Stem Cell Factor (SCF) is a glycoprotein that plays a key role in hematopoiesis acting both as a positive and negative regulator, often in synergy with other cytokines. SCF binds to and activates the SCF receptor (SCFR), a receptor tyrosine kinase. SCF stimulates the proliferation of mast cells and is able to augment the proliferation of both myeloid and lymphoid hematopoietic progenitors in bone marrow culture. It also mediates cell- cell adhesion and acts synergistically with other cytokine.