The innate immune system in allograft rejection and tolerance.

As T cells alone are both necessary and sufficient for the rejection of virtually all allogeneic tissues, much of transplantation immunology has focused on cells of the adaptive immune system. During the past decade, advances in our understanding of innate responses to pathogen-associated molecules have spurred a "rediscovery" of innate immunity. Fueled by this, an increasing body of literature has emerged in which the role of the innate immune system in allograft rejection and tolerance has been examined more closely. This review will give an overview of recent studies and emerging concepts of how the cellular components of the innate immune system participate in the immune response to solid organ transplantation. These important studies highlight the complex interplay between diverse cells of the immune response and provide the basis for optimal strategies of tolerance induction.