TGFB1 and asthma: Since TGFβ1 is also recognised as a potent trophic factor for granulopoiesis [94] and was shown to recruit, activate and prolong survival of neutrophils in other diseases [95], TGFβ1 upregulation and neutrophilia observed in asthma may mutually feedback each other, allowing the establishment of a vicious cycle potentially involved in disease exacerbation.