IL-17 is a type of protein known as a cytokine, which plays a crucial role in the immune system. It is primarily produced by a group of immune cells called T-helper 17 cells. IL-17 helps to coordinate the body's response to infections and inflammation by promoting the recruitment of other immune cells to sites of infection. This cytokine is involved in various autoimmune diseases, such as psoriasis and rheumatoid arthritis, where the immune system mistakenly attacks the body's own tissues. Research on IL-17 has led to the development of targeted therapies that aim to block its action, providing new treatment options for these conditions.