The frequencies of HLA alleles and haplotypes and their distribution among donors and renal patients in the UNOS registry

Systematic review of associations between HLA and renal function

Introduction

Kidney dysfunction is a highly significant disease, both in the United Kingdom and globally. Many previous studies have reported associations between human leukocyte antigens (HLA) and renal function; this systematic review attempts to identify, summarize and appraise all published studies of these associations.

Methods

A literature search was performed using Medline, Embase and Cochrane Central Register of Controlled Trials to identify papers whose keywords included each of the following concepts: HLA, renal failure and genetic association. A total of 245 papers were identified and assessed for eligibility; 35 of these were included in the final study.

Results

A total of 95 HLA types and 14 three‐locus haplotypes were reported to be associated with either increased or decreased renal function. A number of these findings were replicated by independent studies that reported 16 types were protective against renal dysfunction and 15 types were associated with reduced renal function. A total of 20 HLA types were associated with both increased risk of renal disease and decreased risk by independent studies.

Discussion

There is very little consensus on which HLA types have a protective or deleterious effect on renal function. Ethnicity may play a role, with HLA types possibly having different effects among different populations, and it is possible that the different primary diseases that lead to ESRD may have different HLA associations. Some of the studies may contain type I and type II errors caused by insufficient sample sizes, cohort selection and statistical methods. Although we have compiled a comprehensive list of published associations between renal function and HLA, in many cases, it is unclear which associations are reliable. Further studies are required to confirm or refute these findings.

Invasion Rate Versus Diversity in Population Dynamics with Catastrophes

A key question in the current diversity crisis is how diversity has been maintained throughout evolution and how to preserve it. Modern coexistence theories suggest that a high invasion rate of rare new types is directly related to diversity. We show that adding almost any mechanism of catastrophes to a stochastic birth, death, and mutation process with limited carrying capacity induces a novel phase transition characterized by a positive invasion rate but a low diversity. In this phase, new types emerge and grow rapidly, but the resulting growth of very large types decreases diversity. This model also resolves two major drawbacks of neutral evolution models: their failure to explain balancing selection without resorting to fitness differences and the unrealistic time required for the creation of the observed large types. We test this model on a classical case of genetic polymorphism: the HLA locus.

[Determination of HLA-A, -B and -DRB1 polymorphism in brain dead organ donors representative of the Colombian general population, 2007-2014]

INTRODUCTION

Genes encoding for human leukocyte antigens (HLA) are highly polymorphic and of great importance in organ transplantation procedures, as determining allelic frequencies in defined populations is taken into account among the scientific criteria for organ allocation.

OBJECTIVE

The objective of this study was to establish the antigen HLA-A, -B, and -DRB1 haplotype frequencies in organ donors representative of the Colombian population after brain death.

MATERIALS AND METHODS

We conducted a descriptive retrospective study involving 2,506 cadaveric organ donors including an allelic and haplotype analysis of HLA-A, -B and -DRB1; we also determined the Hardy-Weinberg equilibrium.

RESULTS

We identified 21, 43 and 15 allelic loci for groups A*, B* and DRB1*, respectively. We detected 1,268 HLA-A, -B and -DR, 409 HLA-A-B, 383 HLA-DR-B, and 218 HLA-A-DR haplotypes. The three loci were found to be in Hardy-Weinberg equilibrium between the number of heterozygotes observed and the expected number, with p values of ;0.05.

CONCLUSIONS

This study provides information on the allelic distribution of HLA class I and II in organ donors from the six regions in which Colombia is structurally divided to provide transplant services.

Lymphocyte-depleting induction therapy lowers the risk of acute rejection in African American pediatric kidney transplant recipients

The use of lymphocyte-depleting induction immunosuppression has been associated with a reduction in risk of AR after KT among adult recipients, particularly among high-risk subgroups such as AAs. However, data on induction regimen and AR risk are lacking among pediatric KT recipients. We examined outcomes among 7884 first-time pediatric KT recipients using SRTR data (2000-2014). Characteristics were compared across race using Wilcoxon rank-sum tests for continuous and chi-square tests for categorical variables. Risk of AR was estimated using modified Poisson regression, stratified by recipient race, adjusting for recipient age, gender, BMI, primary diagnosis, number of HLA mismatches, maintenance immunosuppression, and donor type. Risk of AR within 1 year was lower in AA recipients receiving lymphocyte-depleting induction (ATG or alemtuzumab; RR, 0.66; 95% CI, 0.52-0.83 P < .001) compared to AA recipients receiving anti-IL-2 receptor antibody induction. This difference was not seen in non-AA recipients receiving lymphocyte-depleting induction (RR, 0.93; 95% CI, 0.81-1.06, P = .26) compared to IL-2 induction. These findings support a role for lymphocyte-depleting induction agents in AA pediatric patients undergoing KT and continued use of IL-2 inhibitor induction in non-AA pediatric KT recipients.

