Granulocyte colony-stimulating factor receptors on granulocytes are down-regulated after endotoxin administration to healthy humans

Granulocyte colony-stimulating factor (G-CSF) is considered an important me diator of host defense against infection, and recombinant G-CSF is administ ered to patients with various infections. G-CSF binds to a specific recepto r that is expressed on granulocytes and monocytes, To obtain insight about the regulation of the G-CSF receptor after an acute infectious challenge, 8 healthy subjects received an intravenous injection of lipopolysaccharide ( LPS; 4 ng/kg), and receptor expression was determined on blood leukocytes b y fluorescence-activated cell sorter analysis, both by measurement of satur ation binding of recombinant G-CSF and by use of an anti-G-CSF-receptor ant ibody. LPS induced a transient decrease in granulocyte, but not monocyte, G -CSF-receptor expression. In whole blood in vitro, not only LPS but also gr am-positive stimuli and proinflammatory cytokines were capable of downmodul ating the G-CSF receptor on granulocytes, Bacterial antigens down-regulate the G-CSF receptor at the surface of granulocytes, which may impair neutrop hil functions important for antibacterial host defense.