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Background: Kidney transplant recipients show sex differences in excess overall mortality risk that vary by donor sex and recipient age. However, whether the excess risk of death with graft function (DWGF) differs by recipient sex is unknown., Methods: In this study, we combined data from 3 of the largest transplant registries worldwide (Scientific Registry of Transplant Recipient, Australia and New Zealand Dialysis and Transplant Registry, and Collaborative Transplant Study) using individual patient data meta-analysis to compare the excess risk of DWGF between male and female recipients of a first deceased donor kidney transplant (1988-2019), conditional on donor sex and recipient age., Results: Among 463 895 individuals examined, when the donor was male, female recipients aged 0 to 12 y experienced a higher excess risk of DWGF than male recipients (relative excess risk 1.68; 95% confidence interval, 1.24-2.29); there were no significant differences in other age intervals or at any age when the donor was female. There was no statistically significant between-cohort heterogeneity., Conclusions: Given the lack of sex differences in the excess risk of DWGF (other than in prepubertal recipients of a male donor kidney) and the known greater excess overall mortality risk for female recipients compared with male recipients in the setting of a male donor, future study is required to characterize potential sex-specific causes of death after graft loss., Competing Interests: A.J.V. has accepted consulting fees and fellowship grant funding from Paladin Labs Inc. A.M. is supported by grants from the German Research Foundation (DFG; ME 3696/5-1 and ME3696/3-1) and the Lower Saxony Ministry of Science and Culture. C.S. is supported by the European Union’s Horizon 2020 Research and Innovation Programme (grant 952512). G.W. is supported by National Health and Medical Research Council Investigator (APP 1195414) and Career Development Fellowship (APP 1147657). R.S.-P. is supported by a Fonds de recherche du Quebec—Santé chercheur boursier clinician award (grant 254386) and Canadian Institutes of Health Research (grant FRN-156730). The other authors declare no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: There is a known recipient sex-dependent association between donor sex and kidney transplant survival. We hypothesized that donor age also modifies the association between donor sex and graft survival., Methods: First, deceased donor kidney transplant recipients (1988-2019, n = 461 364) recorded in the Scientific Registry of Transplant Recipients, the Australia and New Zealand Dialysis and Transplant Registry and the Collaborative Transplant Study were analyzed. We used multivariable Cox regression models to estimate the association between donor sex and death censored graft loss, accounting for the modifying effects of recipient sex and donor age; donor age was categorized as 5-19, 20-34, 35-49, 50-59 and ≥60 years. Results from cohort-specific Cox models were combined using individual patient data meta-analysis., Results: Among female recipients of donors aged <60 years, graft loss hazards did not differ by donor sex; recipients of female donors ≥60 years showed significantly lower graft loss hazards than recipients of male donors of the same age [combined adjusted hazard ratio (aHR) 0.90, 95% CI 0.86-0.94]. Among male recipients, female donors aged <50 years were associated with significantly higher graft loss hazards than same-aged male donors (5-19 years: aHR 1.11, 95% CI 1.02-1.21; 20-34 years: aHR 1.08, 95% CI 1.02-1.15; 35-49 years: aHR 1.07, 95% CI 1.04-1.10). There were no significant differences in graft loss by donor sex among male recipients of donors aged ≥50 years., Conclusion: Donor age modifies the association between donor sex and graft survival. Older female donors were associated with similar or lower hazards of graft failure than older male donors in both male and female recipients, suggesting a better functional reserve of older female donor kidneys., (© The Author(s) 2023. Published by Oxford University Press on behalf of the ERA.)

Worldwide and at all ages, males have a higher mortality risk than females. This mortality bias should be preserved in kidney transplant recipients unless there are sex differences in the effects of transplantation. Here we compared the excess risk of mortality (risk above the general population) in female versus male recipients of all ages recorded in three large transplant databases. This included first deceased donor kidney transplant recipients and accounted for the modifying effects of donor sex and recipient age. After harmonization of variables across cohorts, relative survival models were fitted in each cohort separately and results were combined using individual patient data meta-analysis among 466,892 individuals (1988-2019). When the donor was male, female recipients 0-12 years (Relative Excess Risk 1.54, 95% Confidence Interval 1.20-1.99), 13-24 years (1.17, 1.01-1.34), 25-44 years (1.11, 1.05-1.18) and 60 years and older (1.05, 1.02-1.08) showed higher excess mortality risks than male recipients of the same age. When the donor was female, the Relative Excess Risk for those over 12 years were similar to those when the donor was male. There is a higher excess mortality risk in female than male recipients with differences larger at younger than older ages and only statistically significant when the donor was male. While these findings may be partly explained by the known sex differences in graft loss risks, sex differences in the risks of death with graft function may also contribute. Thus, higher risks in females than males suggest that management needs to be modified to optimize transplant outcomes among females., (Copyright © 2023 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Sex differences in kidney graft loss rates were reported in the United States. Whether these differences are present in other countries is unknown., Methods: We estimated the association between recipient sex and death-censored graft loss in patients of all ages recorded in the Scientific Registry of Transplant Recipients, Australia and New Zealand Dialysis and Transplant Registry, and Collaborative Transplant Study registries who received a first deceased donor kidney transplant (1988-2019). We used multivariable Cox regression models, accounting for the modifying effects of donor sex and recipient age, in each registry separately; results were combined using individual patient data meta-analysis., Results: We analyzed 438 585 patients. Young female patients 13-24 y old had the highest crude graft loss rates (female donor: 5.66; male donor: 5.50 per 100 person-years). Among young recipients of male donors, females showed higher graft loss risks than males (0-12 y: adjusted hazard ratio [aHR] 1.42, (95% confidence interval [CI], 1.17-1.73); 13-24 y: 1.24 (1.17-1.32); 25-44 y: 1.09 (1.06-1.13)). When the donor was female, there were no significant differences by recipient sex among those of age <45 y; however, the aHR for females was 0.93 (0.89-0.98) in 45-59 y-old and 0.89 (0.86-0.93) in ≥ 60 y-old recipients. Findings were similar for all 3 registries in most age intervals; statistically significant heterogeneity was seen only among 13-24-y-old recipients of a female donor (I2 = 71.5%, P = 0.03)., Conclusions: There is an association between recipient sex and kidney transplantation survival that is modified by recipient age and donor sex., Competing Interests: A.J.V. has accepted consulting fees and fellowship grant funding from Paladin Labs Inc. A.M. is supported by grants from the German Research Foundation (DFG; ME 3696/5-1 and ME3696/3-1) and the Lower Saxony Ministry of Science and Culture. G.W. is supported by NHMRC Investigator (APP 1195414) and Career Development Fellowship (APP 1147657). R.S.-P. is supported by a Fonds de recherche du Quebec—Santé chercheur boursier clinician award (grant no. 254386) and CIHR (grant FRN-156730). This study was supported by funding from the Canadian Institutes of Health Research PJT-165832. The other authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Patients aged ≥60 y represent the fastest growing population among kidney transplant recipients and waitlist patients. They show an elevated infection risk and are frequently transplanted with multiple human leukocyte antigen mismatches. Whether the choice of calcineurin inhibitor influences graft survival, mortality, or key secondary outcomes such as infections in this vulnerable recipient population is unknown., Methods: A total of 31 177 kidney transplants from deceased donors performed between 2000 and 2019 at European centers and reported to the Collaborative Transplant Study were analyzed using multivariable Cox and logistic regression analyses. All recipients were ≥60 y old and received tacrolimus (Tac) or cyclosporine A on an intention-to-treat basis, combined with mycophenolic acid or azathioprine plus/minus steroids., Results: The risk of 3-y death-censored graft loss and patient mortality did not differ significantly between Tac- and cyclosporine A-treated patients (hazard ratio 0.98 and 0.95, P = 0.74 and 0.20, respectively). No difference was found in the overall risk of hospitalization for infection (hazard ratio = 0.95, P = 0.19); however, a lower incidence of rejection treatment (hazard ratio = 0.81, P < 0.001) was observed in Tac-treated patients. Assessment of pathogen-specific hospitalizations revealed no difference in the risk of hospitalization due to bacterial infection (odds ratio = 1.00, P = 0.96), but a significantly higher risk of hospitalization due to human polyomavirus infection was found among Tac-treated patients (odds ratio = 2.45, P = 0.002). The incidence of de novo diabetes was higher for Tac-based immunosuppression (odds ratio = 1.79, P < 0.001)., Conclusions: Calcineurin inhibitor selection has no significant influence on death-censored graft survival, mortality, and overall infection risk in ≥60-y-old kidney transplant recipients., Competing Interests: The authors declare no funding or conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Natural killer (NK) cells may contribute to antibody-mediated rejection (ABMR) of renal allografts. The role of distinct NK cell subsets in this specific context, such as NK cells expressing the activating receptor NKG2C, is unknown. Our aim was to investigate whether KLRC2 gene deletion variants which determine NKG2C expression affect the pathogenicity of donor-specific antibodies (DSA) and, if so, influence long-term graft survival. We genotyped the KLRC2 wt/del variants for two distinct kidney transplant cohorts, (i) a cross-sectional cohort of 86 recipients who, on the basis of a positive post-transplant DSA result, all underwent allograft biopsies, and (ii) 1,860 recipients of a deceased donor renal allograft randomly selected from the Collaborative Transplant Study (CTS) database. In the DSA+ patient cohort, KLRC2 wt/wt (80%) was associated with antibody-mediated rejection (ABMR; 65% versus 29% among KLRC2 wt/del subjects; P =0.012), microvascular inflammation [MVI; median g+ptc score: 2 (interquartile range: 0-4) versus 0 (0-1), P =0.002], a molecular classifier of ABMR [0.41 (0.14-0.72) versus 0.10 (0.07-0.27), P =0.001], and elevated NK cell-related transcripts ( P =0.017). In combined analyses of KLRC2 variants and a functional polymorphism in the Fc gamma receptor IIIA gene ( FCGR3A -V/F158), ABMR rates and activity gradually increased with the number of risk genotypes. In DSA+ and CTS cohorts, however, the KLRC2 wt/wt variant did not impact long-term death-censored graft survival, also when combined with the FCGR3A- V158 risk variant. KLRC2 wt/wt may be associated with DSA-triggered MVI and ABMR-associated gene expression patterns, but the findings observed in a highly selected cohort of DSA+ patients did not translate into meaningful graft survival differences in a large multicenter kidney transplant cohort not selected for HLA sensitization., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Vietzen, Döhler, Tran, Süsal, Halloran, Eskandary, Herz, Mayer, Kozakowski, Wahrmann, Ely, Haindl, Puchhammer-Stöckl and Böhmig.)

