The human gamma interferon receptor accessory factor encoded by chromosome 21 transduces the signal for the induction of 2',5'-oligoadenylate-synthetase, resistance to virus cytopathic effect, and major histocompatibility complex class I antigens.

Mouse fibroblasts, and human-mouse hybrid fibroblasts carrying only human chromosome 21, were transfected with cDNA encoding full-length human gamma interferon (IFN-gamma) receptor or chimeric IFN-gamma receptor (extracellular domain of the human receptor; transmembrane and intracellular domains of mouse origin). These transfected mouse cells were sensitive to human IFN-gamma only when human chromosome 21 was present. These results show that the species-specific accessory protein encoded by human chromosome 21 interacts with the extracellular domain of human IFN-gamma receptor and transduces the IFN-gamma signal not only for up-regulation of mouse major histocompatibility complex class I antigen expression but also for the induction of 2',5'-oligoadenylate-synthetase and resistance to virus cytopathic effect.