Consensus terminology
| Term (abbreviation) | Definition |
| Interferon (IFN) | Proteins (cytokines) with anti-viral activity; IFNs are mediators of an anti-viral response. They belong to the type I, type II and type III IFN families. |
| Type I interferon (IFN-I) | The IFNs alpha, beta, omega, kappa, epsilon, secreted by any nucleated cell and binding to the IFNAR, which is expressed on any nucleated cell. |
| Type II interferon (IFN-II) | IFN gamma, mostly secreted by T cells, binding to the IFNGR, which is expressed on most leucocytes. |
| Type III interferon (IFN-III) | IFN lambda, which are structurally more similar to IL-10 but share downstream signalling and gene expression with IFN-I. |
| Interferon-stimulated genes (ISG) | Genes whose expression is known to be upregulated by any kind of IFN. Individual ISGs may not exclusively represent Type I IFN pathway activation. |
| Type I Interferon pathway | Type I IFN pathway is a dynamic, biological system that includes the secretion of type I IFN protein, binding to the IFNAR, initiation of Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathways, expression of IFN-stimulated genes and the expression of IFN-stimulated proteins. |
| Type I Interferon pathway activation | Any evidence for changes in function or levels of the components of the type I IFN pathway. |
| Type I interferon pathway assay | An assay measuring one or more components of the Type I IFN pathway at a molecular or functional level. |
| Interferon stimulated gene expression signature | A qualitative description of coordinated expression of a set of ISGs that is indicative of type I IFN pathway activation. |
| Interferon stimulated gene expression score | A quantitative variable derived from expression of a defined set of ISGs that is indicative of type I IFN pathway activation. |
| Interferon stimulated protein score | A variable derived from expression of a defined set of soluble biomarkers known to be upregulated by IFN, although not specific for type I IFN. |
| Interferonopathy | Mendelian diseases in which there is constitutive type I IFN pathway activation with a causal role in pathology. The clinical picture may resemble RMDs. However, most diseases with IFN pathway activation are polygenic disorders and not mendelian tnterferonopathies. |
RMDs, rheumatic and musculoskeletal diseases.