Main problem: Soluble urokinase plasminogen activator receptor (suPAR) is an immunological risk factor for kidney disease and a prognostic marker for cardiovascular events. Methods: We measured serum suPAR levels in a total of 1,023 kidney transplant recipients either before (cohort 1, n = 474) or at year 1 after transplantation (cohort 2, n = 549). The association of suPAR levels and all-cause and cardiovascular mortality was evaluated by multivariable Cox regression analysis. Results: The highest suPAR tertile compared to the two lower tertiles had a significantly higher risk of all-cause mortality in both cohorts separately (cohort 1: hazard ratio (HR) 1.92, 95% confidence interval (CI) 1.20-3.08, p = 0.007; cohort 2: HR = 2.78, 95% CI 1.51-5.13, p = 0.001) and combined ( n = 1,023, combined HR = 2.14, 95% CI 1.48-3.08, p < 0.001). The association remained significant in the subgroup of patients with normal kidney function (cohort 2: HR = 5.40, 95% CI 1.42-20.5, p = 0.013). The increased mortality risk in patients with high suPAR levels was attributable mainly to an increased rate of cardiovascular death ( n = 1,023, HR = 4.24, 95% CI 1.81-9.96, p < 0.001). Conclusion: A high suPAR level prior to and at 1 year after kidney transplantation was associated with an increased risk of patient death independent of kidney function, predominantly from cardiovascular cause., Competing Interests: CM and MZ, together with the University of Heidelberg, are co-founders of TolerogenixX GmbH, Heidelberg, Germany, a biotechnology company that holds licenses for cell therapies. CM, CSü, and MZ filed a patent application for a cell therapy. JR is cofounder of Trisaq, a biotechnology company developing drugs targeting suPAR. SH and JR are members of the scientific advisory board of Trisaq. JR holds patents and licenses related to suPAR. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Morath, Hayek, Döhler, Nusshag, Sommerer, Zeier, Reiser and Süsal.)

Background: Approximately 1700 children per year with end-stage kidney disease undergo kidney transplantation in Europe and the United States of America; 30%-50% are living donor kidney transplantations. There may be immunological differences between paternal and maternal donors due to transplacental exchange of cells between the mother and fetus during pregnancy leading to microchimerism. We investigated whether the outcome of living-related kidney transplantation in young children is different after maternal compared with paternal organ donation., Methods: Using the international Collaborative Transplant Study (CTS) database, we analyzed epidemiological data of 7247 children and adolescents aged <18 years who had received a kidney transplant from either mother or father. Risk of treated rejection episodes and death-censored graft failure were computed using the Kaplan-Meier method and multivariable Cox regression., Results: In the recipient age group 1-4 years, the rate of treated rejection episodes in recipients of kidneys from maternal donors (N = 195) during the first 2 years post-transplant was significantly lower (hazard ratio HR = 0.47, p = .004) than in patients receiving kidneys from paternal donors (N = 179). This association between donor sex and risk of treated rejections was not observed in children aged 5-9 years. The 5-year death-censored graft survival in children aged 1-4 years with a maternal or paternal donor was comparable., Conclusions: Maternal kidney donation in young pediatric renal transplant recipients is associated with an approximately 50% lower rate of treated rejection than paternal kidney donation. Whether this phenomenon is due to maternal microchimerism-induced donor-specific hyporesponsiveness must be evaluated in prospective mechanistic studies., (© 2021 The Authors. Pediatric Transplantation published by Wiley Periodicals LLC.)

Objectives: Our country Croatia is among the global leaders regarding deceased donation rates, yet we are facing organ shortage and concurrently a sharp decline in our acceptance rates for kidney offers. To reevaluate our organ acceptance policy, we retrospectively analyzed the factors that influenced the posttransplant outcomes of kidneys from elderly deceased donors at our center during a 20-year period and the changes to our organ acceptance criteria during Eurotransplant membership., Materials and Methods: We studied all kidney transplants from donors ≥60 years old during the two 5-year episodes of Eurotransplant membership from 2007 to 2017 (period II and period III) and compared those data to data from the decade before Eurotransplant membership (period I, 1997-2007). Differences in acceptance rates and reasons for the decline of kidney offers between the two 5-year periods of Eurotransplant membership were analyzed., Results: In period I, 14.1% of all kidney allografts were obtained from donors ≥60 years old; in period II and period III the rates were nearly 2-fold higher (27.0% and 25.7%, respectively; P = .007 and P = .008). During the first 5-year period of Eurotransplant membership (period II), we accepted significantly more grafts from marginal donors with a higher number of human leukocyte antigen mismatches compared with period I. Consequently, the 3-month survival rate of kidneys from donors ≥60 years old dropped from 91.1% to as low as 74.2% (P = .034). After application of morestringent human leukocyte antigen matching, especially in human leukocyte antigen DR, and morestringent donor acceptance criteria in period III, graft survival improved to 91.1%., Conclusions: Our experience indicates that careful selection of kidneys from elderly deceased donors and allocation to human leukocyte antigen-matched recipients is important to improve transplant outcomes.

