Host antiviral response: Which type I interferons are produced by virus-infected human cells as an early innate immune defense?

Introduction / Context:
Interferons are pivotal cytokines in the innate antiviral response. Early after infection, cells produce interferons that induce an antiviral state in neighboring cells and modulate immunity.

Given Data / Assumptions:

• Question asks which interferons virus-infected cells produce.
• Options list interferon alpha (IFN-α) and interferon beta (IFN-β).

Concept / Approach:
Type I interferons include multiple IFN-α subtypes (often from plasmacytoid dendritic cells and other leukocytes) and IFN-β (commonly from fibroblasts and many infected cell types). Both are produced upon sensing viral nucleic acids via pattern recognition receptors and activate interferon-stimulated genes.

Step-by-Step Solution:
Identify type I interferons induced by viral infection: IFN-α and IFN-β. Note that both are produced by infected or sentinel cells to signal an antiviral state. Select the combined option indicating both α and β.

Verification / Alternative check:
Gene expression assays show upregulation of IFN-α and IFN-β following RIG-I/MDA5 or TLR signaling; downstream STAT1/STAT2 activation confirms functionality.

Why Other Options Are Wrong:

• Only α or only β: incomplete; both are hallmark type I interferons.
• None of these: incorrect because type I interferons are indeed produced.

Common Pitfalls:
Confusing type I interferons (α/β) with type II interferon (IFN-γ), which is primarily produced by NK and T cells and has different roles.

Final Answer:
Both (a) and (b)