Recombinant Interleukin-12 is a disulfide-linked heterpdimer protein consisting of 306 amino acid residue p40 subunit and a 197 amino acid residue p35 subunit, and migrates due to glycosylation as an approximately 75 kDa protein under non-reducing and reducing conditions in SDS-PAGE. Optimized DNA sequence encoding human Interleukin-12 mature chain was expressed in Chinese Hamster Ovary (CHO) cells.