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

Abstract

Recombinant interleukin 4 (IL 4) down-regulates the expression of CD 14 on normal human monocytes, as assessed by flow cytometry, binding assays with radiolabeled anti-CD 14 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 rIL 4, and was almost complete after 4 days of culture. None of the other recombinant lymphokines tested (IL 1, IL 2, IL 3, IL 5, IL 6, interferon-γ, tumor necrosis factor α and β, granulocytemacrophage colony-stimulating factor) decreased CD14 expression. Metabolic labeling studies with [³⁵S]methionine showed that both the membrane-associated and the soluble form of CD 14 are decreased by IL 4 stimulation. Northern blot analysis showed that incubation of monocytes with IL 4 induced a marked decrease in CD 14 mRNA. Nuclear run-off assays revealed that the IL 4-dependent down-regulation of CD 14 resulted from decreased transcription. Thus, IL 4 exerts specific and opposite effects on the expression of monocytic antigens.