Which cytokine class is produced by virus-infected cells and has antiviral activity?

• A. Chemokines (cytokine)
• B. Interleukins (cytokine)
• C. Interferons (cytokine)
• D. Autocrine (cytokine action)

Answer: (A)

Interferons are produced by virus-infected cells and trigger antiviral defenses in neighboring cells. When a cell detects viral components, it releases interferons (especially type I: IFN-α and IFN-β). They bind to receptors on nearby cells, activating signaling pathways that turn on interferon-stimulated genes. These genes produce proteins that block viral replication—such as inhibiting protein synthesis, degrading viral RNA, and preventing viral spread. Interferons also boost immune responses by increasing MHC class I expression and activating natural killer cells.

Chemokines are focused on recruiting immune cells to the site of infection, not directly inducing an antiviral state. Interleukins encompass a broad group of cytokines with diverse roles in immune signaling, not specifically antiviral in the way interferons are. Autocrine describes how a cell responds to its own cytokines rather than a distinct cytokine class.