Tu1651 Increased Activation of Dendritic Cells Contributes to T-Cell Mediated Colitis but Not Gastritis in DC-TGFBR2 Ko Mice

Abstract

Background: Dendritic cells (DC) play an important role in maintaining the balance between immune activation and tolerance. We have previously demonstrated that TGF β signaling in DCs is critical for maintenance of self-tolerance and that TGF βR2 deficient DCs have increased pro-inflammatory potential. To understand the contribution of T cells in the development of autoimmunity in these mice, we used the model of adoptive T cell transfer into DC-Tgfbr2 KO on Rag-deficient backgorund and followed disease progression. Methods: DC-Tgfbr2 KO mice were bred onto a Rag1-/background and then transferred with total CD3 T cells isolated from Naive wild-type mice. Cremice transferred with CD3 T cells served as controls. Baselines were established with Cre+/Cremice on Rag1-/background injected with PBS. Mice were monitored every week for body weight changes. At the end of 8 weeks, mice were sacrificed and tissues were harvested for histological and proinflammatory cytokine analyses. Spleens and mesenteric lymph nodes (MLNs) were also harvested and analyzed for DC and T cell specific markers by flow cytometry. Results: DCTgfbr2 KO/Rag mice transferred with CD3 T cells were normal until about 5 weeks, after which they showed significant body weight loss as compared to control mice. Flow cytometry analysis of spleen and MLN cells revealed increased expression of MHCII, CD80, CD86 and CD40 on the surface of DCs from DC-Tgfbr2 KO/Rag mice suggesting the presence of more mature and activatedDCs. However the basal expression of these markers was not significantly different between control and KO mice injected with PBS. The proportion of activated T cells based on CD62L and CD44 expression was also elevated in DC-Tgfbr2 KO/Rag mice as compared to Cremice transferred with T cells. Histological analysis revealed increased monocytic and lymphocytic infiltration of the colon, liver and pancreas of DC-Tgfbr2 KO/ Rag mice transferred with T cells whereas control mice showed no significant changes. However, in contrast to DC-Tgfbr2 KO mice which spontaneously developed severe gastritis, DC-Tgfbr2 KO/Rag mice transferred with CD3 T cells did not demonstrate histological symptoms of gastritis. These changes were confirmed with qRT-PCR with increased expression of pro-inflammatory cytokines such as TNFα, IFNγ, IL1β, IL6 and IL12 only in the colon, but not the stomach of DC-Tgfbr2 KO/Ragmice transferred with T cells. Conclusions: Our studies with DC-Tgfbr2 KO/Rag mice demonstrate that maturation and increased stimulation of T cells by TGFβR deficient DCs is an early event that then contributes to the development of autoimmunity. Lack of autoimmune gastritis symptoms indicates that T cells may not be the primary contributing factor and that the role of B cells and autoantibodies in the process cannot be excluded.