A practical guide to chimerism analysis: Review of the literature and testing practices worldwide.

BACKGROUND AND PURPOSE: Currently there are no widely accepted guidelines for chimerism analysis testing in hematopoietic cell transplantation (HCT) patients. The objective of this review is to provide a practical guide to address key aspects of performing and utilizing chimerism testing results. In developing this guide, we conducted a survey of testing practices among laboratories that are accredited for performing engraftment monitoring/chimerism analysis by either the American Society for Histocompatibility & Immunogenetics (ASHI) and/or the European Federation of Immunogenetics (EFI). We interpreted the survey results in the light of pertinent literature as well as the experience in the laboratories of the authors. RECENT DEVELOPMENTS: In recent years there has been significant advances in high throughput molecular methods such as next generation sequencing (NGS) as well as growing access to these technologies in histocompatibility and immunogenetics laboratories. These methods have the potential to improve the performance of chimerism testing in terms of sensitivity, availability of informative genetic markers that distinguish donors from recipients as well as cost. SUMMARY: The results of the survey revealed a great deal of heterogeneity in chimerism testing practices among participating laboratories. The most consistent response indicated monitoring of engraftment within the first 30 days. These responses are reflective of published literature. Additional clinical indications included early detection of impending relapse as well as identification of cases of HLA-loss relapse.

Computational Eurotransplant kidney allocation simulations demonstrate the feasibility and benefit of T-cell epitope matching.

The EuroTransplant Kidney Allocation System (ETKAS) aims at allocating organs to patients on the waiting list fairly whilst optimizing HLA match grades. ETKAS currently considers the number of HLA-A, -B, -DR mismatches. Evidently, epitope matching is biologically and clinically more relevant. We here executed ETKAS-based computer simulations to evaluate the impact of epitope matching on allocation and compared the strategies. A virtual population of 400,000 individuals was generated using the National Marrow Donor Program (NMDP) haplotype frequency dataset of 2011. Using this population, a waiting list of 10,400 patients was constructed and maintained during simulation, matching the 2015 Eurotransplant Annual Report characteristics. Unacceptable antigens were assigned randomly relative to their frequency using HLAMatchmaker. Over 22,600 kidneys were allocated in 10 years in triplicate using Markov Chain Monte Carlo simulations on 32-CPU-core cloud-computing instances. T-cell epitopes were calculated using the www.pirche.com portal. Waiting list effects were evaluated against ETKAS for five epitope matching scenarios. Baseline simulations of ETKAS slightly overestimated reported average HLA match grades. The best balanced scenario maintained prioritisation of HLA A-B-DR fully matched donors while replacing the HLA match grade by PIRCHE-II score and exchanging the HLA mismatch probability (MMP) by epitope MMP. This setup showed no considerable impact on kidney exchange rates and waiting time. PIRCHE-II scores improved, whereas the average HLA match grade diminishes slightly, yet leading to an improved estimated graft survival. We conclude that epitope-based matching in deceased donor kidney allocation is feasible while maintaining equal balances on the waiting list.

Statistical methods versus machine learning techniques for donor-recipient matching in liver transplantation.

Donor-Recipient (D-R) matching is one of the main challenges to be fulfilled nowadays. Due to the increasing number of recipients and the small amount of donors in liver transplantation, the allocation method is crucial. In this paper, to establish a fair comparison, the United Network for Organ Sharing database was used with 4 different end-points (3 months, and 1, 2 and 5 years), with a total of 39, 189 D-R pairs and 28 donor and recipient variables. Modelling techniques were divided into two groups: 1) classical statistical methods, including Logistic Regression (LR) and Naïve Bayes (NB), and 2) standard machine learning techniques, including Multilayer Perceptron (MLP), Random Forest (RF), Gradient Boosting (GB) or Support Vector Machines (SVM), among others. The methods were compared with standard scores, MELD, SOFT and BAR. For the 5-years end-point, LR (AUC = 0.654) outperformed several machine learning techniques, such as MLP (AUC = 0.599), GB (AUC = 0.600), SVM (AUC = 0.624) or RF (AUC = 0.644), among others. Moreover, LR also outperformed standard scores. The same pattern was reproduced for the others 3 end-points. Complex machine learning methods were not able to improve the performance of liver allocation, probably due to the implicit limitations associated to the collection process of the database.

