Kennedy, LJ, Barnes, A, Happ, G. M., Quinnell, R. J., Bennett, D., Angles, J. M.,
Day, M. J., Carmichael, N., Innes, J. F., Isherwood, D., Carter, S. D., Thomson, W,
Tissue Antigens. 2002;59, 3:194-204.
The DLA class II genes in the dog major histocompatibility complex are highly polymorphic.
To date, 52 DLA-DRB1, 16 DLA-DQA1 and 41 DLA-DQB1 allelic sequences have been assigned.
The aim of this study was to examine the intrabreed and interbreed variation of DLA
allele and haplotype frequencies in dogs, and to ascertain whether conserved DLA class
II haplotypes occur within and between different breeds. One thousand and 25 DNA samples
from over 80 different breeds were DLA class II genotyped, the number of dogs per
breed ranging from 1 to 61. DNA sequence based typing and sequence specific oligonucleotide
probing were used to characterize dogs for their DLA-DRB1, DQA1 and DQB1 alleles.
The high frequency of DLA class II homozygous animals (35%), allowed the assignment
of many haplotypes despite the absence of family data. Four new DLA alleles were identified
during the course of this study. Analysis of the data revealed considerable interbreed
variation, not only in allele frequency, but also in the numbers of alleles found
per breed. There was also considerable variation in the number of breeds in which
particular alleles were found. These interbreed variations were found in all three
DLA class II loci tested, and also applied to the three-locus haplotypes identified.
Within this data set, 58 different DLA-DRB1/DQA1/DQB1 three-locus haplotypes were
identified, which were all found in at least two different animals. Some of the haplotypes
appeared to be characteristic of certain breeds. The high interbreed, and relatively
low intrabreed, variation of MHC alleles and haplotypes found in this study could
provide an explanation for reports of interbreed variation of immune responses to
vaccines, viruses and other infections.