Analysis of the regulatory mechanism involved in support of peripheral tolerance for tissue specific self-antigens

Dendritic cells (DC) presenting tissue-specific antigens are thought to induce peripheral (post-thymic) tolerance and also activate autoimmune T cells. Towards this end, we have analyzed presentation of an H/K-ATPase peptide by the MHC class II molecule I-Ad . In BALB/c mice lacking CD4 + CD25 + regulatory T cells, this TCR ligand activates CD4 + T cells that produce destructive gastritis. Using the H/KATPase specific T cell clone TXA-23, we were able to demonstrate that only gastric (g) DC as compared to mesenteric (m) or peripheral (p) DC present H/K-ATPase antigen in healthy BALB/c mice. DC were found to be the only APC type in the gastric lymph node and both, the CD8alphahi "Iymphoid" and the CD8alphalo "myeloid" DC subset were capable of functional presentation of the H/K-ATPase self-antigen. In addition, visual evidence for the uptake of H/K-ATPase by MHC class II+ DC in the stomach and their apparent migration to the draining LN was obtained by immunfluoresence analysis. In ongoing studies we will try to further characterize the immune response initiated by distinct DC subsets upon improvement of our isolation procedure and readout systems. We further plan to perform adoptive transfer experiments with H/K-ATPase alpha chain transgenic T cells and/or TXA-23 cells which will allow us to study the kinetics of uptake, transport and presentation of the H/K-ATPase self-antigen. Thereby we will also be able to analyze the interaction of DC with potentially regulatory T cells which should help to better characterize mechanisms that unbalance a self-tolerant state and lead to the induction of autoimmune effector activity.