Transforming growth factor beta 1 (TGF-β1) is a member of the transforming growth factor beta superfamily of cytokines. The TGF-β1 precursor contains 390 amino acids with an N-terminal signal peptide of 29 amino acids required for secretion from a cell, a 249 amino acid pro-region (latency associated peptide or LAP), and a 112 amino acid C-terminal region that becomes the active TGF-β1 upon activation.Both LAP and TGF-β1 exist as homodimers in circulation, but the disulfide linked homodimers of LAP and TGF-β1 remain non-covalently associated, forming the small latent TGF-β complex (SLC, 100 kD). The large latent TGF-β complex (LLC, 235-260 kD) contains a third component, the latent TGF-β binding protein (LTBP), which is linked to LAP by a single disulfide bond. LTBP does not confer latency but is for efficient secretion of the complex to extracellular sites. Free active TGF-β1 can be released (activated) by many factors, including enzymes and low or high pH.TGF-β1 is nearly 100% conserved across mammalian species. It has diverse biological functions in multiple cellular processes such as regulating proliferation and differentiation of various cell types. TGF-β1 is also an important immunoregulatory cytokine, which is involved in the maintenance of self-tolerance, Th17 differentiation, and T-cell homeostasis.