84 Mitochondrial Stress Induction in the Epithelium Fuels Endoplasmic Reticulum Unfolded Protein Responses via Double-Stranded RNA-Activated Protein Kinase (PKR) Under Conditions of Chronic Intestinal Inflammation

Abstract

ability of these Tregs to suppress the development of chronic gut inflammation. We found, using blinded histopathological analysis, that adoptive transfer of WT T-cells induced moderate-to-severe colitis in RAG-/recipients at 8 wks post transfer whereas transfer of DKO Tcells induced little or no disease. The inability to induce disease by the DKO T-cells was not due to a delay in the onset of disease as we continued to observe significantly less disease even at 25 wks post transfer. Furthermore, failure to induce disease correlated well with large and significant decreases in the numbers of T-cells within the mesenteric lymph nodes (MLNs) and colonic lamina propria (cLP) suggesting that T-cell activation and/or trafficking may be defective in the DKO T-cells. In order to differentiate between these two possibilities we evaluated T-cell activation and trafficking In Vivo using adoptive transfer of congenic CSFE-labeled WT (CD45.1) and DKO (CD45.2) T-cells (107 cells for each) into RAG-/mice. At 7 days following transfer we observed 12and 4-fold fewer T-cells within the MLNs and cLP, respectively of the DKO→RAG-/mice vs. WT→RAG-/animals. In addition, we observed that both WT and DKO T-cells in the cLP generated similar amounts of IFN-γ and IL-17 and lost equivalent amounts of CFSE fluorescence. These data suggested that CD62L and β7 are not required for T-cell activation and polarization In Vivo. In the second series of studies, we found that DKO Tregs were substantially less effective than WT Tregs at suppressing the development of chronic colitis when co-transferred with WT CD4+CD4RBhigh T-cells. Taken together, our data suggest that both L-selectin and β7 are required for the T-cell-dependent induction and suppression of chronic colitis (NIHPO1 47385).