American Journal of Transplantation: Volume 14, Number 12, December 2014

On the cover this month: Regulatory T cells (Tregs), specifically CD4 + T cells that express FoxP3 and the high‐affinity IL2 receptor CD25, have been increasingly recognized as providing critical balance to protective and alloreactive cytotoxic T cell responses. This has, in turn, spawned growing interest in harnessing Tregs as potential tools for the control of T cell–mediated allograft rejection, with many proposing that ex vivo expanded Tregs could be used therapeutically to induce tolerance. This month, Singh et al (page 2691 ) show, in a rigorous preclinical primate model, that sirolimus helps foster Treg persistence and function after ex vivo expansion and adoptive transfer. The work is an important step in designing a Treg‐based clinical trial and a nice demonstration of cellular transfer techniques in primates. Cover design by Ken North, North Design Group .