Background: The use of kidney allografts from ≥70-y-old donors has increased persistently over the last 20 y. Prolonged cold ischemia time (CIT) is well known to increase graft failure risk. However, despite their growing importance, no data are available on the impact of CIT, specifically on survival of allografts from ≥70-y-old donors., Methods: In total, 47 585 kidney transplantations from expanded criteria donors (ECDs) performed during 2000-2017 and reported to the Collaborative Transplant Study were analyzed. The impact of CIT on 5-y death-censored graft and patient survival was studied for transplantations from <70-y (n = 33 305) and ≥70-y-old ECDs (n = 14 280)., Results: Compared with the reference of ≤12 h CIT, a CIT of 13-18 h did not increase the risk of graft failure significantly, either for recipients of kidneys from <70-y or from ≥70-y-old ECDs. In contrast, graft failure risk increased significantly when CIT exceeded 18 h, both in recipients of kidneys from <70-y and, more pronounced, from ≥70-y-old ECDs (CIT 19-24 h: hazard ratio [HR] = 1.19 and 1.24; P < 0.001; CIT ≥24 h: HR = 1.28 and 1.32, P < 0.001 and P =0.003, respectively). Within the 18-h CIT interval, additional HLA matching further improved survival of ECD transplants significantly, whereas the negative impact of a prolonged CIT >18 h was stronger in ≥65-y-old recipients and for transplants with multiple HLA mismatches. The influence of CIT on patient survival was less pronounced., Conclusions: CIT, as long it is kept ≤18 h, has no significant impact on survival of kidney transplants, even from ≥70-y-old ECDs., Competing Interests: The authors declare no funding or conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Due to a widespread organ shortage, the use of expanded criteria donors (ECDs) in kidney transplantation has increased persistently, reaching approximately 40% in recent years. Whether human leucocyte antigen (HLA) matching between donor and recipient should be part of allocation algorithms in transplantation of ECD kidneys, and especially of ECD kidneys from ≥70-year-old donors, is still in question. To this end, 135,529 kidney transplantations performed between 2000 and 2017 and reported to the Collaborative Transplant Study were analysed and the impact of HLA-A+B+DR mismatches on death-censored graft and patient survival as well as on rejection episodes was investigated. Results were stratified according to donor status (standard criteria donor (SCD) versus ECD) and age of ECD. HLA incompatibility increased the five-year death-censored graft failure risk similarly strong in recipients of ECD and SCD transplants (hazard ratio (HR) per HLA mismatch 1.078 and 1.075, respectively; p < .001 for both). Its impact on rejection treatments during the first post-transplant year was also significant but slightly weaker for recipients of ECD transplants (risk ratio (RR) per HLA mismatch 1.10 for ECD transplants and 1.13 for SCD transplants; p < .001 for both). Mortality increased gradually from zero to six HLA mismatches in recipients of SCD transplants, whereas for ECD transplants a significant increase was notable only from zero to more than zero mismatches. A significant but slightly less pronounced impact of HLA incompatibility on graft failure was observed in transplants from ≥70- compared with <70-year-old ECDs (HR per mismatch 1.047 and 1.093; p = .009 and < 0.001, respectively). The influence of HLA mismatches on rejection treatments was the same for both ECD age groups (RR = 1.10, p < .001 and p = .004, respectively). Our data indicate that HLA matching should be part of allocation algorithms not only in transplantation of kidneys from SCDs but also from ECDs., (© 2020 John Wiley & Sons Ltd.)

We analyzed in a cohort of 68,606 first deceased donor kidney transplantations reported to the Collaborative Transplant Study whether an epitope-based matching of donor-recipient pairs using the Predicted Indirectly ReCognizable HLA Epitopes algorithm (PIRCHE-II) is superior to currently applied HLA antigen matching. PIRCHE-II scores were calculated based on split antigen HLA-A, -B, -DRB1 typing and adjusted to the 0-6 range of HLA mismatches. PIRCHE-II scores correlated strongly with the number of HLA mismatches (Spearman ρ = 0.65, P < 0.001). In multivariable analyses both parameters were found to be significant predictors of 5-year death-censored graft loss with high prognostic power [hazard ratio (HR) per adjusted PIRCHE-II score = 1.102, per HLA mismatch = 1.095; z -value PIRCHE-II: 9.8, HLA: 11.2; P < 0.001 for both]. When PIRCHE-II scores and HLA mismatches were analyzed simultaneously, their predictive power decreased but remained significant (PIRCHE-II: P = 0.002; HLA: P < 0.001). Influence of PIRCHE-II was especially strong in presensitized and influence of HLA mismatches in non-sensitized recipients. If the level of HLA-incompatibility was low (0-3 mismatches), PIRCHE-II scores showed a low impact on graft survival (HR = 1.031) and PIRCHE-II matching did not have additional significant benefit ( P = 0.10). However, if the level of HLA-incompatibility was high (4-6 mismatches), PIRCHE-II improved the positive impact of matching compared to applying the traditional HLA matching alone (HR = 1.097, P = 0.005). Our results suggest that the PIRCHE-II score is useful and can be included into kidney allocation algorithms in addition to HLA matching; however, at the resolution level of HLA typing that is currently used for allocation it cannot fully replace traditional HLA matching., Competing Interests: CS declares that he received a minor research grant from the PIRCHE AG. MN is an employee of PIRCHE AG that runs the PIRCHE web-portal. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Unterrainer, Döhler, Niemann, Lachmann and Süsal.)

Adolescent and young adult age is a high-risk window with an alarmingly increased likelihood of premature kidney graft loss due to immunological rejection. Using the large database of the Collaborative Transplant Study, we analyzed whether a more intense and less variable exposure to tacrolimus could counteract this young age-related enhanced immunoreactivity. Kidney graft recipients aged 12-23 years (n = 964) with a 1-year tacrolimus trough level between 4.0 and 10.9 ng/ml had a 5-year graft survival rate of 85.1%, significantly better than the poor 66.1% rate in patients with a trough level below 4.0 ng/ml who showed a 2.38-fold increased risk of graft loss in the multivariable analysis (P < 0.001). This association was not apparent in young children aged 0-11 years (n = 455) and less pronounced in adults aged 24-34 years (n = 1466). However, an intra-patient variability of tacrolimus (IPV) trough level ≥1.5 at post-transplant years 1 and 2 was associated with an increased graft loss risk in both 12- to 23-year-old and 0- to 11-year-old recipients (P < 0.001 and P = 0.045). Patients with high IPV made up as many as 30% of kidney graft recipients, indicating that a more intense and less variable exposure to tacrolimus could improve graft survival strongly in this high-risk group., (© 2020 The Authors. Transplant International published by John Wiley & Sons Ltd on behalf of Steunstichting ESOT.)

Delayed graft function (DGF) occurs in a significant proportion of deceased donor kidney transplant recipients and was associated with graft injury and inferior clinical outcome. The aim of the present multi-center study was to identify the immunological and non-immunological predictors of DGF and to determine its influence on outcome in the presence and absence of human leukocyte antigen (HLA) antibodies. 1,724 patients who received a deceased donor kidney transplant during 2008-2017 and on whom a pre-transplant serum sample was available were studied. Graft survival during the first 3 post-transplant years was analyzed by multivariable Cox regression. Pre-transplant predictors of DGF and influence of DGF and pre-transplant HLA antibodies on biopsy-proven rejections in the first 3 post-transplant months were determined by multivariable logistic regression. Donor age ≥50 years, simultaneous pre-transplant presence of HLA class I and II antibodies, diabetes mellitus as cause of end-stage renal disease, cold ischemia time ≥18 h, and time on dialysis >5 years were associated with increased risk of DGF, while the risk was reduced if gender of donor or recipient was female or the reason for death of donor was trauma. DGF alone doubled the risk for graft loss, more due to impaired death-censored graft than patient survival. In DGF patients, the risk of death-censored graft loss increased further if HLA antibodies (hazard ratio HR=4.75, P < 0.001) or donor-specific HLA antibodies (DSA, HR=7.39, P < 0.001) were present pre-transplant. In the presence of HLA antibodies or DSA, the incidence of biopsy-proven rejections, including antibody-mediated rejections, increased significantly in patients with as well as without DGF. Recipients without DGF and without biopsy-proven rejections during the first 3 months had the highest fraction of patients with good kidney function at year 1, whereas patients with both DGF and rejection showed the lowest rate of good kidney function, especially when organs from ≥65-year-old donors were used. In this new era of transplantation, besides non-immunological factors, also the pre-transplant presence of HLA class I and II antibodies increase the risk of DGF. Measures to prevent the strong negative impact of DGF on outcome are necessary, especially during organ allocation for presensitized patients., (Copyright © 2020 Morath, Döhler, Kälble, Pego da Silva, Echterdiek, Schwenger, Živčić-Ćosić, Katalinić, Kuypers, Benöhr, Haubitz, Ziemann, Nitschke, Emmerich, Pisarski, Karakizlis, Weimer, Ruhenstroth, Scherer, Tran, Mehrabi, Zeier and Süsal.)

