CLONING AND EXPRESSION OF THE CHICKEN INTERFERON-GAMMA GENE

We have cloned the gene for chicken interferon-gamma (ChIFN-gamma) fro m a cDNA expression library generated from a T cell line (CC8.1h) that produces high levels of IFN-gamma activity, CC8.1h constitutively pro duces IFN activity that shares physiochemical properties with mammalia n IFN-gamma, ChIFN-gamma, when secreted by CC8.1h or expressed in tran sfected COS cells, is heat labile, inactivated by exposure to pH 2, an d capable of inducing nitrite production by chicken macrophages, These properties clearly distinguish it from chicken and mammalian type I I FN. The ChIFN-gamma gene codes for a predicted mature protein of 145 a mino acids with a molecular mass of 16.8 kD, There are two potential N -glycosylation sites located near the N terminus, ChIFN-gamma protein shares significant amino acid homology with mammalian IFN-gamma protei ns; in particular it also contains the highly conserved moths that are present in all mammalian IFN-gamma proteins, ChIFN-gamma is 35 and 32 % identical to the equine and human counterparts, respectively, but sh ares only 15% homology with chicken type I IFN, These findings show th at the emergence of the two principal types of IFN predates the diverg ence of avians and mammals that occurred some 350 million years ago.