Divergent cell cycle kinetics underlie the distinct functional capacity of mucosal T cells in Crohn's disease and ulcerative colitis

Background: Different abnormalities of T cell effector function distinguish Crohn's disease ( CD) from ulcerative colitis (UC). Because cell cycling determines effector function, pathogenic events in CD and UC may depend on cell cycle changes unique to each condition. Methods: Cell cycle kinetics, cycle regulatory molecule expression, apoptosis, caspase and telomerase activity, and cellular expansion were evaluated in CD2 and CD3 activated control, CD, and UC lamina propria T cells. Results: Compared with normal cells, CD T cells cycle faster, express increased phosphorylated Rb and decreased phosphorylated p53 levels, display less caspase activity but more telomerase activity, die less, and undergo vigorous cellular expansion. In contrast, UC T cells cycle slower, express normal levels of phosphorylated Rb and p53, display more caspase activity but have no telomerase activity, die more, and have a limited capacity to expand. Conclusions: T cell cycle abnormalities in CD indicate a state of hyperreactivity compatible with loss of tolerance, but a hyporeactive state compatible with anergy in UC. Thus distinct and divergent T cell cycle characteristics underlie the pathogenesis of the two main forms of inflammatory bowel disease.