Influence of Donors' and Recipients' HLA Typing on Renal Function Immediately After Kidney Transplantation

BACKGROUND

The human leukocyte antigen (HLA) system is widely used as a strategy in the search for the etiology of renal function impairment.

OBJECTIVES

This study was carried out to detect the most common HLA alleles' distribution in kidney transplant in both donors and recipients, and clarify the association between HLA alleles and renal dysfunction immediately after transplantation.

PATIENTS AND METHODS

HLA-class I and II alleles typing by PCR-SSOP was performed on a total of 874 recipients aged 40.7 ± 13.8 (male/female: 562/279) and 874 donor aged 27.5 ± 5.3 (male/female: 683/110), between 2006 and 2009 in Baqiyatallah, hospital, Tehran, Iran. In this retrospective, cross sectional study, data were obtained from personal files. Donors aged 40.9 ± 13.6 years and male/female 390/195, while recipients had a mean age 27.5 ± 5.3 and male/female 523/83. Renal dysfunction defined as acute rejection, acute tubular necrosis and Delay graft function.

RESULTS

In this study common alleles at each of the loci for the human leukocyte antigen (HLA) class I (A, B, and C) and class II (DR and DQ) were A2 (n = 186, 33.8%), Bw6 (n = 196, 47.5%), Cw4 (n = 164, 39.7%), DR52 (n = 161, 29.6%), DQ3 (n = 101, 40.1%) for donors; while A2 (n = 200, 34%), BW6 (n = 235, 38.8%), Cw6 (n = 23, 15.2%), DR511 (n = 174, 30.4%), DQ1 (n = 99, 46.3%) for recipients. We detected a total of 139 case of renal dysfunction among RTRs. By the way only cold ischemic time (P = 0.03) and severe anemia (P = 0.000) were significantly associated with renal dysfunction early post kidney transplantation.

CONCLUSIONS

We can predict high risk groups before kidney transplantation and try to establish a screening program for the detection of genetic susceptibility to renal function impairment. HLA typing of the donors and recipients might influence the development of new treatment strategy.

Desensitization for solid organ and hematopoietic stem cell transplantation

Desensitization protocols are being used worldwide to enable kidney transplantation across immunologic barriers, i.e. antibody to donor HLA or ABO antigens, which were once thought to be absolute contraindications to transplantation. Desensitization protocols are also being applied to permit transplantation of HLA mismatched hematopoietic stem cells to patients with antibody to donor HLA, to enhance the opportunity for transplantation of non-renal organs, and to treat antibody-mediated rejection. Although desensitization for organ transplantation carries an increased risk of antibody-mediated rejection, ultimately these transplants extend and enhance the quality of life for solid organ recipients, and desensitization that permits transplantation of hematopoietic stem cells is life saving for patients with limited donor options. Complex patient factors and variability in treatment protocols have made it difficult to identify, precisely, the mechanisms underlying the downregulation of donor-specific antibodies. The mechanisms underlying desensitization may differ among the various protocols in use, although there are likely to be some common features. However, it is likely that desensitization achieves a sort of immune detente by first reducing the immunologic barrier and then by creating an environment in which an autoregulatory process restricts the immune response to the allograft.

The risk of acute rejection and the influence of induction agents in lower-risk African American kidney transplant recipients receiving modern immunosuppression

BACKGROUND

While kidney transplant recipients of African American (AA) descent are frequently considered at increased risk of acute rejection, the value of induction therapy is not defined in settings of lower immunologic risk and modern immunosuppression.

METHODS

Using the Scientific Registry of Transplant Recipients database, we identified 23,244 primary kidney transplant recipients with panel-reactive antibody (PRA) = 0% treated with TAC/MPA and prednisone from 2000 to 2008. We compared acute rejection, graft survival (GS), and patient survival rates among AA and non-AA and further stratified by induction therapy (none, IL2ra, or rATG).

