T-helper 17 cells, or 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 CD4+ T cells and are primarily involved in promoting inflammation. Th17 cells produce specific signaling molecules called cytokines, particularly IL-17, which help recruit other immune cells to sites of infection or injury. These cells are important for fighting off certain pathogens, especially bacteria and fungi. However, an overactive response from Th17 cells can contribute to autoimmune diseases, where the immune system mistakenly attacks the body's own tissues. Balancing Th17 activity is essential for maintaining health.