Sandwich TR-FRET immunoassay for quantitative detection of human Interleukin-12 and Interleukin-23 p40 subunit (hIL-12/IL-23 p40; IL-12B) in cell culture supernatants. The kit does not include a recombinant human IL-12 p40 standard, which must be purchased separately from R&D Systems (catalogue number 309-IL).