RESULTS

One-yr acute rejection was higher in AA than in non-AA overall (14.5% vs. 9.9%, hazard ratio [HR] for acute rejection [AR] 1.43, p < 0.0001) and was higher regardless of induction agent use. Induction therapy was associated with a reduction in AR, but no benefit in GS in AA or non-AA. In AA, rATG (adjusted relative risk [RR] 0.81, CI 0.70-0.94) and IL2ra (adjusted RR 0.80, CI 0.68-0.93) were similarly effective in reducing AR rates, but did not reach comparable outcomes as in non-AA.

CONCLUSION

African Americans who are at otherwise lower immunologic risk have a higher risk of rejection despite modern immunosuppression. Depleting or non-depleting induction therapy similarly reduces but does not entirely mitigate this increased risk, with no impact on three-yr GS.

HLA-A amino acid polymorphism and delayed kidney allograft function

Delayed allograft function (DGF) is a common adverse event in postrenal transplantation. The etiology of DGF is thought to include both nonimmunologic (donor age, cold ischemia time, and recipient race) and immunologic factors. We examined the association of DGF with amino acid mismatches at 66 variable sites of the HLA-A molecule in a prospective cohort study of 697 renal transplant recipients of deceased donors. Using a multivariate logistic regression model adjusted for nonimmunologic risk factors, we show that combinations of a few amino acid mismatches at crucial sites of HLA-A molecules were associated with DGF. In Caucasian recipients, a mismatch at position 62, 95, or 163, all known to be functionally important within the antigen recognition site, was associated with an increased risk for DGF. Furthermore, a decreased risk for DGF was associated with a mismatch at HLA-A family-specific sites (149, 184, 193, or 246), indicating that evolutionary features of HLA-A polymorphism separating HLA-A families and lineages among donor-recipient pairs may correlate with the magnitude of alloreactivity influencing the development of DGF. These findings suggest that amino acid polymorphisms at functionally important positions at the antigen recognition site of the HLA-A molecule have a significant influence on DGF.

Improved Definition of Human Leukocyte Antigen Frequencies Among Minorities and Applicability to Estimates of Transplant Compatibility

BACKGROUND

HLA population data can be applied to estimates of waiting time and probabilities of donor compatibility. Registry data were used for derivation of HLA antigen and haplotype frequencies in a 1996 report. At that time there were several instances of significant deviation from Hardy Weinberg Equilibrium (HWE). Because molecular typing has been increasingly used since 1996, analysis of recent donor phenotypes should provide more accurate HLA frequencies.

METHODS

HLA frequencies were derived from the phenotypes of 12,061 donors entered into the Organ Procurement and Transplantation Network registry from January 1, 2003 to December 31, 2004. Frequencies for HLA-A;B;DR and HLA-A;B, DR, DQ haplotypes were derived from 11,509 and 10,590 donors, respectively. Frequencies of the allele groups encoding serologic antigens were obtained by gene counting and haplotype frequencies were estimated using the expectation maximization algorithm. Fit to HWE was evaluated by an exact test using Markov Chain Monte Carlo methods.

RESULTS

There was clear evidence of improved definition of rarer HLA antigens and haplotypes, particularly among minorities. The reported frequencies of broad antigens decreased overall for HLA-A, B, and DR, with concomitant increases in split antigens. Allele group genotypes among the major ethnic groups were in HWE with the single exception of HLA-A locus alleles among Asians. Improved HLA definition also permitted the first report of DR;DQ and A;B;DR;DQ haplotypes among U.S. donors.

CONCLUSIONS

The noted improvements in HLA definition and the overall lack of significant deviation from HWE indicate the accuracy of these HLA frequencies. These frequencies can therefore be applied for representative estimates of the U.S. donor population.

