Clinical and laboratory features of canine lupus syndromes.

Determination of the specificities of antinuclear antibodies in the sera of 20 dogs presenting with symptoms of a lupus-like syndrome permitted their separation into 2 groups. The first group of 14 dogs all had antibody activity to DNA-histone antigen(s), and 4 of them also had antibodies to native DNA (nDNA). The Farr test with standard buffer was found to be unsatisfactory for the measurement of anti-nDNA antibodies in dog sera due to a high incidence of false positive reactions; these could be eliminated by the inclusion of sodium dodecyl sulfate in the buffer system. The second group of 6 dogs was characterized by the presence of antibodies to extractable nuclear antigen. In every serum tested diseased dogs had a diminished level of circulating thymic factor as compared to controls of the same age, suggesting that a diminution of suppressor T cells may be an etiologic factor.