Platelet involvement in salivary gland inflammation in patients with primary Sjögren's syndrome.

Seventeen consecutive patients under evaluation for Sjögren's syndrome (SS) had a lower lip salivary gland biopsy performed. Using a monoclonal mouse immunoglobulin against human platelet glycoprotein Ib in an indirect immunoperoxidase technique, it was found that platelets accumulate intravascularly in the inflamed salivary glandular areas. Platelets were demonstrated in the interstitial tissue of inflamed salivary glands from two patients. Saliva from 17 consecutive patients with previously well-established primary SS and 11 healthy controls, and blood from 11 of the patients and all controls were then examined for platelets and the platelet-specific release product beta-thromboglobulin (beta-TG). Platelets were not demonstrated in saliva from patients or controls. beta-TG was detected in saliva from five patients (11-150 ng/ml), but in none of the controls. There were no correlations between saliva beta-TG levels and saliva secretion rates or plasma beta-TG levels. We conclude that platelet release of beta-TG into saliva in patients with primary SS most likely is a result of immunoinflammatory reactions in salivary glands. Measurement of beta-TG in saliva may be of value in the estimation of disease activity.