Transforming growth factor-beta 1 (TGF-β1), also known as LAP, is a member of the TGF beta family of growth factors along with three other TGF-β isoforms; TGF-β2 and -3. They are multifunctional cytokines that regulate cell proliferation, growth, differentiation and motility as well as synthesis and deposition of the extracellular matrix (1). They are involved in various physiological processes including embryogenesis, tissue remodeling, wound healing, osteogenesis and immune cell function (1). The three isoforms are secreted predominantly as latent complexes which are stored at the cell surface and in the extracellular matrix. The release of biologically active TGF-β from a latent complex involves proteolytic processing of the complex and/or induction of conformational changes, by proteins such as thrombospondin-1 or MMP (2). TGF-β1 is the most abundant isoform secreted by almost every cell type. Regulatory T cells release TGF-β1 to inhibit the actions of other T cells (3). Similarly, TGF-β1 can inhibit the secretion and activity of many other cytokines including interferon-γ, TNF-α and various interleukins. It can also decrease the expression levels of cytokine receptors, such as the IL-2 receptor, to down-regulate the activity of immune cells. TGF-β1 has similar effects on B cells that also vary according to the differentiation state of the cell (4). It inhibits proliferation and apoptosis of B cells, and plays a role in controlling the expression of antibody, transferrin and MHC class II proteins on immature and mature B cells.

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