Comparison of Risk Scoring Systems in HLA-Matched Related Allogeneic Hematopoietic Stem Cell Transplantation: A Retrospective Cohort Study

Objective: Allogeneic hematopoietic stem cell transplantation (AHSCT) is a potentially curative treatment of choice for many hematological diseases. However, there are some transplantation-related risks. Predicting the risk-benefit ratio prior to AHSCT facilitates the choice of conditioning regimens and posttransplant follow-up. Hence, many risk models have been developed. The aim of the present study was to compare 6 different risk models that are clinically used. Materials and Methods: A total of 259 patients were enrolled in this study. The European Society for Blood and Marrow Transplantation (EBMT), Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI), Age-Adjusted Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI-Age), revised Pretransplant Assessment of Mortality (rPAM), Acute Leukemia-EBMT (AL-EBMT), and Disease Risk Index (DRI) risk models were applied retrospectively. Results: The AL-EBMT, HCT-CI, and HCT-CI-Age scoring systems were found to be predictive for 2-year overall survival (OS) and 2-year non-relapse mortality (NRM) (2-year OS: AL-EBMT, reference vs. score 8.5-10, HR: 1.3, p=0.035; AL-EBMT, reference vs. score >10, HR: 3.8, p=0.001; HCT-CI: reference vs. score 1-2, HR: 1.4, p=0.018; HCT-CI: reference vs. score ≥3, HR: 2.5, p<0.001; HCT-CI-Age: reference vs. score 1-2, HR: 1.3, p<0.001; HCT-CI-Age: reference vs. score ≥3, HR: 3.2, p<0.001) (2-year NRM: AL-EBMT: reference vs. score 8.5-10, HR: 1.61, p<0.001; AL-EBMT: reference vs. score >10, HR: 3.3, p<0.001; HCT-CI: reference vs. score 1-2, HR: 1.3, p=0.028; HCT-CI: reference vs. score ≥3, HR: 2.3, p=0.011; HCT-CI-Age: reference vs. score 1-2, HR: 1.3, p=0.01; HCT-CI-Age: reference vs. score ≥3, HR: 2.4, p=0.003). In terms of the Kaplan-Meier estimates of 2-year OS and 2-year NRM, the risk scoring system with the highest predictive power was found to be AL-EBMT (2-year AUC: 0.59 and 0.60, respectively). The other scores were not found to be predictive for 2-year OS and NRM. Conclusion: In the present study at our bone marrow and stem cell transplant center, it has been demonstrated that the HCT-CI, HCT-CI-Age, and AL-EBMT are good predictors of 2-year NRM and OS.

HLA antibodies are associated with deterioration of kidney allograft function irrespective of donor specificity.

BACKGROUND: Donor-specific antibodies are associated with high immunological risk and poor allograft outcome. Risk and clinical relevance of non-donor-specific HLA antibodies is less clear. METHODS: A retrospective single-center study was conducted in all patients receiving a first kidney transplant at the University hospital of Zürich between 01/2006 and 02/2015. Patients were stratified into 3 groups having either no HLA antibodies at all (NoAB), HLA antibodies with donor specificity (DSA) and HLA antibodies without donor specificity (NonDSA). Allograft outcome was assessed using the slope of the estimated glomerular filtration rate (eGFR slope) starting at 12 months after transplantation. RESULTS: During a median follow-up of 1808 days HLA antibodies were detected in 106 of 238 eligible patients (44%). Out of these, 73 patients (69%) had DSA and 33 patients (31%) had NonDSA only. Medium-term allograft function, as determined by eGFR slope over three years, improved in patients with NoAB (months 12-48: +0.7 ml/min/1.73 m2) but deteriorated significantly in patients with both DSA (months 12-48: -1.5 ml/min per1.73 m2/year, p = 0.015) and NonDSA (months 12-48: -1.8 ml/min per1.73 m2/year, p = 0.03) as compared to the group with NoAB. CONCLUSION: Both, donor-specific and non-donor-specific HLA antibodies are associated with medium-term kidney allograft dysfunction as compared to patients with no HLA antibodies.

