Interleukin-2 (IL-2) is a type of protein known as a cytokine, which plays a crucial role in the immune system. It is primarily produced by T cells, a type of white blood cell, and helps regulate the growth, development, and activity of immune cells. IL-2 is essential for the proliferation of T cells and B cells, which are vital for the body's defense against infections and diseases. IL-2 is also significant in medical treatments, particularly in cancer therapy and autoimmune diseases. It can enhance the immune response, making it a focus of research for therapies that aim to boost the body's ability to fight tumors. Additionally, synthetic forms of IL-2 are used in clinical settings to help patients with certain conditions.