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Pre-B cell colony enhancing factor (PBEF) was originally identified as a cytokine that potentiated the clonal expansion and differentiation of pre-B cells, but it is also acknowledged to be the ubiquitous intracellular enzyme nicotinamide phosphoribosyltranferase (NAMPT) and the adipokine "visfatin". PBEF is constitutively expressed in the fetal membranes where its greatest expression is in the amnion. It has intracellular and extracellular forms. Most of the intracellular functions of PBEF are due to its role as a Nampt which can induce angiogenesis through upregulation of VEGF and VEGFR and secretion of MCP-1. Extracellular PBEF has been shown to increase inflammatory cytokines, such as TNF-α, IL-1β, IL-16, and TGF-β1. PBEF also increases the production of IL-6, TNF-α, and IL-1β in CD14+ monocyctes, macrophages, and dendritic cells, enhances the effectiveness of T cells.