Interleukin 28B is a cytokine with immunomodulatory activity. It up-regulates MHC class I antigen expression, displays potent antiviral activity, and also displays antitumor activity. Its ligand for the heterodimeric class II cytokine receptor composed of IL10RB and IL28RA, and the ligand/receptor complex seems to signal through the Jak-STAT pathway. Recominant Human IL28B isexpressed in human 293 cells as a non-glycosylated monomer with a molecular mass of 24 kDa.