A novel HLA-B null allele (B*4022N) generated by a nonsense codon in the alpha 1 domain

We describe in this work a novel HLA-B null allele designated B*4022N. This new variant was found in a Caucasian individual who was serologically type d for one HLA-B allele as a B-blank, Bw-blank. Retrospective DNA typing by polymerase chain reaction using sequence-specific primers (PCR-SSP) has est ablished the correspondence of this blank allele with the classical HLA-B*4 001 allele. Nucleotide sequence analysis of exon 2 and 3 has revealed the p resence of two adjacent point mutations at position 170 and 171 of exon 2 ( GG to TT). While the first difference is silent, the second leads to the cr eation of a nonsense codon at position 58 of the alpha 1 domain, providing the most likely mechanism underlying the observed null phenotype.