16-P

Abstract

The debate on the usefulness of HLA compatibility in cadaveric kidney transplantation has not always been led by evidence-based medicine but often was a matter of believe. In the early years compatibility was used to prolong graft and patient survival. We showed that base line compatibility, eg. HLA-DR will decrease rejection rate and increase graft survival, while less DSA will be produced and the chance of receiving a second graft increases. Transplantation has to be regarded as an immunization step. The aim of this study was to make a detailed inventory of the effect of HLA mismatches (MM) on sensitization. In a retrospective study using the Eurotransplant data base we analysed the probability of alloantibody formation in 1 (N=6,094) and 2 HLA-A,B MM transplants (N=8,696) within the fully HLA-DR compatible group. Furthermore, we analysed the results of DSA in a group of males returning to the waitlist after a failed transplant (N=1,311). In the 1 and 2 MM HLA-A, B group the probability to produce DSA is 11% and 70% respectively. With more MM virtually all patients will form DSA. In the males returning on the waitlist, we observed that the chance of sensitization depends on the HLA allotype of the donor: MM of HLA-A1, A2, A24, A26 and B49 have a >40% chance to induce DSA while other HLA MM have a chance of ⩽25% to induce antibody (HLA-B62, B27, B56, B57, A31, B18 and B30). Differential immunogenicity is the reason why incompatibilities have a higher or lower probability to induce antibodies. HLA molecules are built up from epitopes, the sum of which results in the antigens as HLA-A1, A2 etc. Epitopes are shared between molecules. If expressed by other than self (=MM) no antibody formation is observed. The results point to the direction that it is possible to establish a patient depended algorithm for intelligent MM (i-MM), which will results in less DSA thus increased survival and even if the number of procured organs remains stable decreases waiting time.