IFN-γ is one of the cytokines that has been cloned in many species, and a large number of studies have been performed on its homology and cross reactivity. One can conclude from these studies that that IFN-γ can be classified in three groups depending on functional and structural homology. The first group is composed of primate and human IFN-γ; the second group comprises IFN-γ from bovine, ovine, deer, porcine and horses. In the third group, we find IFN-γ from mice and rats. In general, most of the cytokines cloned have certain homology in respect to their sequence and so they present cross reactivity.
