IL4 and bronchiolitis: Genetic polymorphisms of SFTPA (surfactant protein A), SFTPD (surfactant protein D), TLR (toll like receptor) 4, TNF (tumor necrosis factor), IL4 (interleukin 4), IL9, IL10, IL8, IL13, IL4RA, and CCL5 have been reportedly associated with a susceptibility to RSV-induced bronchiolitis (Huckabee and Peebles, 2009).