Circulating immune complex concentrations in selected cases of skin disease in dogs.

Serum samples from 25 clinically normal dogs and 137 base-line serum samples from dogs with skin disease were assayed blindly for presence of circulating immune complexes (CIC). The method used was a solid-phase C1q-binding enzyme-linked immunosorbent assay. This assay detected only IgG-containing CIC that were capable of binding C1q. Statistical analysis revealed that dogs with systemic lupus erythematosus, discoid lupus erythematosus, generalized demodicosis, and recurrent staphylococcal pyoderma had significantly higher mean CIC concentrations than did normal dogs. Dogs with other skin diseases had mean CIC concentrations indistinguishable from those of normal dogs. Presence of CIC in dogs with these dermatopathies may have pathogenetic significance or may be the result of the disease process. Further studies are necessary to define the antigens contained in the immune complexes and the importance of CIC in skin disease of dogs.