Evidence for an additional cattle DQB locus

Studying the genetic polymorphism of the major histocompatibility complex c lass II genes in cattle, we identified a sequence (KUH1) which resembles th ose encoding class II beta chains. The gene was shown to be transcribed in peripheral blood leukocytes. Sequence comparisons, Southern blot, and phylo genetic analyses indicate that (1) KUH1 represents a distinct DQB locus, wh ich we propose to designate BoLA-DQB5, (2) DQB5 constitutes an ancient DQB locus which diverged from a common ancestor gene prior to the duplication r esulting in DQB1 and DQB2, (3) DQB5 is associated with haplotypes which con tain DQA5 and a duplicated DQ region.