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Immunoassays | Inflammation & Cytokines

Erenna® IL-21 Immunoassay Kit (Cat# 03-0014-xx)

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The Erenna® IL-21 Immunoassay Kit uses a quantitative fluorescent sandwich immunoassay technique to measure IL-21 in human K2 EDTA plasma samples. A capture antibody specific for IL-21 has been pre-coated onto paramagnetic microparticles (MP). The user pipettes MP, standards, and samples into uncoated microplate wells. During incubation, the IL-21 present in the sample binds to the capture antibody on the coated MP. Unbound molecules are washed away during the subsequent buffer exchange and wash steps. Fluor-labeled detection antibody is added to each well and incubated. This detection antibody recognizes and binds to IL-21 that has been captured onto the MP. During the following wash step the MPs are transferred to a clean plate. Elution buffer is then added and incubated. The elution buffer dissociates the bound protein sandwich from the MP surface, releasing the labeled antibodies. These antibodies are separated during transfer to a final microplate. The plate is loaded into the Erenna System where the labeled molecules are detected and counted. The number of fluor-labeled detection antibodies counted is directly proportional to the amount of IL-21 present in the sample when captured. The amount of IL-21 in unknown samples is interpolated from a standard curve.

Assay Performance

TABLE 1. Analytical sensitivity of the Erenna® IL-21 Immunoassay Kit1
Lower Limit of Detection 0.005 pg/mL
Lower Limit of Quantification2 0.2 pg/mL
Upper Limit of Quantification 100 pg/mL
Low-end CV% Range 1 - 11%
Low-end CV% Average 7%
Recommended Sample Volume 50 μL
Minimum Sample Volume Required3 50 μL

1 See product insert for updated values
2 LLoQ = 20% CV and ± 20% recovery
3 based upon median [IL-21] in a healthy reference

FIGURE 1. [IL-21] in serum from 19 healthy donors, with median and interquartile range. The Erenna® IL-21 Immunoassay Kit reliably quantifies IL-21 in serum from healthy subjects, who have a median [IL-21] of 0.53 pg/mL that is well above the detection limit of 0.005 pg/mL.

FIGURE 2. IL-21 assay low-end standard curve signal (left) and curve fit (right).

Representative data shown for demonstration purposes only. Individual results may vary depending upon samples tested and protocol used.

Biology and Disease

Interleukin-21 (IL-21) is a cytokine with a potent regulatory effect on the immune system. Mainly produced by activated T-cells, IL-21 is responsible for the hematopoiesis of T-, B-, natural killer and dendritic cells. The production and differentiation of these effector cells may lead to an increased immunity against cancerous or virally infected cells. Thus, the role of IL-21 in the regulation of immuno-inflammatory responses has important implications for diseases such as multiple sclerosis, metastatic melanoma and metastatic renal cell carcinoma. Thus IL-21 will remain an attractive subject for drug development. Successful study outcomes will further establish IL-21 immunotherapy as an effective treatment for various cancers and inflammatory diseases.

TABLE 2. Additional UniProtKB/Swiss-Prot Information*
Protein Name: Interleukin-21
UniProtKB/Swiss-Prot ID: Q9HBE4
Protein-protein interaction database: Q9HBE4
Alternative Names: Za11
Gene Names: IL21
Synonym Gene Names:
Function: Cytokine with immunoregulatory activity. May promote the transition between innate and adaptive immunity. Induces the production of IgG1 and IgG3 in B-cells By similarity. May play a role in proliferation and maturation of natural killer (NK) cells in synergy with IL15. May regulate proliferation of mature B- and T-cells in response to activating stimuli. In synergy with IL15 and IL18 stimulates interferon gamma production in T-cells and NK cells. During T-cell mediated immune response may inhibit dendritic cells (DC) activation and maturation.
Biological Processes: cell maturation, immune response, positive regulation of T cell proliferation, positive regulation of interferon-gamma biosynthetic process, signal transduction
Molecular Function: cytokine activity, interleukin-2 receptor binding

* Source Info from www.uniprot.org.

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