PHENOTYPICAL AND FUNCTIONAL-CHARACTERIZATION OF SMALL INTESTINAL TCR-GAMMA-DELTA+ T-CELLS IN CELIAC-DISEASE

Increased numbers of TcR-gamma-delta+ T cells are present in the small intestinal epithelium of patients with coeliac disease (CoD). Their function, however, is unknown. In order to facilitate detailed functional studies, intestinal gamma-delta T cells have been isolated from small intestinal biopsies of patients with CoD (n = 18) and controls (n = 14). As expected, increased numbers of V-delta-1+ TcR-gamma-delta+ T cells were detected in freshly isolated intraepithelial cell suspensions (IEL) from CoD patients. Also, in the in vitro expanded IEL T-cell populations from CoD patients the numbers of V-delta-1+ TcR-gamma-delta+ T cells were increased compared with similar cell cultures from control patients. From IEL cultures derived from six CoD patients, 107 T-cell clones were generated by limiting dilution and analysed. Sixty of these clones were either CD4 or CD8 positive TcR-alpha-beta+ clones. The remaining 47 clones expressed the TcR-gamma-delta. Further phenotypical analysis of the gamma-delta-T-cell clones indicated that the TcR-gamma-delta+ T-cell population in the small intestinal epithelium of CoD patients is heterogeneous: four TcR-gamma-delta phenotypes could be detected and, although the majority of the TcR-gamma-delta+ T cells were CD4-CD8-, gamma-delta-T-cell clones expressing either a CD8-alpha-alpha homodimer, a CD8-alpha-beta heterodimer or CD4 were also identified. In contrast to the TCR-alpha-beta+ IEL, most TcR-gamma-delta+ IEL were CD5 negative. Furthermore, biochemical analysis indicated that the increase in V-delta-1+ gamma-beta-T cells in the small intestinal epithelium of CoD patients was not the result of a monoclonal expansion. The small intestinal epithelium-derived gamma-delta-T-cell clones were functional in vitro since the majority of these clones were able to lyse target cell lines such as K562, Molt4 and Daudi. These novel findings therefore indicate that the gamma-delta-T cells in the small intestine of CoD patients represent a heterogeneous population and that such cells are functional in vitro. The isolation and the in vitro propagation and cloning of these cells may open new avenues for the study of the putative immune mechanisms leading to coeliac disease.