Costimulatory blockade with mTor inhibition abrogates effector T-cell responses allowing regulatory T-cell survival in renal transplantation.

The advent of novel immunosuppressive strategies in renal transplantation, with immunomodulatory properties, might facilitate long-term allograft survival. T-cell depletion, costimulation-blockade and mTor inhibition have been shown to favour anti-donor hyporesponsiveness. Recently, the combination of rATG, belatacept (Bela) and sirolimus (SRL) has been used in kidney transplantation, showing very low incidence of acute rejection and excellent 12-month graft and patient survival. Herein, we have analysed the 1-year evolution of memory/effector and regulatory T cells and assessed the donor-specific T-cell alloimmune response in a group of these patients and compared with others treated with a calcineurin-inhibitor(CNI)-based (rATG/tacrolimus/MMF), and two other Bela-based regimens (rATG/Bela/MMF and basiliximab/Bela/MMF/steroids). During the first year after transplantation, patients receiving rATG/Bela/SRL had significantly higher percentage of Tregs upon the memory T-cell compartment and showed a potent anti-donor suppressive activity. In an in vitro naive and memory/effector T-cell co-culture, the combination of costimulation-blockade and SRL could abrogate both antigen-specific T-cell responses as efficiently as using a CNI drug. The combination of T-cell depletion, costimulation-blockade and mTor inhibition seems to be able to allow Treg survival and inhibit donor-specific alloreactive effector immune responses after kidney transplantation in humans.