IL28B is a newly-discovered type III interferon, with antiviral, antiproliferative, and immunomodulatory functions. Type III IFNs share homology with IL-10 and the IL-10R2 receptor subunit, leading to the speculation that these cytokines might be evolutionarily related. It was recently found that polymorphisms in IFN-lambda-4 (another type III interferon) are associated with circulating IL28B, and higher plasma IL28B are associated with higher production of antibodies to HBV surface antigen. IL28B is associated with the extent of lupus activity, in particular with active serosal and cutaneous disease. Combined treatment with IL28B and sorafenib (a small molecule multikinase inhibitor) facilitates a synergistic effect on suppressing hepatocellular carcinoma cancer growth and promoting cell apoptosis in vitro and in vivo.