Cloning and expression of the cDNA for the murine interferon γ receptor

A murine interferon γ (IFN-γ) receptor cDNA was isolated by screening a murine T-cell hybridoma library prepared in λgt10 with probes prepared from a human IFN-γ receptor cDNA. The 2.1-kilobase (kb) cDNA encoded a serine-rich polypeptide of 477 amino acids that was 52% identical to the human protein. Southern and Northern (RNA) blot analyses indicated the presence of a single receptor gene and a single predominant 2.3-kb receptor transcript. Human embryonic kidney fibroblasts, stably transfected with the murine IFN-γ receptor cDNA, expressed murine IFN-γ receptors as detected by flow cytometry with either ligand or a receptor-specific monoclonal antibody. Nontransfected cells bound neither ligand nor antibody. Radioligand-binding analysis demonstrated that the transfectants expressed 530,000 murine IFN-γ receptors per cell and bound murine IFN-γ with a K(a) of 1 x 10⁹ M^-1. However, despite high-level expression of murine IFN-γ receptors, the transfected human cells responded only to human and not to murine IFN-γ as detected by enhancement of major histocompatibility class I antigen expression and induction of antiviral activity. These results thus document the isolation and expression of a full-length murine IFN-γ receptor cDNA and suggest that additional species-specific components may be necessary to form a biological active IFN-γ receptor.