BIOCHEMICAL-CHARACTERIZATION OF BOVINE MHC DQ ALLELIC VARIANTS BY ONE-DIMENSIONAL ISOELECTRIC-FOCUSING

Previous studies on expressed bovine MHC class II polymorphism using o ne-dimensional isoelectric focusing (1D-IEF) allowed the identificatio n of at least 12 allelic variants of the DRB3 gene. So far, only limit ed data have been available on the expression of other class II genes. The present study involved biochemical analysis of bovine MHC class I I molecules using a set of monoclonal antibodies presupposed to be bov ine DR and DQ reactive. After essential modification of the standard e lectrophoresis conditions used for ID-IEF typing of bovine DR products , biochemical polymorphism was observed for non-DR molecules, revealin g polymorphic sets of basic and acidic focusing bands. Because of the extensive DNA polymorphism described for bovine DQA and DQB genes, and the apparent similarity with the focusing pattern of human DQ product s, these molecules were considered to be the bovine DQ homologues. The definition of the DQ-associated banding patterns was made possible by using two half-sib sire families. Four different DQA-like patterns an d nine DQB-like patterns were detected. Segregation of the DQ types wa s supported by serological class I and class II typing. These results show that it is now possible to discriminate between expressed bovine DR and DQ polymorphism.