Interferon beta (IFN-β) is a monomeric protein and belongs together with IFN-α to the type I interferon family. It shares with IFN-α the same dimeric receptor (IFN-α R1/R2). IFN-β is produced by virally infected cells and fibroblasts, and bears a strong non-specific anti-viral activity, including activation of cytotoxic cells. However, IFN-β can also modulate immune cell proliferation and MHC class I–mediated antigen presentation, and is therefore under investigation as treatment against autoimmune diseases, such as multiple sclerosis. A role for IFN-β has been identified also in control of solid tumor development, and local tumor treatments with IFN-β are under investigation for several cancer conditions. IFN-β is usually produced as recombinant protein in two variants: IFN-β1a and IFN-β1b. IFN-β1a is manufactured in mammalian cells (CHO cells), its sequence is identical to the natural form, and carries glycosylations. IFN-β1b is a mutated form with one amino acid exchange, expressed in E. coli
. IFN-β is active only in species-specific way.