TECK/CCL25 (thymus-expressed chemokine) is expressed in a highly specific fashion by thymic stromal cells and at lower levels in the small intestine. It is probably involved in T cell development and/or in thymic architecture. It is classified in the CC or β subfamily of chemokines. It is now designated CCL25 according to the new chemokine nomenclature. TECK/CCL25 is chemotactic for activated macrophages, thymocytes, and perhaps dendritic cells in vitro. Mouse TECK/CCL25 is located on chromosome 8 and human TECK/CCL25 is located in a syntenic region in chromosome 19pl3.2. It is produced by thymic dendritic cells and epithelial cells. CCR9, formerly known as GPR9-6, has been identified as the TECK/CCL25 receptor.