Interleukin-13 regulates the phenotype and function of human monocytes

The monocyte glycosylphosphatidylinositol (GPI)-linked protein CD14 serves as the receptor for lipopolysaccharide (LPS), and regulates monocyte-lymphocyte interactions. We investigated whether CD14 expression is regulated by interleukin (IL)-13, a member of the chromosome 5 cytokine family. IL-13 inhibited CD14 expression on human monocytes. CD14 down-regulation resulted in the inhibition of LPS-induced release of tumor necrosis factor α, and involved neither shedding nor activation of endogenous GPI-anchor cleaving enzymes. The CD14/actin RNA ratio was decreased 7-fold in IL-13-treated monocytes. Our results suggest that IL-13 down-regulates CD14 by suppressing CD14 RNA expression. Down-regulation of CD14, the LPS receptor, may play a major role in the anti-inflammatory effects of IL-13.