LGR5 (Leucine-rich repeat containing G protein-coupled receptor) is a seven-transmembrane receptor component of the Wnt receptor complex, which specifically acts as a receptor for a family of Wnt pathway agonists called R-spondins. In the mouse antrum, small intestine and stomach Lgr5-positive stem cells give rise to all differentiated cell lineages normally present in a crypt, and at least in mice, Lgr5 has also been shown to lineage-label gastric and intestinal stem cells. LGR5 is likely to be a robust stem cell marker in the human intestine also: in situ hybridization shows localization of LGR5 mRNA to the crypt base mirroring the architecture seen in the mouse. Lgr5+ cells have been shown to lineage-label within mouse small intestinal adenomas, and a considerable proportion of the crypt population expresses Lgr5, suggesting a population of hundreds of potential stem cells in each adenomatous gland. The 4D11F8 monoclonal antibody recognizes an epitope in the center of the leucine-rich repeat (LRR) region of human Lgr5.