Chemokine (C-C motif) receptor 9 (CCR9) is a seven transmembrane protein similar to G protein-coupled receptors. Chemokines and their receptors are key regulators of the thymocytes migration and maturation in normal and inflammation conditions. CCR9 has been found to be differentially expressed by T lymphocytes of the small intestine and colon, where it plays a role in thymocytes recruitment and development and may permit functional specialization of immune responses in different segment of the gastrointestinal tract. In immunohistochemistry, CCR9 is primarily found on the membranes of immune cells in the thymus, lymph nodes and spleen, with some expression on T lymphocytes in gastrointestinal tissue. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804