Selection Of Bone Marrow Donors Research Articles

Germ line ERG haploinsufficiency defines a new syndrome with cytopenia and hematological malignancy predisposition

AbstractThe genomics era has facilitated the discovery of new genes that predispose individuals to bone marrow failure (BMF) and hematological malignancy (HM). We report the discovery of ETS-related gene (ERG), a novel, autosomal dominant BMF/HM predisposition gene. ERG is a highly constrained transcription factor that is critical for definitive hematopoiesis, stem cell function, and platelet maintenance. ERG colocalizes with other transcription factors, including RUNX1 and GATA2, on promoters or enhancers of genes that orchestrate hematopoiesis. We identified a rare heterozygous ERG missense variant in 3 individuals with thrombocytopenia from 1 family and 14 additional ERG variants in unrelated individuals with BMF/HM, including 2 de novo cases and 3 truncating variants. Phenotypes associated with pathogenic germ line ERG variants included cytopenias (thrombocytopenia, neutropenia, and pancytopenia) and HMs (acute myeloid leukemia, myelodysplastic syndrome, and acute lymphoblastic leukemia) with onset before 40 years. Twenty ERG variants (19 missense and 1 truncating), including 3 missense population variants, were functionally characterized. Thirteen potentially pathogenic ETS domain missense variants displayed loss-of-function characteristics, thereby disrupting transcriptional transactivation, DNA binding, and/or nuclear localization. Selected variants overexpressed in mouse fetal liver cells failed to drive myeloid differentiation and cytokine-independent growth in culture and to promote acute erythroleukemia when transplanted into mice, concordant with these being loss-of-function variants. Four individuals displayed somatic genetic rescue by copy neutral loss of heterozygosity. Identification of predisposing germ line ERG variants has clinical implications for patient and family diagnoses, counseling, surveillance, and treatment strategies, including selection of bone marrow donors and cell or gene therapy.

Establishment of reference values based on influential characteristics of hematopoietic stem cells and immune cell subsets in the bone marrow

Hematopoietic stem cell transplantation is still a curative treatment for many haematological cancers. Many factors, such as age, sex, ethnic background, smoking status, and body mass index, affect average reference values in different populations. This study aimed to establish a reference range for the absolute numbers and percentages of healthy individuals' hematopoietic stem cells and immune cells in the bone marrow. Seventy-one healthy donors (32 males and 39 females) were enrolled in the study. Following bone marrow harvesting, using flow cytometry, immunophenotyping was performed to determine the absolute number and percentage of CD34+ stem cells and various immune subsets. We found no statistically significant difference in the absolute count of HSCs or immune cell subsets in the bone marrow between males and females. Regarding age, the younger group had more significant CD34+ and immune cell subsets. Donors with healthier body weights tend to have richer bone marrow cellularity. Establishing a reference value for hematopoietic stem cells and immune cells in the bone marrow based on various influential factors is pivotal for defining bone marrow status and donor selection.

A Validated and Licensed Method of Bone Marrow Aspirate Procurement to Support Advanced Therapy Investigational Medicinal Product (ATIMP) Manufacture

