title: Human neutrophils produce high levels of the interleukin 1 receptor antagonist in response to granulocyte/macrophage colony-stimulating factor and tumor necrosis factor alpha.
abstract: Neutrophils, an abundant cell type at sites of inflammation, have the ability to produce a number of cytokines, including interleukin 1 (IL-1), IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-alpha). In this study, we have examined the ability of human neutrophils to produce the IL-1 receptor antagonist (IL-1Ra), a 17-23-kD protein recently isolated and cloned from macrophages. Since IL-1Ra has been shown to inhibit both the in vitro and in vivo effects of IL-1, its production by large numbers of tissue-invading neutrophils might provide a mechanism by which the effects of IL-1 are regulated in inflammation. Using antibodies that are specific for IL-1Ra and a cDNA probe encoding for this protein, we were able to show that neutrophils constitutively produce IL-1Ra. However, after activation by GM-CSF and TNF-alpha, IL-1Ra was secreted into the extracellular milieu where it constituted the major de novo synthesized product of activated neutrophils. None of a large array of other potent neutrophil agonists were found to affect the production of IL-1Ra by neutrophils. Quantitative measurements by enzyme-linked immunosorbent assay revealed that intracellular IL-1Ra is in eightfold excess of the amount secreted in supernatants when studying nonactivated neutrophils. However, in GM-CSF- and TNF-alpha-activated cells, this difference was reduced to values between four- and fivefold, as virtually all of the de novo synthesized IL-1Ra was secreted. In activated cells, the intracellular content of IL-1Ra was found to be in the 2-2.5-ng/ml range per 10(6) neutrophils, whereas levels reached the 0.5-ng/ml range in supernatants. This would imply that IL-1Ra is produced in excess of IL-1 by a factor of at least 100, an observation that is in agreement with the reported amounts of IL-1Ra needed to inhibit the proinflammatory effects of IL-1. Neutrophils isolated from an inflammatory milieu, the synovial fluid of patients with rheumatoid arthritis, were found to respond to GM-CSF and TNF-alpha in terms of IL-1Ra synthesis, indicating that the in vitro observations made in this study are likely to occur in an inflammatory setting in vivo.
authors.affiliation: Centre de Recherche en Inflammation, Université Laval, Québec, Canada.
authors.forename: S R
authors.initials: SR
authors.lastname: McColl
authors.forename: R
authors.initials: R
authors.lastname: Paquin
authors.forename: C
authors.initials: C
authors.lastname: Ménard
authors.forename: A D
authors.initials: AD
authors.lastname: Beaulieu
mesh_terms: D001172:Arthritis, Rheumatoid / Q000378:metabolism; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000502:physiology*; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D009504:Neutrophils / Q000378:metabolism*; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors*; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins; D013582:Synovial Fluid / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
chemical_list: C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D011506:Proteins; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins; D014409:Tumor Necrosis Factor-alpha; D016178:Granulocyte-Macrophage Colony-Stimulating Factor