Interleukin-17A (IL-17A) is a type of protein known as a cytokine, which plays a crucial role in the immune system. It is primarily produced by a subset of immune cells called T helper 17 (Th17) cells. IL-17A helps to promote inflammation and is involved in the body's defense against infections, particularly fungal and bacterial pathogens. However, excessive production of IL-17A can contribute to various inflammatory diseases, such as psoriasis and rheumatoid arthritis. Researchers are studying IL-17A to better understand its role in these conditions and to develop targeted therapies that can inhibit its activity, potentially improving treatment outcomes for affected individuals.