The Blood & Tissue Establishment (BTE) of Galway University Hospitals supplies sterile bone marrow (BM) aspirate to European cellular manufacturing facilities as a starting material in ATIMP manufacture. We have developed a validated, sterile bone marrow procurement method in accordance with the European Union Tissue & Cells Directive (EUTCD) and Good Manufacturing Practice (GMP). The BTE achieved the requisite procurement licence, from the Irish competent authority, the Health Products Regulatory Authority (HPRA).Under the BTE Quality Management System all standard operating procedures and forms are document controlled, all consumable items are batch accepted, all staff involved undergo training and competency assessment (including adequate sanitisation of the iliac crest), and all issues are recorded and reported appropriately to the HPRA.The prospective donor must first undergo a two part ‘donor assessment’ procedure which evaluates the donor's ‘fitness’ to undergo the procedure, while also having due regard for any potential recipient.Part One of the assessment process requires that the entire procedure is explained by a trained clinician / nurse; a patient information leaflet is provided and written consent obtained. A full blood count, coagulation screen, glucose test, chemistry screen, blood group and virology screen is performed. The virology screen must, at minimum, include the viruses listed by the EUTCD and the donation must take place within 30 days of sample collection. The patient will then undergo a ‘lifestyle questionnaire’ to assess donor medical, travel, sexual and other risk history. Guidance for allowing the donation to proceed will depend on a number of factors, including, whether it is an allogeneic or autologous donation. Consideration is given to the ‘Bone Marrow and Peripheral Blood Stem Cell Donor Selection Guidelines for Unrelated Donors’ of the ‘Guidelines for the Blood Transfusion Services in the United Kingdom’. HPRA and European Centre for Disease Prevention and Control alerts are also incorporated into selection criteria.The Responsible Person (RP) of the BTE (also a Consultant Haematologist) must review the answers to the questionnaire, together with the blood test results and assess whether the donor is fit to proceed to aspiration.Part Two of the assessment process takes place immediately prior to the scheduled aspiration. The donor will repeat the lifestyle questionnaire once more and the answers will be reviewed and compared with the previous questionnaire. The Consultant Haematologist will carry out a clinical examination and assessment of the donor. Upon completion, final donor eligibility is signed off and the aspiration can proceed. The procedure takes place in an operating theatre by a scrubbed Consultant Haematologist. A sterile field is created around the aspiration site. The aspiration site is cleansed with Chlorhexadine. Local anaesthetic (lidocaine 2%) is administered. 11 Gauge BM needles are used to puncture. Syringes are flushed with heparin sodium flushing solution. The flushed syringes are used to withdraw the BM, handed to a sterile assistant and transferred into 10ml lithium heparin vacutainers. The volume of 30ml of BM is aspirated from the iliac crest of both healthy donors (allogeneic) and patients (autologous) enrolled in clinical trials.These vacutainers are capped and inverted several times to prevent clotting, labelled and packaged for transport.The puncture site is dressed, donor vitals are observed and noted post procedure and the donor may be discharged after 2 hours.BM is transported to the manufacturing facility at monitored ambient temperature. Within the Grade A controlled environment, the BM is pooled and 1ml is used to inoculate one aerobic and one anaerobic blood culture bottle (validated for 0.5ml in each, incubated for 14 days, automated detection system).As of July 2017, we have performed 24 collections, 11 of which are allogeneic donations from healthy volunteers. The average white cell count in the aspirate from healthy donors is 43.1 x 106/ml. The sterility is satisfactory, with only one instance of contamination over the 24 collections, where, on the final day of incubation (day 14), we detected propionibacterium spp, a notoriously slow-growing commensal skin flora.Our regulatory approved protocol provides a steady supply of GMP grade bone marrow aspirates for the purpose of clinical trials. DisclosuresNo relevant conflicts of interest to declare.

Bone marrow donor selection and characterization of MSCs is critical for pre-clinical and clinical cell dose production

BackgroundCell based therapies, such as bone marrow derived mesenchymal stem cells (BM-MSCs; also known as mesenchymal stromal cells), are currently under investigation for a number of disease applications. The current challenge facing the field is maintaining the consistency and quality of cells especially for cell dose production for pre-clinical testing and clinical trials. Here we determine how BM-donor variability and thus the derived MSCs factor into selection of the optimal primary cell lineage for cell production and testing in a pre-clinical swine model of trauma induced acute respiratory distress syndrome.MethodsWe harvested bone marrow and generated three different primary BM-MSCs from Yorkshire swine. Cells from these three donors were characterized based on (a) phenotype (morphology, differentiation capacity and flow cytometry), (b) in vitro growth kinetics and metabolic activity, and (c) functional analysis based on inhibition of lung endothelial cell permeability.ResultsCells from each swine donor exhibited varied morphology, growth rate, and doubling times. All expressed the same magnitude of standard MSC cell surface markers by flow cytometry and had similar differentiation potential. Metabolic activity and growth potential at each of the passages varied between the three primary cell cultures. More importantly, the functional potency of the MSCs on inhibition of endothelial permeability was also cell donor dependent.ConclusionThis study suggests that for production of MSCs for cell-based therapy, it is imperative to examine donor variability and characterize derived MSCs for marker expression, growth and differentiation characteristics and testing potency in application dependent assays prior to selection of the optimal cell lineage for large scale expansion and dose production.

