![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Primary_biliary_cirrhosis_low_mag.jpg/640px-Primary_biliary_cirrhosis_low_mag.jpg&w=640&q=50)
Intraepithelial lymphocyte
From Wikipedia, the free encyclopedia
Intraepithelial lymphocytes (IEL) are lymphocytes found in the epithelial layer of mammalian mucosal linings, such as the gastrointestinal (GI) tract and reproductive tract.[1] 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).[2]
Intestinal IELs are long-lived resistant effector cells spread along the entire length of intestine, where they patrol the space between intestinal epithelial cells (IEC) and the basement membrane (the intraepithelial space). Epithelium of small intestine contains approximately 1 IEL per 10 enterocytes.[3] Due to their constant exposure to of antigens at mucosal barrier, they have unique antigen-experienced activated phenotypes and they constantly express CD103 (αE integrin), that is distinct from the conventional T cells in the intestine.[3] IELs are mainly T cells with mixture of subsets. They are divided into two groups – conventional and unconventional IELs.[4]
In mice both groups are retained in almost equal proportions.[5] In humans, the majority of IELs are alpha beta T cells. 15% of IELs are gamma delta T cells and thus represent a minor component of human IELs. However, IELs significantly increase under certain conditions, such as celiac disease.[1]
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Primary_biliary_cirrhosis_low_mag.jpg/640px-Primary_biliary_cirrhosis_low_mag.jpg)