Recipient cytokine genotypes for TNF-alpha and IL-10 and the minor histocompatibility antigens HY and CD31 codon 125 are not associated with occurrence or severity of acute GVHD in unrelated cord blood transplantation: a retrospective analysis

Impact of CTLA4 genotype and other immune response gene polymorphisms on outcomes after single umbilical cord blood transplantation

We evaluated the impact of recipient and cord blood unit (CBU) genetic polymorphisms related to immune response on outcomes after unrelated cord blood transplantations (CBTs). Pretransplant DNA samples from 696 CBUs with malignant diseases were genotyped for NLRP1, NLRP2, NLRP3, TIRAP/Mal, IL10, REL, TNFRSF1B, and CTLA4. HLA compatibility was 6 of 6 in 10%, 5 of 6 in 39%, and ≥4 of 6 in 51% of transplants. Myeloablative conditioning was used in 80%, and in vivo T-cell depletion in 81%, of cases. The median number of total nucleated cells infused was 3.4 × 10⁷/kg. In multivariable analysis, patients receiving CBUs with GG-CTLA4 genotype had poorer neutrophil recovery (hazard ratio [HR], 1.33; P = .02), increased nonrelapse mortality (NRM) (HR, 1.50; P < .01), and inferior disease-free survival (HR, 1.41; P = .02). We performed the same analysis in a more homogeneous subset of cohort 1 (cohort 2, n = 305) of patients who received transplants for acute leukemia, all given a myeloablative conditioning regimen, and with available allele HLA typing (HLA-A, -B, -C, and -DRB1). In this more homogeneous but smaller cohort, we were able to demonstrate that GG-CTLA4-CBU was associated with increased NRM (HR, 1.85; P = .01). Use of GG-CTLA4-CBU was associated with higher mortality after CBT, which may be a useful criterion for CBU selection, when multiple CBUs are available.

Genetics of graft-versus-host disease: the major histocompatibility complex

Graft-versus-host disease (GVHD) is a potentially life-threatening complication of allogeneic hematopoietic cell transplantation. Many genes are presumed to be involved in GVHD, but the best characterized genetic system is that of the human major histocompatibility complex (MHC) located on chromosome 6. Among the hundreds of genes located within the MHC region, the best known and characterized are the classical HLA genes, HLA-A, C, B, DRB1, DQB1, and DPB1. They play a fundamental role in T cell immune responses, and HLA-A, C, and B also function as ligands for the natural killer cell immunoglobulin-like receptors involved in innate immunity. This review highlights the state-of-the art in the field of histocompatibility and immunogenetics of the MHC with respect to genetic risk factors for GVHD.

Immunogenetics of hematopoietic stem cell transplantation: the contribution of microsatellite polymorphism studies

Polymorphisms of short tandem repeats of <10 nucleotides, or microsatellites (Msat), are largely used for post-transplant chimerism analyses in clinical hematopoietic stem cell transplantation (HSCT). Compared to single nucleotide polymorphisms (SNP), they have the advantage of a higher degree of allelic polymorphism and thus a potentially larger degree of informativity. Msat markers contribute to approximately 3% of the human genome and have been highly informative in disease association studies, population genetics, forensic medicine and organ and HSC transplantation. They allowed to expand our knowledge of the haplotypic structure of the HLA complex, including the noncoding sequences in the MHC, and to reach a better characterization of immunological phenotypes. Among the different immunogenetic studies in HSCT patients reviewed here, four Msat loci linked to cytokine genes have been analysed by a number of laboratories as potential candidates markers for HSCT outcome: IFNG, TNFd, IL-10(-1064) and IL-1RN. The low patient numbers and high diversity of clinical parameters account for some heterogeneity of the results. Among the trends starting to emerge from these studies, specific TNFd Msat alleles seem to be associated with acute graft-versus-host disease and mortality. Patient/donor Msat incompatibilities have also been used as surrogate markers to map biologically relevant polymorphisms, with a main focus on MHC-resident genetic variation. High throughput SNP typing and next-generation sequencing technologies will allow acquisition of large-scale genomic data and should allow refined analyses of clinically relevant genotypes in the transplantation settting, although the heterogeneity of the study cohorts will remain an issue. The analysis of Msat polymorphisms may still have a place in functional studies on the impact of Msat diversity in the control of immune response gene expression.

