Origin and biology of the allogeneic response

Abstract

The recognition by the immune system of nonself determinants on cells, tissues, or organs transplanted between genetically disparate members ofthe same species can leadtoapotent allogeneic response that is responsible for rejection. We review here fundamental concepts that underlie the origins and biology of allorecognition in the mammalian immune system. We examine why and how T cells are alloreactive and discuss emerging evidence of allor-ecognition by innate immune cells. The nature of T cells (näi{dotless}ve vs. memory) and the allo-antigen presentation pathways (direct, indirect, and semidirect) that initiate the allogeneic response are outlined. © 2013 Cold Spring Harbor Laboratory Press; all rights reserved.