A transcription factor regulates hypoxia in severe asthma exacerbations and hypoxia-inducible factor-1 (HIF-1), and deficiency of HIF-1α reduces Th17 cells development with increased Treg differentiation [141], and study has confirmed that less airway inflammation in HIF-1α-/- experimental mice [142] is believed to be due to reduced Th17 cells. This evidence concerns the gene HIF1A and asthma.