IL-13, produced primarily by Th2 cells and to a lesser extent by mast and NK cells, is an immunoregulatory cytokine. Its various functions include induction of matrix metalloproteinases, enhancement of IgE secretion from activated B cells and B cell proliferation. Additionally, IL-13 plays a role in the inhibition of the expression of inflammatory cytokines including IL-1β, TNF-α, IL-6 and IL-8.