NCI, NHLBI first international consensus conference on late effects after pediatric hematopoietic cell transplantation: etiology and pathogenesis of late effects after HCT performed in childhood--methodologic challenges

Hematopoietic cell transplantation (HCT) is now a curative option for certain categories of patients with hematologic malignancies and other life-threatening illnesses. Technical and supportive care has resulted in survival rates that exceed 70% for those who survive the first 2 years after HCT. However, long-term survivors carry a high burden of morbidity, including endocrinopathies, musculoskeletal disorders, cardiopulmonary compromise, and subsequent malignancies. Understanding the etiologic pathways that lead to specific post-HCT morbidities is critical to developing targeted prevention and intervention strategies. Understanding the molecular underpinnings associated with graft-versus-host disease (GVHD), organ toxicity, relapse, opportunistic infection, and other long-term complications now recognized as health care concerns will have significant impact on translational research aimed at developing novel targeted therapies for controlling chronic GVHD, facilitating tolerance and immune reconstitution, reducing risk of relapse and secondary malignancies, minimizing chronic metabolic disorders, and improving quality of life. However, several methodological challenges exist in achieving these goals; these issues are discussed in detail in this paper.

Gene expression profile of cytokines in patients with chronic graft-versus-host disease after allogeneic hematopoietic stem cell transplantation with reduced conditioning

There are no reliable markers useful to predict the onset or the evolution of chronic graft-versus-host disease (cGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT), although several candidate biomarkers have been identified from limited hypothesis-driven studies. In this study we evaluated 14 patients who received a reduced intensity conditioning HSCT. Seven patients had cGVHD, whereas 7 never developed cGVHD during the period of observation. The expression of 114 cytokines in immunoselected cell populations was explored by microarray analysis and 11 cytokines were selected for further evaluation by real-time PCR. Differential gene expression measurements showed a significant up-regulation for INFγ (interferon, gamma) in CD8+ and for TNFSF3 (tumor necrosis factor superfamily, member 3) and for TNFSF10 (tumor necrosis factor superfamily, member 10) in CD14+ cell population when comparing cGVHD with control samples. The expression levels were significantly decreased for TNFSF10 in CD8+ cell population and for TNFSF12 (tumor necrosis factor superfamily, member 12) and for PDGFβ (platelet-derived growth factor, beta) in CD4+. Our data seem to suggest that different immune populations can play a role in cGVHD pathogenesis and the early detection of gene expression profile in these patients could be useful in the monitoring of GVHD. We hypothesized that PDGFβ down-regulation could represent a negative feedback to compensate for enhanced expression of its receptor recently reported.

Tumor necrosis factor-alpha gene polymorphisms are associated with severity of acute graft-versus-host disease following matched unrelated donor bone marrow transplantation in children: a Pediatric Blood and Marrow Transplant Consortium study

Tumor necrosis factor (TNF)-alpha plays a significant role in conditioning related toxicities and the development of acute graft-versus-host disease (aGVHD). TNF-alpha gene polymorphisms are associated with rejection after organ transplantation and aGVHD in matched related donor blood and marrow transplantation (BMT) recipients. Few studies have been published on unrelated donor BMT in the pediatric age group. In this study, we examined the relationship between specific polymorphisms in TNF pathway genes and the occurrence and severity of aGVHD. Recipient single-nucleotide polymorphisms (SNPs) in TNF-alpha and TNF receptor superfamily members 1A (TNFRSF1A) and 1B (TNFRSF1B) were investigated. In a multi-institutional Pediatric Blood and Marrow Transplant Consortium trial, a total of 180 pediatric patients (mean age, 11.0 years) were prospectively evaluated for clinical outcomes after matched unrelated donor BMT. All patients received myeloablative conditioning and two-drug GVHD prophylaxis with cyclosporine or tacrolimus, with methotrexate in the majority of patients. TNF-alpha genotypes were not correlated with the overall incidence of aGVHD. Significant associations were seen between TNF-alpha variant alleles and the severity of aGVHD (grade II-IV and grade III-IV), especially when analyzed in whites only (n = 165). Grade II-IV aGVHD was correlated with recipient -857T allele (hazard ratio [HR], 0.47; P = .04), -238A allele (HR, 1.76; P = .002), and d3/d3 genotype (HR, 0.64; P = .03). Severe (grade III-IV) aGVHD was associated with TNF-alpha -1031C allele (HR, 2.38; P = .03), -863A allele (HR, 3.18; P = .003), and d4/d4 genotype (HR, 2.82; P = .01). After adjusting for clinical factors, the association of -1031C, -863A, -238A, and d4/d4 genotypes with severity of aGVHD remained statistically significant. No correlation between selected SNPs in TNFRSF1A or TNFRSF1B and the incidence or severity of aGVHD was found. Our findings indicate clinically important relationships between genetic polymorphisms in TNF-alpha and the severity of aGVHD in this cohort. Improved understanding of this relationship may allow for a risk-adjusted approach to GVHD prevention in pediatric BMT.

