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

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

Answer: (B)

Interferons are antiviral cytokines produced by virus-infected cells that help establish an antiviral state in neighboring cells. When released, they bind to receptors on nearby cells and induce the expression of antiviral proteins (such as PKR and other interferon-stimulated genes) that inhibit viral replication. They also enhance immune responses by upregulating MHC class I and activating natural killer cells.

Chemokines mainly guide immune cells to sites of infection, not directly establishing antiviral states. Interleukins cover a broad range of signaling molecules with diverse roles in immunity, not specifically antiviral defense. Autocrine describes a mode of cytokine action where a cell responds to cytokines it itself secretes, rather than naming a cytokine class.