Independent Origin of IFN-α and IFN-β in Birds and Mammals

Abstract
Phylogenetic analysis of type I interferon (IFN) from birds and mammals strongly supported the hypothesis that the gene duplication giving rise to the α and β families of mammalian IFN occurred after the divergence of birds from mammals, whereas the bird IFN that have been designated α and β duplicated independently in the avian lineage. Therefore, IFN designated α and β in birds are not orthologous to those similarly designated in mammals.