Dendritic cells present a tissue-specific autoantigen under steady state and autoimmune conditions in the draining lymph node

The MHC-dependent presentation of processed tissue-specific self-antigens maintains peripheral (extra-thymic) tolerance but also can lead to activation of autoreactive T cells. Although hematopoietic antigen-presenting cells have been shown to participate in these processes, the isolation and characterization of the specific cells responsible for mediating such diverse events has not yet been accomplished. We have analyzed the presentation of an endogenous, gastric-specific H⁺/K⁺-ATPase peptide by dendritic cells (DC) in the context of the MHC class II molecule I-Ad. DC (CD11c⁺, MHC class IIbright, CD80low, CD86^+/-, CD40^+/-) were isolated from the draining gastric lymph node (gDC) and from the peripheral lymph node (pDC) or mesenteric lymph node (mDC) of unmanipulated healthy BALB/c mice. Isolated DC were then assessed for their capacity to induce IFN-γ synthesis by the H⁺/K⁺-ATPase-specific CD4⁺ T-cell clone TXA-23. In contrast to pDC or mDC, gDC significantly increased IFN-γ production by TXA-23. Visual evidence for the uptake of H⁺/K⁺-ATPase by DC in the stomach and their apparent migration to the draining lymph node (LN) was obtained by immunofluoresence staining and confocal microscopy analysis. Using a monoclonal antibody (2G11) against the H⁺/K⁺-ATPase beta-subunit, H⁺/K⁺-ATPase was consistently detected within CD11c⁺ DC in gastric LN sections but not in peripheral LN sections. In addition, we were able to detect CD11c⁺ DC in close proximity to H⁺/K⁺-ATPase-positive parietal cells in the stomach mucosa. Upon the induction of experimental autoimmune gastritis, DC were found among the first cells to infiltrate the stomach mucosa. Moreover, proportions as well as absolute numbers of DC, along with B cells, were found to be substantially increased in the gastric LN but not in the peripheral LN at later timepoints. In line with this, the frequency of H⁺/K⁺-ATPase staining in CD11c⁺ cells selectively increased in the gLN. Analysis of DC function further suggests that overall gDC presentation of H⁺/K⁺-ATPase increases in diseased animals. These results provide the first clear identification of DC as the cells involved in the uptake and presentation of a tissue-specific antigen in normal animals, and the augmentation of such presentation during the development of overt autoimmune disease.