In several deceased donor kidney allocation systems, organs from elderly donors are allocated primarily to elderly recipients. The Eurotransplant Senior Program (ESP) was implemented in 1999, and since then, especially in Europe, the use of organs from elderly donors has steadily increased. The proportion of ≥60-year-old donors reported to the Collaborative Transplant Study (CTS) by European centers has doubled, from 21% in 2000-2001 to 42% in 2016-2017. Therefore, in the era of organ shortage it is a matter of debate whether kidney organs from elderly donors should only be allocated to elderly recipients or whether <65-year-old recipients can also benefit from these generally as "marginal" categorized organs. To discuss this issue, a European Consensus Meeting was organized by the CTS on April 12, 2018, in Heidelberg, in which 36 experts participated. Based on available evidence, it was unanimously concluded that kidney organs from 65- to 74-year-old donors can also be allocated to 55- to 64-year-old recipients, especially if these organs are from donors with no history of hypertension, no increased creatinine, no cerebrovascular death, and no other reasons for defining a marginal donor, such as diabetes or cancer., (© 2020 Steunstichting ESOT. Published by John Wiley & Sons Ltd.)

There is a growing shortage of kidney donors leading to extended transplant waiting times associated with increased mortality. To expand the donor pool, clinicians nowadays regularly accept organs from elderly donors, including those aged ≥70 years. There is only limited and conflicting data whether kidneys from these elderly donors allow for satisfactory allograft outcome rates. To asses this question, the 5-year death censored graft survival of 116,870 adult first deceased donor kidney allograft recipients that were transplanted at European centers between 1997 and 2016 and reported to the "Collaborative Transplant Study" were analyzed using Kaplan-Meier analysis and country stratified Cox regression. The combinations of the two transplant periods 1997-2006 and 2007-2016 with the donor age categories 18-49, 50-59, 60-69, and ≥70 years were considered. From 1997-2006 to 2007-2016, the median donor age increased from 50 to 55 years and the proportion of kidneys from ≥60-year-old donors rose from 24.1 to 38.8%. At the same time, the proportion of kidneys from ≥70-year-old donors more than doubled (6.7 vs. 15.4%). Between 1997-2006 and 2007-2016, the 5-year graft survival improved in all donor age categories. During 2007-2016, the 5-year death censored graft survival of kidneys from ≥70-year-old donors was comparable to that of kidneys from 60 to 69-year-old donors during 1997-2006. This was true both for younger recipients (18-64 years) and older recipients (≥65 years). Among the younger recipients, 45-64-year-old recipients showed the best death censored graft survival rates for kidneys from old donors. In the country-stratified Cox regression analysis, compared to the reference of grafts from 18 to 49-year-old donors, the hazard ratio for grafts from ≥70-year-old donors during 2007-2016 was 1.92, exactly the same as the hazard ratio for grafts from 60 to 69-year-old donors during 1997-2006. Our analysis indicates that within only one further decade (1997-2006 vs. 2007-2016) the 5-year death censored graft survival of kidneys from ≥70-year old donors improved to the level of kidneys from 60 to 69-year-old donors in the previous decade., (Copyright © 2019 Echterdiek, Schwenger, Döhler, Latus, Kitterer, Heemann and Süsal.)

Intra-patient variability (IPV) of tacrolimus trough level has been associated with poor outcome after kidney transplantation. These findings were derived from single-center analyses and restricted mainly to measurements early after transplantation. We analyzed in a multicenter effort whether high IPV of tacrolimus levels at posttransplant years 1, 2, and 3 was associated with impaired clinical outcome. More than 6600 patients who received a deceased donor kidney transplant during 2000-2014 and had a functioning graft for >3 years were studied. Graft survival was significantly impaired with increasing IPV (P < 0.001). As compared to patients with a low IPV of <30%, the risk of graft loss during years 4-6 increased 32% in patients with an IPV of 30% to 44% and 66% in patients with an IPV of ≥45% (P = 0.002 and P < 0.001). About one-third of patients showed an IPV of ≥30% with substantially impaired outcome. Even in patients with good outcome during the first 3 posttransplant years, a high IPV was associated with inferior graft survival. Our data indicate that a fluctuating tacrolimus trough level at years 1, 2, and 3 posttransplant is a major problem in kidney transplantation., (© 2019 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background: Systolic blood pressure (SBP) and diastolic blood pressure (DBP) are important predictors of graft and patient survival in renal transplantation. Pulse pressure (PP), the difference between systolic and diastolic pressure, has been associated with cardiovascular and renal morbidity in nontransplant epidemiological studies and clinical trials., Methods: In this large retrospective analysis of prospectively collected data, transplant recipients from 1995 to 2015 were examined for patient and death-censored graft survival., Results: In 43 006 recipients, a higher 1-year PP was significantly associated with inferior 10-year patient and death-censored graft survival. In patients 60 years or older, SBP but not DBP was associated with 10-year survival, an effect that was pronounced in patients with a normal SBP of <140 mm Hg and an increased PP of 60 mm Hg or greater, highlighting the superior impact of PP on survival in elderly recipients. In recipients 60 years or older, higher PP was associated with increased mortality due to circulatory system diseases but not to infection or cancer. The combination of PP 60 mm Hg or greater and high SBP of 140 mm Hg or greater showed the strongest association with death-censored graft survival across all age groups., Conclusions: We found convincing evidence that PP 1-year posttransplant is predictive of patient survival, especially in elderly recipients with normal SBP. Combined analysis of SBP and PP showed that high PP confers additional predictive information for patient survival beyond that derived from analysis of SBP alone. With regard to prediction of death-censored graft survival, the combination of high SBP and high PP showed the best correlation across all age groups.

Background: Whether kidney transplant recipients who were treated for a malignant tumor before transplantation are at an increased risk of developing a tumor posttransplantation has not been adequately quantified and characterized., Methods: We studied more than 270 000 patients on whom pretransplant and posttransplant malignancy data were reported to the Collaborative Transplant Study. More than 4000 of these patients were treated for pretransplant malignancy. The posttransplant tumor incidence in these patients was compared to that in recipients without a pretransplant tumor. Cox regression, considering multiple confounders, was applied., Results: Significant increases in posttransplant tumor incidence with hazard ratio ranging from 2.10 to 5.47 (all P < 0.001) were observed for tumors in the site-specific pretransplant locations, suggesting tumor recurrences. There were also significantly increased de novo tumors in new locations with hazard ratio ranging from 1.28 to 1.89. Pretransplant basal cell carcinoma of the skin and male genital cancer were associated with significantly increased death-censored graft survival, suggesting impaired immune responsiveness against transplanted kidneys. Time interval from pretransplant tumor occurrence to transplantation and posttransplant mammalian target of rapamycin inhibitor treatment was not found to be of significant relevance in this study., Conclusions: Patients who experienced a pretransplant tumor are at significant risk of tumor recurrence, regardless of the length of interval between tumor treatment and transplantation. There is also some increased risk for de novo tumors, suggesting impaired immune surveillance. Impaired tumor immunity appears to extend to a lower rate of transplant rejection because patients with pretransplant tumors tended to show improved death-censored graft survival.

