CD4 and asthma: CD4+ T cell-derived Th1/Th2 imbalance is an initiating factor in ozone exacerbated asthma through PVT1-miR-15a-5p/miR-29c-3p signaling [154], and miR-15b-5p is considered a biomarker for identifying patients with asthma chronic obstructive pulmonary disease overlap [155].