Interferons are proteins produced by the body's cells in response to viral infections and other stimuli. They play 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 eliminate infected cells. There are three main types of interferons: Type I, Type II, and Type III. Each type has distinct functions and is produced by different cells. Type I interferons, for example, are primarily produced by fibroblasts and macrophages, while Type II interferons are produced by T cells and natural killer cells.