Journal of leukocyte biology
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The primary interleukin-4 (IL-4) receptor complex on monocytes (type I IL-4 receptor) includes the 140-kDa alpha chain (IL-4R alpha) and the IL-2 receptor gamma chain, gamma(c), which heterodimerize for intracellular signaling, resulting in suppression of lipopolysaccharide (LPS)-inducible inflammatory mediator production. The activity of IL-13 on human monocytes is very similar to that of IL-4 because the predominant signaling chain (IL-4R alpha) is common to both receptors. In fact, IL-4R alpha with IL-13R alpha1 is designated both as an IL-13 receptor and the type II IL-4 receptor. ⋯ There was a similar loss of IL-13R alpha1 mRNA on monocyte differentiation. In turn, there was a significant reduction in the ability of IL-4 and IL-13 to activate STAT6. These findings suggest that different functional responses to IL-4 and IL-13 by human monocytes and macrophages may result from reduced expression of gamma(c) and IL-13R alpha1.