Sequence analysis of exons 1, 2, 3, 4 and 5 of the HLA-B5/35 cross-reacting group.

The HLA-B5/35 cross-reacting group (CREG) is a set of closely related antigens including HLA-B35, B51, B52, B53 and B78. The nucleotide sequences of exon 1 through 5 of the B5/35 CREG were determined to assess the level of polymorphism. For exons 2 and 3, the previously described sequence-based typing (SBT) strategy was applied, the nucleotide sequences of exon 1, 4 and 5 were determined by allele-specific sequencing. A total of 225 unrelated individuals were HLA-B typed by heterozygous sequencing of exons 2 and 3. In the B5/35 CREG, 26 different alleles were identified, whereas 63 non-B5/35 CREG alleles were sequenced. The SBT strategy was proven to be reliable and efficient for high resolution typing of the B5/35 CREG. The nucleotide sequences of exon 1, 4 and 5 were determined for the 26 different B5/35 CREG alleles to establish the level of polymorphism. For seven different alleles, of which the exon 1, 4 and 5 sequences were hitherto unknown, the sequences were elucidated and in agreement with the known B5/35 sequences. Nineteen HLA-B5/35 CREG alleles with previously published exon 1, 4 and 5 sequences were sequenced in at least two individuals. Three new alleles were identified. The first, B5204, showed a difference at position 200 compared to B52011, which was previously considered a conserved position. The other two alleles, B3542 and B51015, showed exon 2 and 3 sequences identical to B35011 and B51011, but differences in exons 1 and 4, respectively. B3542 had differences at position 25 and 72 and B51015 showed a difference at position 636. More polymorphism might be present outside exons 2 and 3 than previously thought.