FLT3 is a Type III tyrosine kinase cell surface receptor found on primitive bone marrow stem cells. The FLT3 ligand is a hematopoietic growth factor that stimulates cells via a set of structurally related tyrosine kinase receptors. This FLT3 Ligand promotes the differentiation of multiple hematopoietic cell lineages and is expressed as a non-covalently-linked dimer by T-cells, bone marrow, and thymic fibroblasts.