IL-6, or Interleukin-6, is a type of protein known as a cytokine, which plays a crucial role in the immune system. It is produced by various cells, including macrophages and T-cells, and helps regulate inflammation and the body's response to infections. Elevated levels of IL-6 can indicate an ongoing inflammatory process or infection. In addition to its role in immune response, IL-6 is involved in various physiological processes, such as the regulation of metabolism and the stimulation of B-cells to produce antibodies. Abnormal levels of IL-6 have been linked to several diseases, including autoimmune disorders and certain types of cancer.