*Purpose: Based on decades-long basic studies in animal models, we have applied combined kidney and donor bone marrow transplantation (CKBMT) for induction of allograft tolerance in HLA-mismatched kidney transplant recipients. Here, we report the long-term results (>10 years) of the recipients who received CKBMT with a nonmyeloablative regimen.

*Methods: The preparative conditioning regimen included Cyclophosphamide, local thymic irradiation, peri-transplant anti-CD2 mAb (Siplizumab) and post-transplant CNI (NKD03). The protocol was later revised by adding two doses (modified NKD03) or four doses (ITN036) of rituximab and post-transplant steroids. A total of 10 subjects, age 22-46, 6 males and 4 females, were enrolled into these studies and donors were all HLA one-haplotype mismatched parents or siblings.

*Results: Seven of ten subjects were successfully tapered off of all immunosuppression (IS) for >5 years with four of them still IS-free for 9-16 years with normal kidney function. IS was eventually reinstituted in three subjects due to recurrence of the original kidney disease or chronic rejection. Protocol biopsies and anti-donor immunological responses have been assessed at 10-15 years.

*Conclusions: Durable long-term renal allograft tolerance in HLA mismatched kidney transplantation is possible in humans by induction of transient mixed chimerism

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