SCF is a stromal cell-derived cytokine synthesized by fibroblasts and other cell types. SCF promotes proliferation and early differentiation of cells at the level of multipotent stem cells. It has been suggested that SCF is essential for optimal production of various hematopoietic lineages, mainly because of its ability to prevent apoptosis when co-stimulated with other cytokines. The receptor for SCF, designated SCFR (CD117) is the oncogene designated as KIT. The biological activities of SCF are considerably synergised by colony stimulating factors; GM-CSF and G-CSF, and by IL7, EPO and some other growth and differentiation factors. In combination with IL7, SCF stimulates the proliferation of pre-B cells. SCF is also a potent chemoattractant for cells expressing the kit receptor. Recombinant Human SCF expressed in human 293 cells is a monomeric glycoprotein with a molecular mass of 35 to 45 kDa.