CSF1, also known as macrophage colony-stimulating factor 1, is a hematopoietic growth factor that is the primary regulator of the survival, proliferation, differentiation and function of mononuclear phagocytes. It is a four alpha-helical bundle cytokine and its active form is found extracellularly as a disulfide linked homodimer. This protein plays important roles in innate immunity, cancer and inflammatory diseases, including systemic lupus erythematosus, arthritis, atherosclerosis and obesity. In several conditions, activation of macrophages involves a CSF1 autocrine loop. In addition, secreted and cell-surface isoforms of CSF1 can have differential effects in inflammation and immunity. Recombinant human CSF1, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.