Inclusion Criteria:  fulfill the criteria of the 2016 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification for primary SS with moderate or high activity of SS, which was defined as EULAR primary SS disease activity index (ESSDAI) ≥5 with serological activity defined as elevated C-reactive protein, erythrocyte sedimentation rate (ESR), and/or immunoglobulin G (IgG) level (excluding acute and chronic infection and other factors)  Exclusion Criteria:  patients diagnosed with an active central nervous system disease or dysfunction of a major organ (heart, liver, kidney) pregnant or lactating women current severe infections undergoing glucocorticoids or immunosuppressants treatment with stable dosage for less than 12 weeks