Assessment of differences in HLA-A, -B, and -DRB1 allele mismatches among African-American and non-African-American recipients of deceased kidney transplants

Among recipients of deceased donor kidney transplants, African-Americans experience a more rapid rate of kidney allograft loss than non-African-Americans. The purpose of this study was to characterize and quantify the HLA-A, -B, and -DRB1 allele mismatches and amino acid substitutions at antigen recognition sites among African-American and non-African-American recipients of deceased donor kidney transplants matched at the antigen level. In recipients with zero HLA antigen mismatches, the degree of one or two HLA allele mismatches for both racial groups combined was 47%, 29%, and 11% at HLA-DRB1, HLA-B, and HLA-A, respectively. There was a greater number of allele mismatches in African-Americans than non-African-Americans at HLA-A (P < .0001), -B (P = .096), and -DRB1 loci (P < .0001). For both racial groups, the HLA allele mismatches were predominantly at A2 for HLA-A; B35 and B44 for HLA-B; but multiple specificities for HLA-DRB1. The observed amino acid mismatches were concentrated at a few functional positions in the antigen binding site of HLA-A and -B and -DRB1 molecules. Future studies are ongoing to assess the impact of these HLA mismatches on kidney allograft loss.

Overcoming Immunologic Incompatibility: Transplanting the Difficult to Transplant Patient

Immunologic incompatibilities between donor and recipient have limited the access to renal transplantation for many patients. Previously the presence of donor-specific alloantibodies directed against donor major histocompatibility complex (MHC) antigens or natural antibodies directed against donor ABO blood group antigens was considered an absolute contraindication to renal transplantation. However, with the current understanding of humoral immune responses, superior immunosuppressive agents, and improved diagnosis and treatment of antibody-mediated rejection, renal transplantation can be safely performed with outstanding results despite the presence of donor-specific antibody. In this review we discuss the biology of antibody-mediated rejection and sensitization. We discuss the diagnostic tests necessary to characterize the type, affinity, and avidity of the donor-directed antibodies. Current methods for performing renal transplants across ABO and human leukocyte antigen (HLA)-sensitized barriers are covered, including the potential morbidities. The rest of the review focuses on advances in managing these antibodies to increase the likelihood of receiving a deceased donor kidney or allow transplantation from a living donor against whom one has a prohibitive antibody.

HLA alleles and haplotypes among the lakota sioux: report of the ASHI minority workshops, part III

Human leukocyte antigen (HLA) class I and II alleles were defined for 302 Lakota Sioux American Indians as part of the American Society for Histocompatibility and Immunogenetics coordinated studies on minority populations. The study group was comprised of adult volunteers from the Cheyenne River and Ogala Sioux tribes residing, respectively, on the Cheyenne River and Pine Ridge Reservations in South Dakota. Of the participants, 263 (87%) claimed full American Indian ancestry through both maternal and paternal grandparents. The study group included 25 nuclear families that were informative for genotyping. HLA phenotypes from 202 adults with no other known first-degree relative included in the study were used for calculation of allele and haplotype frequencies by maximum likelihood estimation. HLA-A, -B, and -Cw alleles were found to be in Hardy Weinberg equilibrium. Deviation from equilibrium was observed for DRB1 alleles (p=0.01), but could be attributed to the sample size and the occurrence of some genotypes with low expected frequencies. Polymorphism among the Sioux was limited with four to seven alleles comprising >80% of those observed at each locus. Several alleles were found at high frequency (0.05-0.30) among the Sioux that are also prevalent in other Native Americans and Alaska Natives, including: A*2402, *3101, and *0206; B*3501,*3901, *5101, and *2705; Cw*0702, *0404, and *03041; DRB1*0407, *0404, *1402, and *16021; and DQB1*0301, *0302, and *0402. DRB1*0811, which has been only previously described in Navajo and Tlingit Indians, was found to occur at a frequency of 0.119 among the Sioux. Two new alleles were defined among the Sioux: Cw*0204 and DRB1*040703, which were found in two and four individuals, respectively. In the haplotype analyses, significant linkage disequilibrium (p<0.00001) was seen in all pairwise comparisons of loci and numerous two and three locus haplotypes were found to have strong, positive linkage disequilibrium values. The two most common extended haplotypes among the Sioux, determined by maximum likelihood estimation and genotyping were: A*31012, B*3501, Cw*0404, DRB1*0407; and A*24021, B*3501, Cw*0404, DRB1*0404.

