Genetic analysis of an inherited deficiency of the third component of complement in Brittany spaniel dogs.

Genetically determined C3 deficiency in Brittany spaniel dogs shares a number of biochemical and clinical characteristics with the human disorder. In humans, the gene for C3 deficiency is a null gene that is allelic to the structural gene for C3 and is not linked to the major histocompatibility locus. The current study used allotype analysis of canine C3 in order to demonstrate that the gene for C3 deficiency in these dogs is also a null gene allelic to the structural gene for C3. In addition, preliminary pedigree analysis suggests that the gene for canine C3 deficiency is apparently not closely linked to the major histocompatibility complex of the dog. Thus, it appears that C3 deficiency in Brittany spaniel dogs not only shares biochemical and clinical features with C3 deficiency in humans, but also shares some genetic characteristics with the human disorder.