Risk assessment in haematopoietic stem cell transplantation: Pre–transplant patient and donor factors: non-HLA genetics

Non-HLA genetics involving the study of single-nucleotide polymorphisms (SNPs) and microsatellites of cytokine and cytokine receptor genes, and as well as genes associated with response to infection and therapeutic drugs, are currently being studied for associations with diseases, including autoimmune disease, cancer and solid-organ transplant rejection. This chapter will summarize the potential role of non-HLA genetics in predicting outcome of haematopoietic stem-cell transplantation (HSCT) and how genotyping for non-HLA genes may give insight into the immunobiology of HSCT complications, including GvHD and infectious episodes. Future directions - including the role of pharmacogenomics, use of the research results for individualized medicine, and interpretation of data - will also be discussed.

New directions in the genomics of allogeneic hematopoietic stem cell transplantation

Despite optimal supportive care and high-resolution HLA matching, complications such as GVHD and infection remain major barriers to the success of allogeneic HCT (allo-HCT). This has led to growing interest in the non-HLA genetic determinants of complications after allo-HCT. Most studies have examined genetic predictors of GVHD, relapse, and mortality and have focused on 3 main areas: minor histocompatibility antigen (miHAs), inflammatory mediators of GVHD, and more recently NK cell-mediated allorecognition. The genetic basis of other outcomes such as infection and drug toxicity are less well studied but are being actively investigated. High-throughput methodologies such as single nucleotide polymorphism arrays are enabling the study of hundreds of thousands of genetic markers throughout the genome and the interrogation of novel genetic variants such as copy number variations. These data offer the opportunity to better predict those at risk of complications and to identify novel targets for therapeutic intervention. This review examines the current data regarding the non-HLA genomics of allo-HCT and appraises the promises and pitfalls for integration of this new genetic information into clinical transplantation practice.

Role of non-HLA genetic polymorphisms in graft-versus-host disease after haematopoietic stem cell transplantation

Graft-versus-host disease (GvHD) is the main complication after haematopoietic stem cells transplantation (HSCT) and acute forms (aGvHD) occur in 20-40% of cases even after donor (D) and recipient (R) HLA matching, apparently because of D/R minor histocompatibility antigen (mHA) mismatches and cytokine polymorphisms. The genotype of cytokines and mHA of 77 haematological R following HSCT from HLA identical siblings were determined to detect genetic polymorphisms correlated with GvHD. We analysed TNFA (-863 C/A, -857 C/T and G/A at positions -574, -376, -308, -244, -238), IL-10 (-1082 G/A, -819 C/A, -592 C/T), IL-1B (T/C +3953), IL-1RA (VNTR), HA-1 (H/R allele) and CD-31 (C/G at codon 125, A/G at codon 563). Allele frequencies were in Hardy-Weinberg equilibrium and similar to those of 77 healthy controls. We observed positive correlations between a lower risk of clinically significant aGvHD and both the presence of -1082G -819C -592C IL-10 haplotype when both R and D are considered together and the absence of R IL-1RA allele 2. Furthermore, we observed an association between the absence of TNF-A -238 A allele and the risk of extensive chronic GvHD. mHA and cytokines genotyping would thus seem a valid source of information for the prior identification of recipients with a higher risk of aGvHD.

