Interleukin-13 (IL-13) is a cytokine secreted from type 2 T helper (Th2) cells. IL-13 has overlapping functions with interleukin-4 (IL-4), including the induction of immunoglobulin E (IgE) secretion from B cells, and the inhibition of interleukin-1 β (IL-1 β), Tumor Necrosis Factor α (TNF-α), interleukin-8 (IL-8), and interleukin-6 (IL-6) inflammatory cytokine expression. IL-13 also regulates immune cell inflammation in response to the pathophysiological changes of surrounding non-immune cells. The IL-13 receptor consists of the IL-4Ra and IL-13Ra1 subunits. IL-13 can also bind the IL-13Ra2 receptor with high affinity. IL-13 functions are mediated through the JAK/STAT signaling pathway. Human and mouse IL-13 are cross-reactive.