ITGAE

Integrin, alpha E (ITGAE) also known as CD103 (cluster of differentiation 103) is an is_associated_with::integrin protein that in human is encoded by the ITGAE is_associated_with::gene. CD103 binds integrin beta 7 (β7– is_associated_with::ITGB7) to form the complete heterodimeric integrin molecule αEβ7, which has no distinct name. The αEβ7 complex is often referred to as "CD103" though this appellation strictly refers only to the αE chain. Note that the β7 subunit can bind with other integrin α chains, such as α4 (is_associated_with::CD49d).

Tissue distribution
CD103 is expressed widely on is_associated_with::intraepithelial lymphocyte (IEL) T cells (both αβ T cells and is_associated_with::γδ T cells) and on some peripheral is_associated_with::regulatory T cells (Tregs). It has also been reported on is_associated_with::lamina propria T cells. A subset of is_associated_with::dendritic cells in the gut is_associated_with::mucosa and in is_associated_with::mesenteric lymph nodes also expresses this marker and is known as CD103 DCs.

It is useful in identifying is_associated_with::Hairy cell leukemia which is positive for this marker in contrast to most other hematologic malignancies which are negative for CD103 except is_associated_with::Enteropathy associated T cell lymphoma.

Function
The chief ligand for αEβ7 is E-cadherin, an adhesion molecule (CAM) found on epithelial cells. It is probably important for T cell homing to the intestinal sites.

Tregs are important for decreasing the immune response and appear to play a crucial role in the prevention of is_associated_with::autoimmune diseases. Tregs are defined as is_associated_with::CD4+/is_associated_with::CD25+/Foxp3+ cells. Some CD4+/FoxP3− cells also express is_associated_with::CD103 and have been attributed regulatory activity. It is unclear whether the presence of CD103 on Treg cells represents a specialized feature for Treg, or Treg differentiation of IEL T cells.