Abstract: Objective:To investigate the serological characteristics and immunological features of primary Sjogren's syndrome (pSS).Methods:A total of 62 patients with pSS were studied.All the cases was were diagnosed according to the American European consensus criteria (AECC) of 2002.The main clinical and immunological features were analyzed.Results:The common initial clinical symptoms included xerostomia,xerophthalmia,hypokalemia and arthralgia.Reynaud phenomenon was rarely seen.Positive ANA and anti-SSA52 (+) antibodies were frequently detected (83.9% and 85.5%).The rates of RF titer and IgG levels were 72.6% and 79.0% respectively.The percentage of CD4⁺ T cells and the ration of CD4⁺/CD8⁺ T cells in peripheral blood of pSS patients were lower than that of healthy controls.The expression rate of CD16⁺56⁺ in peripheral bloods of pSS patients (5.8±2.6)%were lower than that of reference value (10.0±3.8)%.Conclusions:Anti-SSA-52 (+) antibody is a frequent immunological marker among pSS patients.Low CD4⁺/CD8⁺ T-lymphocyte ratio may be a significant risk factor for the development of lymphoma in pSS.Lower expression of CD16⁺56⁺ determines the extent to which the NK cells lose the immune supervision,which may increase the incidence of lymphoma in pSS patients.