Mouse IL-6 ELISA Assay

Additional Information

Assay Background

Interleukin 6 (IL-6) is a multifunctional cytokine that plays important roles in host defense, acute phase reactions, immune responses, nerve cell functions and hematopoiesis (1-5). It is expressed by a variety of normal and transformed lymphoid and nonlymphoid cells.

IL-6 is a prototypic member of the IL-6 superfamily of cytokines that share gp130 as a component required for signal transduction (4). The mouse (6), rat (7) and human (8, 9) IL-6 cDNAs have been cloned. The mouse IL-6 cDNA encodes a 211 amino acid (aa) residue precursor polypeptide with a hydrophobic signal sequence that is cleaved to generate the 187 aa residue mature protein. Mouse to rat and human, there is approximately 87% and 39% aa identity, respectively. Although human and mouse IL-6 are equally active on mouse cells, mouse IL-6 is not active on human cells (10).

The high-affinity IL-6 receptor complex, which mediates IL-6 bioactivity, consists of two membrane glycoproteins. The production of IL-6 is upregulated by numerous signals such as mitogenic or antigenic stimulation, lipopolysaccharides, calcium ionophores, cytokines and viruses. IL-4, IL-10 and IL-13 inhibit IL-6 expression in monocytes.

Assay Procedure

1. Prepare all reagents and working standards as directed in the previous sections.
2. Determine the number of microwell strips required to test the desired number of samples plus appropriate number of wells needed for running blanks and standards. Remove extra microwell strips from holder and store in foil bag with the desiccant provided at 2-8°C sealed tightly.
3. Add 100 µL of Standard, control, or sample, per well. Cover with the adhesive strip provided. Incubate for 1.5 hours at 37°C.
4. Aspirate each well and wash, repeating the process three times for a total of four washes. Wash by filling each well with Wash Buffer (350 µL) using a squirt bottle, manifold dispenser or auto-washer. Complete removal of liquid at each step is essential to good performance. After the last wash, remove any remaining Wash Buffer by aspirating or decanting. Invert the plate and blot it against clean paper towels.
5. Add 100 µL of the working solution of Biotin-Conjugate to each well. Cover with a new adhesive strip and incubate 1 hour at 37°C.
6. Repeat the aspiration/wash.
7. Add 100 µL of the working solution of Streptavidin-HRP to each well. Cover with a new adhesive strip and incubate for 30 minutes at 37°C Avoid placing the plate in direct light.
8. Repeat the aspiration/wash.
9. Add 100 µL of Substrate Solution to each well. Incubate for 10-20 minutes at 37°C. Avoid placing the plate in direct light.
10. Add 100 µL of Stop Solution to each well. Gently tap the plate to ensure thorough mixing.
11. Determine the optical density of each well immediately, using a microplate reader set to 450 nm.(optionally 630nm as the reference wave length; 610-650nm is acceptable)