Objective To investigate the expression of interleukin-17 in the salivary gland and peripheral blood of patients with primary Sjogren's syndrome (pSS).Methods Biopsy specimens of labial glands were collected from 30 patients and 5 controls.Immunohistochemistry examination was conducted to detect IL-17 expression cells (Th-17),while CD45RO and CD20 were tested by using monoclonal antibodies.IL-17 levels were assessed by ELISA in 30 pSS patients and 20 healthy controls.Results Th-17 cell numbers in the salivary glands of pSS patients with few infiltrating lymphocytes were lower than that with massive infiltrating lymphocytes (15±5 vs 21±8,P＜0.05).However,the percentage of Th-17 positive cells over the total infiltrating lymphocytes in the salivary glands of pSS patients with few infiltrating lymph-ocytes was higher than that with massive infiltrating lymphocytes (P＜0.05).There was no expression of IL-17 in the controls.The distribution pattern of Th-17 was shown that Th-17 cells were distributed evenly in the salivary glands of pSS patients with few infiltrating lymphocytes,but only appeared in the periphery zone of massive or focal infiltration in the glands of pSS patients with massive infiltrating lymphocytes.The amount of Th-17 positive cells were associated with the disease activity which was evaluated by levels of erythrocyte sedimentation rate (r=0.557,P＜0.05).There was no significant differ-ence in IL-17 levels of peripheral blood between patients with pSS and normal controls.Conclusion The results of this study have shown that Th-17 is expressed in the salivary glands of patients with pSS,which indicates that IL-17 may play an important role in the pathogenesis of salivary gland destruction.