POLYMORPHISM OF BOVINE MHC CLASS-II GENES - JOINT REPORT OF THE FIFTHINTERNATIONAL BOVINE LYMPHOCYTE ANTIGEN (BOLA) WORKSHOP, INTERLAKEN, SWITZERLAND, 1-AUGUST-1992

Polymorphism of the bovine DRB, DQA, DQB, DYA, DOB and DIB genes was i nvestigated using restriction fragment length polymorphism (RFLP) anal ysis, isoelectric focusing (IEF), class II serology and polymerase cha in reaction (PCR) based typing techniques. The simultaneous applicatio n of multiple typing techniques and the characterization of multiple g enes resulted in a greatly enhanced picture of the bovine class II reg ions. Thirty-eight class IIa (DR-DQ) and 5 class IIb (DYA-DOB-DIB) hap lotypes were defined. It was found that IEF types were associated with DRB3 polymorphism defined by DRB3 PCR-RFLP and DRB3 microsatellite PC R. Serologically defined polymorphism was associated with distinct mol ecular/IEF motifs and, therefore, DR and DQ specificities could be ten tatively distinguished. Although the DR and DQ genes are tightly linke d, neither DR nor DQ typing defined all of the class IIa region polymo rphism. Furthermore, even the most powerful DRB3 typing technique, DRB 3 PCR-RFLP, failed to detect all expressed DRB3 polymorphism. All dete cted DRB3 polymorphism could, however, be distinguished with a combina tion of two molecular techniques: DRB3 PCR-RFLP and DRB3 microsatellit e PCR. RFLP typing with transmembrane probes detected significantly le ss polymorphism than typing with cDNA or exon probes. However, the tra nsmembrane probes were useful because they were locus specific. The pr esence of only 5 of 12 possible class IIb haplotypes was unexpected an d indicates that the DYA, DOB and DIB genes are tightly linked.