TGF-beta 3 (transforming growth factor beta 3) Is a pleiotropic cytokine that regulates immune function, proliferation, and epithelial-mesenchymal transition. Disulfide-linked homodimers of LAP and TGF-beta 3 remain non-covalently associated after secretion, forming the small latent TGF-beta 3 complex. Covalent linkage of LAP to one of three latent TGF-beta binding proteins (LTBPs) creates a large latent complex that may interact with the extracellular matrix. Bioactive TGF-beta is released by proteolytic cleavage. TGF-beta 3 signals through a receptor complex containing TGF-beta RII and either TGF-beta RI/ALK5 or ALK1.