The ACK2 antibody is specific for CD117, also called c-Kit, a 145 kDa cytokine receptor important in the development of hematopoietic stem cells, in oogenesis, and for functional activity of immune cells such as NK and mast cells. c-Kit binds to a ligand known as stem cell factor (SCF), or alternatively as mast cell growth factor. Ligand binding promotes the activation (dimerization) and subsequent tyrosine kinase activity of the c-Kit receptor and triggers key survival, expansion and maturation signals during hematopoietic progenitor cell development. Conversely, shedding of extracellular domain of c-Kit receptor is reported to induce inactivation or apoptosis within these cells. The survival signaling activity of c-Kit confers a proto-oncogenic attribute to the receptor, as overexpression or mutations in this protein are associated with tumor development.The ACK2 antibody is widely utilized as a marker to identify hematopoietic progenitors, and to neutralize receptor-ligand binding in vitro and in vivo.