A DNA sequence encoding the p35 subunit of human IL12, termed as IL12A (NP_000873.2) (Met1-Ser219) was fused with the C-terminal His-tagged Fc region of human IgG1 at the C-terminus, constructed the plasmid 1; A DNA sequence encoding the human IL27B, (NP_005746.2) (Met1-Lys229) was fused with the C-terminal flag-tagged Fc region of human IgG1 at the C-terminus, constructed the plasmid 2. The two plasmids were co-expressed and the heterodimer was purified.