To Compare the Efficacy and Safety of Tripterygium (TW) Versus AZA in the Maintenance Therapy for Lupus Nephritis

Inclusion Criteria: 1. Patients who signed written informed consent form; 2. SLE patient, aged between 18-60 years, female or male; 3. Patients diagnosed lupus nephritis according to ISN/RPS 2003 classification criteria, class Ⅲ, Ⅳ,Ⅳ+Ⅴ, Ⅲ+Ⅴ or Ⅴ LN by renal biopsy; 4. All patients received induction therapy for 6-12 months, including MMF, CTX, FK506 or multi-target therapy; 5. When recruited in the study, patients received partial remission or complete remission for 3 months; * Complete remission: proteinuria \< 0.4 g/24h, negative urine sediment, serum albumin \> 35 g/L, elevated scr \< 0.3 mg/dl, no extra-renal complications; * Partial remission: proteinuria \< 1.0 g/24h, urine RBC \< 500000/ml without casts, serum albumin \> 35 g/L, elevated scr \<0.3 mg/dl, no extra-renal complications. Exclusion Criteria: 1. Patients who didn't sign written informed consent form or could not obey the protocol; 2. Patients who didn't received the CR or PR criterion; 3. Patients who have impaired liver function, with ALT/GPT or AST/GOT twice more than the normal upper limit; 4. WBC \< 3000/mm3 in peripheral blood; 5. Patients with abnormal of central nervous system.