Hiperinmunización: una realidad y un reto. A propósito de un caso / No disponible

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Peripheral Donor-specific Antibodies Are Associated With Histology and Cellular Subtypes in Protocol Liver Biopsies of Pediatric Recipients.

BACKGROUND: The cellular infiltrate in protocol liver biopsies (PB) following pediatric liver transplantation remains mostly uncharacterized, yet there is increasing concern about the role of inflammation and fibrosis in long-term liver allografts. We aimed to define cell types in PB and to analyze their relationship with donor-specific antibodies (DSA) and histological phenotype. METHODS: PB were performed at least 1 year after transplantation. We identified 4 phenotypes: normal, fibrosis, inflammation, inflammation with fibrosis. Cell types were counted after immunostaining for CD3, CD4, CD8, CD68, CD20, MUM1, and FoxP3. RESULTS: Forty-four patients underwent 1 PB between 2000 and 2015. Eleven percent (5/44) of PB displayed normal histology, 13.6% (6/44) fibrosis, 34.1% (15/44) inflammation, and 40.9% (18/44) inflammation and fibrosis. The main cell types in the portal tracts and lobules were CD3+ and CD68+ cells. Frequency of de novo DSA was 63% (27/44). The presence of CD8+ cells in the lobules was associated with fibrosis. Inflammation and fibrosis in PB were associated with the presence of circulating de novo DSA, number of de novo DSA, and C1q binding activity when compared to other phenotypes. CONCLUSIONS: T cells (CD3+) and macrophages (CD68+) were the most prevalent cell-types in PB. In the presence of inflammation, portal tracts were enriched in CD3+, CD20+ but displayed fewer CD68+. This coincided with the presence and number of de novo DSA. How these cellular and humoral actors interact is unclear, but peripheral DSA may be a marker of immune cellular activity in the seemingly quiescent allograft.

Ensuring HLA-matched platelet support requires an ethnic diverse donor population.

BACKGROUND: Patients refractory for platelet transfusions benefit from human leukocyte antigen (HLA)-matched platelet transfusions. Differences in ethnic background of patients and donors could hamper the availability of sufficient numbers of HLA-matched donors for all patients. We evaluated our HLA-matched donor program and explored the role of ethnic background of patients related to the number of available donors. METHODS: We performed a cohort study among consecutive patients who received HLA-matched platelet concentrates in the Netherlands between 1994 and 2017. The number of available matched donors was determined per patient. Haplotypes were constructed from genotypes with computer software (PyPop). Based on haplotypes, HaploStats, an algorithm from the National Marrow Donor Program, was used to assess the most likely ethnic background for patients with 5 or fewer and 30 or more donors. RESULTS: HLA typing was available for 19,478 donors in September 2017. A total of 1206 patients received 12,350 HLA-matched transfusions. A median of 83 (interquartile range, 18-266) donors were available per patient. For 95 (10.3%) patients, 5 or fewer donors were available. These patients were more likely to have an African American background, whereas patients with 30 or more donors were more often from Caucasian origin, compared with Caucasian origin for patients with 30 donors. CONCLUSION: Adequate transfusion support could be guaranteed for most but not all refractory patients. More non-Caucasian donors are required to ensure the availability of HLA-matched donors for all patients in the Netherlands.

Ten Years of Kidney Paired Donation at Mayo Clinic: The Benefits of Incorporating ABO/HLA Compatible Pairs.