P015 Bone marrow donor selection in the presence of both allogeneic and syngeneic donors

Syngeneic transplants provide an interesting dilemma with respect to donor selection. The risk of relapse is higher for patients with AML undergoing syngeneic transplant vs. HLA-matched sibling transplant, however, rates of graft versus host disease and transplant related mortality have historically been lower with syngeneic transplants. Thus, HLA -matched sibling donors are preferred to identical twin donors for patients undergoing transplant for malignant diseases (ie. AML) to optimize the impact of graft vs. leukemia (GvL) whereas identical twin donors are ideal for non-malignant disorders. We present a patient with AML who had both an HLA matched sibling donor as well as an identical twin. He was initially transplanted with the HLA matched sibling donor successfully however, at 6 months post transplant he developed severe neutropenia (ANC = 0). Chimerism studies revealed 95% DNA from the related donor T cells at this time. The cause of his neutropenia was autoimmune in nature and refractory to multiple immunosuppressive medications and therefore he underwent a second transplant this time using his identical twin as the donor. The patient’s neutrophils engrafted and he has undergone a complete recovery post transplant. Chimerism studies after the second transplant reveal that 85% of the DNA is from the second donor’s T cells. Typically, chimerism studies with syngeneic transplant are not helpful as the patient and donor are identical. However in this case, chimerism studies were possible to determine the engraftment of the initial related donor to the patient/twin. This case illustrates that optimal donor selection depends on disease when an identical twin and an HLA matched sibling donor are available. It also showcases the interesting results of chimerism testing in a patient who has received both an allogeneic and a syngeneic transplant.

HLA genetic diversity in Hungarians and Hungarian Gypsies: complementary differentiation patterns and demographic signals revealed by HLA-A, -B and -DRB1 in Central Europe.

Systematic analyses of human leukocyte antigen (HLA) profiles in different populations may increase the efficiency of bone marrow donor selection and help reconstructing human peopling history. We typed HLA-A, -B, and -DRB1 allele groups in two bone marrow donor cohorts of 2402 Hungarians and 186 Hungarian Gypsies and compared them with several Central-European, Spanish Gypsy, and Indian populations. Our results indicate that different European Gypsy populations share a common origin but diverged genetically as a consequence of founder effect and rapid genetic drift, whereas other European populations are related genetically in relation to geography. This study also suggests that while HLA-A accurately depicts the effects of genetic drift, HLA-B, and -DRB1 conserve more signatures of ancient population relationships, as a result of balancing selection.

HLA-A, B and DRB1 allele and haplotype frequencies in volunteer bone marrow donors from the north of Parana State

