Leukemia inhibitory factor--a puzzling polyfunctional regulator.

LIF seems likely to have important functions in the early developing embryo and in adult life can influence platelet formation, osteoblast and neuronal function, calcium and lipid metabolism and the production of acute-phase proteins. LIF appears usually to be produced and to function locally in various tissues, an arrangement that would minimize unwanted actions of this polyfunctional regulator. Nevertheless it remains puzzling what purpose is achieved by use of a regulator with potent actions on such a wide range of apparently unrelated tissues.