Sequence duplication at the 3' end of BoLA-DQB genes suggests multiple allelic lineages.

Full-length cDNAs encoding the DQB genes expressed by three BoLA class II haplotypes (DH8A, DH15B, and DH24A) were amplified by reverse-transcription polymerase chain reaction, cloned, and sequenced. The sequence data revealed that the DH8A haplotype expressed two DQB genes (DQB*1005 and DQB*1201) while the DH15B and DH24A haplotypes expressed the same single gene (DQB*0101). Comparison of the three alleles showed that the 3' untranslated (3'UT) sequence of the DQB*1201 allele contained a duplication of about 200 bp. This repeat was also found in other DQB alleles from cattle and sheep, but only in haplotypes with duplicated DQB genes. This 200-bp repeat and other features of the 3'UT may provide useful markers of DQB evolution, allowing us to distinguish and selectively amplify the different DQB loci.