Interleukin-6 (IL-6) is a type of protein known as a cytokine, which plays a crucial role in the immune response. It is produced by various cells, including macrophages, T cells, and fibroblasts, and helps regulate inflammation and the body's defense against infections. IL-6 is involved in the activation of immune cells and the production of antibodies. In addition to its role in immunity, IL-6 is also linked to various diseases, including autoimmune disorders and cancers. Elevated levels of IL-6 can indicate chronic inflammation and are often associated with conditions like rheumatoid arthritis and COVID-19. Understanding IL-6 is important for developing targeted therapies for these diseases.