TGFβ3 is a member of the TGF-β superfamily subgroup defined by its structural and functional similarities.TGF-β3 and β1, β2 act as cellular switches to regulate immune function, cell proliferation and epithelial-mesenchymal transition. The human TGF-β3 cDNA encodes the 412 aa precursor, which contains 20 aa signaling peptides and 392 aa proteins. Mature human TGF-β3 shares 100%, 99%, and 98% homology with mouse/dog/horse, rat, and porcine TGF-β3, respectively.TGF-β3 has high affinity for TGF-βRII, a type II serine/threonine kinase receptor. This receptor phosphorylates and activates the type I serine/threonine kinase receptor TGF-βRI or ALK-1 to regulate transcription via Smad phosphorylation.