IFNAR-1, the type I IFN receptor subunit 1, is coexpressed with IFNAR-2 on nearly all cells and make up the heterodimeric receptor complex that binds to all type I IFNs (IFN-alpha/beta). Type I IFNs are a group of structurally and functionally related cytokines that have been shown to promote anti-viral, anti-microbial, anti-tumor, and autoimmune responses. Ligand binding to the IFN-alpha/beta receptor complex leads to the tyrosine phosphorylation and activation of IFNAR-1-associated Tyk2 and IFNAR-2-associated Jak1 signal transductions.