FLT3 gene encodes the class III receptor tyrosine, the kinase responsible for regulating the process of hematopoiesis. The receptor is composed of an extracellular component made up of five immunoglobulin-like areas as well as a transmembrane region and a cytoplasmic-based kinase region split in two through a kinase insert domain. 

FLT3 antigen is a genetic change or mutation that occurs in the cells of leukemia. Between 20 and 30 percent of patients who suffer from AML have this mutation. The FLT3 gene encodes for an enzyme called FLT3 which helps white blood cells to grow. The mutation of this gene promotes the development of unnatural leukemia cells.

The people who have the FLT3 mutation are diagnosed with a severe form of leukemia, which is more likely to return after treatment. FLT3 can be described as a tyrosine-protein Kinase which acts as a cell-surface receptor for Cytokine FLT3LG and regulates the proliferation, differentiation and life span of hemopoietic progenitors and Dendritic cells. 

FLT3 was initially identified through its presence in the hematopoietic stem/progenitor cell (PMID 7077245). It is essential in the development of the normal hematopoietic stem/progenitor cell. Changes that result in permanent activation of this receptor cause acute myeloid leukemia and acute lymphoblastic leukemia.

FMS-related tyrosine-kinase 3 (FLT3 is also known as FLK2) is part of the Type III receptor tyrosine kinase family, which includes c Kit, PDGFR and M-CSF receptors. FLT3 is found on the early hematopoietic progenitor cells and helps to promote differentiation and growth within the human hematopoietic system.