T helper 17 (Th17) cells are a subset of T cells that play a crucial role in the immune system. They are primarily involved in defending the body against fungal and bacterial infections. Th17 cells produce specific signaling molecules called cytokines, particularly IL-17, which help recruit other immune cells to sites of infection and inflammation. These cells are also linked to various autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis, due to their inflammatory properties. Understanding Th17 cells is important for developing targeted therapies to manage these conditions and improve immune responses.