On treatment of tuberculosis in heterogeneous populations

Global eradication of tuberculosis (TB) is an international agenda. Thus understanding effects of treatment of TB in different settings is crucial. In previous work, we introduced the framework for a mathematical model of epidemic TB in demographically distinct, heterogeneous populations. Simulations showed the importance of genetic susceptibility in determining endemic prevalence levels. In the work presented here, we include treatment and investigate different strategies for treatment of latent and active TB disease in heterogeneous populations. We illustrate how the presence of a genetically susceptible subpopulation dramatically alters effects of treatment in the same way a core population does in the setting of sexually transmitted diseases. In addition, we evaluate treatment strategies that focus specifically on this subpopulation, and our results indicate that genetically susceptible subpopulations should be accounted for when designing treatment strategies to achieve the greatest reduction in disease prevalence.

Comparing epidemic tuberculosis in demographically distinct heterogeneous populations

There is wide variation in endemic tuberculosis (TB) levels between countries and we seek to identify possible causes of these differences. In this study we present an epidemiological model of Mycobacterium tuberculosis infection to investigate the effects of host genetics and demographic factors on epidemic TB. We discuss the general framework for this approach and present analytical results to identify important parameters affecting steady-state prevalence and incidence rates of TB disease. We then use numerical simulations of our model to observe the effects of a genetically susceptible subpopulation on TB disease dynamics at the population level. Finally, we simulate infection within a genetically heterogeneous population in two demographic settings: India (a typical population with high TB prevalence) and the USA (a typical population with low TB prevalence). Results show that changes in transmission parameters, the fraction of the population genetically susceptible to infection, and demographic factors strongly affect TB prevalence and incidence rates.

HLA antigens, alleles and haplotypes among the Yup'ik Alaska natives: report of the ASHI Minority Workshops, Part II

As part of the American Society for Histocompatibility and Immunogenetics coordinated studies among minority populations, human leukocyte antigen (HLA) alleles were defined for 460 volunteer Yup'ik Eskimos from the Yukon Kuskokwim delta region of southwestern Alaska. The study group included 252 adults with no other first-degree relatives and 48 informative nuclear families. Full Yupik ancestry through both maternal and paternal grandparents was claimed by 81.1% of participants. HLA-A, -B, -Cw, -DRB1, and -DQB1 alleles were determined by SBT, SSOP, reverse SSOP, and/or RSCA according to the protocols of five participating laboratories. Polymorphism was limited with 3-6 alleles comprising > 80% of the alleles observed at each locus. Homozygosity was high, particularly at the HLA-A and -DQB1 loci, with 36.6% and 44% of individuals having a single allele defined at these respective loci. HLA-A, -B, and -DRB1 alleles were in Hardy-Weinberg equilibrium, whereas HLA-Cw and -DQB1 alleles gave significant deviation (p = 0.002; 0.005). Significant linkage disequilibrium (p < or = 0.00001) was observed in all pairwise evaluations. A new Cw*0806 allele was observed in high linkage disequilibrium with B*4801(Delta = 0.099; Delta(rel) = 1.0). Three extended haplotypes were found to have frequencies > 5%, the most prevalent being A*2402; B*4801; DRB1*0401; DQB1*0301 (0.0933). Comparison of available class I data indicate that the Yup'ik share several common alleles with other Native American populations, including: A*2402, *0206, *6801; B*1501, *2705, *3501, *4002, *4801, *5101; and Cw*0202, *0304, *0401. Comparisons of class II data also confirm a close relationship of the Yup'ik to two other Eskimo populations, Siberian and East Greenland Eskimos. DRB1*0401 and *1101, which occur in high frequency among these Eskimo populations, but not in other Native Americans, were also prevalent among the Yup'ik, with respective frequencies of 0.232 and 0.107.

Antigen, allele, and haplotype frequencies report of the ASHI minority antigens workshops: part 1, African-Americans

HLA typing was performed on 977 African Americans residing throughout most of the United States. Class I and class II antigens and class II alleles were defined for all individuals and class I alleles were determined for a subset of individuals. The occurrence of 854 of the individuals in family groups permitted direct counting of allele and haplotype frequencies. The data were analyzed for antigen, allele, and haplotype frequencies; recombination frequencies; segregation distortion; distribution of haplotype frequencies; linkage disequilibria; and geographic distribution of DR antigens. Tables of the antigen, allele, the most common two and three point haplotypes, and 88 extended haplotypes that include class I and class II alleles are presented. Notable findings include a lower than expected frequency of recombination between the B and DR loci (theta= 0.0013), lower than expected frequency of inheritance (44.5% vs 54.5%) of the DRB1*1503; DQB1*0602 haplotype, lower than anticipated linkage disequilibrium values for DR; DQ haplotypes, and a skewed geographic distribution of DR antigens.

