LIF (Leukemia Inhibitory Factor) is a pleiotropic member of the IL-6 family of cytokines. It functions through a heterodimeric receptor complex containing a ligand-binding subunit, LIF R alpha/CD118, and a signal transducing subunit, gp130. gp130 also serves as a subunit of the receptor complexes for Oncostatin M, Cardiotrophin-1, CNTF, IL-6, IL-11, and IL-27. LIF supports uterine implantation of the embryo, pluripotency in embryonic stem cells, and proliferation of progenitor cells. It promotes regulatory T cell and inhibits Th17 cell differentiation, and it is required by the thymic epithelium to support T cell maturation. It promotes motor neuron survival and oligodendrocyte myelination, enhances adrenal production of cortisol and aldosterone, and promotes differentiation of adipocytes and cardiac smooth muscle cells. LIF can also function as an autocrine growth factor in pancreatic cancer and can induce formation of immunosuppressive tumor-associated macrophages.