The impact of HLA matching on unrelated donor hematopoietic stem cell transplantation in Korean children

A walk through the development of human leukocyte antigen typing: from serologic techniques to next-generation sequencing

Human leukocyte antigen (HLA) is a group of glycoproteins encoded by the major histocompatibility complex (MHC) that plays a pivotal role in the host's immune defense. Given that the MHC represents the most polymorphic region in the human genome, HLA typing is crucial in organ transplantation. It significantly influences graft rejection, graft-versus-host disease, and the overall patient outcome by mediating the discrimination between self and nonself. HLA typing technology began with serological methods and has evolved rapidly alongside advances in molecular technologies, progressing from DNA-based typing to next- or third-generation sequencing. These advancements have increased the accuracy of HLA typing and reduced ambiguities, leading to marked improvements in transplantation outcomes. Additionally, numerous novel HLA alleles have been identified. In this review, we explore the developmental history and future prospects of HLA typing technology, which promises to further benefit the field of transplantation.

Clinical implications of HLA locus mismatching in unrelated donor hematopoietic cell transplantation: a meta-analysis

It remains controversial that the impacts of individual HLA locus mismatches on clinical outcomes of patients receiving unrelated-donor hematopoietic cell transplantation (HCT), as compared to HLA allele matched controls. We conducted a meta-analysis to address these issues. Four databases (PubMed, Embase, Web of Science and the Cochrane Library) were searched to select eligible studies. All donor-recipient pairs were high-resolution typing for HLA-A, -B, -C, -DRB1, DQB1 and DPB1 loci. Multivariate-adjusted hazard ratios (HRs) were extracted and pooled using a random-effects model. A total of 36 studies were included, with 100,072 patients receiving HCT. Surprisingly, we found that HLA-DQB1 locus mismatches had no significantly increased risk of multiple outcomes including acute and chronic graft-versus-host disease (GVHD), overall mortality and disease relapse (HR, 1.07; P = .153; HR, 1.07; P = .271; HR, 1.09; P = .230; HR, 1.07; P = .142 and HR, 1.02; P = .806, respectively). Mismatched HLA-DPB1 was significantly associated with a reduced risk of disease relapse (HR, 0.74; P < .001) but not with increased risks of transplant-related mortality (TRM) and overall mortality (HR, 1.09; P = .591; I² = 74.2% and HR, 1.03; P = .460, respectively). In conclusion, HLA-DQB1 locus mismatches is a permissive mismatching. HLA-DPB1 locus mismatches significantly protect against leukemia relapse. Refining effects of individual HLA locus mismatches contributes to predicting prognosis of patients receiving unrelated donor HCT.

Matched unrelated donor transplants-State of the art in the 21st century

Hematopoietic stem cell transplantation (HSCT) is the therapy of choice in many hematological malignant and non-malignant diseases by using human leukocyte antigen (HLA)-matched siblings as stem cell source but only one third of the patients will have HLA-matched siblings. Hence, physicians rely on the availability of matched unrelated donors (URD). The possibility of finding a matched URD is now more than 70% due to continuous expansion of URD registries around the world. The use of URD in adult patients is steadily increasing and in the last 8 years has superseded the numbers of matched sibling donor transplants and has become the most commonly used stem cell source. There is also an increasing trend to use peripheral blood (PB) stem cells rather than bone marrow (BM) stem cells. Outcomes following URD transplants depend mainly upon the indication and urgency of transplant, age and comorbidities of recipients, cytomegalovirus (CMV) matching/mismatching between donor and the recipient, and degree of HLA matching. In some studies outcome of unrelated stem cell transplants in terms of treatment-related mortality (TRM), disease-free survival (DFS), and overall survival (OS) is comparable to sibling donors.

Role of HLA in Hematopoietic Stem Cell Transplantation

The selection of hematopoietic stem cell transplantation (HSCT) donors includes a rigorous assessment of the availability and human leukocyte antigen (HLA) match status of donors. HLA plays a critical role in HSCT, but its involvement in HSCT is constantly in flux because of changing technologies and variations in clinical transplantation results. The increased availability of HSCT through the use of HLA-mismatched related and unrelated donors is feasible with a more complete understanding of permissible HLA mismatches and the role of killer-cell immunoglobulin-like receptor (KIR) genes in HSCT. The influence of nongenetic factors on the tolerability of HLA mismatching has recently become evident, demonstrating a need for the integration of both genetic and nongenetic variables in donor selection.

Peri-engraftment syndrome in allogeneic hematopoietic SCT

Engraftment syndrome (ES) and pre-engraftment syndrome (pre-ES) are both inflammatory conditions that occur after hematopoietic SCT (HSCT) and are characterized by non-infectious fever and skin rash. Although the pathogenesis is not fully understood, both syndromes are similar, and could be defined as a new clinical syndrome, named as peri-engraftment syndrome (peri-ES). We retrospectively analyzed the clinical records in 176 pediatric patients, following allogeneic HSCT. We utilized the definition of ES by Spitzer as the diagnostic criteria, excluding 'within 96 h of engraftment' criteria. Thirty cases developed peri-ES with a cumulative incidence of 17.0%. High cumulative incidence (50%) was seen in patients who underwent a double-unit cord blood transplantation (DUCBT; P<0.01). Clinical findings of peri-ES are similar, regardless of the onset day, and encephalopathy was the most severe complication. In the DUCBT cohort, the use of TBI and early complete chimerism (≤ day 21) were identified as risk factors that predispose the development of peri-ES. We determined that both, ES and pre-ES, might have similar causes, which could be included in peri-ES. Particularly, it occurred more in DUCBT patients, which means that not only neutrophil engraftment but also immune reactions within the two units might contribute to peri-ES.