BACKGROUND: We examined the 10-year experience of Mayo Clinic's kidney paired donation (KPD).We aimed to determine the benefits for the recipients of enrolled ABO/HLA compatible pairs and determine the factors associated with prolonged KPD waiting time. METHODS: We performed a retrospective study of 332 kidney transplants facilitated by the Mayo 3-site KPD program from September 2007 to June 2018. RESULTS: The median (interquartile range) time from KPD entry to transplantation was 89 days (42-187 days). The factors independently associated with receiving a transplant >3 months after KPD entry included recipient blood type O and calculated panel reactive antibodies ≥98%. Fifty-four ABO/HLA compatible pairs participated in KPD for the following reasons: cytomegalovirus mismatch (18.5% [10/54]), Epstein-Barr virus (EBV) mismatch (EBV) (9.3% [5/54]), age/size mismatch (51.9% [28/54]), or altruistic reasons (20.3% [11/54]). Cytomegalovirus and EBV mismatch were avoided in 90% (9/10) and 100% (5/5) of cases. Recipients who entered KPD for age/size mismatch and altruistic reasons received kidneys from donors with lower Living Kidney Donor Profile Index scores than their actual donor (median [interquartile range] 31.5 [12.3-47]; P < 0.001 and 26 (-1 to 46); P = 0.01 points lower, respectively). Median time to transplant from KPD entry for compatible pair recipients was 70 days (41-163 days), and 44.4% (24/54) of these transplants were preemptive. All chains/swaps incorporating compatible pairs included ABO/HLA incompatible pairs. CONCLUSIONS: KPD should be considered for all living donor/recipient pairs because the recipients of these pairs can derive personal benefit from KPD while increasing the donor pool for difficult to match pairs.

Eplet mismatch analysis and allograft outcome across racially diverse groups in a pediatric transplant cohort: a single-center analysis.

HLA eplet mismatch load has been suggested as an improvement to HLA antigen mismatch determination for organ selection. Given that eplet mismatches are determined based on amino acid sequence difference among HLA alleles, and that the frequency of HLA alleles varies between racial groups, we investigated the correlation between eplet mismatch load and allograft outcomes in 110 pediatric kidney transplant recipients who received their first organ from a donor of the same race (SRT) versus a donor of a different race (DRT). Adjusted modified Poisson regression was used to assess the interaction between eplet mismatch load and race mismatch and its effect on outcome. Caucasians and living donor recipients had lower eplet mismatched loads against their donors compared with non-Caucasian and deceased donor recipients. Overall, for the entire population, the risk of de novo HLA-DSA development was significantly increased with higher eplet loads (p < 0.001). Compared with the SRT group, the DRT group had higher eplet loads when compared with their donor, for HLA class I but not HLA class II molecules; however, there was no significant difference in the incidence of de novo HLA-DSA between the 2 groups. The risk of rejection increased significantly for DRT compared with SRT, only when class I eplet load was ≥ 70 (p = 0.04). Together this data show that eplet mismatch load analysis is an effective tool for alloimmune risk assessment. If considered for donor selection, acceptable eplet mismatch loads determined from studies in homogenous populations may restrict transplantation across racially diverse donor and patient groups with no evidence of poor outcome. Therefore, an acceptable eplet mismatch load threshold must consider the heterogeneity of the transplant population.

Posttransplant Outcomes for cPRA-100% Recipients Under the New Kidney Allocation System.

BACKGROUND: There is concern in the transplant community that outcomes for the most highly sensitized recipients might be poor under Kidney Allocation System (KAS) high prioritization. METHODS: To study this, we compared posttransplant outcomes of 525 pre-KAS (December 4, 2009, to December 3, 2014) calculated panel-reactive antibodies (cPRA)-100% recipients to 3026 post-KAS (December 4, 2014, to December 3, 2017) cPRA-100% recipients using SRTR data. We compared mortality and death-censored graft survival using Cox regression, acute rejection, and delayed graft function (DGF) using logistic regression, and length of stay (LOS) using negative binomial regression. RESULTS: Compared with pre-KAS recipients, post-KAS recipients were allocated kidneys with lower Kidney Donor Profile Index (median 30% versus 35%, P < 0.001) but longer cold ischemic time (CIT) (median 21.0 h versus 18.6 h, P < 0.001). Compared with pre-KAS cPRA-100% recipients, those post-KAS had higher 3-year patient survival (93.6% versus 91.4%, P = 0.04) and 3-year death-censored graft survival (93.7% versus 90.6%, P = 0.005). The incidence of DGF (29.3% versus 29.2%, P = 0.9), acute rejection (11.2% versus 11.7%, P = 0.8), and median LOS (5 d versus 5d, P = 0.2) were similar between pre-KAS and post-KAS recipients. After accounting for secular trends and adjusting for recipient characteristics, post-KAS recipients had no difference in mortality (adjusted hazard ratio [aHR]: 0.861.623.06, P = 0.1), death-censored graft failure (aHR: 0.521.001.91, P > 0.9), DGF (adjusted odds ratio [aOR]: 0.580.861.27, P = 0.4), acute rejection (aOR: 0.610.941.43, P = 0.8), and LOS (adjusted LOS ratio: 0.981.161.36, P = 0.08). CONCLUSIONS: We did not find any statistically significant worsening of outcomes for cPRA-100% recipients under KAS, although longer-term monitoring of posttransplant mortality is warranted.

