Behçet's disease: possible role of secretory component deficiency, synovial inclusions, and fibrinolytic abnormality in the various manifestations of the disease.

Detailed study of four patients with BD, four controls with recurrent aphthous stomatitis, and 12 healthy controls has demonstrated markedly decreased levels of salivary SC in both its free and bound forms, and normal total protein concentration in BD salivas. In two BD patients, SC deficiency was also found in jejunal fluids. Depressed in vitro response of blood T cells to mitogens was also noted in BD. Levels of IgA in serum were normal, as well as total numbers of T cells and IgA-carrying B cells in blood. A fluid phase abnormality of the fibrinolytic system as tested by the clot lysis assay was demonstrated in the blood from BD patients. Studies of BD SF and synovial membrane by light and electron microscopy showed inclusions composed of degenerated neutrophils inside monocytes. Abnormalities of host defense mechanisms at the mucous membrane level due to SC deficiency, together with a systemic T cell functional defect and fibrinolytic abnormality, could be important mechanisms in the pathogenesis of recurrent mucosal ulcers and thrombosis in BD.