To compare salivary cytokine profiles in patients with primary Sjögren's syndrome (pSS), non-SS sicca controls, and non-sicca controls, and to investigate whether cytokine levels are correlated with clinical parameters of pSS patients.
Un-stimulated whole saliva samples were obtained from pSS patients (n=30) classified according to the criteria of the American European Consensus Group. Age- and gender-matched non-SS sicca patients (n=30) and non-sicca subjects (n=25) served as controls. Salivary IFN-γ, TNF-α, IL-1, IL-4, IL-6, IL-10, IL-12p40, and IL-17 levels were measured using a multiplex Luminex® bead-based assay.
pSS patients and non-SS sicca controls had significantly lower salivary flow rates (SFRs) than non-sicca controls, and pSS patients showed a more profound decrease than non-SS sicca controls. In addition, pSS patients and non-SS sicca controls had higher levels of IFN-γ, TNF-α, IL-1, IL-4, IL-10, IL-12p40, and IL-17 in their saliva than non-sicca controls. Salivary TNF-α levels were higher in pSS patients than in non-SS sicca controls. Th-1/Th-2 ratios, represented by INF-γ/IL-4 and TNF-α /IL-4 ratios, were significantly higher in pSS patients than in non-SS sicca controls. SFR was found to be correlated with INF-γ/IL-4 ratio (r=0.411 p=0.024), and focus score to be correlated with TNF-α/IL-4 ratio (r=0.581, p=0.023) in pSS patients.
Th-1, Th-2, and Th17 cytokine levels were found to be elevated in the saliva of pSS patients compared with non-sicca controls. However, considerable overlap was observed between the salivary cytokine levels of pSS patients and of non-SS sicca controls. The features that most differentiated pSS and non-SS sicca were higher TNF-α levels and Th-1/Th-2 ratios. Th-1/Th-2 ratio was also found to be correlated with the clinical parameters of pSS.