growth factor. Dysregulation of TGF-? activation and signaling may result in apoptosis. Many cells synthesize TGF-? and almost all of them have specific receptors for this peptide. TGF-?1, TGF-?2, and TGF-?3 all function through the same receptor signaling systems.

TGF-?1 was first identified in human platelets as a protein with a molecular mass of 25 kilodaltons