Prevention of alloantibody formation would be a good alternative to the unsatisfactory treatment, which in the case of transplantation results often into secondary problems like degenerative diseases such as cancer (Opelz and D?hler, 2010). HLA-DR Compatibility Many mostly European organ exchange organizations allocate kidneys on the basis of HLA matching by giving more points to better matched patients than those with a lower matching degree (Doxiadis et al., 2004; Johnson et al., 2010). waiting NOV time for a retransplant. Even if the number of organ donors remains the same a lowering of the mean waiting time is expected because of the longer period of graft survival. strong class=”kwd-title” Keywords: kidney transplantation, HLA-DR, matching, compatibility Introduction The role of HLA compatibility as a parameter for allocation of kidneys from deceased donors to patients on the kidney waiting list remains a matter of debate. It is well accepted that the best possible organ for an end stage renal disease patient is a fully HLA compatible kidney. The arguments of those acting against compatibility do not follow scientific criteria. Both graft and patient survival in post mortal kidney transplantation are significantly better in compatible groups compared to kidneys transplanted with incompatibilities (Doxiadis et al., 2004; Kaneku and Terasaki, 2006; Opelz and D?hler, 2007; Johnson et al., 2010). The same holds true for kidneys from living donors (Opelz, 1997). Furthermore, HLA incompatible organs are the source of HLA antigens toward which the patient can, even under immunosuppressive therapy, form alloantibodies. Following the rules of Immunology this step is triggered by the patients own HLA system. These alloantibodies are currently suggested to be the main cause of graft destruction (Sijpkens et al., 1999). Furthermore, incompatibilities render the patient (highly) sensitized and after primary graft loss more difficult to be offered a suitable donor kidney for retransplantation. Alloantibodies have been related not only to acute but especially to chronic allograft dysfunction, better discussed as chronic rejection. Intervening therapies are used to treat patients with alloantibodies such as intravenous immunoglobulines (Glotz et al., 1993; Gebel and Halloran, 2010), anti-CD20 monoclonal antibodies recognizing the B cells and proteasome inhibitors as Bortezomib (Trivedi et al., 2010). The results are not always satisfactory. Prevention of alloantibody formation would be a good alternative to the unsatisfactory treatment, which in the case of transplantation results often into secondary problems like degenerative diseases such as cancer (Opelz and D?hler, 2010). HLA-DR Compatibility Many mostly European organ exchange organizations allocate kidneys on the basis of HLA matching by giving more points to better matched patients than those with a lower matching degree (Doxiadis et al., 2004; Johnson et al., 2010). A selection of a specific locus, e.g., HLA-DR, is not yet the rule. Earlier it has been shown that HLA-DR compatibility leads to an increased graft survival for patients receiving a primary graft. The effect of HLA-A, B compatibility disappears when patients receive a HLA-DR incompatible organ (Doxiadis et al., 2007). These results have been obtained using a large number of transplant ( em N /em ?=?35,205) in the transplantation period of 1985C2005. In a follow-up study retransplants were analyzed (Doxiadis et al., 2010). For the same period as shown above post mortem kidney retransplants were selected. The recipients were 18?years old while the donors were over 5?years 3PO old. Transplants performed via 3PO special Eurotransplant programs were excluded. End point of this analysis was graft loss censored for death with functioning graft. KaplanCMeier product limit method was used to estimate survival rates. For the estimation of relative risks (hazard ratios) for different variables Cox proportional hazard regression was used. Adjusted survival curves were plotted using the same procedure. All analyses were performed with the SPSS statistical package, version 14 (SPSS Inc., Chicago, IL, USA). The course of post transplantation follow-up was analyzed in the three separate phases post transplantation: initial ( 1?year), intermediate (1 to 5?years), and late phase (5?years follow-up). The results of these analyses are similar to the ones obtained for the primary transplants. The effect of HLA-A, B compatibility exists as expected over time and mimics the results already shown for primary transplants. By introducing an HLA-DR incompatibility the effect of HLA-A, B compatibility disappears (Doxiadis et al., 2010). The risk factors in multivariate 3PO analysis showed that 3PO donor age already reported for the primary grafting and also in many other studies and sensitization degree of the patient at transplantation are deleterious for the patient. Finally, HLA-A, B incompatibility is an independent factor resulting in a higher graft loss in the first phase (1?year) post transplantation, presumably because of alloantibodies or unreported earlier sensitization of the patients. These results are based on a seroequivalent HLA-DR typing (DR1CDR18) or a molecular typing.