Interferons are a group of proteins that produced by immune cells. They play an instrumental role in defending the body from viruses by interfering with viral reproduction. It stimulates the surrounding cells to synthesize proteins that would prevent the viruses from multiplying. They also help to regulate the immune system by “inhibit[ing] B-lymphocyte activation, enhance[ing] T-lymphocyte (T-cell) activity, and increas[ing] the cellular-destruction capability of natural killer cells” (Citation 9). Like interleukins, interferons are also a type of cytokines.There are three types of interferons: alpha, beta, and gamma. Alpha and beta forms are Type I Interferons while gamma falls into Type II. Type I interferons can be produced by almost any cell upon stimulation by a virus; their primary function is to induce viral resistance in cells. Type II interferon is secreted only by natural killer cells and T lymphocytes; its main purpose is to signal the immune system to respond to infectious agents or cancerous growth. Alpha interferons are used to treat hairy cell leukemia, hepatitis B & C, and genital warts, while beta interferons are used in treating multiple sclerosis. Gamma interferons have been used for treating chronic granulomatous disease.