Animal-free Recombinant Human FLT3 Ligand is expressed from human 293 cells as a monomeric glycoprotein with an apparent molecular mass of 24 to 30 kDa. This cytokine is produced in a serum-free, chemically defined media. The molecular mass is a narrower range than reported when this cytokine is expressed in insect Sf21 cells (17 to 30 kDa), emphasizing the difference in glycosylation in different expression systems. FLT3 Ligand is a growth factor that regulates proliferation of early hematopoietic cells. FLT3 Ligand binds to cells expressing the tyrosine kinase receptor FLT3. FLT3 Ligand by itself does not stimulate proliferation of early hematopoietic cells, but synergizes with other CSFs and interleukins to induce growth and differentiation.