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Transplant arteriosclerosis (TA) is the hallmark of chronic allograft dysfunction (CAD) affecting transplanted organs in the long term [1,2]. These fibroproliferative lesions lead to neointimal thickening of arteries in all transplanted allografts [2]. Luminal narrowing then leads to graft ischemia and organ demise. To date, there are no known tolerance induction strategies that prevent TA [3,4]. Therefore, this study was designed to test the hypothesis that human regulatory T cells (Treg cells) expanded ex vivo could prevent TA. Here we show the comparative capacity of Treg cells, sorted via two separate strategies, to prevent TA in a clinically relevant chimeric humanized mouse system. We found that the in vivo development of TA in human arteries was prevented with the treatment of ex vivo expanded human Treg cells. Additionally, we show that Treg cells sorted based on the low expression of CD127 (IL-7Rα) provide a more potent therapy to conventional Treg cells. Our results demonstrate, for the first time, that human Treg cells can inhibit TA by impairing effector function and graft infiltration. We anticipate our findings to serve as a foundation for the clinical development of therapeutics targeting TA in both allograft transplantation and other immune-mediated causes of vasculopathy [5].

Alemtuzumab (CAMPATH-1H) is a depleting agent introduced recently in transplantation and often used with reduced maintenance immunosuppression. In the current study we investigated the immune response of 13 kidney allograft recipients treated with alemtuzumab followed by weaned immunosuppression with reduced dose of mycophenolate mofetil (MMF) and tacrolimus. Tacrolimus was switched to sirolimus at 6 months and MMF withdrawn at 12 months after transplantation.We found that after alemtuzumab induction the recovery of CD8 + T cells was much faster than that of CD4

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