Barriers to successful transplantation of the sensitized patient

Antibody present in the transplant recipient that yields a positive crossmatch with donor cells has long been considered a contraindication and an absolute barrier to transplantation. However, improved methods of antibody detection and characterization have shown that some reactivity with donor cells may be inconsequential to transplantation. Furthermore, the development of treatment protocols to downregulate the humoral immune response has shown that the barrier of sensitization can be overcome, permitting safe transplantation of the sensitized patient. Both of these factors have not only led to an increased rate of transplantation among sensitized patients but have also added to our understanding of the immune response and immune regulation. Here, we review the characteristics of antibodies believed to be relevant to transplant success and the various approaches to dealing with them.