IL22RA1 and asthma: On the other hand, it has been shown that IL-22R1 is expressed on not only lung epithelial cells but also airway smooth muscle cells (ASMCs) in humans and that IL-22 enhances the proliferation and migration of human ASMCs [43–45], suggesting that IL-22 may involve in smooth muscle cell hyperplasia, a key pathological feature of asthma, in human airways.