Antibodies to salivary duct cells, and other autoantibodies, in patients with Sjögren's syndrome and other idiopathic autoimmune diseases.

Sera from thirty patients with Sjögren's syndrome were studied for the presence of antibodies to salivary duct cells. In sixteen cases (53%) a positive result was obtained. The antibodies were present in the IgG globulins, in the IgM globulins also in nearly 50% of the IgG-positive cases, and rarely in the IgA globulins. One-third of the antibodies proved to be complement-fixing. No antibodies were found in normal controls matched for sex and age. An antinuclear factor (ANF) was demonstrated in 77% of the sera. A rheumatoid factor was shown in 48% of the sera using a modified Waaler–Rose test and in 100% using a Latex fixation test. Antibodies to smooth muscle were present in 19%. Antibodies to skeletal muscle, gastric parietal cells, thyroid antigens, adrenocortex and mitochondria were found in frequencies which did not differ significantly from those in matched controls. No correlation was demonstrated between antibodies to salivary duct cells and any of the other antibodies mentioned. Antibodies to salivary duct cells could only be absorbed with salivary gland tissue and not with other tissues. Antibodies to salivary duct cells were also found in patients with rheumatoid arthritis (22%), systemic lupus erythematosus (SLE) (18%) and myasthenia gravis (11%). They were extremely rare in patients with pernicious anaemia, autoimmune thyroiditis and idiopathic adrenocortical insufficiency. The antibodies could not be confirmed as being directed against the patient's own parotid tissue, probably due to loss of antigenic determinants as a result of the disease process. However, other findings support the opinion that Sjögren's syndrome is an idiopathic autoimmune disease.