T-helper 17 (Th17) cells are a type of immune cell that play a crucial role in the body's defense against infections. They are a subset of T-helper cells, which are essential for coordinating the immune response. Th17 cells produce specific signaling molecules called cytokines, particularly interleukin-17 (IL-17), which help recruit other immune cells to sites of infection or inflammation. These cells are particularly important in fighting off certain types of bacteria and fungi. However, an overactive Th17 response can contribute to autoimmune diseases, where the immune system mistakenly attacks the body's own tissues. Understanding Th17 cells is vital for developing therapies for these conditions.