TRANSPLANTATION IMMUNOLOGY

The practice of clinical and experimental transplantation continues to evolve at a rapid pace. To appreciate the current transplant practice s, it is first necessary to review transplant immunology in its proper context, ie, as a component of the complex series of events that prom ote the repair of damaged tissues. These processes are generally catag orized as inflammation, immunity, and tissue repair/reinforcement. In general, there are 3 forms of graft rejection:hyperacute, acute, and c hronic rejection. All 3 forms of graft rejection represent pathologic consequences of one or more of these repair-related processes. The var ious graft rejection responses also illustrate several complex immunol ogic principles that need to be considered. These include the definiti on of an alloantigen, the structure and function of major histocompati bility complex molecules, and the behavior of antigen-presenting cells and alloreactive T cells. This review combines these concepts and pri nciples into a discussion of the 3 forms of graft rejection, each of w hich is addressed at the level of histopathology, pathobiology, incide nce, and clinical strategies.