An Intra-Peyer’s Patch Gene Transfer Model for Studying Mucosal Tolerance: Distinct Roles of B7 and IL-12 in Mucosal T Cell Tolerance

Abstract

Development of mucosal immunity and tolerance requires coordinated expression of a number of genes within the mucosa-associated lymphoid tissue (MALT). To study the roles of these genes in the MALT, we have established a MALT-specific gene transfer model using replication-defective adenovirus as vector. In this model, the target gene of interest is directly delivered into the Peyer’s patch by intra-Peyer’s patch injection of the recombinant virus. Using this gene transfer model, we investigated the roles of B7-1 and IL-12 in the development of mucosal tolerance. We found that intra-Peyer’s patch injection of OVA induced Ag-specific T cell hyporesponsiveness, as manifested by decreased T cell proliferation and IL-2/IFN-γ production upon subsequent immune challenge. Intra-Peyer’s patch B7-1 gene transfer at the time of OVA administration partially reversed the inhibition of T cell proliferation and IL-2 secretion, but had no effect on IFN-γ production. By contrast, intra-Peyer’s patch IL-12 gene transfer completely restored T cell proliferation and IFN-γ secretion and partially reversed IL-2 inhibition. Using an adoptive TCR transgenic model, we further demonstrated that B7 and IL-12 played distinct roles during the inductive phase of mucosal tolerance. B7 selectively increased T cell proliferation and IL-2 secretion without affecting IFN-γ production, whereas IL-12 increased both IL-2 and IFN-γ production. These results indicate that B7 alone may not be sufficient to abrogate mucosal tolerance, and that cytokines such as IL-12 may also be required. Based on these findings, we propose a new model to explain the paradoxical roles of B7 in mucosal immunity and tolerance.

Gene transfer approaches for the treatment of inflammatory bowel disease

“…Within the Peyer's patches, macrophages and epithelial cells were transgene positive, whereas T-and B lymphocytes were not transduced. 51 This is consistent with the observation that lymphocytes are only poorly receptive to adenovirus infection, because they express only low levels of coxsackie and adenovirus receptor (CAR) for virus attachment through the fibre capsid protein and display only small amounts of av-integrins required for interaction with penton-base proteins and virus internalization. 52,53 Interestingly, studies in mice with experimental colitis as a model for human IBD showed that disruption of intestinal epithelial integrity and other histopathological alterations during mucosal inflammation increased transduction of lamina propria mononuclear cells (LPMC) by adenoviral vectors.…”

“…Chen et al 51 reported successful gene transfer into the Peyer's patches by direct injection of recombinant Ad5. Within the Peyer's patches, macrophages and epithelial cells were transgene positive, whereas T-and B lymphocytes were not transduced.…”

CTLA-4 Signaling Regulates the Intensity of Hypersensitivity Responses to Food Antigens, but is Not Decisive in the Induction of Sensitization

“…In the mouse intestine, this population of Tr cells has been shown to constitutively express CTLA-4 and is able to control intestinal inflammation (22). Crosslinking of CTLA-4 (resulting in CTLA-4 signaling) can induce TGF-␤ production by murine CD4 ϩ T cells (23) and the suppressive effect of these Tr cells has been demonstrated to be TGF-␤ dependent (22). The disruption of Tr cell function by anti-CTLA-4 treatment may have played an important role in the increased immune responses against peanut allergens that were observed in the present study.…”

B7 Interactions with CD28 and CTLA-4 Control Tolerance or Induction of Mucosal Inflammation in Chronic Experimental Colitis

“…CD4 ϩ T cells, especially after CD28 cross-linking, also express high levels of CD40 ligand, which interacts with CD40 expressed on APC to promote IL-12 secretion (36) and B7 expression. Furthermore, IL-12 may act synergistically with B7.1 to abrogate mucosal T cell tolerance and to induce intestinal inflammation (48). According to recent report (49), this priming occurs in regional Ag-draining lymph nodes and will be followed by homing of the Ag-primed cells to the lamina propria of the gut.…”