A Virtual Crossmatch-based Strategy Facilitates Sharing of Deceased Donor Kidneys for Highly Sensitized Recipients.

BACKGROUND: It is estimated that 19.2% of kidneys exported for candidates with >98% calculated panel reactive antibodies are transplanted into unintended recipients, most commonly due to positive physical crossmatch (PXM). We describe the application of a virtual crossmatch (VXM) that has resulted in a very low rate of transplantation into unintended recipients. METHODS: We performed a retrospective review of kidneys imported to our center to assess the reasons driving late reallocation based on the type of pretransplant crossmatch used for the intended recipient. RESULTS: From December 2014 to October 2017, 254 kidneys were imported based on our assessment of a VXM. Of these, 215 (84.6%) were transplanted without a pretransplant PXM. The remaining 39 (15.4%) recipients required a PXM on admission using a new sample because they did not have an HLA antibody test within the preceding 3 months or because they had a recent blood transfusion. A total of 93% of the imported kidneys were transplanted into intended recipients. There were 18 late reallocations: 9 (3.5%) due to identification of a new recipient medical problem upon admission, 5 (2%) due to suboptimal organ quality on arrival, and only 4 (1.6%) due to a positive PXM or HLA antibody concern. A total of 42% of the recipients of imported kidneys had a 100% calculated panel reactive antibodies. There were no hyperacute rejections and very infrequent acute rejection in the first year suggesting no evidence for immunologic memory response. CONCLUSIONS: Seamless sharing is within reach, even when kidneys are shipped long distances for highly sensitized recipients. Late reallocations can be almost entirely avoided with a strategy that relies heavily on VXM.

Number of Antibody-verified Eplet in HLA-C Locus as an Independent Factor of T-cell-Mediated Rejection After Liver Transplantation.

BACKGROUND: HLA mismatching is a risk factor for graft rejection in solid organ transplantation. Its definition is being rethought with the introduction of the eplets in organ allocation. The eplets are highly polymorphic regions of the HLA molecule that help to explain cross-reactivity of HLA antigens. The effect of eplet mismatch is well documented in renal and lung transplantation but there is no clear evidence in liver transplantation. METHODS: Forty-three consecutive liver-graft donor/recipient pairs performed at our center from 2016 to 2018 were HLA typed. The quantification of antibody-verified eplets (VerEp) mismatch was performed with HLA-matchmaker 2.1 version. RESULTS: A total of 9 patients suffered an episode of T-cell-mediated rejection (TCMR). No significant differences were observed in the number of A, B, DRB, DQA, and DQB VerEp. However, the mean of mismatches VerEp in locus C (VerEpC) was significantly increased in patients with acute rejection: 3.89 (1.36) versus 2.32 (1.82), P = 0.021. A total of 22 patients with high load of VerEpC (>2) had an increased risk of TCMR (P = 0.008). The time of TCMR-free after liver transplant was statistically reduced in high-load VerEpC group (log-rank test P = 0.019). Multivariate analysis demonstrated that high load of VerEpC was independently associated with TCMR (P = 0.038). CONCLUSIONS: Patients with no or 1 eplet mismatch at the C locus are less likely to suffer TCMR after liver transplantation.

Antibodies Against ARHGDIB and ARHGDIB Gene Expression Associate With Kidney Allograft Outcome.

