Inheritance of serum autoantibody, reduced serum IgA and autoimmune disease in a canine breeding colony.

Immunological parameters were examined in 113 English cocker spaniel dogs from two breeding kennels. Dogs from kennel 1 (n = 86) were grouped as having idiopathic cardiomyopathy (n = 19), autoimmune or other disease (n = 7) or being clinically normal (n = 60). Dogs from kennel 2 (n = 27) were all clinically normal and used for comparative purposes. There was a high incidence of serum antinuclear antibody (ANA) amongst all groups from kennel 1 (39/82 dogs tested), with anti-thyroglobulin and anti-erythrocyte antibodies also recorded in a dog with systemic lupus erythematosus. Thirty percent of dogs with idiopathic cardiomyopathy had anti-mitochondrial antibody. Thirteen dogs from kennel 1 had reduced serum IgA (< or = 0.3 mg/ml), but there was no consistent abnormality in the concentration of serum IgG, IgM, complement C3 or C4 in these thirteen dogs, or other dogs from this kennel. No immunological abnormality was recorded in dogs from kennel 2. Pedigree analysis of dogs from kennel 1 revealed inheritance of autoimmune disease, serum ANA and low serum IgA within several breeding lines. Inheritance of idiopathic cardiomyopathy was recorded through three generations and a strong association demonstrated between the presence of this disorder and a particular complement C4 phenotype (C4: 4).