Interferon is a type of protein produced by the body's cells in response to viral infections. It plays a crucial role in the immune system by signaling neighboring cells to enhance their defenses against viruses. Interferons can also activate immune cells, such as T cells and natural killer cells, which help to eliminate infected cells. There are three main types of interferons: Type I, Type II, and Type III. Each type has different functions and is produced by various cells in the body. Interferons are also used as medical treatments for certain diseases, including some types of cancer and viral infections like hepatitis and multiple sclerosis.