Donor selection for unrelated cord blood transplants

The number of unrelated cord blood transplants is increasing, with more than 8000 patients reported worldwide. Criteria of donor choice have been identified. Cell dose measured by number of nucleated cells is the most important factor, thus increases in cell dose can partially overcome the presence of HLA incompatibilities. Overall, increasing the number of HLA incompatibilities is associated with non-engraftment, but it also decreases the risk of relapse in patients with malignant disease, resulting in an absence of effect of HLA incompatibilities on event-free survival (survival without relapse or complications related to the transplant). However, in patients with non-malignant disorders, increasing the number of HLA incompatibilities decreases the overall survival. These results show that criteria of donor choice based on number of infused cells, number of HLA incompatibilities and diagnosis improve outcomes of unrelated cord blood transplants. Currently, owing to the possibility of using a non HLA identical donor, most patients can find a donor, increasing the need for the development of the inventory of cord blood banks. Methods of improving engraftment are currently under investigation.

Association of TNFd and IL-10 polymorphisms with mortality in unrelated hematopoietic stem cell transplantation

BACKGROUND

Non-HLA immunogenetic polymorphisms may influence outcome of hematopoietic stem cell transplantation (HSCT). In this study, we have determined the role of TNFa, TNFd, IL-10, IL-1, IL-1Ra, and IL-4R polymorphisms in patients transplanted with HSC of an unrelated donor.

METHODS

The allelic variants of four SNPs (IL-10-1082, IL-1beta-511, IL-4R-3223, IL-4R-1902) and four microsatellites (TNFa, TNFd, IL-10-1064, IL-1Ra) were determined in 131 unrelated patient/donor pairs typed for HLA-A/B/C/DR/DQ (four digits).

RESULTS

The allelic distribution of the polymorphisms was similar to that previously reported in Caucasoid populations. Patient and donor TNFd and patient IL-10-1064 polymorphisms correlated with mortality in univariate analysis. Patients with TNFd1/d2/d3 genotypes had 3-year survival rates of 65%. A gradual decrease in survival rates was observed for patients with TNFd3/d3 genotypes (50%, p=n.s.), TNFd4 (46%, P=0.08), and TNFd5 (33%, P=0.03). A multivariate analysis of 10/10 matched patients revealed that the following patient genotypes correlated with lower survival: TNFd3/d3 (RR 4.08, P=0.026) TNFd4 (RR 3.78, P=0.032) and TNFd5 (RR 6.69, P=0.021) all compared to TNFd1/d2/d3 genotypes. Patient IL-10 (12, 14, 15) microsatellite alleles correlated with lower 3-year survival (28%) when compared to IL-10 (<12) (56%, P=0.052) and to Il-10 (13) alleles (60%, P=0.0023). In multivariate analysis this correlation remained significant only in recipients of HSCT of 10/10 HLA matched donors (RR=2.96, P=0.038).

CONCLUSION

The data demonstrate a significant correlation of the TNFd and IL-10-1064 microsatellite polymorphisms with mortality after unrelated HSCT. They support the hypothesis that simple genomic tests, in addition to precise HLA matching, may contribute to determine prognosis in patients undergoing unrelated HSCT.

Genetics of Risk Factors for Graft-Versus-Host Disease

Modern understanding of the genetic basis of graft-versus-host disease (GVHD) in allogeneic hematopoietic stem cell transplantation (HSCT) involves knowledge of human leukocyte antigen (HLA), killer immunoglobulin-like receptors (KIR), cytokine genes, and their interactions. Insights into the immunogenetic basis of GVHD come from long-standing clinical experience in the use of myeloablative conditioning regimens and donor bone marrow as the grafting source. Under these circumstances, donor T-cell recognition of host HLA can cause GVHD. The recent elucidation of HLA class I as ligands for natural killer (NK) cell inhibitory KIR demonstrates that GVHD is the result of a complex interplay between the innate and adaptive immune responses. The extent to which T cells and NK cells contribute to clinical GVHD is a function of the host post-conditioning environment, immunosuppressive treatments, and the content of the graft source. The contribution of donor and host genetic differences in cytokine genes in modulating risks of GVHD has recently been recognized.

