Interferon-gamma is a type of protein known as a cytokine, produced mainly by T cells and natural killer cells in the immune system. It plays a crucial role in enhancing the immune response, particularly against infections and tumors. By activating immune cells, it helps the body fight off pathogens and can also influence the behavior of other cells. This cytokine is important for regulating various immune functions, including the activation of macrophages, which are cells that engulf and destroy pathogens. Additionally, interferon-gamma is used in medical treatments for certain conditions, such as chronic granulomatous disease and some types of cancer.