Extended HLA-DPB1 polymorphism: an RNA approach for HLA-DPB1 typing

Most of the 119 human leukocyte antigen (HLA)-DPB1 alleles are defined by polymorphism in six hypervariable regions (HVRs) in exon 2 of the HLA-DPB1 gene. We investigated how DPB1 polymorphism is represented in the entire coding region. An RNA sequencing-based typing (SBT) approach was developed for the identification of HLA-DPB1 polymorphism from the 5′ untranslated region (UTR) through the 3′-UTR. B-cell lymphoblastoid cell lines, encoding 16 different DPB1 alleles, were studied. Results show additional HLA-DPB1 polymorphism in exons 1, 3, 4 and 5 and the 5′ and 3′-UTR. Four new HLA-DPB1 alleles were identified, DPB1*0502, DPB1*0602, DPB1*0802 and DPB1*0902, which have exon 2 sequences identical to other DPB1 alleles but differ in the extended region. The additional polymorphism represents two main polymorphic lineages in the DPB1 alleles. Among the HVRs in exon 2, only HVR F correlates with these two main lineages.