Probability of finding HLA-mismatched related or unrelated marrow or cord blood donors

Given recent improvements in the technology of transplantation and histocompatibility testing, it is now possible to contemplate using related or unrelated allogeneic hematologic stem cell donors with high degrees of HLA disparity. This paper is a follow-up of an earlier publication on the probability of finding a matched donor (Transplantation 60:778-783, 1995) and addresses the probability of finding a partially mismatched donor. Assuming that a four of six antigen HLA-A, -B, -DR match is acceptable, it is possible to find unrelated donors for patients of any race from a putative registry with fewer than 10,000 potential donors. Further, storing cord blood from newborns in families with a known genetic disease would yield an acceptable future stem cell transplant product in nearly 40% of cases. These results show the potential impact of cord blood donors and emphasize the importance of improvements in transplantation using partially mismatched donors.

The national impact of the 1995 changes to the UNOS renal allocation system. United Network for Organ Sharing

In 1995, changes in the United Network for Organ Sharing (UNOS) renal allocation policies expanded the mandatory share (MS) category to include zero antigen mismatches (0 mm), increased points for waiting time and for pediatric status, and eliminated points for certain HLA match grades. Data from the national scientific registry on 11344 and 11652 renal allograft recipients were analyzed for periods prior to and following the policy changes to assess the impact on organ allocation. The overall frequency of transplants going to non-Caucasians increased between the study periods, but the increase was significant only in the MS category. The proportion of MS transplants nearly doubled for African-Americans, increasing from 5.5% to 10.5%, while Hispanic/Latino recipients experienced a smaller increase, from 7.2% to 8.9%. The increased numbers of MS transplants clearly resulted from the inclusion of the 0 mm in the MS category. Among the NMS transplants, the average number of mismatched HLA antigens increased slightly. No effect of the additional points for waiting time was observed among recipients of non-mandatory share (NMS) transplants. The increase in mean waiting time until transplant for NMS recipients was attributable to the growth in the size of the waiting list. In contrast, there was a significant increase in mean waiting time for MS recipients. There were no significant changes in the proportions of sensitized or pediatric recipients between the study periods. In conclusion, only the changes in the MS policies appeared to have any significant effect on renal allocation. Further efforts will be required to address increasing allocation to patients disadvantaged by sensitization and/or prolonged waiting times.

Good genes, oxidative stress and condition-dependent sexual signals

The immune and the detoxication systems of animals are characterized by allelic polymorphisms, which underlie individual differences in ability to combat assaults from pathogens and toxic compounds. Previous studies have shown that females may improve offspring survival by selecting mates on the basis of sexual ornaments and signals that honestly reveal health. In many cases the expression of these ornaments appears to be particularly sensitive to oxidative stress. Activated immune and detoxication systems often generate oxidative stress by an extensive production of reactive metabolites and free radicals. Given that tolerance or resistance to toxic compounds and pathogens can be inherited, female choice should promote the evolution of male ornaments that reliably reveal the status of the bearers' level of oxidative stress. Hence, oxidative stress may be one important agent linking the expression of sexual ornaments to genetic variation in fitness-related traits, thus promoting the evolution of female mate choice and male sexual ornamentation, a controversial issue in evolutionary biology ever since Darwin.

Effects of changes in the criteria for nationally shared kidney transplants for HLA-matched patients

BACKGROUND

Nine years ago, a prospective trial began in all U.S. transplant centers to determine whether the results of renal transplantation would improve with the nationwide shipment of kidneys from cadaveric donors to HLA-matched patients. Since then, the stringency of criteria for HLA matching have been liberalized twice, from sharing only those kidneys that matched at all six HLA-A, -B, -DR antigens, to sharing phenotypically HLA-matched kidneys, and most recently to sharing zero HLA-mismatched kidneys.

METHODS

Data reported to the United Network for Organ Sharing Scientific Renal Transplant Registry from October 1987 to December 1996 were analyzed to examine the transplant results of nationally shared HLA-matched kidneys and the effects of changes to the HLA matching criteria on graft survival and the distribution of HLA-matched kidneys.

