Alternatives, we chose to use the DSS model of colitis to determine if T cells reactive against luminal antigens could be developed in vivo in an experimental colitis model using wild type mice. The DSS-induced 1317923 colitis model is advocated as a highly relevant model for IBD, being sensitive to common IBD therapeutics [15], sharing a similar gene expression as IBD [26] and displaying T cell accumulation in the inflamed colon [20,27] similar to what is found in IBD patients [28]. Furthermore, many have observed a chronic pathology that develops after the acute inflammation has passed, which includes changes in crypt morphology with lymphocytosis and a Th1/Th2 cytokine profile [14,21,22,29]. This chronic pathology could be caused by memory T cells. Memory T cells are known to function as sentinels of the immune system and often 11967625 reside in the periphery [30]. During DSS-induced inflammation, tertiary lymphoid structures that are adjacent to the intestinal epithelial layer develop [31], which likely house resident memory T cells. We found increased numbers of TCM cells in our colon mononuclear cell suspensions of our DSS-treated mice. TCM are differentiated mainly on the expression of CD62L, an adhesion molecule that allows them to enter and stay in lymphoid tissues like colon patches. Increased TCM in the colon during DSS colitis could be responsible for the chronic colitis pathology later found in mice [21]. TCM are known to regain effector functions and expandwhen they re-encounter their cognate antigens [32], which would lead to immune cascades that re-ignite inflammation. We found that during DSS colitis, both FD&C Yellow 5 conventional T cells and Tregs were generated against oral antigens, while healthy mice only developed OVA-reactive Tregs. Classically, exposure to oral antigens leads to Foxp3+ Treg responses that control untoward responses to microbiota and food antigens that are induced via CD103+ DCs producing TGF, retinoic acid and prostaglandins [23]. However, in the DSS model of colitis, the (-)-Calyculin A web weakening of the mucus barrier allows the penetration of bacteria to the underlying immune cells [17]. This likely leads to the release of an abundance of proinflammatory cytokines [33], and this would allow the generation of other non-regulatory CD4+ T cell effector subsets. This concept was supported by our ability to only detect OVA-directed conventional T cells in DSS-treated mice. We were only able to find oral antigen reactive T cells and cytokine-producing effector T cells within the spleen and not the mLN. Literature supports this observation as T cells are known to travel to the spleen after the resolution of acute inflammation [30]. Moreover, Hall et al. demonstrated that after resolution of acute DSS colitis (day 25 after the start of DSS), there is a striking increase of activated CD4+ T cells in the spleen, while the percentage of activated T cells within the mLN normalizes [34]. We cannot eliminate the possibility that examination of mLNs using a more refined technique, such as tetramer staining, may reveal the presence of OVA-reactive T cells. However, despite lack of sensitivity, it is clear that OVAdirected responses are more pronounced in the spleen at the time point that we tested. To our knowledge, we have demonstrated for the first time that oral antigen-specific T cells form during DSS colitis and that they can be found systemically after the resolution of colitis. This gives added depth and usefulness to the DSS colitis model, speci.Alternatives, we chose to use the DSS model of colitis to determine if T cells reactive against luminal antigens could be developed in vivo in an experimental colitis model using wild type mice. The DSS-induced 1317923 colitis model is advocated as a highly relevant model for IBD, being sensitive to common IBD therapeutics [15], sharing a similar gene expression as IBD [26] and displaying T cell accumulation in the inflamed colon [20,27] similar to what is found in IBD patients [28]. Furthermore, many have observed a chronic pathology that develops after the acute inflammation has passed, which includes changes in crypt morphology with lymphocytosis and a Th1/Th2 cytokine profile [14,21,22,29]. This chronic pathology could be caused by memory T cells. Memory T cells are known to function as sentinels of the immune system and often 11967625 reside in the periphery [30]. During DSS-induced inflammation, tertiary lymphoid structures that are adjacent to the intestinal epithelial layer develop [31], which likely house resident memory T cells. We found increased numbers of TCM cells in our colon mononuclear cell suspensions of our DSS-treated mice. TCM are differentiated mainly on the expression of CD62L, an adhesion molecule that allows them to enter and stay in lymphoid tissues like colon patches. Increased TCM in the colon during DSS colitis could be responsible for the chronic colitis pathology later found in mice [21]. TCM are known to regain effector functions and expandwhen they re-encounter their cognate antigens [32], which would lead to immune cascades that re-ignite inflammation. We found that during DSS colitis, both conventional T cells and Tregs were generated against oral antigens, while healthy mice only developed OVA-reactive Tregs. Classically, exposure to oral antigens leads to Foxp3+ Treg responses that control untoward responses to microbiota and food antigens that are induced via CD103+ DCs producing TGF, retinoic acid and prostaglandins [23]. However, in the DSS model of colitis, the weakening of the mucus barrier allows the penetration of bacteria to the underlying immune cells [17]. This likely leads to the release of an abundance of proinflammatory cytokines [33], and this would allow the generation of other non-regulatory CD4+ T cell effector subsets. This concept was supported by our ability to only detect OVA-directed conventional T cells in DSS-treated mice. We were only able to find oral antigen reactive T cells and cytokine-producing effector T cells within the spleen and not the mLN. Literature supports this observation as T cells are known to travel to the spleen after the resolution of acute inflammation [30]. Moreover, Hall et al. demonstrated that after resolution of acute DSS colitis (day 25 after the start of DSS), there is a striking increase of activated CD4+ T cells in the spleen, while the percentage of activated T cells within the mLN normalizes [34]. We cannot eliminate the possibility that examination of mLNs using a more refined technique, such as tetramer staining, may reveal the presence of OVA-reactive T cells. However, despite lack of sensitivity, it is clear that OVAdirected responses are more pronounced in the spleen at the time point that we tested. To our knowledge, we have demonstrated for the first time that oral antigen-specific T cells form during DSS colitis and that they can be found systemically after the resolution of colitis. This gives added depth and usefulness to the DSS colitis model, speci.
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