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Guillonneau1 C., C. Séveno1, A-S. Dugast, X-L. Li, K. Renaudin, F. Haspot, C. Usal, J. Véziers, I. Anegon* and B. Vanhove*.

2007 | J. Immunol. 179: 8164.


Despite accumulating evidence for the importance of allospecific CD8+ regulatory T cells (Tregs) in tolerant rodents and free immunosuppression transplant recipients, mechanisms underlying CD8+ Treg-mediated tolerance remain unclear. By using a model of transplantation tolerance mediated by CD8+ Tregs following CD40Ig treatment in rats, in this study, we show that the accumulation of tolerogenic CD8+ Tregs and plasmacytoid dendritic cells (pDCs) in allograft and spleen but not lymph nodes was associated with tolerance induction in vascularized allograft recipients. pDCs preferentially induced tolerogenic CD8+ Tregs to suppress CD4+ effector cells responses to first-donor Ags in vitro. When tolerogenic CD8+ Tregs were not in contact with CD4+ effector cells, suppression was mediated by IDO. Contact with CD4+ effector cells resulted in alternative suppressive mechanisms implicating IFN-g and fibroleukin-2. In vivo, both IDO and IFN-g were involved in tolerance induction, suggesting that contact with CD4+ effector cells is crucial to modulate CD8+ Tregs function in vivo. In conclusion, CD8+ Tregs and pDCs interactions were necessary for suppression of CD4+ T cells and involved different mechanisms modulated by the presence of cell contact between CD8+ Tregs, pDCs, and CD4+ effector cells. The Journal of Immunology, 2010, 185: 823–833.