IL17A and asthma: IL-17A has been reported to increase airway smooth muscle contraction on methacholine stimulation and drive migration of airway smooth muscle cells in murine models of allergic inflammation and in patients with asthma.9, 14, 15 IL-17A binds to the receptor subunits IL-17RA and C, which are expressed on epithelial and mesenchymal cells as well as on some immune cell populations such as lymphocytes, dendritic cells, and monocytes/macrophages in the lung.16