BackgroundKnowledge of allele and haplotype frequencies of the human leukocyte antigen (HLA) system is important in the search for unrelated bone marrow donors. The Brazilian population is very heterogeneous and the HLA system is highly informative of populations because of the high level of polymorphisms.AimThe aim of this study was to characterize the immunogenetic profile of ethnic groups (Caucasians, Afro-Brazilians and Asians) in the north of Parana State.MethodsA study was carried out of 3978 voluntary bone marrow donors registered in the Brazilian National Bone Marrow Donor Registry and typed for the HLA-A, B and DRB1 (low resolution) loci. The alleles were characterized by the polymerase chain reaction sequence-specific oligonucleotides method using the LabType SSO kit (One Lambda, CA, USA). The ARLEQUIN v.3.11 computer program was used to calculate allele and haplotype frequenciesResultsThe most common alleles found in Caucasians were HLA-A*02, 24, 01; HLA-B*35, 44, 51; DRB1*11, 13, 07; for Afro-Brazilians they were HLA-A*02, 03, 30; HLA-B*35, 15, 44; DRB1*13, 11, 03; and for Asians they were: HLA-A*24, 02, 26; HLA-B*40, 51, 52; DRB1*04, 15, 09. The most common haplotype combinations were: HLA-A*01, B*08, DRB1*03 and HLA-A*29, B*44, DRB1*07 for Caucasians; HLA-A*29, B*44, DRB1*07 and HLA-A*01, B*08 and DRB1*03 for Afro-Brazilians; and HLA-A*24, B*52, DRB1*15 and HLA-A*24, B*40 and DRB1*09 for Asians.ConclusionThere is a need to target and expand bone marrow donor campaigns in the north of Parana State. The data of this study may be used as a reference by the Instituto Nacional de Cancer/Brazilian National Bone Marrow Donor Registry to evaluate the immunogenetic profile of populations in specific regions and in the selection of bone marrow donors

Successful Prevention of Acute Graft-versus-Host Disease Using Low-Dose Antithymocyte Globulin after Mismatched, Unrelated, Hematopoietic Stem Cell Transplantation for Acute Myelogenous Leukemia

In this study, we investigated the effects of low-dose antithymocyte globulin (ATG, thymoglobulin) in the prevention of acute graft-versus-host disease (aGVHD) in mismatched, unrelated hematopoietic stem cell transplantations (uHSCTs) in patients with the single disease entity of acute myelogenous leukemia (AML). Patients (n = 103) with a variable risk for AML who received uHSCTs from available Asian and Caucasian donors were enrolled. First, we compared HLA-matched (group 1, n = 54) and HLA-mismatched (group 2, n = 49) transplantation patients. Then, we divided the patients in group 2, who had received transplants from allele(s)/antigen-mismatched donors, into 2 subgroups: patients who used ATG (group 3, n = 24) and those who did not (group 4, n = 25). To prevent the development of aGVHD, the patients in group 3 received ATG at a dose of 1.25 mg/kg body weight per day for 2 consecutive days, together with our standard regimen of methotrexate (MTX) and tacrolimus. The median CD34(+) cell infusion was 4.2 x 10(6)/kg (range: 1.2-34.4). The median patient age was 41 years (range: 16-57), and the median follow-up duration of patients who were event-free survivors was 23 months (range: 2-72). The overall incidences of aGVHD and chronic GVHD (cGVHD) were 38% and 56%, respectively. Of 48 evaluable patients in group 2, 10 (21%) developed moderate to severe aGVHD (grades II-IV). In contrast, 2 (8%) of the 24 patients in group 3 and 7 (29%) of the 24 evaluated patients in group 4 required therapy for aGVHD (grades II-IV; P = .038). The incidence of cGVHD was not different between groups 3 and 4. The estimated probabilities of overall survival (OS) and event-free survival (EFS) at 2 years for group 2 were 55% and 44%, respectively. In comparison, the estimated probabilities of OS and EFS at 2 years for groups 3 and 4 were 68% versus 38% (P = .043) and 58% versus 38% (P = .103), respectively. The overall cumulative incidence of nonrelapse mortality (NRM) was 29% in group 2. The cumulative incidence of NRM differed markedly between group 3 (16%; 95% confidence interval [CI], 4%-28%) and group 4 (44%, 95% CI, 34%-54%) (P = .013). We found no difference in cytomegalovirus (CMV) reactivation between groups 3 and 4. These results suggest that in mismatched uHSCT, a low dose of ATG (total 2.5 mg/kg) may prevent moderate to severe aGVHD, with comparable rates of relapse and CMV reactivation and a greatly decreased rate of NRM.

