T-cell inhibition does not aggravate bacterial translocation from rat small bowel

T-cell mediated immunity has been proposed to have an important function in the defence against translocating microbes from the gastrointestinal tract. After small bowel transplantation massive T-cell immunosuppression is necessary to avoid rejection. As a consequence, infections with intestinal bacteria are the main contributors to mortality in this setting. This could further imply that T cells are important in limiting bacterial translocation. In a model for bacterial translocation from small bowel in the rat we examined the outcome of T-cell inactivation.

The studies were performed in a model of bacterial translocation from a Thiry-Vella loop of small bowel in the rat. The animals were treated with an anti-alpha/beta T-cell receptor monoclonal antibody (R73). Inhibition of T-cell activation was also made using the immunosuppressive drug cyclosporin A. All animals were sacrificed on day 3 postoperatively and translocation to the mesenteric lymph nodes, liver, spleen, lung and blood was evaluated.

Treatment with R73 resulted in an almost complete labelling of T cells but did not result in any increased bacterial translocation compared to animals treated with saline. Neither did immunosuppression with cyclosporin A.

In the model of bacterial translocation from a defunctionalised loop of small bowel the inhibition of T cells does not increase bacterial translocation to mesenteric lymph nodes or promote the systemic spread of the translocating bacteria. This indicates that T cells do not have any important protective function against translocating microbes from defunctionalised small bowel.