What are interferons?

• A. Antibodies produced by B cells
• B. Lipids involved in inflammation
• C. Enzymes that digest pathogens
• D. Small proteins released by activated lymphocytes and macrophages, and by tissue cells infected with viruses that slow viral replication and make other cells more resistant to viral infection

Answer: (D)

Interferons are small protein signals released by activated lymphocytes and macrophages, and by tissue cells that have been infected with viruses. They act as cytokines that create an antiviral state in neighboring cells, slowing viral replication and making those cells more resistant to infection. This protective effect comes from inducing antiviral proteins in surrounding cells that can inhibit viral gene expression and protein synthesis, helping to limit the spread of the virus. Interferons also help coordinate the immune response by enhancing the activity of natural killer cells and promoting antigen presentation.

They are not antibodies produced by B cells, not lipids involved in inflammation, and not enzymes that digest pathogens, which is why those options don’t fit.