Immunology · Cytokines and molecules
Type I interferons (α, β) !
- Molecule
Type I interferons are an early antiviral warning: an infected cell releases them so its neighbours resist the virus. In lupus they are overactive.
Updated 2026-11-01
What it is
Type I interferons include about 13 IFN-α subtypes, IFN-β and several minor members. Infected cells release them after sensing viral nucleic acids through pattern-recognition receptors, and plasmacytoid dendritic cells produce very large amounts. All of them use one receptor (IFNAR1/IFNAR2), which activates JAK1 and TYK2, forms the ISGF3 complex (STAT1, STAT2, IRF9) and switches on hundreds of interferon-stimulated genes that block viral replication.
Step by step
- A virus infects a cell; sensors detect its RNA or DNA.
- The cell (or a nearby plasmacytoid dendritic cell) releases IFN-α and IFN-β.
- The interferons bind IFNAR on neighbouring cells, activating JAK1 and TYK2.
- ISGF3 enters the nucleus and switches on interferon-stimulated genes.
- Neighbouring cells become resistant to the virus, raise MHC class I and alert NK cells.
Clinical notes
- Systemic lupus erythematosus: immune complexes containing nucleic acids stimulate plasmacytoid dendritic cells; anifrolumab is an anti-IFNAR1 antibody.
- Multiple sclerosis: IFN-β reduces relapses (it does not cure the disease).
- Pegylated IFN-α was a backbone of hepatitis C therapy before direct-acting antivirals and is still used in some hepatitis B cases.
- Type I interferonopathies: inherited excess of interferon signalling with inflammation from infancy.
- In some bacterial infections, including tuberculosis, excess type I interferon harms the host.
Test yourself
Think of the answer, then tap the question to see it.
Which receptor do all type I interferons use?
IFNAR, made of IFNAR1 and IFNAR2, which signals through JAK1 and TYK2.
Which cell is the main producer of IFN-α in lupus?
The plasmacytoid dendritic cell, stimulated by nucleic acid-containing immune complexes.
What is anifrolumab and how does it act?
A human monoclonal antibody against IFNAR1; it blocks the signalling of all type I interferons in lupus.
Related
- Cytokines: the table to know
- Interferon-γ
- Fc receptors, BCR and TCR
- Dendritic cell (professional antigen-presenting cell)
- Natural killer cell
- Pattern recognition: PAMPs, DAMPs, Toll-like receptors
- Autoantibodies: the table to know
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Microorganisms
In Pharmacology
Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.
Sources: The Dual Nature of Type I and Type II Interferons (Frontiers in Immunology, 2018); What's New in the Treatment of Systemic Lupus Erythematosus (Frontiers in Medicine, 2021); Interferon Beta-1a Subcutaneous Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); 21.2 Barrier Defenses and the Innate Immune Response - Anatomy and Physiology 2e | OpenStax (OpenStax, 2022).
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Representative model, for educational purposes only.