Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) is a protein that plays a crucial role in the immune system. It stimulates the production and function of granulocytes and macrophages, which are types of white blood cells essential for fighting infections and responding to inflammation. GM-CSF is produced by various cells, including T cells, macrophages, and fibroblasts. In medical settings, GM-CSF is used as a therapeutic agent to enhance the immune response, particularly in patients undergoing chemotherapy or those with certain blood disorders. It can help increase the number of white blood cells, improving the body’s ability to combat infections and recover from treatments.