GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR DOWN-REGULATES CD14 EXPRESSION ON MONOCYTES

CD14 is a differentiation-stage-linked glycosyl-phophatidyl-inositol-l inked glycoprotein on human peripheral blood monocytes and tissue macr ophages, which functions as a receptor for lipopolysaccharide, Here, t he effects of granulocyte-macrophage colony-stimulating factor (GM-CSF ), a cytokine with proliferation- and differentiation-inducing propert ies on myeloid lineage cells, were studied on CD14 expression by perip heral blood cells. GM-CSF down-regulated the membrane expression of CD 14 on monocytes, while it up-regulated expression on neutrophils. GM-C SF also decreased the spontaneous release of CD14 in monocyte culture supernatants. Down-regulation of CD14 expression and release was accom panied by a decrease in the mRNA transcript for CD14, suggesting that it most likely reflects an effect on the transcriptional level. The fu nctional significance of this phenomenon, and its potential relation t o the terminal differentiation of monocytes, are discussed.