Multiplex Genotyping of Human Minor Histocompatibility Antigens

Minor histocompatibility antigens (mHAg) induce major histocompatibility complex-restricted, T cell-mediated immune responses that may contribute to increased risk of graft-versus-host disease and graft-versus-leukemia effects. Unlike human leukocyte antigen genes, mHAg are encoded by genetically and functionally unrelated genes located throughout the chromosome. The role of mHAg in stem cell transplantation and the population frequencies of mHAg alleles remain unknown due in part to the lack of suitable high throughput methods for genotyping these diverse genes. Here we describe the development and utility of a multiplexed Luminex assay for genotyping human mHAg, including HA-1, HA-2, HA-3, HA-8, HB-1, CD31(125), and CD31(563). The assay uses a multiplexed, allele-independent, gated amplification of mHAg genes followed by differential detection of allele-specific primer extension products using the MultiCode PLx system (EraGen Biosciences, Madison, WI). The alleles are interrogated using a multiplex allele-specific primer extension reaction using primers tagged with EraCodes. The products are hybridized to Luminex beads and the hybridization duplexes are detected using streptavidin-phycoerythrin. The assay resolved the mHAg genotypes of 259 Caucasian donors and provided population estimates of mHAg gene and phenotypic frequencies. All mHAg alleles evaluated in this study exhibited Hardy-Weinberg equilibrium, although some mHAg phenotypes were present in large majority of individuals tested (HA-2, HB-1). This assay will provide a valuable tool for determining mHAg frequencies in other ethnic populations, as well as for establishing the clinical importance of mHAg disparities in stem cell transplantation.

Non-HLA immunogenetics in hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) provides a unique environment in which to evaluate the role of immunogenetics of both the donor and the recipient to success of the procedure. The central role of HLA matching in HSCT has been established; however, recipients of allogeneic HSCT incur the risk of graft versus host disease (GVHD) even when the donor is a sibling who shares the major histocompatibility genes. Therefore, the perfect HLA match does not represent the optimal genetic make up. Other genetic systems operate and affect the various outcomes of HSCT, including GVHD, infections, transplant-related mortality, and overall survival. Minor histocompatibility antigens contribute to the control of GVHD as well as graft versus leukaemia reactions. In addition, genes controlling inflammatory processes, including cytokines, chemokines and their receptors, can modulate GVHD, and genes from both arms of the immune response (innate and adaptive) are strong candidates for susceptibility factors to infections in allogenic transplantation.

Human leukocyte antigen matching in cord blood transplantation

Cord blood transplants are now widely used for allogeneic hematopoietic stem cell transplants (HSCT) in patients with various hematologic disorders. One advantage of this source of stem cells is the decrease of graft-versus-host disease (GVHD) because of the immaturity of lymphocytes at birth. The role of human leukocyte antigen (HLA) for donor search and post-transplant outcomes is not very well described. The Eurocord Registry has analyzed more than 1,000 cases of unrelated cord blood transplants (UCBT). Results show that HLA matching is important for engraftment and graft versus leukemia but not for survival and GVHD. Allelic matching for HLA-A, -B, -C, -DRB1, and -DQB1 shows that the number of mismatches is very high and does not allow identification of prognostic factors. Contrary to the criteria of donor choice for an unrelated bone marrow transplant where HLA allelic matching is important, in the case of cord blood transplants the number of nucleated cells infused is the most important predictor of success.

IL-10 promoter gene polymorphism associated with the occurrence of chronic GVHD and its clinical course during systemic immunosuppressive treatment for chronic GVHD after allogeneic peripheral blood stem cell transplantation

BACKGROUND

The current study attempted to evaluate the association between IL-10 promoter gene polymorphism and transplant outcomes including the occurrence of chronic graft-versus-host disease (GVHD) and its clinical course during systemic immunosuppressive treatment (IST) among 60 recipients of cytokine-mobilized peripheral blood stem cell (PBSC) from HLA-matched sibling donors.

METHODS

We analyzed 3 single-nucleotide polymorphisms in proximal region of IL-10 promoter gene (-1082/-819/-592).

