The first example discovered of a viroceptor (virus-encoded receptor homolog) targeted against the interferon family was the M-T7 gene product of myxoma virus, a secreted glycoprotein of 37kDa that shares sequence similarity to the external ligand-binding domain of the cellular IFNγ receptor. Later, M-T7 was shown to be closely related to a variety of homologous genes in many other poxviruses that share sequence homology to the same domain of the cellular receptors. Studies have shown that these poxvirus IFNγ receptors bind and inhibit IFNγ in a relatively species-specific fashion, with the highest affinity generally being to the ligand derived from the host species of the particular poxvirus.