Diamond Blackfan anaemia in the UK: clinical and genetic heterogeneity.

A detailed family study was undertaken of patients notified to the UK Diamond Blackfan Anaemia (DBA) Registry. RPS19 mutations were detected in 16 of 104 families, including two patients with deletions detected by intragenic loss of heterozygosity of tightly linked polymorphisms. In two further cases, polymorphisms were used to determine the parental allele of origin of RPS19 point mutations. A review of clinical details of patients with mutations and patients in the literature having identical or equivalent mutations revealed evidence for a genotype:phenotype correlation with respect to the prevalence of physical anomalies, and the occurrence of mild or variable haematological severity. Nine of 60 patients had a known family history of DBA. Haematological abnormalities, including raised red cell adenosine deaminase activity, were found in first-degree relatives of 16 of 51 (31%) of patients not previously considered to have familial DBA. Results of both parents and any siblings were normal in only 35 of 60 (58%) of cases, who were therefore assumed to have sporadic de novo DBA. The classical inheritance pattern for DBA is autosomal dominant; however, 12 of 60 families (20%) had more than one affected child despite normal results in both parents. These results have important implications for genetic counselling, and for the selection of potential sibling bone marrow donors.

Evaluation of heteroduplex analysis for selection of unrelated bone marrow donors

Evaluation of heteroduplex analysis for selection of unrelated bone marrow donors

Reflections

Genomics is affecting all areas of medicine. In transfusion medicine, DNA-based genotyping is being used as an alternative to serological antibody-based methods to determine blood groups for matching donor to recipient. Most antigenic polymorphisms are due to single nucleotide polymorphism changes in the respective genes, and DNA arrays that target these changes have been validated by comparison with antibody-based typing. Importantly, the ability to test for antigens for which there are no serologic reagents is a major medical advance to identify antibodies and find compatible donor units, and can be life-saving. This review summarizes the evolving use and applications of genotyping for red cell and platelet blood group antigens affecting several areas of medicine. These include prenatal medicine for evaluating risk of fetal or neonatal disease and candidates for Rh-immune globulin; transplantation for bone marrow donor selection and transfusion support for highly alloimmunized patients and for confirmation of A2 status of kidney donors; hematology for comprehensive typing for patients with anemia requiring chronic transfusion; and oncology for patients receiving monoclonal antibody therapies that interfere with pretransfusion testing. A genomics approach allows, for the first time, the ability to routinely select donor units antigen matched to recipients for more than ABO/RhD to reduce complications. Of relevance, the growth of whole-genome sequencing in chronic disease and for general health will provide patients' comprehensive extended blood group profile as part of their medical record to be used to inform selection of the optimal transfusion therapy.

Cytotoxic T-lymphocyte precursor frequency (CTLp-f) as a tool for distinguishing permissible from non-permissible class I mismatches in T-cell-depleted allogeneic bone marrow transplantation

Matching for HLA has been the gold standard in bone marrow donor selection. But, with the ever increasing number of identified HLA alleles, it is becoming more difficult to find a fully HLA-identical donor other than a sibling. Retrospective analysis revealed that HLA mismatches do not necessarily give rise to acute graft-versus-host-disease (GVHD). However, we have no means of defining these ‘permissible’ mismatches before bone marrow transplantation (BMT). Thus, we set out to establish whether functional matching by means of helper and cytotoxic T-lymphocyte precursor frequency analysis (HTLp-f and CTLp-f respectively) can be applied to this end. Fifty-five recipient–donor pairs other than HLA-identical siblings, the recipient of which received a T-cell-depleted graft, were analysed by high-resolution HLA typing and/or HTLp-f/CTLp-f analysis. The predictive value of the CTLp-f assay for development of acute GVHD was confirmed. More importantly, our data indicate that the CTLp-f assay was able to discriminate permissible from non-permissible HLA-A, -B or -Cw mismatches, but not for DRB/DQB mismatches. The absolute number of alloreactive CTLs present in the graft correlated with the risk of acute GVHD. Although HTLp-f and CTLp-f together had a high negative predictive value, HTLp-f outcome by itself was not correlated with acute GVHD. As we have no evidence yet that HTLp-f or CTLp-f can identify permissible DRB/DQB mismatches, high-resolution matching for these antigens remains the best option. The combination of high-resolution DRB/DQB typing and the CTLp-f assay would enable the accurate prediction of the risk of acute GVHD while extending the pool of potential donors. Furthermore, it would enable adjustment of the number of T- cells in the graft accordingly to improve clinical outcome.