RESULTS

In the current study, only two haplotypes (1082*A/819*T/592*A [ATA] and 1082*A/819*C/592*C [ACC]) were found. An increased occurrence of chronic GVHD was noted dependent on the IL-10 haplotypes (43% vs. 68% vs. 96% in ACC/ACC vs. ATA/ACC vs. ATA/ATA haplotype, P=0.003). In a logistic regression based on multinomial model, ATA/ATA homozygote had 7-fold increasing risk of the development of chronic GVHD compared with ACC/ACC homozygote. The incidence of chronic GVHD at 1 year was 46%+/-20%, 64%+/-10%, and 82%+/-5% in ACC/ACC, ATA/ACC and ATA/ATA group, respectively (P=0.0266). Plus, the duration of systemic IST was significantly shorter in recipients without ATA-haplotype comparing with those with ATA haplotype (339 days vs. 1,146 days, P=0.0091).

CONCLUSION

IL-10 promoter gene polymorphism was found to be apparently associated with chronic GVHD after allogeneic peripheral blood stem cell transplantation from HLA-matched sibling donors.

Genomic screening and complications of hematopoietic stem cell transplantation: has the time come?

The occurrence of toxic complications following hematopoietic stem cell transplantation (HSCT) is highly variable and dependent on a multitude of host, donor, and treatment factors. The increasingly broad indications for HSCT and the need to provide this treatment option to older and/or more debilitated patients emphasizes the importance of refining our methods of predicting and ameliorating these toxicities. Late complications (occurring after day 100) also pose a threat to quality of life after HSCT. Genetic polymorphisms in key molecular pathways in the host are likely to contribute significantly to the observed variability in the development HSCT-associated complications. Hepatic veno-occlusive disease and acute lung injury, two of the most serious organ toxicities that occur, represent useful paradigms for the identification of genetic polymorphisms in enzyme systems that modulate local and systemic responses to oxidant stress during transplant conditioning therapy. Ongoing studies in this area are providing clues to the prevention of adverse clinical outcomes based on the genetic milieu. This review of studies in HSCT that explore genetic risk factors for transplant complications indicates that significant progress is being made in this rapidly evolving area. However, further large-scale clinical and translational studies are needed before genomic screening can be widely used to individualize treatment.

Genetic polymorphisms predicting the outcome of bone marrow transplants

Analysis of non-histocompatibility leucocyte antigen (HLA) functional genomics, together with conventional risk factors in haematopoietic stem cell transplantation (HSCT) can lead to predicting outcome in HLA-matched sibling transplant recipients. Polymorphisms of cytokine genes including tumour necrosis factor alpha, interleukin-10, interferon gamma and interleukin (IL)-6, associate with more severe acute graft-versus-host disease (aGvHD). Donor genotype for IL-1 receptor antagonist (IL-1Ra) has been associated with reduced aGvHD severity. Other genotypes (patient IL-1Ra, IL-6 and donor IL-1 alpha) have been associated with chronic GvHD, or overall survival (Vitamin D receptor and oestrogen receptor). Polymorphisms within genes associated with host defence/inflammatory responses (mannose binding lectin genes, myeloperoxidase genes and the FC gamma receptors) have been associated with infections. Polymorphisms of pharmacogenes, such as methylenetetrahydrofolate-reductase, have been associated with aGvHD and other post-transplant complications. The NOD2 gene polymorphism, associated with Crohn's disease, has been shown to be associated with risk of gut GvHD. The majority of the studies have been carried out in single centre HLA-matched sibling cohorts and in relatively few matched unrelated donor transplants. This review gives an overall perspective of the current field of non-HLA genetics with regard to HSCT outcome, clinical relevance and potential application of the results to clinical management of HSCT.

Cord blood transplantation in adult patients

Early clinical reports outlining outcomes for primarily pediatric patients undergoing UCB transplantation point to delayed time to hematopoietic recovery and favorable incidence and severity of GvHD. Recently, clinical reports in adult patients identified the feasibility of UCB transplantation for those patients lacking an available histocompatible-related or unrelated adult donor Intensive clinical and laboratory research is ongoing focused on strategies to foster UCB allogeneic donor engraftment thereby allowing wider application of this stem cell source for patients requiring allogeneic transplantation.

