Background: Blockade of the integrin α4β7 has promise as a therapy for inflammatory bowel disease. α4β7 plays diverse roles in the intestinal immune system, including lymphocyte homing and lymphoid tissue formation; however, the effects of α4β7 blockade on these processes during inflammation and their relationship to the efficacy of α4β7 blockade and its potential untoward effects are largely unknown.
Methods: α4β7 function was inhibited by genetic manipulation or antibody blockade. The effects of these manipulations on lymphoid tissues and the presence of lymphocyte subpopulations in the murine small intestine and colon were evaluated in the unchallenged state, during the acute injury dextran sodium sulfate model, and during the splenocyte transfer chronic inflammation model.
Results: α4β7 inhibition resulted in a decrease in the B-lymphocyte population in the diffuse lamina propria and a decrease in the number of lymphoid aggregates in the uninflamed intestine and in the acute injury model. α4β7 blockade did not reduce the Foxp3- T-lymphocyte population but did decrease the Foxp3+ T-lymphocyte population located selectively within the lymphoid aggregates in the uninflamed intestine and in the acute injury model. In contrast, α4β7 blockade reduced the intestinal T-lymphocyte population and decreased the production of inflammatory cytokines in the T-lymphocyte mediated chronic inflammation model.
Conclusions: These findings demonstrate differential use of α4β7 by B-lymphocytes, Foxp3- T-lymphocytes, and Foxp3+ T-lymphocytes to home to the gut, and suggest that α4β7 blockade may serve as a targeted therapy that selectively inhibits the accumulation of pathogenic T-lymphocyte populations in the chronically inflamed intestine.