CSP1, which is most commonly known as Colony Stimulating Factor 1 (CSF-1), also referred to as Macrophage Colony-Stimulating Factor (M-CSF). CSP1/CSF-1 is a hematopoietic cytokine that is essential for the development, survival, and function of mononuclear phagocytes, including monocytes, tissue-resident macrophages, and osteoclasts. It exerts its effects by binding to and activating the colony-stimulating factor 1 receptor (CSF-1R, also known as c-FMS or CD115).