Histocompatibility studies in a closely bred colony of dogs. 3. Genetic definition of the DL-A system of canine histocompatibility, with particular reference to the comparative immunogenicity of the major transplantable organs.

The segregation of the canine DL-A leukocyte group antigen(s) b, c, d, e, f, g, h, k, l, and m has been traced in 141 consecutive matings in the Cooperstown Colony of beagles. All of the leukocyte antigen(s) were regularly transmitted en bloc from parent to offspring, with no instance of independent segregation. A total of 23 haplotypes, including six different DL-A antigen patterns (gl, bkhfm, bkcd, e, be, fgl) was observed. 31 different DL-A phenotypes were observed in a population of 100 mongrel dogs. A number of statistically significant positive and negative associations between individual DL-A antigenic components occurred in this population. The results support the concept of the DL-A system as a complex immunogenetic system governed by a single region (or locus) of an autosomal pair of chromosomes. Studies of skin, kidney, heart, and liver allografts in the Cooperstown Colony indicated that the longest allograft survivals occur under genetically and serologically defined conditions of donor-recipient DL-A compatibility. Skin and renal allografts generally behaved in parallel fashion, while cardiac allografts survived for longer periods of time (MST = 47.1 days) than kidneys (MST = 28.1 days) or skin (MST = 25.1 days) under conditions of DL-A identity. Heart transplants were rejected at a more rapid rate than kidney, however, in DL-A-incompatible donor-recipient combinations. Liver transplants were accorded the longest survival time (MST = 76.2 days) under conditions of DL-A identity, but were rejected at a rapid rate (MST = 5 days) in DL-A-incompatible nonlittermate donor-recipient pairs. The results provide further evidence that the DL-A system is the principal system of histocompatibility in the canine species. The differences in survival of different organs under similar conditions of donor-recipient DL-A compatibility suggest, however, the existence of a number of unknown variables which may also be capable of significantly affecting allograft behavior.