The evolution of kidney allograft survival remains insufficiently studied in the context of the changing donor and recipient demographics. Since European data are lacking we performed a cohort study (1986-2015) that, based on the Collaborative Transplant Study, included 108 787 recipients of brain-death kidney donors in 135 hospitals across 21 European countries. We analyzed the hazard rate of kidney failure after transplantation. Between 1986 and 1999, improvement in graft survival was more pronounced in the short term than in the long term: one-, five- and ten-year hazard rates after transplantation declined 64% (95% confidence interval, 61%-66%), 53% (49%-57%) and 45% (39%-50%), respectively. Between 2000 and 2015, hazard rates at one, five and ten years post-transplant declined respectively 22% (12-30%), 47% (36-56%) and 64% (45-76%). Improvement in graft survival in the first five years post-transplant was significantly less since 2000, while improvement after five years was comparable to before. During the 2000-2015 period improvement of graft survival was greater in the long than in the short term. These changes were independent of changing donor and recipient characteristics, and reflect the evolution in global kidney transplant management over the past decades. Unfortunately, after accounting for the evolution of donor and recipient characteristics, we found that short-term improvement in graft survival decreased since 2000, while long-term improvement remained unchanged in Europe. Thus, deceleration of short-term graft survival improvement in more recent years illustrates an unmet need for innovation., (Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Based on an analysis of 542 pediatric kidney transplants recorded by the UK Transplant Registry from 2000 to 2012, it was concluded that the survival rate of HLA poorly matched living donor transplants is not inferior to that of HLA well-matched deceased donor transplants., Methods: We analyzed the impact of HLA matching on kidney graft survival in 3627 pediatric living donor transplants performed during 2000 to 2015 using the data of the Collaborative Transplant Study. The impact of HLA mismatches on graft survival was analyzed and survival rates of transplants from poorly matched living donors were compared with those from well-matched deceased donors. Multivariate Cox regression analysis was used to account for the influence of confounders., Results: HLA matching had a statistically significant impact on graft survival of pediatric kidney transplants (P < 0.001). Ten-year graft survival of pediatric transplants from living donors with 4 to 6 HLA-A+B+DR mismatches was significantly worse than that of transplants from well-matched deceased donors with 0 to 1 HLA mismatch (log rank, P = 0.006)., Conclusions: In pediatric kidney transplantation, graft survival of kidneys from deceased donors with 0 to 1 HLA mismatches compares favorably with that of grafts from living donors with 4 to 6 HLA mismatches. If possible, living donor pediatric kidney transplants should be performed from donors with fewer than 4 HLA-A+B+DR mismatches.

FoxP3 and Vav1 are known to be involved in the development of regulatory T cells. Two polymorphic sites in the FoxP3 promoter (rs3761548 and a (GT) n -dinucleotide repeat) and 2 single nucleotide polymorphisms in intron 1 of the Vav1 gene (rs2546133 and rs2617822) have been shown to correlate with gene expression levels. We investigated a potential impact of FoxP3 and Vav1 genetic variants on kidney allograft failure using samples and data of the Collaborative Transplant Study. A cohort of 384 kidney transplant patients was tested. We found no significant association of FoxP3 promoter rs3761548 or (GT) n repeat length with presumed immunological graft failure. The genotype frequencies of Vav1 intron polymorphisms did not significantly differ between patients with graft failure and matched controls., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Patients with previous cancer have increasingly been accepted for renal transplantation. Posttransplant cancer risk and survival rates of these patients are unknown. Our objective was to assess the risk of posttransplant cancer in this patient group., Methods: In this retrospective, nested case-control study, we assessed the outcome of all (n = 95) renal transplanted patients with pretransplant cancer diagnoses in the Uppsala-Örebro region, Sweden. The control group was obtained from the Collaborative Transplant Study registry and included European patients without pretransplant cancer. The other control group comprised the entire renal transplanted population in Uppsala. Development of recurrent cancer, de novo cancer, and patient survival were determined., Results: Patients with pretransplant cancer showed higher incidence of posttransplant cancers and shorter survival compared with the control groups (P < 0.001). No obvious pattern in malignant diagnoses was observed. Death-censored graft survival was unaffected., Conclusions: Despite previously adequate cancer treatments and favorable prognoses, almost half of the patients experienced a posttransplant cancer. These observations do not justify abstaining from transplanting all patients with previous malignancies, because more than 50% of the patients survive 10 years posttransplantation. A careful oncological surveillance pretransplant as well as posttransplant is recommended.

Background: Antibody induction with polyclonal rabbit-antithymocyte globulin (rATG) or an interleukin-2 receptor antagonist (IL-2RA) is widely used in kidney transplantation., Methods: Collaborative Transplant Study data from 38 311 first deceased-donor kidney transplants (2004-13) were analysed. Transplants were classified as 'normal risk' or 'increased risk' according to current guidelines. Cox regression analysis was applied to subpopulations of propensity score-matched recipients., Results: rATG or IL-2RA induction was given to 64% of increased-risk and 53% of normal-risk patients, respectively. rATG and IL-2RA induction were each associated with reduced risk for graft loss versus no induction in increased-risk patients [hazard ratio (HR) 0.85, P = 0.046 and HR 0.89, P = 0.011, respectively]. The HR values for incidence of treated rejection in increased-risk patients for rATG and IL-2RA versus no induction were 0.75 (P = 0.037) and 0.77 (P < 0.001), respectively. In the normal risk subpopulation, neither induction therapy significantly affected the risk of graft loss or treated rejection. Hospitalization for infection was increased by rATG (P < 0.001) and IL-2RA (P < 0.001) induction. In contrast to patients transplanted during 1994-2003, among patients transplanted during 2004-13, rATG did not significantly affect the risk of non-Hodgkin's lymphoma versus no induction (P = 0.68)., Conclusion: Induction therapy following kidney transplantation should be targeted to increased-risk transplants. In this analysis, a beneficial effect of antibody induction in normal-risk transplants could not be demonstrated., (© The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

Background: Evidence is limited regarding the effect of de novo therapy with mammalian target of rapamycin (mTOR) inhibitors on cancer risk after kidney transplantation., Methods: Collaborative Transplant Study data from 78 146 adult recipients of first deceased-donor kidney transplants (1999-2013) were analysed (4279 mTOR inhibitor, 73 867 no mTOR inhibitor) using standard methods. Propensity score matching was performed for analysis of basal cell and squamous cell skin cancer., Results: Standardized incidence ratios (SIR) versus a matched non-transplant population showed reduced tumour incidence in recipients with de novo mTOR inhibitor therapy compared with no mTOR inhibitor for non-melanoma skin cancer (NMSC) (SIR 5.1 versus 6.1; P =0.019) but not non-NMSC cancers (SIR 1.6 versus 1.7; P =0.35). Within propensity score-matched groups (n = 4265), multivariable Cox regression analysis showed a trend to reduced NMSC with mTOR inhibition [hazard ratio (HR) 0.77; P =0.063] but not for all non-NMSC tumours (HR 0.94; P= 0.59). A significant effect for mTOR inhibition was observed for basal cell carcinoma of the skin (HR 0.56; P= 0.004) but not squamous cell carcinoma (HR 0.87; P= 0.54)., Conclusions: De novo mTOR inhibition was associated with a substantially and significantly reduced risk of basal cell carcinoma of the skin after kidney transplantation. A significant reduction of the incidence of other cancers was not found., (© The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

Background: It is an unresolved issue why some kidney transplant recipients with pretransplant donor-specific HLA antibodies (DSA) show a high transplant failure rate, whereas in other patients DSA do not harm the graft. We investigated whether help from preactivated T-cells might be necessary for DSA to exert a deleterious effect., Methods: The impact of pretransplant DSA and immune activation marker soluble CD30 (sCD30) on 3-year graft survival was analyzed in 385 presensitized kidney transplant recipients., Findings: A deleterious influence of pretransplant DSA on graft survival was evident only in patients who were positive for the immune activation marker sCD30. In the absence of sCD30 positivity, 3-year graft survival was virtually identical in patients with or without DSA (83.1±3.9% and 84.3±2.8%, P=0.81). A strikingly lower 3-year graft survival rate of 62.1±6.4% was observed in patients who were both sCD30 and DSA positive (HR 2.92, P<0.001). Even in the presence of strong DSA with ≥5000 MFI, the 3-year graft survival rate was high if the recipients were sCD30 negative., Interpretation: Pretransplant DSA have a significantly deleterious impact on graft survival only in the presence of high pretransplant levels of the activation marker sCD30., (Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.)