RESULTS

The overall 1-year graft survival rate of 5102 HLA-matched transplants was 88% compared with 81% for 58,207 recipients of kidneys with at least one HLA mismatch (P < 0.001). HLA-matched kidneys had a projected 12-year graft half-life, 50% higher than the 8-year half-life of mismatched grafts (P < 0.01). After the first change in the match criteria in August 1990, 1365 phenotypically matched kidneys with fewer than six HLA antigens identified had an 89% 1-year graft survival rate compared with 84% for 466 six antigen-matched kidneys transplanted before the change. After March 1995, 1067 zero HLA-mismatched kidneys that were not phenotypically identical nor six antigen matched, had a 1-year graft survival rate of 88%. Graft survival has not decreased as a result of these changes in the criteria for national sharing, despite an increase in the percentage of matched transplants from 2.5% during the six antigen-match era to 15.5% during the zero antigen-mismatch era.

CONCLUSIONS

Changes to the United Network for Organ Sharing policy for national sharing of HLA-matched kidneys have increased the number of patients, and especially minority patients, who can benefit by receiving a well-matched graft without compromising the high graft survival rates provided by an HLA-matched kidney.

An analysis of discrepancies in HLA phenotypes of cadaver donors in the united network for organ sharing registry

BACKGROUND

HLA matching is an important component of the United Network for Organ Sharing algorithm for kidney allocation and is the primary factor in the mandatory sharing of kidneys that have zero HLA antigens mismatched with specific patients on the waiting list. An assessment of the HLA-A, -B, and -DR antigen discrepancy rate in the Organ Procurement and Transplantation Network database is desirable to judge the adequacy of the HLA typing data upon which the allocation program is based.

METHODS

A subset of the Organ Procurement and Transplantation Network database, composed of 10,047 cadaver donor HLA phenotypes that have been repeated by laboratories affiliated with organ recipient centers, was analyzed for the overall rate of HLA phenotype discrepancy and for the type and frequency of discrepancies of the individual HLA antigen assignments. The United Network for Organ Sharing HLA antigen equivalences were applied to the data.

RESULTS

Fourteen percent of 12,419 HLA typing comparisons were discrepant in at least one HLA antigen of six possible antigens per phenotype. Of a possible 74,514 individual HLA antigen assignments, 2.7% were discrepant. For African-American donors, the discrepancy rate was 5.1% as compared with 2.4% for Caucasian donors. The most frequent type of discrepancy was the assignment of an antigen blank versus a named antigen.

CONCLUSIONS

The discrepancy rate is comparatively low and can be expected to improve as more laboratories adopt methods for HLA typing by DNA typing techniques. It is recommended that the HLA data be further reviewed by the laboratories for possible typographical errors and that centers review the UNOS listing of HLA antigen equivalences and encourage laboratories to split HLA antigens.

HLA gene and haplotype frequencies in the North American population: the National Marrow Donor Program Donor Registry

BACKGROUND

As of May 1, 1995, the National Marrow Donor Program had a donor registry consisting of over 1.35 million HLA-typed volunteers recruited from most major cities and states in the United States. This registry represents the largest single HLA-typed pool of normal individuals in the world.

METHODS

We analyzed the HLA-A, -B, -DR locus phenotypes of the National Marrow Donor Program donors in order to estimate gene and haplotype frequencies for major racial groups of the United States: Caucasian American, Asian American, African American, Latin American, and Native American. The large size of the database allowed us to calculate the frequencies of relatively rare antigens and haplotypes with more accuracy than previous studies.

RESULTS

We observed 89,522 distinguishable HLA-A, -B phenotypes in 1,351,260 HLA-A, -B-typed donors and 302,867 distinguishable HLA-A, -B, -DR phenotypes in 406,503 HLA-A, -B, -DR-typed donors. Gene and haplotype frequencies differed remarkably among the five racial groups, with African Americans and Asian Americans having a large number of haplotypes that were specific to their racial groups, whereas Caucasian Americans, Latin Americans, and Native Americans shared a number of common haplotypes.

CONCLUSIONS

These data represent an important resource for investigators in the fields of transplantation and population genetics. The gene and haplotype frequencies can be used to aid clinicians in advising patients about the probability of finding a match within a specific ethnic group, or to determine donor recruitment goals and strategies. The information is also a valuable resource for individuals who are interested in population genetics, selection and evolution of polymorphic human genes, and HLA-disease association.

