Leukemia inhibitory factor, also known as LIF, is a pleiotropic cytokine that is expressed by a wide variety of cells including activated T lymphocytes, monocytes, mast cells and neuronal cells. It is involved in the induction of hematopoietic differentiation in normal and myeloid leukemia cells, induction of neuronal cell differentiation, regulator of mesenchymal to epithelial conversion during kidney development, and may also have a role in immune tolerance at the maternal-fetal interface.