RecruitingPhase 1Combination productDelayed Immunological Tolerance in Patients With Well-functioning Pre-existing HLA-matched Kidney TransplantsThe study seeks to determine if patients with a pre-existing, well-functioning kidney transplant from a HLA-identical living donor can be withdrawn from immunosuppressive medications without compromising allograft function through hematopoietic stem cell (HPSC) infusion from the same donor. HPSC infusion will be preceded by a conditioning regimen of total lymphoid irradiation (TLI) and rabbit anti-thymocyte globulin (rATG).