IFN -?-1,-2, and -3 (also known as IL-29, IL-28A and IL-28B respectively) are distantly related to the IL-10 family and Interferons. All three IFN-?s uses a distinct receptor system composed of an IFN-?R1 subunit (also called CRF2-12) and IL-10R2 subunit (also called CRF2-14). Signaling through this receptor system induces antiviral defense similar but distinct than the type I Interferons.(Kotenko, SV. et al. Nat Immunology 2003 [1] p. 69-77). Recombinant human IFN-? 2 is a 19.6 kDa protein containing 174 amino acid residues.