Background Solid organ transplant recipients are at increased risk of developing malignancies. The objective of this prospective, observational, one-armed study was to study the feasibility to add a mammalian target of rapamycin (mTOR) inhibitor to the immunosuppressive regimen in transplanted patients with post-transplant malignancies. During the trial the need to improve identification of post-transplant malignancies and to reassure adequate oncological treatment of these patients became evident. Multidisciplinary team (MDT) evaluation of oncological and immunosuppressive treatments was implemented for all patients with malignancies after renal or combined renal and pancreas transplantation because of the trial. Material and methods At Uppsala University Hospital, Sweden, a MDT consisting of transplant surgeons, nephrologists, oncologists and dermatologists evaluated 120 renal or combined renal and pancreas-transplanted recipients diagnosed with malignancies from September 2006 to July 2012. To identify all malignancies, the population was linked to the Regional Tumor Registry (RTR). We recorded to which extent a switch to mTOR inhibitors was possible and how often the originally planned oncological managements were adjusted. All patients were followed for three years. (ClinicalTrials.gov: NCT02241564). Results In 76 of 120 patients (63%) a switch to mTOR inhibitors was possible. Immunosuppression was interrupted in seven patients (6%), reduced in three patients (2%) and remained unchanged in 34 of 120 patients (28%). Identification of post-transplant malignancies increased significantly after linkage to RTR (p = 0.015). The initially recommended oncological treatment was adjusted in 23 of 44 patients (52%) with solid or hematological malignancies; 36 of these patients (82%) were treated according to national guidelines. Conclusion In two thirds of the patients the immunosuppressive treatment could be changed to an mTOR inhibitor with anti-tumor effects in transplanted patients with post-transplant malignancies. The use of regional tumor registers considerably improved the identification of patients with post-transplant malignancies indicating that post-transplant malignancies might be timely underreported in transplant registers.

Presensitized kidney transplant recipients are at high-risk for early antibody-mediated rejection. We studied the impact of pre- and post-transplant donor-specific human leukocyte antigen (HLA) antibodies (DSA) and T-cell-activation on the occurrence of antibody-mediated rejection episodes (AMR) and graft loss (AMR-GL) in a unique cohort of 80 desensitized high-risk kidney transplant recipients. Patients with pre-transplant DSA demonstrated more AMR episodes than patients without DSA, but did not show a significantly increased rate of AMR-GL. The rates of AMR and AMR-GL were not significantly increased in patients with complement split product (C1q)-binding pre-transplant DSA. Pre-transplant C1q-DSA became undetectable post-transplant in 11 of 13 (85%) patients; 2 (18%) of these 11 patients showed AMR but no AMR-GL. In contrast, the post-transplant presence of C1q-DSA was associated with significantly higher rates of AMR (86 vs 33 vs 0%; P < 0.001) and AMR-GL (86 vs 0 vs 0%; log-rank P < 0.001) compared with post-transplant DSA without C1q-binding or the absence of DSA. Patients with both pre-transplant DSA and evidence of pre-transplant T-cell-activation as indicated by soluble CD30-positivity showed a significantly increased risk for AMR-GL [HR = 11.1, 95% confidence interval (CI) = 1.68-73.4; log-rank P = 0.013]. In these high-risk patients, AMR-GL was associated with total DSA in combination with T-cell-activation pre-transplant, and de novo or persistent C1q-binding DSA post-transplant., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Evidence is limited regarding the effect of stopping smoking before kidney transplantation., Methods: Collaborative Transplant Study data from 46 548 recipients of first kidney transplants (1995-2012) were analyzed to 10 years after transplantation., Results: Compared with patients who had never smoked (n = 31,462), patients who stopped smoking before transplantation (n = 10,291) only had a modestly increased risk of all-cause graft failure (hazard ratio [HR], 1.1; 95% confidence interval [95% CI], 1.0-1.1; P < 0.001) or death (HR,1.1; 95% CI, 1.0-1.2; P < 0.001) and a similar risk of death-censored graft failure (HR,1.0, 95% CI, 1.0-1.1; P = 0.19), but a 40% increase in death from malignancy (HR, 1.4; 95% CI, 1.2-1.7; P < 0.001). The risk of events was generally markedly higher in patients who continued to smoke (n = 4795) versus those who had stopped. For tumors of the lip, oral cavity and pharynx, digestive organs, respiratory tract, female genitalia and urinary tract, HR values increased significantly from never-smoked to former smokers to current smokers. The risk of respiratory tumors or cervical cancer was approximately halved when smoking was stopped versus continued., Conclusions: This large series provides clear evidence that patients who stop smoking before transplantation experience substantial benefits, including a substantial reduction in certain types of malignancy.

Background: The association of donor-specific HLA antibodies (DSA) with kidney graft failure has been addressed previously; however, the majority of studies were based on small numbers of patients with graft failure., Methods: We investigated 83 patients with failed kidney transplants for a possible association of de novo development and persistence or loss of pre-existing DSA with graft failure. Single Antigen Bead assay-detected DSA and non-DSA antibodies were compared between patients with graft loss and matched controls with functioning grafts., Results: The incidence of weak de novo DSA or non-DSA at a mean fluorescence intensity of 500 or higher was higher in the graft loss than in the nonrejector group (76% vs 40%, P < 0.001). Because of the low number of patients developing de novo DSA, the DSA results did not reach statistical significance (only 22% of patients with graft loss developed de novo DSA). However, at all cutoffs, there was a significantly higher rate of graft loss in patients with de novo non-DSA. The incidence of strong pretransplant DSA that persist after transplantation was higher in the graft loss group (10% vs 1%, P = 0.034). When C1q-binding ability in sera of rejectors and nonrejectors with posttransplant de novo or persistent DSA was compared, none of the nonrejectors demonstrated C1q positivity, whereas 43% of patients with graft loss showed C1q-positive antibodies, although not necessarily donor-specific (P < 0.001)., Conclusions: Our data show that the posttransplant presence of persisting or de novo HLA antibodies, especially if C1q binding, is associated with graft loss, even if the antibodies are not specific for mismatched donor HLA.

Background: It is unknown how death with a functioning graft (DWFG) is affected in renal transplant recipients who receive prophylaxis for cytomegalovirus (CMV) infection., Methods: Data from 61,927 adult recipients of a deceased donor kidney transplant in 1990 to 2012 registered with the Collaborative Transplant Study were analyzed., Results: Cytomegalovirus prophylaxis was administered in 18%, 75%, 27% and 34% of R-/D- (recipient-negative, donor-negative), R-/D+, R+/D- and R+/D+ transplants, respectively. Only in R-/D+ transplants was CMV prophylaxis associated with significantly improved patient survival versus no prophylaxis (P<0.001). Unexpectedly, in the R-/D+ subgroup, DWFG because of infection was not significantly affected by use of CMV prophylaxis (P=0.16) but death from cardiovascular disease was significantly lower (P<0.001). Cox regression analysis confirmed that the primary impact of CMV prophylaxis on DWFG in R-/D+ transplants was because of reduced cardiovascular death (hazard ratio, 0.66; 95% confidence interval, 0.51-0.85; P=0.002), an effect restricted to patients aged 40 years or older (hazard ratio, 0.61; 95% confidence interval, 0.46-0.81; P<0.001)., Conclusion: We conclude that CMV prophylaxis is associated with a significant benefit for risk of cardiovascular DWFG among R-/D+ kidney transplant patients aged ≥ 40 years. Cytomegalovirus prophylaxis appears particularly critical in this patient subpopulation.

Complement-mediated humoral rejection has become the main focus of research in organ transplantation. The aim of this study was to investigate the possible association of the complement C5aR gene 450 C/T polymorphism in antibody-mediated renal allograft rejection. This polymorphism was investigated in 290 first deceased donor kidney graft recipients with well functioning grafts and no rejection treatment during the first transplant year (WFG), 265 recipients with graft failure within the first transplant year (F), and 187 healthy controls. Frequency of the 450 CT genotype was lower in the total population of 555 kidney recipients (4.7%) than in 187 healthy controls (8.6%), but the difference was not statistically significant (P = 0.065). A significantly higher frequency of CT genotype was found in F patients (CT: 6.8%) when compared to WFG patients (CT: 2.8%, P = 0.027). The CT genotype was also significantly lower in WFG patients than in healthy controls (P = 0.009). Low frequency of the C5aR 450 CT genotype, which apparently is a feature of certain kidney diseases, appears to be associated with good graft outcome in kidney transplantation and might be helpful for identifying recipients who are at low risk for graft rejection., (© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Reports from experienced centers suggest that recipients of an ABO-incompatible living-donor kidney transplant after reduction of ABO antibodies experience no penalty in graft and patient survival versus ABO-compatible transplants, but confirmation that these results can be widely replicated is lacking., Methods: Living-donor kidney transplants from ABO-incompatible donors after ABO antibody reduction registered with the Collaborative Transplant Study during 2005 to 2012 were analyzed and compared with (i) a matched group of ABO-compatible transplant recipients and (ii) all ABO-compatible transplants from centers that performed at least five ABO-incompatible grafts during the study period., Results: One thousand four hundred twenty living-donor ABO-incompatible kidney transplants were analyzed. Three-year death-censored graft survival was virtually identical for ABO-incompatible transplants versus matched and center controls (P=0.92 and P=0.60, respectively). Patient survival rates were also similar (P=0.15 and P=0.11, respectively). Early patient survival was lower in ABO-incompatible grafts (P=0.006 vs. matched controls; P=0.001 vs. center controls) because of a higher rate of early infectious death (P=0.037 and P<0.001, respectively). Death-censored graft and patient survival were not significantly affected by induction therapy and anti-CD20 treatment. ABO antibody reduction by column adsorption was associated with similar death-censored graft survival to plasmapheresis., Conclusion: In this analysis of prospectively collected data from a large series of ABO-incompatible living-donor kidney transplants performed at 101 centers, death-censored graft and patient survival rates were similar to those achieved in ABO-compatible control groups over the same period.