Cytotoxic T-lymphocyte precursor frequency (CTLp-f) as a tool for distinguishing permissible from non-permissible class I mismatches in T-cell-depleted allogeneic bone marrow transplantation.

Matching for HLA has been the gold standard in bone marrow donor selection. But, with the ever increasing number of identified HLA alleles, it is becoming more difficult to find a fully HLA-identical donor other than a sibling. Retrospective analysis revealed that HLA mismatches do not necessarily give rise to acute graft-versus-host-disease (GVHD). However, we have no means of defining these 'permissible' mismatches before bone marrow transplantation (BMT). Thus, we set out to establish whether functional matching by means of helper and cytotoxic T-lymphocyte precursor frequency analysis (HTLp-f and CTLp-f respectively) can be applied to this end. Fifty-five recipient-donor pairs other than HLA-identical siblings, the recipient of which received a T-cell-depleted graft, were analysed by high-resolution HLA typing and/or HTLp-f/CTLp-f analysis. The predictive value of the CTLp-f assay for development of acute GVHD was confirmed. More importantly, our data indicate that the CTLp-f assay was able to discriminate permissible from non-permissible HLA-A, -B or -Cw mismatches, but not for DRB/DQB mismatches. The absolute number of alloreactive CTLs present in the graft correlated with the risk of acute GVHD. Although HTLp-f and CTLp-f together had a high negative predictive value, HTLp-f outcome by itself was not correlated with acute GVHD. As we have no evidence yet that HTLp-f or CTLp-f can identify permissible DRB/DQB mismatches, high-resolution matching for these antigens remains the best option. The combination of high-resolution DRB/DQB typing and the CTLp-f assay would enable the accurate prediction of the risk of acute GVHD while extending the pool of potential donors. Furthermore, it would enable adjustment of the number of T- cells in the graft accordingly to improve clinical outcome.

HLA-B44 subtyping in the Catalan population using reference strand mediated conformation analysis. Implications for the selection of unrelated bone marrow donors.

Cytotoxic T lymphocytes (CTLs) reactive against the disparity between HLA-B*4402 and HLA-B*4403 have been reported after unrelated donor bone marrow transplantation. These CTLs have been associated with acute graft-versus-host disease and graft rejection. This study describes the HLA-B44-subtyping in the Catalan population using reference-strand mediated conformation analysis. It has been performed on 297 unrelated HLA-B44+ cord blood units from the Barcelona Cord Blood Bank (Barcelona, Spain). We have found a predominance of HLA-B*4403 (66.04%) over HLA-B*4402 (33.02%), whereas the predominant HLA-B44 allele in Northern Europe and the United States is HLA-B*4402. This inverted proportion between HLA-B44 subtypes in Mediterranean populations compared with other Caucasian populations suggests that HLA-B44 subtyping should be performed when an HLA-B44+ unrelated donor marrow is identified.

Sequencing of two HLA-A blank alleles: implications in unrelated bone marrow donor matching.

