Molecular, serological and genetic studies on two new HLA-DRB1 alleles - HLA-DRB1*0704 and HLA-DRB1*1507

Two new HLA-DRB1 alleles (DRB1*0704 and DRB1*1507) were detected during routine polymerase chain reaction (PCR)-based typing of two Caucasoid bone marrow panel donors due to apparent DRBI* "blanks" being associated with unexpected DRB4, DRB5 and DQB1 alleles. HLA-DRB1*0704 differed from DRB1*0701 by five consecutive nucleotides at positions 217 to 221 of exon 2 encoding two amino acids substitutions of tyrosine to asparagine at codons 77 and valine to tyrosine at codon 78. DRB1*1507 differed from DRB1*1501 by a single nucleotide at position 127 encoding an amino acid substitution of phenylalanine to tyrosine at codon 47. Their specificities were unequivocally assigned by serology as HLA-DR7 and DR15, respectively, and family and population studies allowed their likely HLA-A,B,C,DR,DQ and complement (Bf, C4A, C4B) bearing haplotypes to be identified. No further examples were found in 19,113 HLA-DR,DQ typed donors from the Welsh Bone Marrow Donor Registry indicating that both these alleles have a phenotype frequency of <0.01% and a gene frequency of <0.00003.