Human IL-1 beta/IL-1F2 Quantikine ELISA Kit Summary

Product Summary

The Quantikine Human IL-1 beta Immunoassay is a 3.5 or 4.5 hour solid phase ELISA designed to measure IL-1 beta in cell culture supernates, serum, and plasma. It contains E. coli-expressed recombinant human IL-1 beta and antibodies raised against the recombinant factor. It has been shown to quantitate recombinant human IL-1 beta accurately. Results obtained using natural IL-1 beta showed linear curves that were parallel to the standard curves obtained using the Quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for natural IL-1 beta. Reports indicate that this and other ELISA kits calibrated using mature IL-1 beta as a standard will detect, but considerably underestimate, the unprocessed IL-1 beta precursor present in samples. In biological samples other than cell lysates, the precursor form of IL-1 beta is usually not the predominant form of IL-1 beta present and, additionally, is not biologically active. Therefore, results obtained using this kit should provide a useful measure of the levels of active IL-1 beta present in biological fluids.

Preparation and Storage

Background: IL-1 beta/IL-1F2

The Interleukin 1 (IL-1) family of proteins consists of the classic members IL-1 alpha, IL-1 beta, and IL-1ra, plus IL-18, IL-33 and IL-1F5-F10. IL-1 alpha and IL-1 beta bind to the same cell surface receptors and share biological functions. IL-1 is not produced by unstimulated cells of healthy individuals with the exception of skin keratinocytes, some epithelial cells, and certain cells of the central nervous system. However, in response to inflammatory agents, infections, or microbial endotoxins, a dramatic increase in the production of IL-1 by macrophages and various other cell types is observed. IL-1 beta plays a central role in immune and inflammatory responses, bone remodeling, fever, carbohydrate metabolism, and GH/IGF-I physiology. Inappropriate or prolonged production of IL-1 has been implicated in a variety of pathological conditions including sepsis, rheumatoid arthritis, inflammatory bowel disease, acute and chronic myelogenous leukemia, insulin dependent diabetes mellitus, atherosclerosis, neuronal injury, and aging-related diseases. 

IL-1 alpha and IL-1 beta are structurally related polypeptides that show approximately 25% homology at the amino acid level. Both are synthesized as 31 kDa precursors that are subsequently cleaved into mature proteins of approximately 17.5 kDa. Cleavage of the IL-1 beta precursor by Caspase-1/ICE is a key step in the inflammatory response. Neither IL-1 alpha nor IL-1 beta contains a typical hydrophobic signal peptide, but evidence suggests that these factors can be secreted by non-classical pathways. A portion of unprocessed IL-1 alpha can be presented on the cell membrane and may retain biological activity. The precursor form of IL-1 beta, unlike the IL-1 alpha precursor, shows little or no biological activity in comparison to the processed form. Both unprocessed and mature forms of IL-1 beta are exported from the cell. 

IL-1 alpha and IL-1 beta exert their effects through immunoglobulin superfamily receptors that additionally bind IL-1ra. The 80 kDa transmembrane type I receptor (IL-1 RI) is expressed on T cells, fibroblasts, keratinocytes, endothelial cells, synovial lining cells, chondrocytes, and hepatocytes. The 68 kDa transmembrane type II receptor (IL-1 RII) is expressed on B cells, neutrophils, and bone marrow cells. The two IL-1 receptor types show approximately 28% homology in their extracellular domains but differ significantly in that the type II receptor has a cytoplasmic domain of only 29 amino acids (aa), whereas the type I receptor has a 213 aa cytoplasmic domain. IL-1 RII does not appear to signal in response to IL-1 and may function as a decoy receptor that attenuates IL-1 function. The IL-1 receptor accessory protein (IL-1 RAcP) associates with IL-1 RI and is required for IL-1 RI signal transduction. IL-1ra is a secreted molecule that functions as a competitive inhibitor of IL-1. Soluble forms of both IL-1 RI and IL-1 RII have been detected in human plasma, synovial fluids, and the conditioned media of several human cell lines. In addition, IL-1 binding proteins that resemble soluble IL-1 RII are encoded by vaccinia and cowpox viruses..

Assay Procedure

Refer to the product datasheet for the complete assay procedure.

Bring all reagents and samples to room temperature before use. It is recommended that all samples, standards, and controls be assayed in duplicate.

1.     Prepare all reagents, standard dilutions, and samples as directed in the product insert.

2.     Remove excess microplate strips from the plate frame, return them to the foil pouch containing the desiccant pack, and reseal.

3.     Add 50 μL of Assay Diluent to each well.

4.     Add 200 μL of Standard, control, or sample to each well. Cover with a plate sealer, and incubate at room temperature for 2 hours.

5.     Aspirate each well and wash, repeating the process 4 times for a total of 5 washes.

6.     Add 200 μL of Conjugate to each well. Cover with a new plate sealer, and incubate at room temperature for 2 hours.

7.     Aspirate and wash 5 times.

8.     Add 50 μL Substrate Solution to each well.

9.     Add 50 μL of Stop Solution to each well. Read at 450 nm within 30 minutes. Set wavelength correction to 540 nm or 570 nm.