Clinical and Prognostic Value of Discrepancies in Microsatellite DNA Regions Between Recipient and Donor in Human Leukocyte Antigen-Identical Allogeneic Transplantation Setting

Identifying the degree of major histocompatibility complex matching in genetically unrelated dogs with the use of microsatellite markers

BACKGROUND

The dog has served as an important experimental model for biomedical research such as transplantation and developing immunosuppressive agents. Although major histocompatibility complex (MHC) in dogs is a dominant factor of graft rejection, it has not been well investigated in dogs compared with human. For that reason, imprecise cross-matching or time-consuming sequence-based typing methods have generally been used to choose specific donor and recipient pairs. Investigation of matching distribution of MHC in dogs with the use of simple and accurate methods would be beneficial for biomedical researchers. The aim of this study was to identify the diversity of dog leukocyte antigen (DLA) types in genetically unrelated dogs by means of microsatellite markers.

METHODS

Thirty-three Beagle and Shih-Tzu dogs, which were negative in cross-matching, were chosen. The genomic DNA was isolated from peripheral blood leukocytes, and highly polymorphic short tandem repeats located in MHC class I and II were amplified with the use of specific primers.

RESULTS

Among all of the dogs, MHC matching groups, including class I full match-class II full match (M-M), class I full match-class II haplo match (M-H), class I haplo match-class II full match (H-M), class I haplo match-class II haplo match (H-H) groups, were ∼1.55%, 0.39%, 1.94%, and 6.59%, respectively. MHC class I nonmatch-class II nonmatch (U-U) groups were 58.14% of the total dogs.

CONCLUSIONS

Because differences of histocompatibility between donor and recipient leads to various allograft rejections, knowledge of the distribution of MHC matching in unrelated dogs would be helpful in designing studies and to get more accurate results from experiments using dog transplantation models.

Correlation between microsatellite discrepancy scores and transplant outcome after haemopoietic SCT for pediatric ALL

Microsatellite analyses show that self-reported ethnicity often correlates poorly with true genetic ancestry. As unknown ancestral differences could potentially have an impact on transplant outcome, we developed an average allele length discrepancy (AALD) score to assess allele length discrepancy between donor/recipient (D/R) using microsatellites analysed routinely in post-transplant chimeric assessment. This was then compared with outcome in a homogeneously treated cohort of pediatric patients undergoing high-resolution sibling or matched unrelated donor transplantation for acute lymphoblastic leukemia (ALL). AALD scores formed a numeric continuum ranging from 0 to 1.4 (median 0.76) for sibling pairs and 0.8-2.17 (median 1.6) for high-resolution matched unrelated donor (HR-MUD) pairs. There was a trend for worse OS with increasing AALD score, which reached statistical significance above a threshold of 1.7 for OS. Patients whose transplants had an AALD score of ⩾1.8 had a risk of non-relapse mortality 4.9 times greater (P=0.025) and relapse risk three times greater (P=0.058) than those scoring <1.8. This approach will now be explored in a Centre International for Blood and Marrow Transplantation Research (CIBMTR) study of 750 D/R pairs across all disease groups; if confirmed, it has the potential to improve donor selection for patients with multiple prospective donors.

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.