β7 integrin controls immunogenic and tolerogenic mucosal B cell responses

IgA production in the gut-associated lymphoid tissue represents a pivotal defense mechanism against luminal pathogens. The other important challenge for the GALT is the induction of local and systemic hyporesponsiveness (tolerance) to dietary antigens and luminal bacterial flora to prevent allergies or deleterious immunologic reactions to food or environmental antigens. In this study we analyzed the impact of beta 7 integrin on immunogenic and tolerogenic B cell responses in the gastrointestinal tract. beta 7 integrin deficient mice failed to mount a normal intestinal IgA response to ovalbumin and cholera toxin, whereas the IgG response was unchanged in comparison to control mice. Oral B cell tolerance to ovalbumin, measured as the suppression of specific serum IgG responses, did not develop in the absence of beta 7 integrin. After adoptive transfer of spleen cells from beta 7 integrin +/+ mice into RAG-2 deficient or RAG-2/beta 7 integrin double deficient mice, only RAG-2 deficient mice were able to develop oral B cell tolerance. These observations suggest that beta 7 integrin expression on cells of the innate immune system contributes to the critical role of beta 7 integrin in the process of B cell tolerance. (C) 2012 Elsevier Inc. All rights reserved.