The pro-inflammatory role of TGF-β in established asthma may be related to asthma highly inflammatory environment that includes high concentrations of IL-6 and IL-21 (152), which in mice induce Th17 differentiation in the presence of low levels of TGF-β (31, 153) (in human, the presence of IL-1β is also required (32)). Here, TGFB1 is linked to asthma.