The canine major histocompatibility complex. Population study of DLA-D alleles using a panel of homozygous typing cells.

The frequencies of 12 DLA-D alleles in a random canine population were determined in one-way mixed lymphocyte cultures using a panel of homozygous typing cells established in this laboratory. The homozygous typing cells served as stimulators for responder lymphocytes obtained from 160 random dogs. The results of these studies were compared to those with lymphocytes from 75 dogs in our research laboratory. DLA-D allelic frequencies were estimated by maximum likelihood techniques. The use of a relative response (RR) less than or equal to 5% as a definition of a typing response resulted in the recognition of a total allele frequency of 59% in dogs from the research laboratory. Three of the 12 DLA-D alleles were not detected. Typing responses of cells from random dogs to the 12 DLA-D alleles were determined using RRs less than or equal to 5%, less than or equal to 10%, less than or equal to 15%, and less than or equal to 20%. With RRs of less than or equal to 5%, less than or equal to 10%, and less than or equal to 15%, the total allele frequencies recognized were 39%, 47%, and 55%, respectively. Within each of these % RR ranges all but one of the DLA-D alleles were detected. With an RR less than or equal to 20% the total allele frequency recognized was 58% and all 12 alleles were detected. Our results indicate that an RR of less than or equal to 10% could be used to define a phenotypic DLA-D typing response in the dog. The level of allelic frequencies detected in both the research and random canine populations indicates the need to identify additional DLA-D alleles through expanded family studies using mixed lymphocyte culture and homozygous cell typing.