BACKGROUND: The impact of donor-specific anti-HLA antibodies (DSA) on antibody-mediated rejection (AMR) and kidney allograft failure is well established. However, the relevance of non-HLA antibodies remains unclear. METHODS: We investigated 13 pretransplant non-HLA antibodies and their association with histology of AMR (AMRh) and kidney allograft failure. We included single kidney recipients (n = 203) with AMRh, according to the Banff 2017 classification and matched AMRh-free controls (n = 219). Non-HLA antibodies were assessed using multiplex Luminex assay. RESULTS: Of the selected non-HLA antibodies (against agrin, adipocyte plasma membrane-associated protein, Rho GDP-dissociation inhibitor 2 [ARHGDIB], Rho guanine nucleotide exchange factor 6, angiotensin-II type 1 receptor, endothelin type A receptor, lamin B1, BPI fold-containing family B member 1, peroxisomal trans-2-enoyl-coenzyme A reductase, phospholipase A2 receptor, protein kinase C zeta type, tubulin beta-4B class IVb, vimentin), only antibodies against ARHGDIB (adjusted median fluorescence intensity [aMFI] ≥ 1000), a minor histocompatibility antigen, associated with graft failure, in univariate and multivariate models (hazard ratio = 2.7; 95% confidence interval [CI],1.3-5.4; P = 0.007). There was a 19.5-fold (95% CI, 6.0-63.9; P < 0.0001) increased risk of graft failure in patients positive for both DSA and anti-ARHGDIB antibodies (aMFI ≥ 1000) versus patients negative for both DSA and anti-ARHGDIB antibodies, compared with a 4.4-fold (95% CI, 2.4-8.2; P < 0.0001) increased risk in patients with only DSA, and a 4.1-fold (95% CI, 1.4-11.7; P = 0.009) increased risk in patients with only anti-ARHGDIB antibodies above 2000 aMFI. AMRh associated with increased intrarenal expression of the ARHGDIB gene. In the absence of AMRh and DSA, anti-ARHGDIB antibodies were not clearly associated with graft failure. CONCLUSIONS: The presence of pretransplant anti-ARHGDIB antibodies has an additive effect in patients with DSA on the risk of graft failure via AMRh. Other investigated non-HLA antibodies, including antibodies against angiotensin-II type 1 receptor, did not contribute to risk stratification and could not explain the histology of AMR in the absence of DSA.

Immunosuppression and Graft Rejection in Living-related HLA-identical Renal Transplantation: The RADOVFULL Study.

BACKGROUND: We aimed to describe the immunosuppressive regimens and graft rejection rates in living-related HLA-identical (LR HLAid) renal transplantation. METHODS: We performed a retrospective multicenter analysis of the French national database for LR HLAid renal transplantations performed between 2002 and 2012. Univariate and multivariate analysis were performed to determine risk factors for graft rejection in LR HLAid recipients. RESULTS: A total of 27 218 renal transplantations were performed, of whom 163 had a LR HLAid donor. About immunosuppressive treatment, <60% of the cohort had induction therapy with polyclonal or monoclonal antibodies, 28% did not receive calcineurin inhibitors, and 36% did not receive steroids in maintenance. Biopsy-proven acute rejection was diagnosed in 21 patients (12.9%). Rejection occurred on an average of 24 months after transplantation, in 28.5% of the cases after minimization of immunosuppression. Factors associated with rejection were age of recipient (OR, 0.91 [0.84-0.96]; P = 0.003), the body mass index of donors (odds ratio [OR], 1.22 [1.04-1.46]; P = 0.01), and minimization of immunosuppression (OR, 26.2 [5.48-166.6]; P < 0.001). Overall and graft survival rates were not statistically different according to rejection at 1, 5, and 10 years posttransplantation. CONCLUSIONS: Minimization of immunosuppression should be done with caution in LR HLAid renal transplantations.

Single haplotype admixture models using large scale HLA genotype frequencies to reproduce human admixture.

The human leukocyte antigen (HLA) is the most polymorphic region in humans. Anthropologists use HLA to trace populations' migration and evolution. However, recent admixture between populations can mask the ancestral haplotype frequency distribution. We present a statistical method based on high-resolution HLA haplotype frequencies to resolve population admixture using a non-negative matrix factorization formalism and validated using haplotype frequencies from 56 world populations. The result is a minimal set of source components (SCs) decoding roughly 90% of the total variance in the studied admixtures. These SCs agree with the geographical distribution, phylogenies, and recent admixture events of the studied groups. With the growing population of multi-ethnic individuals, or individuals that do not report race/ethnic information, the HLA matching process for stem-cell and solid organ transplants is becoming more challenging. The presented algorithm provides a framework that facilitates the breakdown of highly admixed populations into SCs, which can be used to better match the rapidly growing population of multi-ethnic individuals worldwide.

