TLI, TBI, ATG & Hematopoietic Stem Cell Transplantation and Recipient T Regs Therapy in Living Donor Kidney Transplantation

It has been demonstrated that hematopoietic mixed chimerism or the coexistence of both donor and recipient immune cells can lead to tolerance to the graft in absence of graft versus host disease (GVHD). The goal of this pilot study is to determine if recipients of living donor kidney transplant can be successfully withdraw from immunosuppressive drugs. The patients will receive a preparatory regimen consisting of TLI and a low single dose of TBI and ATG following their kidney transplantation. Two weeks later, they will receive purified hematopoietic stem cells (CD34+) and Tcells that have been collected 6 weeks prior from their kidney donor. Regulatory T cells (Tregs) that have been collected from the recipient prior to the transplantation and expanded in vitro will be infuse the following day to enhance the chance of engraftment of the donor bone marrow cells. If chimerism develops and persists, the immunosuppressive drug will be tapered and stop. Mycophenolate mofetil (MMF) will be stopped 12 months after transplantation and if the chimerism remains stable, tacrolimus will be stopped 6 months later. The dose of Tregs will be escalated if the % of donor chimerism is not at least 25% during the first 60 days.