Key words: DLA; MHC; dogs; genetics Acknowledgment: L.J.K. is supported by a grant from the Wellcome Trust. Received 4 September, revised, accepted for publication 18 November 1998 Copyright c Munksgaard 1999 Tissue Antigens . ISSN 0001-2815 Tissue Antigens 1999: 53: 184–189 Printed in Denmark . All rights reserved 184 L.J. Kennedy DLA-DRB1 polymorphisms in dogs defined S.D. Carter by sequence-specific oligonucleotide probes A. Barnes S. Bell (SSOP) D. Bennett B. Ollier W. Thomson Abstract: To date, DNA sequences for 29 dog DLA-DRB1 alleles have been reported. However, no data exists on the frequencies of these alleles within the general dog population, nor is there any indication of whether there is interbreed variation of allele distribution. We have addressed this by estab- lishing a molecular based sequence-specific oligonucleotide probing (SSOP) method to identify all of the known broad DRB1 types and we have used this to type a random panel of dogs. A series of oligonucleotide probes were designed to detect known polymorphisms in the three DRB1 hypervari- able regions, together with two distinctive motifs in other regions of exon 2. This set of probes enabled us to assign broad DRB1 types. Two hundred and eighteen dogs were SSOP typed for DRB1. All but 4 of the published DLA-DRB1 alleles were identified in these animals. Interbreed variation in both allele distributions and allele frequencies were observed, which may be useful in the study of genetic variation between breeds. This variation also has implications for the selection of control groups for studies aimed at identifying MHC associations with disease susceptibility in the dog. The canine major histocompatibility complex (MHC), also referred to as the dog leukocyte antigen (DLA) complex, has been previously characterised using serological and cellular techniques. Three inter- national workshops on canine immunogenetics (1–4), have demon- strated that the DLA system is similar to the MHC in other species, including man. Serological data from these workshops suggested three class I loci, DLA-A, -B and -C. Mixed lymphocyte culture (MLC) was used to demonstrate a DLA-D class II locus. In the dog, DLA-A, -B and -C are expressed on all lymphocytes, and it was assumed that they were the equivalent of HLA-A, -B and -C in humans. Other data, however, demonstrated that DLA-B was a class II molecule, (5–9) and thus, all canine lymphocytes express DLA class II on their surface. Despite the widespread use of the dog as a model in transplan- tation biology, analysis of the canine MHC using molecular methods has only begun recently. Initially, human class II cDNA probes were Authors’ affiliations: L.J. Kennedy 1 , S.D. Carter 2 , A. Barnes 2 , S. Bell 2 , D. Bennett 3 , B. Ollier 1 , W. Thomson 1 1 School of Epidemiology and Health Sciences, University of Manchester, Manchester, UK, 2 Veterinary Clinical Science, University of Liverpool, Liverpool, UK, 3 Veterinary Clinical Studies, University of Glasgow, Glasgow, UK Correspondence to: Lorna Kennedy School of Epidemiology and Health Sciences University of Manchester Stopford Building Oxford Road Manchester M13 9PT UK Fax: π44 161 275 5043 E-mail: Lorna/fs1.ser.man.ac.uk