IL33 and asthma: Interestingly, in the ovalbumin-induced asthma mouse model, the expression of pathogenic Th2 cells in ST2-/- and IL33-/- mice is reduced significantly compared with ST2+/+ and IL33+/+ mice, resulting in observable improvement of pulmonary fibrosis, collagen deposition, and the prominent decrease in fibrosis-related gene expression, which indicates that ST2hi memory pathogenic Th2 cells are involved in the establishment of airway fibrosis (91).