Flow cytometry description of a novel CD3-/CD7+ intraepithelial lymphocyte subset in human duodenal biopsies: potential diagnostic value in coeliac disease.

Intraepithelial lymphocytes (IEL) represent a heterogeneous cellular compartment of unknown functions and controversial ontogeny. Previous observations in humans indicate that the majority of IEL subsets express the CD3 complex associated with either the alphabeta or the gammadelta T-cell receptor components, and describe the characteristic increase of CD3+TCRgammadelta+ IEL in coeliac disease. In the present work, we analyze the surface antigen expression of intraepithelial lymphocytes isolated from duodenal biopsies of control subjects and coeliac disease patients. We describe a CD3-CD7 + IEL subset frequently found in control subjects (41.41+/-21.8), with the following features: 1) most of these cells are CD45R0+ CD103+ and CD44- CD28- CD5-; 2) a significant percentage express CD56 (44.7%+/-21.3), CD2 (55.1%+/-16.2), and CD94 (16.2%+/-7.3). Furthermore, they are CD122+ and CD25-; 3) this CD3- IEL subset exhibit an activated phenotype expressing higher levels of CD69, CD103, and CD38 than the CD3+ subset. Interestingly, this CD3- subset is drastically reduced in CD patients (2.2+/-2.9 in active disease, 6.3+/-4.6 in treated patients versus 41.4+/-21.8 in control subjects). The imbalanced ratio "increased TCRgammadelta versus decreased CD3- CD7+" is a permanent finding in CD patients following clinical and histological remission. This parameter might provide helpful diagnostic information (easily obtained by 3-color FCM from diagnostic biopsies), and suggest a potential implication in the pathogenesis of coeliac disease.