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Between January 2018 and June 2021, the Ezer Mizion recruited 223,960 donors. All donors were typed for their HLA class I and II alleles at high resolution by Next Generation Sequencing techniques. Comparison between the sequences obtained from these donors and those in the IPD‐IMGT/HLA Database, revealed 122 Novel HLA alleles that were found in 133 donors. Most of the alleles, 94 (77%) were identified in the HLA class I genes (30, 35, and 29 in HLA‐A, ‐B, and –C, respectively), and 28 (23%) were detected in the HLA class II genes (9 in HLA‐DRB1 and ‐DQB1 and 10 in ‐DPB1). Most of these novel alleles, 106 (86.9%) comprised single nucleotide variation (SNV), 9 (7.4%) present multiple amino acids variation, 4 and 3 were generated because of deletions and insertions, respectively. Ten of these novel alleles were seen to be null alleles. [ABSTRACT FROM AUTHOR]

Between 2008 and April 2018, we recruited more than 37 000 potential Arab donors to the Hadassah Bone Marrow Donor Registry, all of whom were typed for high resolution HLA‐A, ‐B, and ‐DRB1. In addition, more than 22% of them were also typed for their HLA‐C and ‐DQB1 alleles. A comparison of the sequences obtained from these donors with the IPD‐IMGT/HLA Database showed 33 novel alleles from five loci (HLA‐A, ‐B, ‐C, ‐DR, ‐DQ). All of these novel HLA alleles were detected in the local Arab communities; 79% of these alleles have not been described in other groups yet and remain unique to the local Arab communities. [ABSTRACT FROM AUTHOR]

Aim: The Arab Bone Marrow Registry in Hadassah Medical Center collected HLA typings for 18,000 Arab adult donors. We used this information to estimate population allele and haplotype frequencies (HFs). Methods: We calculated HLA A∼B∼DRB1 HFs from 1,541 Christian Arab (CA) and 16,129 Muslim Arab (MA) donors typed by SBT, resolving phase and allelic ambiguity using Expectation Maximization. HFs were estimated at the four-digit level. Results: The most common CA haplotype was A∗33:01∼B∗14:02∼DRB1∗01:02 at a frequency of 1.6%, which is the fifth most common MA haplotype at 0.9%. This haplotype was the second ranked in the US Middle Eastern/North Coast of Africa (MENAFC) at 0.8% and is also a common Jewish haplotype. The most common MA haplotype was A∗01:01∼B∗52:01∼DRB1∗15:02 at 1.4%, which is ranked 41st in CA at 0.04%. This haplotype was ranked 12th in MENAFC at 0.26%. The fourth ranked haplotype for both CA and MA, A∗02:05∼B∗50:01∼DRB1∗07:01, is the most common in Saudi Arabia, Kuwait and Qatar and the fourth most common among Jewish populations. Average homozygosity for CA and MA for HLA-A, -B and -DRB1 was estimated at 6.7% and 6.2% while the top 30 haplotypes had a cumulative frequency of 25% and 19% respectively indicating higher MA genetic diversity. Interestingly, eight DRB1 alleles: 01:02, 03:01, 04:03, 07:01, 11:01, 11:04, 13:03 and 15:02 constituted over 63% of the allele frequencies for both CA and MA while 97% and 30% of patients served by the Arab registry had one or two of these alleles respectively. Additionally, DRB1∗03:01 occurred without the common Caucasian B∗08:01 association in about 85% of CA and MA donors. Clinical data showed that 40% of transplants were for Arab patients while others were for patients worldwide. Conclusions: Comparing CA and MA to other published HFs, it is clear that some haplotypes have migrated across populations while others remain isolated, thus adding these donors to the world registry is vital to increase genetic diversity for the benefits of all patients. [Copyright &y& Elsevier]