and asthma.