The hyperimmunized patient: from sensitization toward transplantation.

Hyperimmunized patients tend to accumulate on renal transplant waiting lists because their high level of sensitization leads to positive crossmatches with almost all potential organ donors. The origins of sensitization and the different efforts made to find crossmatch-negative donors for these patients are discussed. Special emphasis is given to a local strategy based on the determination of HLA-A and -B mismatches, against which the patient did not form alloantibodies, the so-called acceptable mismatches. Kidney donor selection is based on compatibility with the patients' own HLA antigens in combination with the acceptable HLA-A and -B antigens and can be operated from a central organ-sharing office.