IFN -u-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-lambdas uses a distinct receptor system composed of an IFN-uR1 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. Recombinant human IFN-lamda 2 is a 19.6kD protein containing 174aa.