Description of the first HLA–DRB1 null allele

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Abstract
We, in this paper, describe the identification of the novel human leukocyte antigen (HLA) blank allele DRB1*0710N that was detected in a male individual of Caucasian origin. The complete HLA class I typing was A*01, A*02, B*18, B*44, DRB1*0710N, DRB1*11, DQB1*02, and DQB1*03. Compared to DRB1*070101, the new variant is characterized by two consecutive nucleotide deletions at positions 175 and 176 of exon 2, leading to a frame shift that results in a stop codon (TAA), 6 bp further downstream. We identified three different possibilities as to which nucleotides were deleted to result in this non-expressed DRB1 allele. To verify the non-expression of the gene, an Epstein–Barr virus (EBV)-transformed B-lymphoblastoid cell line (B-LCL) of the individual was established and analyzed by flow cytometry for the cell surface expression of HLA–DRB1*07. Despite this non-expression of the cell surface protein, transcription of the DRB1*0710N sequence into messenger RNA (mRNA) was demonstrated.