Purity >95% as determined by SDS-PAGE. Fms-related tyrosine kinase 3 ligand (FLT-3 ligand) is a growth factor that regulates hematopoietic cell proliferation. FLT-3 ligand signalling is transmitted through the fms-related tyrosine kinase 3 (FLT-3) receptor. FLT-3 ligand promotes the long-term expansion and differentiation of pro-B cells in the presence of interleukin 7 (IL-7,) or in combination of IL-7 and interleukin 3 (IL-3).