Transforming growth factor beta 2 (TGF-β2) is synthesized as a prepro-cytokine with a 19 amino acid (aa) signal sequence, a 283 aa pro-region, and a 112 aa mature segment. The mature region of human TGF-β2 is 71 % and 80 % identical with human TGF-β1 and TGF-β3 and 97 % identical with the corresponding mouse protein. It is expressed by a variety of cells, including osteoclasts, thymic epithelium, keratinocytes, hepatocytes, chief cells of the stomach, satellite cells, etc. TGF-β2 has marked cross-species bioactivity (e.g., human TGF-β2 is active on mouse cells, while porcine TGF-β2 is active on rabbit cells). TGF-β2 has four fundamental activities: it is a growth inhibitor for most types of cells; it enhances the deposition of extracellular matrix; it is immunosuppressive, suppressing APC expression of both IL-12 and CD40L while upregulating IL-10 secretion; and during fetal development, it is expressed in discrete areas, such as epithelium, myocardium, cartilage and bone of extremities and in the nervous system, suggesting specific functions.