IL13 and asthma: At least three groups of related genes have shown linkage to asthma susceptibility: genes that govern innate immune responses to environmental threats (CD14, TLR2, TLR4, TLR6, NOD1 and NOD2); genes involved in differentiation and activation of Th2 cells (IL-4, IL-13, IL-4R and GATA3); and genes that activate a broad range of inflammatory functions including recruitment of leukocytes to epithelial and endothelial surfaces (TNF, LTα, CCL5, CCL24 and CCL26) [2].