Clinical relevance of a newly identified HLA-A24-restricted minor histocompatibility antigen epitope derived from BCL2A1, ACC-1, in patients receiving HLA genotypically matched unrelated bone marrow transplant

Minor histocompatibility antigens (mHAs) are major histocompatibility complex (MHC)-associated peptides, which trigger T-cell responses that mediate graft versus host disease (GVHD) and graft versus leukaemia effects. We recently identified a new mHA epitope, termed ACC-1, which is presented by HLA-A*2402 and encoded by BCL2A1, whose expression is restricted to haematopoietic cells including leukaemic cells. HLA-A24/ACC-1 tetramer detected the presence of ACC-1-specific CD8+ cells in the peripheral blood of a patient up to 7 months following transplantation, and these tetramer-positive cells were expandable in vitro by ACC-1 peptide stimulation. A retrospective analysis of 320 patients with HLA-A*2402 who had received a human leucocyte antigen (HLA) genotypically matched unrelated donor through the Japan Marrow Donor Programme was conducted to determine whether ACC-1 disparity is associated with adverse clinical outcomes such as GVHD. Among these patients, ACC-1 disparity was detected in 55 (17.2%) donor/recipient pairs. After adjusting for known risk factors, the hazard ratios or odds ratios of acute and chronic GVHD, relapse and disease-free survival were not statistically different between patients receiving ACC-1 compatible and incompatible transplantation. These data suggest that disparity of haematopoietic cell-specific mHA, ACC-1, is unlikely at least to augment GVHD, and that T cells specific for ACC-1 may also be used for immunotherapy of recurring leukaemia without GVHD.

New Developments in Allotransplant Immunology

After allogeneic stem cell transplantation, the establishment of the donor’s immune system in an antigenically distinct recipient confers a therapeutic graft-versus-malignancy effect, but also causes graft-versus-host disease (GVHD) and protracted immune dysfunction. In the last decade, a molecular-level description of alloimmune interactions and the process of immune recovery leading to tolerance has emerged. Here, new developments in understanding alloresponses, genetic factors that modify them, and strategies to control immune reconstitution are described.

In Section I, Dr. John Barrett and colleagues describe the cellular and molecular basis of the alloresponse and the mechanisms underlying the three major outcomes of engraftment, GVHD and the graft-versus-leukemia (GVL) effect. Increasing knowledge of leukemia-restricted antigens suggests ways to separate GVHD and GVL. Recent findings highlight a central role of hematopoietic-derived antigen-presenting cells in the initiation of GVHD and distinct properties of natural killer (NK) cell alloreactivity in engraftment and GVL that are of therapeutic importance. Finally, a detailed map of cellular immune recovery post-transplant is emerging which highlights the importance of post-thymic lymphocytes in determining outcome in the critical first few months following stem cell transplantation. Factors that modify immune reconstitution include immunosuppression, GVHD, the cytokine milieu and poorly-defined homeostatic mechanisms which encourage irregular T cell expansions driven by immunodominant T cell–antigen interactions.

In Section II, Prof. Anne Dickinson and colleagues describe genetic polymorphisms outside the human leukocyte antigen (HLA) system that determine the nature of immune reconstitution after allogeneic stem cell transplantation (SCT) and thereby affect transplant outcomethrough GVHD, GVL, and transplant-related mortality. Polymorphisms in cytokine gene promotors and other less characterized genes affect the cytokine milieu of the recipient and the immune reactivity of the donor. Some cytokine gene polymorphisms are significantly associated with transplant outcome. Other non-HLA genes strongly affecting alloresponses code for minor histocompatibility antigens (mHA). Differences between donor and recipient mHA cause GVHD or GVL reactions or graft rejection. Both cytokine gene polymorphisms (CGP) and mHA differences resulting on donor-recipient incompatibilities can be jointly assessed in the skin explant assay as a functional way to select the most suitable donor or the best transplant approach for the recipient.

In Section III, Dr. Nelson Chao describes non-pharmaceutical techniques to control immune reconstitution post-transplant. T cells stimulated by host alloantigens can be distinguished from resting T cells by the expression of a variety of activation markers (IL-2 receptor, FAS, CD69, CD71) and by an increased photosensitivity to rhodamine dyes. These differences form the basis for eliminating GVHD-reactive T cells in vitro while conserving GVL and anti-viral immunity. Other attempts to control immune reactions post-transplant include the insertion of suicide genes into the transplanted T cells for effective termination of GVHD reactions, the removal of CD62 ligand expressing cells, and the modulation of T cell reactivity by favoring Th2, Tc2 lymphocyte subset expansion. These technologies could eliminate GVHD while preserving T cell responses to leukemia and reactivating viruses.