Intrathymic deletion of MHC class I-restricted cytotoxic T cell precursors by constitutive cross-presentation of exogenous antigen

Abstract

Cross-priming of cytotoxic T lymphocytes by professional antigen-presenting cells (APC) is a potential hazard to self tolerance because it exposes naive T cells to tissue-specific self antigens in the context of co-stimulatory signals. Here we show that cross-presentation of exogenous material occurs constitutively within the thymus. Although efficient cross-presentation is a property of relatively few APC it results in thymocyte deletion both in vitro and in vivo, suggesting that intrathymic cross-presentation can operate as an effective component of tolerance to circulating self antigens. The capacity of minor cell populations to mediate thymocyte deletion but not positive selection reflects an underlying difference in the biology of these two processes.

Central tolerance spares the private high‐avidity CD4+ T‐cell repertoire specific for an islet antigen in NOD mice

“…To ensure that these different polymorphisms did not break tolerance to mS100β protein, we immunized NOD WT and NOD Tssp°with mS100β 1-15 peptide and analyzed their CD4 + T-cell recall responses to the same peptide. Both NOD WT and NOD Tssp°mice responded to mS100β [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and, as observed upon protein immunization, NOD Tssp°mice were hyporesponsive showing, a 40% reduction (mean±SEM at 50μg/ml peptide; WT = 8.4±0.8 versus KO = 5.2±0.7) as compared to NOD WT control mice (Fig. 1D).…”

“…When required, the hybridomas were FACS-sorted to select population with homogenous TCR and CD4 staining. 5×10 4 hybridomas were stimulated in the presence of 4-5×10 5 NOD splenocytes and graded dose of mS100β [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . Twenty-four hours later, IL-2 production was measured using the IL2-dependent CTL.L cell line.…”

“…Hence, T cell-depleted BM cells from NOD WT mice were co-injected with either Tssp°NODscid BM cells as a source of TSSP-deficient APC or, as control, NODscid BM cells into lethally irradiated NOD WT or NOD Tssp°recipient mice. A ratio of 3:1 NOD WT BM cells and WT or Tssp°NODscid BM cells was used given that less than 10% of antigen-presenting APC are sufficient to induce complete deletion of Ag-specific thymocytes [14]. Nine to 12 weeks post reconstitution the responses of the different chimeras to mS100β 1-15 peptide and, as a control, the OVA 323-339 peptide were analyzed following peptide immunization.…”

“…Strikingly the (A/V)PSGGSNAKL CDR3α sequence was also widely used by NOD Tssp°hybridomas and, remarkably, some hybridomas from NOD WT and NOD Tssp°expressed the very same (6W05, 6W21 and 5K09, 5K22, 5K31) or extremely similar (5K02, 6K01 and 1W03, 6W06, and 6W19) TCRα and TCRβ rearrangements. Given that these specific aa sequences were not germline encoded, these clonotypes likely provide a proliferative advantage in response to mS100β [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] (Table 2 and Supporting Information Table 2). …”

“…45: 1946Immunol. -1956 sufficient to induce complete deletion of Ag-specific thymocytes [14]. Nine to 12 weeks post reconstitution the responses of the different chimeras to mS100β 1-15 peptide and, as a control, the OVA 323-339 peptide were analyzed following peptide immunization.…”