Abstract
Human leukocyte antigen (HLA) allele and haplotype frequency distribution varies widely between different ethnicities and geographical areas. Matching for HLA alleles is essential for successful related and unrelated stem cell transplantation. Among the Saudi population, data on HLA alleles and haplotypes are limited. A cross-sectional study was performed on 28,927 bone marrow donors. The most frequent HLA alleles were HLA-A*02:01:01G (20.2%), A*24:02:01G (7.5%); B*51:01:01G (19.0%), B*50:01:01G (12.3%); C*06:02:01G (16.7%), C*07:02:01G (12.2%); DRB1*07:01:01 (15.7%), DRB1*03:01:01G (13.3%); DQB1*02:01:01G (29.9%), DQB1*03:02:01G (13.2%); and DPB1*04:01:01G (35.2%), DPB1*02:01:02G (21.8%). The most frequent HLA-A~C~B~DRB1~DQB1 haplotypes were A*02:01:01G~C*06:02:01G~B*50:01:01G~DRB1*07:01:01G~DQB1*02:01:01G (1.9%) and A*02:05:01G~C*06:02:01G~B*50:01:01G~DRB1*07:01:01G~DQB1*02:01:01G (1.6%). The most frequent HLA-A~C~B~DRB1~DQB1~DPB1 haplotypes were A*02:01:01G~C*15:02:01G~B*51:01:01G~DRB1*04:02~DQB1*03:02:01G~DPB1*04:01:0G (1%) and A*02:01:01G~C*07:02:01G~B*07:02:01G~DRB1*15:01:01G~DQB1*06:02:01G~ DPB1*04:01:01G (0.9%). Based on these haplotype frequencies, we provide forecasts for the fraction of patients with full matching and single mismatched donors for 3 to 6 loci depending on the registry size. With one million donors, about 50% of the patients would find an 8/8 match and 90% a 7/8 match. These data are essential for registry planning, finding unrelated stem cell donors, population genetic studies, and HLA disease associations.
Highlights
The human leukocyte antigen (HLA) system is encoded by the most polymorphic genes known, located on the short arm of chromosome 6 [1]
A total of 103 HLA-A alleles, 154 HLA-B alleles, 76 HLA-C alleles, 96 HLA-DRB1 alleles, 37 HLA-DQB1 alleles, and 48 HLADPB1 alleles were found in our cohort
Four new alleles were identified in this Saudi cohort (HLA-A∗02:433, HLA-A∗02: 434, HLA-C∗14:02:13, and HLA-DRB1∗14:145); the data are available on Allele frequency and published [14,15,16]
Summary
The human leukocyte antigen (HLA) system is encoded by the most polymorphic genes known, located on the short arm of chromosome 6 [1]. Recent advances in sequencing technologies helped in unraveling a vast number of new HLA alleles. The HLA system plays an essential role in activating the immune system through the presentation of processed antigens to CD4+ and CD8+ T cells. HLA is a key player in the success of organ and stem cell transplantation. Mismatch in both HLA class I and II alleles between donor and recipient is a major cause of organ rejection, graft failure, and graft-vs host disease following hematopoietic stem transplantation [3]. Certain HLA alleles were found to be associated with autoimmune diseases, such as ankylosing spondylitis, Type I diabetes, Behçet’s disease, celiac disease, and rheumatoid arthritis [4]
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