The interferons (IFN) consist of two groups of cytokines that are designated as Type I and Type II IFN. Type I IFN consist of four major classes: IFNα, IFNβ, IFNω and IFNτ, whereas IFNγ is the only Type II IFN. The large number of Type I IFN could be explained by redundancy, a different pattern of expression in different tissues or different functions for different IFN. The hypothesis of different functions for different IFN requires different receptors for each IFN. The receptors for Type I (IFNα, IFNβ, IFNω) and Type II (IFNγ) IFN have been identified and characterized. The IFNγ receptor consists of two transmembrane chains, IFNGR-1 and IFNGR- 2, both of which are required for activity. The IFNGR-1 chain binds the IFNγ ligand, whereas the IFNGR-2 chain is required for signal transduction. An analogous paradigm exists for Type I IFN (IFNα/β/ω) receptor. This receptor appears to consist of two chains, IFNAR-1 and IFNAR-2, that can be present in different forms. Thus, the IFNAR-1 chain is present as the full chain (IFNAR-1a) and a splice-variant (IFNAR-1s); the IFNAR-2 chain exists as a soluble, short and long forms, IFNAR-2a, IFNAR-2b and IFNAR-2c, respectively. Most likely, the IFNAR-1a and IFNAR-2c chains represent the predominantly active form. The various Type I IFN exhibit different interactions with the receptor components and these different patterns of interactions may reflect their different biological activities and help to explain the existence of this large family of IFNα species, as well of IFNβ and IFNω.
|Original language||English (US)|
|Number of pages||18|
|Journal||Reviews in Clinical and Experimental Hematology|
|State||Published - 1998|
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