DNA-based methods can type for HLA antigens with no or very low cell surface expression. The role of such serological blank antigens in bone marrow donor selection is unknown. HLA-A serological blank antigens detected in two leukemic patients were cloned and sequenced from genomic DNA. mRNA expression and exon 3 splicing were determined by reverse transcriptase-polymerase chain reaction (PCR). Two patients typed A2/x and A3/x by serology were revealed to be A*01/A*0201 and A*03/A*24 by DNA typing. The HLA-A*O1 blank antigen was identified as the A*0104N allele with a C insertion in exon 4, which results in a stop codon. The HLA-A*24 blank antigen was identified as the A*2402102L allele characterized by a mutation in intron 2 leading to impaired splicing of mainly exon 3. As a consequence, functional A24 mRNA was reduced to less than 5% compared with the other HLA-A allele. For both patients, a search for an unrelated donor was initiated on the basis of the functional absence of the serologically blank allele. The second patient with the A*24 blank antigen could undergo transplantation with marrow from a "fully A/B/C/DRB1/DRB5/DQB1-compatible" donor, homozygous for the A antigen. Donor T cells did not react against the patient in a pretransplantation cytotoxic T lymphocyte precursor frequency test known to detect all class I incompatibilities. However, despite this functional pretransplantation compatibility, the patient died 44 days after bone marrow transplantation, suffering from graft-versus-host disease grade IV. The presence of potentially functional A*2402 mRNA could be demonstrated by reverse transcriptase-PCR and sequencing: 50% of the A24 mRNA molecules were estimated to contain exon 3 with a correct splice site. These findings show that serological blank antigens with low mRNA expression might still be recognized after bone marrow transplantation. The determination of such alleles by molecular methods and the assessment of mRNA expression should therefore be included in the unrelated bone marrow donor search protocol.

Molecular Typing Shows a High Level of HLA Class I Incompatibility in Serologically Well Matched Donor/Patient Pairs: Implications for Unrelated Bone Marrow Donor Selection

In comparison with HLA-matched sibling bone marrow transplants, unrelated donor transplants are associated with increased graft-versus-host disease and graft failure. This is likely in part due to HLA incompatibilities not identified by current matching strategies. High resolution DNA-based typing methods for HLA class II loci have improved donor selection and treatment outcome in unrelated donor bone marrow transplantation. By using DNA-based typing methods for HLA-A and -B on a cohort of 100 potential bone marrow donor/patient pairs, we find that serological typing for HLA class I is limited in its ability to identify incompatibilities in unrelated pairs. Furthermore, the incompatibilities identified are associated with the presence at high frequency of alloreactive cytotoxic T-lymphocyte precursors. DNA typing also indicates that HLA-C mismatches are common in HLA-A and -B serologically matched pairs. Such mismatches appear to be significantly less immunogenic with respect to cytotoxic T-lymphocyte recognition, but are expected to influence natural killer cell activity. Thus, improved resolution of HLA class I shows many previously undisclosed mismatches that appear to be immunologically functional. Use of high resolution typing methods in routine matching is expected to improve unrelated donor selection and transplant outcome.

Molecular Typing Shows a High Level of HLA Class I Incompatibility in Serologically Well Matched Donor/Patient Pairs: Implications for Unrelated Bone Marrow Donor Selection

AbstractIn comparison with HLA-matched sibling bone marrow transplants, unrelated donor transplants are associated with increased graft-versus-host disease and graft failure. This is likely in part due to HLA incompatibilities not identified by current matching strategies. High resolution DNA-based typing methods for HLA class II loci have improved donor selection and treatment outcome in unrelated donor bone marrow transplantation. By using DNA-based typing methods for HLA-A and -B on a cohort of 100 potential bone marrow donor/patient pairs, we find that serological typing for HLA class I is limited in its ability to identify incompatibilities in unrelated pairs. Furthermore, the incompatibilities identified are associated with the presence at high frequency of alloreactive cytotoxic T-lymphocyte precursors. DNA typing also indicates that HLA-C mismatches are common in HLA-A and -B serologically matched pairs. Such mismatches appear to be significantly less immunogenic with respect to cytotoxic T-lymphocyte recognition, but are expected to influence natural killer cell activity. Thus, improved resolution of HLA class I shows many previously undisclosed mismatches that appear to be immunologically functional. Use of high resolution typing methods in routine matching is expected to improve unrelated donor selection and transplant outcome.

