IL-12 is secreted by activated B lymphocytes and macrophages as a 70 kD heterodimeric glycoprotein comprised of disulfide-bonded 35 kD and 40 kD subunits. IL-23 is a heterodimeric cytokine composed of two disulfide-linked subunits, a p19 subunit that is unique to IL-23, and a p40 subunit that is shared with IL-12. IL-23 is secreted by activated macrophages and dendritic cells. The disulfide-linked p40 homodimer can bind to IL-12 receptors and antagonize the activities of bioactive IL-12. IL-12/IL-23 p40 monomer is secreted in vast excess of IL-12 p70 heterodimer; IL-12/IL-23 p40 monomer has no activity and is antagonistic to IL-12 p70 with only 1/10th the activity of p40 homodimer. The antibodies in the mouse IL-12/IL-23 (p40) Legend MAX™ ELISA Kit react with the p40 subunit of mouse IL-12 and IL-23, as monomer and homodimer.

Cytokine detection

IL-12, IL-23 and IL-35 share common subunits, utilizing combinations of p40, p19 and p35 proteins. Caution must be used when selecting antibodies and assays when specific identification, measurement, as well as activation state discrimination, is required.

1. Active IL-12 consists of two subunits: p40 + p35.
2. p40 can also exist as a monomer (IL-12 p40) or a homodimer (IL-12 p80).
3. Besides contributing to IL-12, p40 is also found in IL-23, a heterodimer of p40 and p19.
4. Similarly, p35 not only contributes to IL-12, but is also found in the heterodimer IL-35 (p35 and EBI3).

Note that assays using antibodies specific for the p40 subunit will be unable to discriminate between the active IL-12, monomeric p40, dimeric p40, and IL-23; likewise, assays using p35 detection alone will pick up both IL-12 (heterodimer) and IL-35.

BioLegend ELISA assays

BioLegend’s LEGEND MAX™ Human IL-12/IL-23 (p40) ELISA Kit is a sandwich Enzyme-Linked Immunosorbent Assay (ELISA), in which, a human IL-12/IL-23 (p40) specific monoclonal antibody is pre-coated on a 96-well strip-well plate.

This Human IL-12/IL-23 (p40) ELISA Kit is specifically designed for the accurate quantitation of human IL-12/IL-23 (p40) from cell culture supernatant, serum, plasma or other bodily fluids. It is ready-to-use, accurate, and sensitive.