Quantitative and functional characteristics of intestinal-homing memory T cells: analysis of Crohn's disease patients and healthy controls

Circulating memory T cells can be subdivided on the basis of beta7 integrin expression. The beta7(+) population contains cells primed in the intestine capable of homing back to the gut. We hypothesized that cytokine production by beta7(+) memory T cells reflects the specialized mucosal compartment in which they were primed. Flow cytometry of whole blood was used to assess numbers of beta7(+) (beta7(hi) and beta7(int)) and beta7(-) memory T cells and their production of Th1 and regulatory cytokines in healthy controls and Crohn's disease patients. In controls, beta7(+) and beta7(-) memory T cells displayed a similar qualitative profile of cytokine production but the beta7(+) population was enriched for cytokine-producing effector cells. In addition, the beta7(hi) population contained more cytokine-producing cells than the beta7(int) population, suggesting a gradient of cytokine production based on beta7 integrin expression. In active Crohn's disease, there was altered expression of beta7 integrin with a decrease in intestinal-homing memory T cells and an increase in systemic memory T cells. Furthermore, there was a selective loss of IL-10 and increase in TGF-beta in both beta7(+) and beta7(-) memory T cell subsets which may contribute to the pathogenesis of the inflammatory process in Crohn's disease.