Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that belongs to the IL-6 receptor family. It binds to a heterodimeric membrane receptor made up of a LIF-specific subunit, gp190, and the subunit gp130. The LIF complex receptor signals though STAT3 and JAK kinases. LIF expression has been observed in various tissues including the thymus, lung, and neuronal tissue. LIF displays diverse biological effects, but is best known for its ability to inhibit the differentiation of embryonic stem cells in mice and contributes to stem cell self-renewal. It is involved in the induction of hematopoietic differentiation in normal and myeloid leukemia cells, as well as the induction of neuronal cell differentiation. It also regulates mesenchymal to epithelial conversion during kidney development, and also may have a role in immune tolerance at the maternal-fetal interface. LIF can be upregulated by pro-inflammatory cytokines such as TNF-α and IL-17. Elevated levels of LIF have been found in cases of rheumatoid arthritis, neural injury, systemic inflammation, and tuberculosis.