Transforming growth factor beta 1 ( TGF-β1) is one of three closely related mammalian members of the large TGF-beta superfamily that shares a characteristic cystine knot structure. TGF-β1 is a highly pleiotropic cytokine that acts as  a cellular switch. It is responsible for regulating processes such as immune function, proliferation, and mesenchymal transition. Human TGF-β1 encodes a 390 amino acid (aa) precursor that contains a 29 aa signal peptide and a 361 aa proprotein. TGF-β1 regulates many cellular processes including growth, differentiation, extracellular matrix formation, and immunosuppression. This kit provides the assay-specific components for the quantitative determination of TGF-β1 in human samples.