Type I interferons have what dual roles in antiviral defense and cancer therapy?

• A. They induce antiviral states and activate immune cells
• B. They suppress immune responses
• C. They are not used clinically
• D. They directly kill tumor cells

Answer: (A)

Type I interferons work by both turning on antiviral defenses inside cells and by rallying the immune system. When they bind to receptors on cells, they trigger a cascade that makes many interferon-stimulated genes. Those genes produce proteins that block viral replication, degrade viral RNA, and shut down viral protein synthesis, creating an antiviral state in cells. At the same time, these interferons boost immune responses: they activate natural killer cells, promote maturation and antigen presentation by dendritic cells, and enhance cytotoxic T cell activity. In cancer therapy, these same effects help the body recognize and attack tumor cells and can slow tumor growth in certain contexts. That combination—inducing antiviral states and activating immune cells for immune-mediated defense against cancer—captures the dual roles. The other options don’t fit: they do not primarily suppress immune responses, they are used clinically in several viral infections and cancers, and their anti-tumor effects are not mainly from directly killing tumor cells.