Download this assay page in pdf format.
Analyte: Interleukin-1 soluble receptor antagonist
Specimen Type: Serum
Optimum Volume: 1.0 mL
|3 d||6 mo||1.4 y|
Reporting units: pg/mL
Biological or Clinical Significance:
Interleukin-1 receptor antagonist (IL-1ra; also known as IL-1F3) is a 22 – 25 kDa member of the IL-1 family of cytokines. IL-1ra is a pure cytokine receptor antagonist that has no signal transduction-initiating activity. It is an acute phase protein that exists to dampen inflammation. IL-1 (β) is initially produced by monocytes in response to a variety of stimuli. Circulating IL-1 then binds to widely expressed IL-1 type I receptors (IL-1 RI) and initiates a number of pro-inflammatory events. On endothelial cells (EC), IL-1 induces PGE2 and IL-6 release, generating fever, thrombocytosis, and hepatic acute phase protein production. In synovial joints, IL-1 induces chondrocyte nitric oxide production, an event that leads to reduced collagen synthesis and chondrocyte apoptosis. Finally, IL-1 increase neutrophil counts, both in blood and tissue, and thus is able to promote a pro-inflammatory environment in multiple locations. IL-1ra blocks IL-1 action through competitive inhibition. More correctly, although IL-1ra fills the IL-1 binding site in IL-1 RI, it is also unable to orchestrate the creation of a signal-transducing IL-1 RI:IL-1R Accessory protein (IL-1 R AcP) heterodimer complex. Effective IL-1ra concentrations are generally 100-fold greater than local IL-1 concentrations. This is because the IL-1ra half-life is but 6 min, and very few IL-1 type I receptors need to be engaged by IL-1 to elicit a cellular response.
Principle of Test Method:
The Quantikine® Human IL-1ra Immunoassay is a 4.5 h solid phase ELISA designed to measure IL-1ra in cell culture supernates, serum, and plasma. It contains E. coli-derived recombinant human IL-1ra as well as antibodies raised against the recombinant factor. This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for IL-1ra has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any IL-1ra present is bound by the immobilized antibody. After washing away any unbound substances, an enzyme-linked polyclonal antibody specific for IL-1ra is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of IL-1ra bound in the initial step. The color development is stopped and the intensity of the color is measured at a wavelength of 450 nm with a correction wavelength at 544 nm.
1. Danis VA, Millington M, Hyland VJ, Grennan D. Cytokine production by normal human monocytes: inter-subject variation and relationship to an IL-1 receptor antagonist (IL-1Ra) gene polymorphism. Clin Exp Immunol 1995; 99:303-310.
2. Willis C, Morris JM, Danis V, Gallery EDM. Cytokine production by peripheral blood monocytes during the normal human ovulatory menstrual cycle. Human Reprod 2003; 18:1173-1178.
3. Lekander M, Elofsson S, Neve IM, Hansson LO, Unden AL. Self-rated health is related to levels of circulating cytokines. Psycho Med 2004; 66:559-563.