Salivary and serum interleukin 6 in primary Sjögren's syndrome

To measure interleukin 6 (IL-6) salivary and serum concentrations in primary Sjögren's syndrome (SS), to correlate these data with the clinical presentation in patients, and to determine if salivary IL-6 is reflective of local exocrine involvement or of the underlying autoimmune disorder.

Thirty-one patients with primary SS, 15 with primary biliary cirrhosis (PBC), and 14 healthy controls were studied. Parotid secretion was stimulated with 2% citric acid and collected using a Carlson-Crittenden collector. Concentrations of salivary and serum IL-6 were determined using a high sensitivity ELISA. Serologic autoimmune disease markers and salivary functional and histopathologic disease markers in the patients with SS were correlated with salivary and serum IL-6 levels.

Mean serum IL-6 concentrations were elevated in both patient groups (SS = 3.05 pg/ml, PBC = 3.07 pg/ml, healthy subjects = 0.843 pg/ml). Mean stimulated salivary IL-6 concentrations were elevated only in the patients with SS (16.21 pg/ml) compared to the PBC (1.07 pg/ml) and healthy subjects (0.769 pg/ml). No correlation was found between serum and salivary IL-6 concentrations for any group. Positive correlations were found between salivary IL-6 concentrations and serum IgG concentrations and between salivary IL-6 and erythrocyte sedimentation rate. Higher IL-6 concentrations were associated with increased disease activity.

Salivary IL-6 concentration is elevated in SS compared to healthy subjects and patients with another systemic autoimmune disease without salivary gland involvement. Elevated salivary IL-6 concentrations in SS are reflective of local exocrine involvement and may serve as a useful monitor of disease activity.