THE CURRENT excitement in research on transforming growth factor—β (TGF-β) comes from its multiple actions on almost every type of cell and its potential for therapeutic use in common clinical conditions for which there are no adequate pharmacologic agents. Although TGF-β was identified originally in an assay that measured its ability to enhance the growth of fibroblasts in soft agar ("transformation"), its true importance is as a mediator of normal cellular physiology, in particular during normal formation of tissues (as in embryogenesis) and during tissue response to injury (as in inflammation and repair). Almost all cells have been shown to make TGF-β in one of its molecular forms, and al— most all normal cells have receptors for TGF-β.
Transforming growth factor—β1 is a highly stable peptide that consists of two identical chains, each containing 112 amino acids. It was first isolated and characterized from human platelets and placentas as well
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