IL-2, or Interleukin-2, is a type of protein known as a cytokine, which plays a crucial role in the immune system. It is produced by T cells, a kind of white blood cell, and helps regulate the growth and activity of other immune cells. By promoting the proliferation of T cells and B cells, IL-2 enhances the body's ability to fight infections and diseases. In addition to its natural functions, IL-2 is also used in medical treatments, particularly for certain types of cancer. Researchers have found that boosting IL-2 levels can help stimulate the immune response against tumors, making it a valuable tool in immunotherapy.