Patient registries are a useful tool to measure outcomes and compare the effectiveness of therapies in a specific patient population. High data quality and completeness are therefore advantageous for registry analysis. Data integration from multiple sources may increase completeness of the data. The pediatric renal transplantation registry CERTAIN identified Eurotransplant (ET) and the Collaborative Transplant Study (CTS) as possible partners for data exchange. Import and export interfaces with CTS and ET were implemented. All parties reached their projected goals and benefit from the exchange.

Background: Angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) are widely prescribed after kidney transplantation, but evidence for an improvement in outcomes is mixed. A recent trial demonstrated a significantly lower incidence of major cardiovascular events in ACEI-treated recipients., Methods: Collaborative Transplant Study data on cardiovascular death during years 2 to 10 after kidney transplantation in patients with a functioning graft were analyzed according to whether ACEI/ARB or other antihypertensive therapy (excluding diuretics) was administered at year 1., Results: Of 39,251 transplants analyzed, 15,250 (38.9%) received ACEI/ARB and 24,001 (61.1%) received other antihypertensive therapy at year 1 after transplantation. The mean duration of follow-up was 5.8 years. During years 2 to 10 after transplantation, cardiovascular death occurred in 918 patients (cumulative incidence=4.7%) with a functioning graft. The rate of cardiovascular death was similar in patients who received ACEI/ARB therapy or other antihypertensive treatment overall and in subpopulations of patients who were considered by the transplant center to be at an increased cardiovascular risk, had no pretransplant risk factors, were aged 60 years and older, were treated for diabetes at year 1, or had serum creatinine of 130 μmol/L or higher at year 1. Multivariable Cox regression analysis confirmed that treatment with ACEI/ARB did not confer a beneficial effect beyond that conferred by other antihypertensive treatments on the cumulative incidence of cardiovascular death during years 2 to 10 (hazard ratio=1.1, P=0.24)., Conclusions: This large-scale retrospective analysis of prospectively collected data shows that the rate of cardiovascular death in kidney transplant recipients receiving ACEI/ARB or other antihypertensive medications is virtually identical.

Death with a functioning graft remains a major challenge following kidney transplantation. Steroid dosing may be a modifiable risk factor. Collaborative Transplant Study (CTS) data were analyzed to assess the relationship between long-term steroid dose and death with function during years 2-5 posttransplant in 41 953 adult recipients of a deceased-donor kidney transplant during 1995-2010. Steroid dose at year 1 correlated significantly with death with function overall, and with death due to cardiovascular disease or infection (all p < 0.001). In patients with optimal graft function (serum creatinine <130 µmol/L) and no anti-rejection treatment during (a) year 1 (b) years 1 and 2, these significant associations remained (all p < 0.001). The center-specific incidence of steroid withdrawal during year 2 showed a significant inverse association with death due to cardiovascular disease (p < 0.001) or infection (p < 0.001) overall, and within the subpopulation with good graft function and no rejection during year 1 (p = 0.002 and p < 0.001, respectively). Maintenance steroid dose shows a highly significant association with death with a functioning graft caused by cardiovascular disease or infection during years 2-5 after kidney transplantation, even in patients with good graft outcomes in whom steroid treatment would appear to be unnecessary., (© Copyright 2013 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background: Recipient death is a leading cause for renal allograft loss. Cardiovascular mortality is the most important cause of death among this patient group. Single nucleotide polymorphisms (SNPs) in a noncoding region close to the CDKN2a/b senescence genes have been associated with higher cardiovascular morbidity and mortality in nontransplant populations., Methods: We selected 2064 renal transplant recipients: 688 with a known cardiovascular cause of death and 1376 matched controls. DNA specimens were genotyped for the three SNPs with known risk allele (rs10757274, rs2383206, and rs10757278) and one SNP without risk allele (rs518394). Genotyping results were analyzed according to the frequency of risk alleles in the two groups., Results: The risk allele for three SNPs was detected significantly more often in patients with a known cardiovascular cause of death than in matched controls (all P<0.05). Diabetes and time on dialysis were modifiers of this effect with the presence of high-risk alleles having a stronger impact in diabetic patients and those with longer dialysis time. There was no difference between groups for the investigated SNP without risk allele., Conclusions: Our results support data from large cohort studies in normal nontransplant populations, which suggested a higher risk for cardiovascular events in individuals carrying certain SNPs in senescence-associated genes. Notably, this finding was obtained in a population known to be at increased risk of cardiovascular death.

Natural killer (NK) cell function can be modulated by the killer cell immunoglobulin-like receptors (KIR) which interact with human leukocyte antigen (HLA) class I molecules on target cells. KIR-ligand mismatching has recently been shown by van Bergen et al. (American Journal of Transplantation 2011; 11(9): 1959-1964) to be a significant risk factor for long-term graft loss in HLA-A, -B and -DR compatible kidney transplants. To verify this potentially important finding, we performed genotyping of 608 deceased-donor kidney graft recipients and their HLA-A, -B and -DR compatible donors for KIR and HLA, using samples and clinical data provided by the Collaborative Transplant Study. Graft survival of KIR-ligand-matched and -mismatched transplants was compared. We found no impact of KIR-ligand mismatching on 10-year graft survival in HLA-A, -B, -DR compatible kidney transplants. Further analysis did not reveal a significant effect of recipient activating/inhibitory KIR or KIR genotypes on graft survival. Our data do not support the concept that KIR-HLA matching might serve as a tool to improve long-term renal allograft survival., (© Copyright 2013 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background: Cytomegalovirus (CMV) remains an important pathogen in transplant patients, and valacyclovir (VACV) prophylaxis 8 g/day has been used in high-risk CMV-seromismatched [D+/R-] renal transplant patients to decrease CMV disease. Neurotoxic adverse effects have limited its use, and the aim of the present study was to retrospectively evaluate low-dose VACV prophylaxis, 3 g/day for 90 days after transplantation, in 102 D+/R- renal transplant patients., Methods: We compared patient and graft survival rates up to 5 years after transplantation with the data from the Collaborative Transplant Study Group (CTS) database. The incidence of CMV disease, rejection and neurotoxic adverse effects was analyzed up to 1 year after transplantation., Results: The patient and graft survival rates up to 5 years were comparable with those derived from the CTS. CMV disease was diagnosed in 25% of the patients and 2% developed tissue-invasive CMV disease. The rejection frequency was 22% and neurotoxic adverse effects were seen in 2% of the patients., Conclusions: Low-dose VACV prophylaxis (3 g/day) for 90 days post-transplantation results in high patient and graft survival rates and reduces the incidence of CMV disease. Neurotoxic adverse effects are minimal. We believe that low-dose VACV prophylaxis should be considered to form one of the arms in future prospective comparison studies for the prevention of CMV disease in the high-risk D+/R- population of renal transplant patients.

