Interleukin 4 down-regulates the expression of CD14 in normal human monocytes

Recombinant interleukin 4 (IL4) down-regulates the expression of CD14 on normal human monocytes, as assessed by flow cytometry, binding assays with radiolabeled anti-CD14 monoclonal antibody (mAb), and immunoprecipitation of 125I-labeled monocytes with anti-CD14 mAb. In parallel, CD23 expression on monocytes was strongly increased by IL4 stimulation, as assessed by both flow cytometry and immunoprecipitation. Down-regulation of surface CD14 was first detectable after 24-36 h of incubation with rIL4, and was almost complete after 4 days of culture. None of the other recombinant lymphokines tested (IL1, IL2, IL3, IL5, IL6, interferon-gamma, tumor necrosis factor alpha and beta, granulocyte-macrophage colony-stimulating factor) decreased CD14 expression. Metabolic labeling studies with [35S]methionine showed that both the membrane-associated and the soluble form of CD14 are decreased by IL4 stimulation. Northern blot analysis showed that incubation of monocytes with IL4 induced a marked decrease in CD14 mRNA. Nuclear run-off assays revealed that the IL4-dependent down-regulation of CD14 resulted from decreased transcription. Thus, IL4 exerts specific and opposite effects on the expression of monocytic antigens.