title: Production of IL-1 receptor antagonist by human in vitro-derived macrophages. Effects of lipopolysaccharide and granulocyte-macrophage colony-stimulating factor.
abstract: The objective of these experiments was to evaluate the production of IL-1ra, a specific receptor antagonist of IL-1, by human in vitro-derived macrophages, a model for differentiated macrophages. IL-1ra protein levels in supernatants and lysates of cultured cells were determined by a specific ELISA. Relative steady-state IL-1ra mRNA levels were measured using a specific cDNA probe. Human monocytes were differentiated by 6 days culture in either medium or granulocyte-macrophage colony-stimulating factor (GM-CSF), after which the effects of subsequent LPS and/or GM-CSF on the production of IL-1ra were evaluated. In vitro-derived macrophages cultured in medium for 6 days constitutively produced IL-1ra protein during the 24-h period of the 7th day in culture. The constitutive production of IL-1ra by medium-aged cells correlated with low steady-state IL-1ra mRNA levels determined over this same time period. In contrast, cells cultured for 6 days in GM-CSF synthesized significantly increased levels of IL-1ra protein during the 7th day in culture but the secreted levels remained unchanged. Cells differentiated in GM-CSF displayed enhanced steady-state levels of IL-1ra mRNA in comparison with cells aged in medium. Stimulation of in vitro-derived macrophages aged for 6 days in medium or in GM-CSF, with LPS or adherent IgG, did not result in increased levels of IL-1ra protein production in comparison with non-LPS stimulated cells. The IL-1ra protein detected in the supernatants of cells differentiated in GM-CSF was biologically active in the IL-1-augmented murine thymocyte proliferation assay. By Western blot analysis, the IL-1ra protein in the in vitro-derived macrophage supernatants was predominantly the 22- to 24-kDa glycosylated species, whereas the lysates contained additional lower molecular weight forms. These results suggest that as monocytes differentiate in vitro into macrophages, they constitutively produce IL-1ra protein and that this production is enhanced by the continuous presence of GM-CSF.
authors.affiliation: Rheumatology Section, Medical Service, Denver Veterans Administration Medical Center, CO 80220.
authors.forename: R W
authors.initials: RW
authors.lastname: Janson
authors.forename: K R
authors.initials: KR
authors.lastname: Hance
authors.forename: W P
authors.initials: WP
authors.lastname: Arend
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000037:antagonists & inhibitors; D008070:Lipopolysaccharides; D008213:Lymphocyte Activation / Q000187:drug effects; D008264:Macrophages / Q000378:metabolism*; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D012795:Sialoglycoproteins
chemical_list: C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D008070:Lipopolysaccharides; D011506:Proteins; D012333:RNA, Messenger; D012795:Sialoglycoproteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor