Immunity of Allograft Rejection: An Overview

Abstract

Transplantation between genetically disparate individuals of the same species evokes numerous changes in the host and the graft. In general, the outcome of a transplanted organ is determined by two closely interrelated components. The first component is the biology of the foreign graft (i.e., type of organ and its macro-and microenvironments, the anatomic location, the type of vascular connection, the circumstance surrounding organ harvest and transplant, and the genetic differences between the donor and the recipient). The second component is the nature and intensity of immune responses that develop in the recipient after encountering that specific foreign tissue. The immunity of allograft rejection involves a number of powerful, complex, interrelated, and well-orchestrated immune mechanisms and is only partially understood. This destructive immune response, if left unchecked, can and almost universally does, lead to complete destruction of the transplanted organ over time. This chapter offers an overview of the features and mechanisms of the immune system that work in concert to interact with and reject the organ allograft. Subsequent chapters will describe the role of distinct components that affect the immunology characteristic of the rejection response.