Central tolerance to self-antigen expressed by cortical epithelial cells.

The exposure of developing thymocytes to high-affinity self-Ag results in T cell tolerance. A predominant mechanism for this is clonal deletion; though receptor editing, anergy induction, and positive selection of regulatory T cells have also been described. It is unclear what signals are involved in determining different tolerance mechanisms. In particular, OT-I mice displayed receptor editing when the high-affinity self-Ag was expressed in cortical epithelial cells (cEC) using the human keratin 14 promoter. To test the hypothesis that receptor editing is a consequence of a unique instruction given by cEC presenting self-Ag, we created mice expressing the 2C and HY ligands under control of the keratin 14 promoter. Alternatively, we studied the fate of developing T cells in OT-I mice where Ag was presented by all thymic APC. Surprisingly, we found that the tolerance mechanism was not influenced by the APC subset involved in presentation. Clonal deletion was observed in 2C and HY models even when Ag was presented only by cEC; and receptor editing was observed in OT-I mice even when Ag was presented by all thymic APC. These results suggest that different TCRs show intrinsic differences in thymic tolerance mechanism.