Contribution of non-HLA incompatibility between donor and recipient to kidney allograft survival: genome-wide analysis in a prospective cohort.

BACKGROUND: The introduction of HLA matching of donors and recipients was a breakthrough in kidney transplantation. However, half of all transplanted kidneys still fail within 15 years after transplantation. Epidemiological data suggest a fundamental role of non-HLA alloimmunity. METHODS: We genotyped 477 pairs of deceased donors and first kidney transplant recipients with stable graft function at three months that were transplanted between Dec 1, 2005, and April 30, 2015. Genome-wide genetic mismatches in non-synonymous single nucleotide polymorphisms (nsSNPs) were calculated to identify incompatibilities in transmembrane and secreted proteins. We estimated the association between nsSNP mismatch and graft loss in a Cox proportional hazard model, adjusting for HLA mismatch and clinical covariates. Customised peptide arrays were generated to screen for antibodies against genotype-derived mismatched epitopes in 25 patients with biopsy-confirmed chronic antibody-mediated rejection. FINDINGS: 59 268 nsSNPs affecting a transmembrane or secreted protein were analysed. The median number of nsSNP mismatches in immune-accessible transmembrane and secreted proteins between donors and recipients was 1892 (IQR 1850-1936). The degree of nsSNP mismatch was independently associated with graft loss in a multivariable model adjusted for HLA eplet mismatch (HLA-A, HLA-B, HLA-C, HLA-DP, HLA-DQ, and HLA-DR). Each increase by a unit of one IQR had an HR of 1·68 (95% CI 1·17-2·41, p=0·005). 5-year death censored graft survival was 98% in the quartile with the lowest mismatch, 91% in the second quartile, 89% in the third quartile, and 82% in the highest quartile (p=0·003, log-rank test). Customised peptide arrays verified a donor-specific alloimmune response to genetically predicted mismatched epitopes. INTERPRETATION: Genetic mismatch of non-HLA haplotypes coding for transmembrane or secreted proteins is associated with an increased risk of functional graft loss independently of HLA incompatibility. As in HLA alloimmunity, donor-specific alloantibodies can be identified against genotype derived non-HLA epitopes. FUNDING: Austrian Science Fund, WWTF (Vienna Science and Technology Fund), and Ministry of Health of the Czech Republic.

Frequência dos alelos do sistema antígeno leucocitário humano em doadores e pacientes pré-transplante de medula óssea / Human leukocyte antigen alleles frequency in donors and pre-transplant patients from bone marrow

Introdução: O estudo da frequência dos alelos detectados nos doadores e pacientes previamente selecionados para o transplante de medula óssea permite estimar as reais chances de um paciente em lista de espera encontrar um doador com antígeno leucocitário humano (Human leucocite antigen; HLA) idêntico não relacionado, além de facilitar e direcionar o planejamento do crescimento do Registro Nacional deDoadores de Medula Óssea. Objetivo: Descrever e analisar afrequência dos alelos do sistema HLA de classe I (HLA-A, -B e -C) e classe II (HLA-DRB1 e -DQB1) de doadores e pacientespré-transplante de medula óssea, do Hospital de Câncer deBarretos. Material e Métodos: Um total de 98 amostras dedoadores e 106 amostras de pacientes foi selecionado comtipificações em alta resolução, no período de outubro de 2014a outubro de 2015. As amostras foram tipificadas para os lociHLA-A, -B, -C, -DR e -DQ. Resultados: O predomínio daraça branca reflete a composição étnica do Brasil. As doençasde base mais comuns que levaram o paciente ao transplanteforam a leucemia aguda linfóide (34%) e mieloide (29,2%).Os grupos alélicos mais frequentes nos registros foramA*02, A*24, A*03, A*01, B*35, B*44, C*07, DQB1*03,DQB1*05, DQB1*06, DRB1*01 e DRB1*13. Conclusão: Osresultados encontrados reforçam a importância de conhecero perfil demográfico e imunogenético das regiões do Brasil,contribuindo desta forma na redução do tempo de espera porum doador histocompatível

