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 and are characterized by their production of the cytokine IL-17. This cytokine helps recruit other immune cells to sites of inflammation, enhancing the body's ability to fight off pathogens. These cells are particularly important in combating fungal and bacterial infections, as well as in the development of certain autoimmune diseases. Dysregulation of Th17 cells can lead to excessive inflammation, contributing to conditions like multiple sclerosis and rheumatoid arthritis.