An additional complexity is that both endogenous and administered IFNs may interact in an additive, synergetic or cross‐inhibitory manner, as demonstrated for the interplay between IFNα and IFNγ (Lasfar et al, 2014) and the intricate relationship between IFNα and IFNλ in hepatitis C (Duong et al, 2014; Egli et al, 2014b). The gene discussed is IFNA1; the disease is hepatitis C virus infection.