Current methodologies of human leukocyte antigen typing utilized for bone marrow donor selection.

Matching for human leukocyte antigen (HLA) loci is the most crucial factor in the selection of bone marrow donors. The techniques utilized to assign HLA type have evolved significantly since the application of polymerase chain reaction-based methodologies. A significant challenge for DNA typing methodologies is to be able to maintain high resolution typing with the ever-increasing numbers of defined HLA alleles. To date, over 800 HLA class I and class II alleles have been identified by sequencing analysis, and this number shows no sign of reaching a plateau. It is only with high allelic level resolution typing analysis that an accurate definition of the role that individual HLA loci play in determining transplant outcome can be achieved, and this is a major goal for the future.

Optimizing a limiting dilution culture system for quantifying the frequency of interleukin-2-producing alloreactive T helper lymphocytes.

The development of sensitive, specific, and reproducible techniques to quantify T cells with direct allospecificity has potential applications in the selection of bone marrow donors and in the monitoring of the antidonor alloresponse in patients after organ transplantation. Such data may provide an objective basis for altering existing immunosuppression, monitoring novel antirejection therapies, and predicting long-term graft outcome. We have previously published a correlation between donor antirecipient T helper frequencies (HTLf) and the severity of acute graft-versus-host disease after bone marrow transplantation. Using the same assay protocol, we have described the development of donor-specific hyporesponsiveness in a proportion of renal transplant recipients. However, several imperfections existed in the protocols used in these studies. Cellular interactions within the stimulator and the responder cell populations, and back stimulation of T cells within the stimulator cell population, could give rise to extraneous interleukin-2 and alter the validity or estimation of derived recipient antidonor HTLf. Using peripheral blood mononuclear cells as the responding population and splenic mononuclear cells as the stimulating population, we have examined the possible effects of these cellular interactions on the results of limiting dilution analysis assays for HTLf measurement. These interactions have the ability to alter the validity or estimation of HTLf. We show that by depleting the responder population of HLA class II+ cells and depleting T cells from the stimulating population, these interactions are effectively abrogated. On the basis of the findings reported here, we describe an optimized HTLf assay which is sensitive, specific, and reproducible. This has obvious applications in the analysis of alloimmune responses in transplantation.

A single [3H]thymidine-based limiting dilution analysis to determine HTLp and CTLp frequencies for bone marrow donor selection.

Histocompatibility between recipient and donor is a critical factor in allogeneic BMT which, to a large extent, determines the incidence of GVHD after BMT. Functional histocompatibility assays, such as the helper T lymphocyte precursor frequency assay (HTLp) and the cytotoxic T lymphocyte precursor frequency assay (CTLp), have proved to be helpful tools in facilitating donor selection procedures. However, a major drawback of these assays is that they are laborious and require large numbers of cells. We therefore adapted a [3H]thymidine-based assay, the 'JAM' test, as a read-out for CTLp frequencies, to replace the more cumbersome 51Cr-release assay. Furthermore, we applied an experimental setup that enables the assessment of HTLp and CTLp frequencies from a single limiting dilution assay to reduce the number of cells needed. The newly developed assay is relatively easy to perform and has the advantage that different subsets of T cells can be quantified in a single ongoing alloreaction. When the combined assay was applied in unrelated donor selection it proved to be a sensitive method that enables differentiation in suitability of distinct donors for a single patient. Therefore, the combined HTLp/CTLp assay appears to be a practical and sensitive method for identifying functional histocompatibility in related and unrelated donor/recipient combinations.