IL-1 receptor antagonist in saliva; characterization in normal saliva and reduced concentration in Sjögren's syndrome (SS).

The characterization of a salivary factor cross-reacting with IL-1 receptor antagonist (IL-1Ra) is described. The apparent molecular weights of two species were 23 kD, consistent with the secreted peptide (sIL-1Ra), and 20 kD, consistent with the intracellular peptide (icIL-1Ra). It had an inhibitory activity on IL-1-stimulated fibroblasts, which is characteristic of IL-1Ra. Its source was the oral mucosa and not the salivary glands. Saliva from patients with SS contained significantly less IL-1Ra than saliva from controls. The decrease was marked in patients with early dental loss but whose xerostomia was still partial. In SS, the salivary IL-1/IL-1Ra imbalance may promote inflammatory lesions in the mouth and impede mucosal cell differentiation.