sentences:  This hypothesis is supported by observations that cell lines with low IFNAR1 expression respond to IFNβ but not IFNα.IFNAR2 is the high affinity subunit, originally cloned in 1994, composed of two FNII-like subdomains, termed D1 and D2.Type I IFNs bind D1 and D2 with a typical binding affinity between 0.4–5nM; IFNβ binds at a slightly lower affinity (0.1nM).