Background: Kidney graft survival has never been systematically compared between Europe and the United States., Methods: Applying period analysis to first deceased-donor (DD) and living-donor kidney grafts from the United Network for Organ Sharing/Organ Procurement and Transplantation Network for the United States and the Collaborative Transplant Study for Europe, we compared overall and age-specific 1-, 5-, and 10-year graft survival for Europeans and white, African, and Hispanic Americans for the 2005 to 2008 period. A Cox regression model was used to adjust for differences in patient characteristics., Results: For the 2005 to 2008 period, 1-year survival for DD grafts was equal (91%) between Europeans and white and Hispanic Americans, whereas it was slightly lower for African Americans (89%). In contrast, overall 5- and 10-year graft survival rates were considerably higher for Europe (77 and 56%, respectively) than for any of the three U.S. populations (whites, 71 and 46%, Hispanic, 73 and 48%, and African American, 62 and 34%). Differences were largest for recipient ages 0 to 17 and 18 to 29 and generally increased beyond 3 to 4 years after transplantation. Survival patterns for living-donor grafts were similar as those seen for DD grafts. Adjusted hazard ratios for graft failure in United Network for Organ Sharing white Americans ranged between 1.5 and 2.3 (all P<0.001) for 2 to 5 years after transplantation, indicating that lower graft survival is not explained by differences in baseline patient characteristics., Conclusions: Long-term kidney graft survival rates are markedly lower in the United States compared with Europe. Identifying actionable factors explaining long-term graft survival differences between Europe and the United States is a high priority for improving long-term graft survival.

Background: Whether mismatches between donor and recipient of a kidney transplant at the HLA allele level can elicit an immune response strong enough to impact graft survival is not known., Methods: We examined the influence of HLA-DRB1 allele level mismatch on graft survival based on high-resolution typing, utilizing blood samples and clinical data provided by the Collaborative Transplant Study. HLA-DRB1*04 was selected as a model for this investigation because it is the most common HLA-DRB1 allele group and consists of several alleles with relatively high frequencies, allowing for analysis of transplants matched at the antigen level but mismatched at the allele level. Nine hundred and ninety-six recipient/donor pairs were typed for HLA-DRB1 at high resolution., Results: No effect of HLA-DRB1*04 allele mismatch was observed in first transplants. However, in retransplants, HLA-DRB1*04 allele mismatch was associated with significantly decreased graft survival, albeit only in sensitized (PRA>5%) patients (hazard ratio 3.98, P=0.014)., Conclusion: Our finding reinforces the concept that HLA compatibility significantly influences the outcome of kidney transplants, in sensitized retransplant recipients even at the allele level.

Analysis of data from the international Collaborative Transplant Study has revealed striking relationships between human leukocyte antigen mismatching and graft survival, the incidence of death from cardiovascular disease or infection, the occurrence of non-Hodgkin lymphoma, and onset of post-transplant osteoporosis and bone fracture following kidney transplantation from a deceased donor.

The impact of variation within genes responsible for the disposition and metabolism of calcineurin inhibitors (CNIs) on clinical outcomes in kidney transplantation is not well understood. Furthermore, the potential influence of donor, rather than recipient, genotypes on clinical endpoints is unknown. Here, we investigated the associations between donor and recipient gene variants with outcome among 4471 white, CNI-treated kidney transplant recipients. We tested for 52 single-nucleotide polymorphisms (SNPs) across five genes: CYP3A4, CYP3A5, ABCB1 (MDR1; encoding P-glycoprotein), NR1I2 (encoding the pregnane X receptor), and PPIA (encoding cyclophilin). In a discovery cohort of 811 patients from Birmingham, United Kingdom, kidney donor CC genotype at C3435T (rs1045642) within ABCB1, a variant known to alter protein expression, was associated with an increased risk for long-term graft failure compared with non-CC genotype (hazard ratio [HR], 1.69; 95% confidence interval [CI], 1.20-2.40; P=0.003). No other donor or recipient SNPs were associated with graft survival or mortality. We validated this association in 675 donors from Belfast, United Kingdom (HR, 1.68; 95% CI, 1.21-2.32; P=0.002), and in 2985 donors from the Collaborative Transplant Study (HR, 1.84; 95% CI, 1.08-3.13; P=0.006). In conclusion, these data suggest that an ABCB1 variant known to alter protein expression represents an attractive candidate for future study and risk stratification in kidney transplantation.

HLA mismatches may correlate with risk of death with a functioning graft (DWFG) because of requirement for higher immunosuppression doses and more antirejection therapy. Deceased-donor kidney transplants (n = 177 584) performed 1990-2009 and reported to the Collaborative Transplant Study were analyzed. The incidence of DWFG was found to be 4.8% during year 1 posttransplant and 7.7% during years 2-5 (Kaplan-Meier estimates). Most frequent causes of DWFG were infection, cardiovascular disease and malignancy (32.2%, 30.9% and 3.6% in year 1; 16.4%, 29.6% and 15.9% in years 2-5). HLA-A + B + DR mismatches were significantly associated with DWFG during year 1 (p < 0.001), a correlation that diminished but persisted during years 2-5 (p < 0.001). HLA mismatch was associated with DWFG because of infection (p < 0.001 during year 1, p = 0.043 during years 2-5) or cardiovascular disease (p < 0.001 during year 1, p = 0.030 during years 2-5) but not malignancy. There was also a significant association between HLA mismatch and hospitalization for viral (p < 0.001) or bacterial (p = 0.002) infection. Multivariable analysis showed that mismatches for HLA class II were more strongly associated with both hospitalization and DWFG than mismatches for HLA class I., (© Copyright 2012 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background: Interindividual variation in inosine monophosphate dehydrogenase (IMPDH) enzyme activity and adverse effects caused by mycophenolate mofetil (MMF) inhibition may be genetically determined, and if so, transplant recipients should receive personalized dosing regimens of MMF, which would maximize efficacy and minimize toxicity. Some studies have demonstrated a relationship between the single nucleotide polymorphism and the risk of acute rejection with IMPDH I variants rs2278293 and rs2278294 and IMPDH II variant rs11706052, whereas others have failed to exhibit an effect. The aim of this work was to investigate the influence of these polymorphisms on acute rejection rates, graft survival and function, and MMF doses in a large cohort of patients., Methods: A random sample of 1040 recipients from the Collaborative Transplant Study DNA bank was genotyped for the variants IMPDH I rs2278293 and rs2278294 and IMPDH II rs11706052., Results: The presence of the T (rs2278293) and G alleles (rs2278294) in the IMPDH I variants and carriage of the G allele (rs11706052) in the IMPDH II variant did not increase the risk of rejection or affect graft function by 1 year after transplantation. There was no association with MMF dose tolerated at 1 year. Furthermore, these polymorphisms did not impact graft or patient survival at 5 years., Conclusion: This study represents the largest cohort of patients with the longest follow-up to date and does not support previous evidence for an association between these IMPDH variants and renal allograft rejection and graft survival.

Whether treatment with angiotensin-converting enzyme inhibitors (ACEi) and/or angiotensin receptor blockers (ARB) increases the risk of cancer is controversial. Collaborative transplant study data were analyzed according to whether kidney transplant recipients were treated with ACEi/ARB at year 1. Twenty-four thousand and ninety patients were studied of whom 9079 (38%) patients received ACEi/ARB. There were 872 nonskin malignancies during years 2-8 posttransplant, including 107 respiratory/intrathoracic tumors. The standardized incidence ratio (SIR) for all nonskin malignancies was similar between the ACEi/ARB (1.91) and no ACEi/ARB (1.81) groups (p = 0.42). For respiratory/intrathoracic tumors, however, SIR was significantly higher with ACEi/ARB (1.65 vs. 1.09 for no ACEi/ARB, p = 0.033). Multivariate Cox regression analysis showed that ACEi/ARB treatment was not associated with an increased risk of respiratory/intrathoracic tumors in nonsmokers. In patients with a history of smoking, however, the risk of respiratory/intrathoracic tumors was 2.77 (95% CI 1.19-6.43, p = 0.018) in patients without ACEi/ARB treatment as compared to 7.10 (95% CI 3.27-15.4, p < 0.001) in patients treated with ACEi/ARB. Our data indicate that in kidney transplant recipients, ACEi/ARB treatment is associated with a significant increase in the rate of respiratory/intrathoracic tumors in the subpopulation of patients with a history of smoking., (©2011 The Authors Journal compilation © 2011 The American Society of Transplantation and the American Society of Transplant Surgeons.)