IL4 and asthma: In addition, IL-4, IL-5 and TNF-α are essential for the development of AHR, mucus production and fibrosis in asthma.49, 50, 51 Similarly, chemokines, such as CCL11 and CCL24, may also contribute to AHR and fibrogenesis in animal models of asthma.42, 48 In our studies, there was a marked decrease in levels of these cytokines, which accompanied the resolution of the eosinophil numbers.