American Journal of Transplantation: Volume 20, Number 1, January 2020

On the cover: We typically think of allograft rejection as being a clear demonstration of an adaptive immune response driven by the specific antigen receptors of T and B cells interacting with alloantigen expressing cells. In this issue of AJT, Ochando et al ( page 10) introduce a primer on “trained immunity.” Trained immunity is the term given to a functional program of the innate immune system characterized by nonpermanent epigenetic and metabolic reprogramming of macrophages. Ample evidence has accumulated for a direct role of monocytes and macrophages, including a capacity for allo‐like differentiation by these cells of self and nonself. This minireview deserves attention as it reminds us to avoid “overtraining” our thoughts about graft rejection and remaining cognizant of the breadth of immune elements involved in graft acceptance and rejection. Cover design by Megan Llewellyn, Duke University Department of Surgery .