Primary Sjögren's Syndrome (pSS) is an autoimmune disorder characterized by keratoconjunctivitis sicca and xerostomia. In addition, various extraglandular manifestations may develop. Several immunomodulating agents have been attempted in the treatment of pSS without achieving satisfactory results. Currently, there is no approved systemic treatment for pSS. Dysfunction of regulatory T (Treg) cells has been detected in diverse autoimmune diseases, which can be promoted by interleukin-2 (IL-2). The investigators hypothesized that low-dose IL-2 could be a novel therapy in active pSS patients. This clinical study will test the efficacy and safety of low dose IL-2 treatment in pSS. The investigators perform a single-centre, double-blind pilot trial with hrIL-2 in pSS. The investigators evaluate the effectiveness and safeness of low-dose hrIL-2 for primary Sjögren's Syndrome by randomized controlled study (hrIL-2 (N = 30) versus placebo group (N = 30)).

Each pSS patients (n=60) with Scores>=6 on ESSDAI received low-dose IL-2 or placebo (active group: placebo group =1:1, 1 million units every other day subcutaneously (HrIL-2 1X 106, ip, Qod) for a period of 14 days. After a 14-day rest, another cycle started) for 3 cycles. The end points were safety, clinical and immunologic response.

Inclusion Criteria:

• Diagnosis of a primary Sjögren´s Syndrome
• ESSDAI score ≥ 6
• Liver values above 1,5 ULN
• Stable low dose systemic use of Glucocorticoids（<=7.5mg） in the last 4 weeks before begin with Study medication

Exclusion Criteria:

• Secondary Sjögren's Syndrome
• Pre-treatment with Cyclosporine A
• Receiving cyclosphosphamide, corticosteroid bolus with dose over 1 mg/kg, rituximab, belimumab, other immunosuppressives
• Infection
• Neoplasia
• Relevant cardiac, pulmonary, neurologic or psychiatric disease
• Life-Vaccination within 4 weeks before begin with study medication
• Pregnant or breast-feeding
• Weight under 45kg or more than 80kg