INTERLEUKIN-13 REGULATES THE PHENOTYPE AND FUNCTION OF HUMAN MONOCYTES

The monocyte glycosylphosphatidylinositol (GPI)-linked protein CD14 se rves as the receptor for lipopolysaccharide (LPS), and regulates monoc yte-lymphocyte interactions. We investigated whether CD14 expression i s regulated by interleukin (IL)-13, a member of the chromosome 5 cytok ine family. IL-13 inhibited CD14 expression on human monocytes. CD14 d own-regulation resulted in the inhibition of LPS-induced release of tu mor necrosis factor alpha, and involved neither shedding nor activatio n of endogenous GPI-anchor-cleaving enzymes. The CD14/actin RNA ratio was decreased 7-fold in IL-13-treated monocytes. Our results suggest t hat IL-13 down-regulates CD14 by suppressing CD14 RNA expression. Down -regulation of CD14, the LPS receptor, may play a major role in the an ti-inflammatory effects of IL-13.