Intraepithelial lymphocytes (IEL) are lymphocytes found in the epithelial layer of mammalian mucosal linings, such as the gastrointestinal (GI) tract and reproductive tract. However, unlike other T cells, IELs do not need priming. Upon encountering antigens, they immediately release cytokines and cause killing of infected target cells. In the GI tract, they are components of gut-associated lymphoid tissue (GALT).
An elevated IEL population, as determined by biopsy, typically indicates ongoing inflammation within the mucosa. In diseases such as celiac sprue, IEL elevation throughout the small intestine is one of many specific markers.
Alternatively, elevated IEL populations can be a marker for developing neoplasia in the tissue such as found in cervical and prostate cancers, as well as some colorectal cancers, particularly those associated with Lynch syndrome (hereditary non-polyposis colon cancer <HNPCC>). IELs themselves can, when chronically activated, undergo mutation that can lead to lymphoma.
- Defranco, Anthony L; Locksley, Richard M; Robertson, Miranda. 2007. Immunity: The Immune Response in Infection and Inflammatory Disease. New Science Press Ltd. 218-219.
- Hopper AD, Hurlstone DP, Leeds JS, McAlindon ME, Dube AK, Stephenson TJ, Sanders DS (2006). "The occurrence of terminal ileal histological abnormalities in patients with celiac disease". Dig. Liver Dis. 38 (11): 815–9. doi:10.1016/j.dld.2006.04.003. PMID 16787773.
- Bellizzi AM, Frankel WL (2009). "Colorectal cancer due to deficiency in DNA mismatch repair function: a review". Advances in Anatomic Pathology. 16 (6): 405–417. doi:10.1097/PAP.0b013e3181bb6bdc. PMID 19851131.
- Meresse, Bertrand; Malamut, Georgia; Cerf-Bensussan, Nadine (2012-06-29). "Celiac disease: an immunological jigsaw". Immunity. 36 (6): 907–919. doi:10.1016/j.immuni.2012.06.006. ISSN 1097-4180. PMID 22749351.