Introduction: The study of allele frequencies detected in donors and patients previously selected for bone marrow transplantation allows us to estimate the real chances of a patient in the waiting list to find an Human leucocite antigen (HLA) identical unrelated donor. This also facilitates and drives the growth planning of the Brazilian Registry of planning Bone Marrow Transplantation (REDOME). Objective: Describe and analyze the frequency of HLA class I alleles (HLA-A*, -B* and ­C*) and class II alleles, genotypes, and haplotypes(HLA-DRB1* and -DQB1*) from donors and bone marrowpre-transplant patients. Material and Methods: A total of 98donor samples and 106 patient samples were selected withhigh resolution typing, from October 2014 to October 2015.Samples were typed for HLA-A, -B, -C, -DR and -DQ loci.Results: The predominance of the white race reflects theethnic composition of Brazil. The most common underlyingdiseases that led to transplantation patients were acutelymphoid leukemia (34%) and myeloid (29.2%). The mostfrequent allelic groups were A*02, A*24, A*03, A*01, B*35,B*44, C*07, DQB1*03, DQB1*05, DQB1*06, DRB1*01 andDRB1*13. Conclusion: The results reinforce the importanceof understanding the demographic and immunogenic profilefrom Brazilian Regions. This can contribute to the reduction ofwaiting time for a histocompatible donor.

HLA-Mismatched Microtransplant in Older Patients Newly Diagnosed With Acute Myeloid Leukemia: Results From the Microtransplantation Interest Group.

IMPORTANCE: The outcome of older patients with acute myeloid leukemia (AML) remains unsatisfactory. Recent studies have shown that HLA-mismatched microtransplant could improve outcomes in such patients. OBJECTIVE: To evaluate outcomes in different age groups among older patients with newly diagnosed AML who receive HLA-mismatched microtransplant. DESIGN, SETTING, AND PARTICIPANTS: This multicenter clinical study included 185 patients with de novo AML at 12 centers in China, the United States, and Spain in the Microtransplantation Interest Group. Patients were divided into the following 4 age groups: 60 to 64 years, 65 to 69 years, 70 to 74 years, and 75 to 85 years. The study period was May 1, 2006, to July 31, 2015. EXPOSURES: Induction chemotherapy and postremission therapy with cytarabine hydrochloride with or without anthracycline, followed by highly HLA-mismatched related or fully mismatched unrelated donor cell infusion. No graft-vs-host disease prophylaxis was used. MAIN OUTCOMES AND MEASURES: The primary end point of the study was to evaluate the complete remission rates, leukemia-free survival, and overall survival in different age groups. Additional end points of the study included hematopoietic recovery, graft-vs-host disease, relapse rate, nonrelapse mortality, and other treatment-related toxicities. RESULTS: Among 185 patients, the median age was 67 years (range, 60-85 years), and 75 (40.5%) were female. The denominators in adjusted percentages in overall survival, leukemia-free survival, relapse, and nonrelapse mortality are not the sample proportions of observations. The overall complete remission rate was not significantly different among the 4 age groups (75.4% [52 of 69], 70.2% [33 of 47], 79.1% [34 of 43], and 73.1% [19 of 26). The 1-year overall survival rates were 87.7%, 85.8%, and 77.8% in the first 3 age groups, which were much higher than the rate in the fourth age group (51.7%) (P = .004, P = .008, and P = .04, respectively). The 2-year overall survival rates were 63.7% and 66.8% in the first 2 age groups, which were higher than the rates in the last 2 age groups (34.2% and 14.8%) (P = .02, P = .03, P < .001, and P < .001, respectively). The 1-year cumulative incidences of nonrelapse mortality were 10.2%, 0%, 3.4%, and 26.0% in the 4 age groups and 8.1% in all patients. The median times to neutrophil and platelet recovery were 12 days and 14 days after induction chemotherapy, respectively. Five patients had full or mixed donor engraftment, and 30.8% (8 of 26) of patients demonstrated donor microchimerism. Two patients (1.1%) developed severe acute graft-vs-host disease. CONCLUSIONS AND RELEVANCE: Microtransplant achieved a high complete remission rate in AML patients aged 60 to 85 years and higher 1-year overall survival in those aged 60 to 74 years.