Determination of unacceptable HLA antigen mismatches in kidney transplant recipients: recommendations of the German Society for Immunogenetics.

One of the major tasks of histocompatibility and immunogenetics laboratories is the pretransplant determination of unacceptable antigen mismatches (UAM) in kidney transplant recipients. In this procedure, human leucocyte antigen (HLA) specificities are defined against which the patient has circulating alloantibodies that are expected to harm the transplanted organ. Using the information on UAM and the potential donor's complete HLA typing, prediction of the crossmatch result, the so called 'virtual crossmatch', is possible. Currently, the laboratories are using different algorithms for the determination of UAM, and depending on the algorithm, more or fewer organ offers are excluded for patients with a similar antibody profile. In order to bring homogeneity into the allocation of organs to immunized patients in Germany, the German Society for Immunogenetics established, on the basis of current knowledge, recommendations for the determination of UAM. The UAM recommendations, which are thought to serve as a common tool for responsible physicians at different transplant centers, contain technical issues that need to be considered and are individualized for sensitized patients with a high or intermediate risk of antibody-mediated rejection. The present review contains these recommendations and puts them into perspective to current international practice.

Influence of test technique on sensitization status of patients on the kidney transplant waiting list.

The exquisitely sensitive single antigen bead (SAB) technique was shown to detect human leukocyte antigen (HLA) antibodies in sera of healthy male blood donors. Such false reactions can have an impact on critical decisions, especially with respect to the determination of unacceptable HLA-antigen mismatches in patients awaiting a kidney transplant. We tested pretransplant sera of 534 patients on the kidney waiting list using complement-dependent cytotoxicity (CDC), enzyme-linked immunosorbent assay (ELISA) and SAB in parallel. Evidence of HLA antibodies was obtained in 5% of patients using CDC, 14% using ELISA, and 81% using SAB. Among patients without history of an immunizing event, 77% showed evidence of HLA antibodies in SAB. In contrast 98% of these patients were negative in ELISA and CDC. In patients without an immunizing event, SAB-detected antibodies reacted not always weakly but with mean fluorescence intensity (MFI) values as high as 14 440. High-MFI-value antibodies were found in some of these patients with HLA specificities that are rather common in general population, consideration of which would lead to unjustified exclusion of potential kidney donors. False SAB reactions can be unveiled by testing with additional antibody assays. Denial of donor kidneys to recipients based on HLA-antibody specificities detected exclusively in the SAB assay is not advisable.

Superiority of AbCross enzyme-linked immunosorbent assay cross-match over the B-cell complement-dependent lymphocytotoxicity cross-match.

BACKGROUND: The AbCross enzyme-linked immunosorbent assay (ELISA) cross-match is a recently introduced solid phase cross-match technique with several technical advantages over the currently available Antibody Monitoring System ELISA cross-match. METHODS: In the present study, we investigated the potential superiority of AbCross over the traditional complement-dependent lymphocytotoxicity (CDC) B-cell cross-match (BXM). Pretransplant sera of 271 kidney transplant recipients who were transplanted at our center between 1998 and 2010 were tested in ELISA screening for the presence of human leukocyte antigen (HLA) antibodies and in AbCross and CDC for antibody reactivity against solubilized donor HLA class I and II antigens and donor B cells, respectively. RESULTS: Patients positive for HLA class I or II antibodies on ELISA screening had a significantly poorer graft outcome 2 years after transplantation than recipients who were negative for HLA antibodies (21% vs 6% graft loss; P = .002). Corresponding with this finding, 37 recipients positive for HLA antibodies in AbCross against donor HLA class I or II antigens had a 2-year post-transplant graft loss rate of 19%, which is significantly higher than the 8% rate in 186 recipients who were negative for both antibody classes in AbCross (P = .043). The 2-year graft loss rate in 34 AbCross positive but BXM negative patients was 21%, compared with 7% in 172 AbCross and BXM negative patients (P = .012) and 9% in 11 AbCross negative but BXM positive patients (P = .39). CONCLUSIONS: Our data indicate that the AbCross ELISA cross-match is superior to the CDC BXM, most likely because it detects antibodies against donor HLA antigens at a higher sensitivity.

Smoking following renal transplantation in Hungary and its possible deleterious effect on renal graft function.

Smoking is a known risk factor for kidney damage and also influences graft function following renal transplantation. Because smoking habits following kidney transplantation are not systematically evaluated, we analyzed them in a single center in Hungary. The survey was conducted among 402 randomly selected kidney graft recipients. We assessed smoking-related questions as well as clinical kidney disease and transplantation data. Posttransplantation renal function was analyzed based on serum creatinine values at 1 month and at 3 years after transplantation. In our study 25% (n = 102) of patients continued to smoke after transplantation. Smokers who received grafts displayed a significantly younger age compared with nonsmokers (40.1 +/- 13.4 vs 47.1 +/- 12.7 years; P < .001) independent of underlying kidney disease. Posttransplantation kidney function in smokers did not differ at 1 month after engraftment, but was significantly impaired at 3 years as assessed based on serum creatinine levels: 138.9 +/- 42.4 versus 128.4 +/- 48.5 micromol/L (P < .05). Decrease of renal function correlated with smoking intensity defined in pack-years (r(2) = 0.102; P < .05). Smoking is common following kidney transplantation in Hungary and might represent a risk factor for kidney damage following renal transplantation. Therefore, effective tobacco-dependence treatment is necessary in this patient population.