CD28(+) intraepithelial lymphocytes with long telomeres are recruited within the inflamed ileal mucosa in Crohn disease

Crohn disease is a chronic inflammatory bowel disease that involves all the intestine but predominantly alters the ileum. The disease largely depends on T cells, but the biologic role of intestinal intraepithelial lymphocytes (IEL) in transmural inflammation remains poorly characterized. To address this issue, a comparison oi IEL and lamina propria lymphocytes (LPL) isolat ed from the uninvolved and the inflamed ileal mucosa oi Crohn disease patie nts was performed. More CD8(+) IEL (26% versus 8%) from the inflamed ileal mucosa expressed the CD28 receptor and the CD11a integrin than IEL from the uninvolved ileal mucosa, which were mostly CD28(-). IEL had longer telomer es in the inflamed than in the uninvolved areas and a TCR VP repertoire mor e similar to circulating T cells, suggesting that the increased proportion of CD28(+) TCR alpha beta (+) IEL within the inflamed mucosa is more likely due to recruited lymphocytes from the periphery that populate the epitheli al layer than to the acquisition of the CD28 molecule by activated resident lymphocytes. In the uninvolved ileal mucosa, IEL from Crohn disease patien ts had shorter telomeric lengths than IEL front control patients, suggestin g that they have been chronically stimulated. Such perturbation of the IEL population within tile ileal mucosa could contribute to the inflammation in Crohn disease. (C) American Society for Histocompatibility and Immunogenet ics, 2001. Published by Elsevier Science Inc.