sentences:  Type I IFNs bind SD1-3 with a typical binding affinity between 0.5–5μM; IFNα1 and IFNβ are exceptions with binding affinities of 220nM and 100nM, respectively.Type I IFNs have a binding association rate of 5x105M/s with a variable dissociation rate that determines type I IFN subtype affinity for IFNAR1.IFNAR1 cytoplasmic domain associates with Tyk2 and Tyk2 is required for membrane expression of IFNAR1.