CSF1R, or Colony Stimulating Factor 1 Receptor, is a protein found on the surface of certain cells in the body. It plays a crucial role in the development and function of macrophages, which are important immune cells that help fight infections and clear debris. The receptor is activated by its ligand, CSF1 (Colony Stimulating Factor 1), leading to various cellular responses. Abnormalities in CSF1R signaling have been linked to several diseases, including certain types of cancer and autoimmune disorders, making it a target for therapeutic research.