Linked suppression in peripheral T cell tolerance to the house bust mite derived allergen Der p 1

Background: Peripheral tolerance is required to maintain balance within the immune system. A feature of peripheral tolerance is linked suppression, in which tolerance induced to a single T cell epitope inhibits the response t o all epitopes in the same protein. It is suggested that this phenomenon is mediated by regulatory T cells through either the activity of immunopressi ve cytokines or direct cell contact. In previous experiments we failed to d etect inhibitory cytokines when T cells from mice rendered tolerant by intr anasal delivery of the immunodominant peptide of Der p 1 (p 1, 110-131) wer e restimulated with peptide in vitro. Therefore, the aim of this study was to determine if cognate interactions between T cells mediated by Notch/Delt a signaling induce and maintain peripheral T cell tolerance. Methods: Using in situ hybridization and viral mediated gene transfer, the expression and function of Delta1 were investigated in a murine model of T cell tolerance to Der p ? in vivo. Results: Delta1 expression is increased on peripheral T cells during the induction of tolerance with high-dose peptide delivered intranasally and when tolerant animals are rechallenged under immunogenic c onditions. Peptide p 1, 110-131-specific CD4+ T cells transfected with Delt a1 inhibited the response of antigen-primed T cells and induced linked supp ression. Conclusions: High-dose peptide delivered intranasally induces tran sient expression of Delta 1 on inhibitory CD4+ T cells. Ligation of the Not ch1 receptor on neighbouring T cells by Delta1+ regulatory T cells inhibits clonal expansion of the former and mediates linked suppression.