ABSTRACT
The designation of interferons as “Type I” originated more than 25 years ago, to distinguish one class of interferons, characterized by lack of inactivation after exposure to pH2, from another antiviral protein that was acid-labile and was referred to as “Type II” interferon. Later on, type II IFN was called immune IFN, and has since become IFN-γ. It is a lymphokine that displays no molecular homology with type I IFNs, but shares some biological activities. In fact, the activities of type I and type II IFNs are intimately related, in that type I IFN can up-or down-regulate the production of type II IFN, and type II IFN can induce the synthesis of type I IFN.Moreover, the signal transduction pathways of type I and type II IFN partly overlap.
