Targeting Trained Immunity in Organ Transplantation
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. Trained immunity is the term given to a functional program of the innate immune system characterized by non-permanent 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 non-self. This concept 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.