Strategies for determining HLA compatibility in related donor bone marrow transplantation

BACKGROUND

Although HLA identity between donor and recipient is no longer an absolute requirement for bone marrow transplantation, knowledge of the degree of HLA compatibility is necessary for determining the induction and immunosuppression regimen to be used. In cases of related donor transplantation, HLA compatibility may be assessed by defining the HLA phenotypes at the allele level using high-resolution, DNA-based typing methods or by determining the genotypes of the patient and potential donor from the HLA phenotypes, ascertained by low-resolution typing, of their family members.

METHODS

We developed an algorithm that can be used to assess the relative costs of these two approaches. We applied population frequencies for HLA-DR alleles to this algorithm to determine at what cost per test ratio for high-resolution:low-resolution testing the costs of the two approaches are equal.

RESULTS

In transplants involving a sibling pair who have the same HLA-A, -B, and -DR antigens, these values are 1.16-1.83 for African-Americans and 1.23-1.97 for Caucasians, depending on the relatives available for testing. With a slight increase in the resolution level achieved with DR antigen testing, the range of values becomes 1.10-1.74. We also estimated that the probability that two antigenically identical siblings have identical HLA-DRB1 alleles is >99% for both African-Americans and Caucasians. A review of 615 cases from our transplant program showed that all of 192 pairs of antigenically identical patients and sibling donors were genotypically or allelically identical, indicating that this estimate is valid.

CONCLUSIONS

Transplant programs can apply these algorithms to determine the most cost-effective scheme for histocompatibility testing.

Detection of HLA class I-specific antibodies by the QuikScreen enzyme-linked immunosorbent assay

The GTI QuikScreen test is an enzyme-linked immunosorbent assay (ELISA) that uses soluble HLA class I antigens as targets. In tests of 5,893 human serum specimens, we evaluated the reliability, sensitivity, and utility of the GTI QuikScreen test for detecting HLA class I-specific antibody. We found that the test could reliably detect HLA-specific antibodies of the immunoglobulin G (IgG) but not the IgM class. The degree of correlation with lymphocytotoxicity testing varied among the different serum sources, with the best correlation achieved with sera from renal transplant candidates (r > 0.7) and the poorest with sera from patients with end-stage liver disease (r = 0.26), possibly because of elevated alkaline phosphatase levels in the liver patients. Test reproducibility was high (96%), and test failure rate was low (1.7%). The test sensitivity is comparable to that of the antiglobulin cytotoxicity and, possibly, even flow cytometric tests. There was a highly significant (P < 0.001) correlation between the optical densities obtained in the ELISA and the percent panel reactive antibody determined by cytotoxicity testing. Therefore, although designed only to determine the presence or absence of HLA-specific antibody, GTI QuikScreen test results also provided an indication of the extent of sensitization. The test is one of the most effective and efficient ways to determine if antibodies producing a positive result in crossmatch tests are specific for HLA class I antigens. As an adjunct to serum screening by cytotoxicity testing, the GTI QuikScreen test can produce a substantial savings of time and effort that reduces the cost to the laboratory and to the patient.

Local impact of 1995 changes in the renal transplant allocation system

In 1995, changes to the United Network for Organ Sharing renal allocation system eliminated points for certain HLA matches, increased points for waiting time and for pediatric patients, and extended the mandatory share rule to include the zero-antigen mismatch. We analyzed data, from the period December 1993 to August 1996, on 393 donors, 348 kidney-only cadaveric transplants, and 615 patients ranked first or second on the allocation lists generated for each donor, to assess the effect of the changes in the point system. There was an appreciable (46%) but not significant increase in the frequency of transplants occurring under the mandatory share rule, with a greater relative increase seen in African-Americans than in Caucasians. Recipients of transplants not falling under the mandatory share rule had an increased average waiting time but no increase in sensitization or HLA mismatch, whereas patients ranked at the top of the allocation list had higher levels of sensitization but no increase in waiting time. There was an appreciable increase in the percentage of transplants occurring in African-Americans. Of the various changes we observed, only those involving the mandatory share rule could be attributed to changes in the allocation system, whereas others paralleled changes in the composition of our local waiting list.