The objective of this study is to assess the efficacy and safety of rituximab combining with low-dose mycophenolate mofetil in the induction therapy of proliferative lupus nephritis in children.

Inclusion Criteria:

1. Children aged 3-18 years old, regardless of sex;
2. SLE patients who meet the 2019 EULAR/ACR SLE criteria or the 2012 SLICC diagnostic criteria;
3. Diagnosed as lupus nephritis and the classification was consistent with proliferative lupus nephritis (type III or IV, with or without type V);
4. White blood cell count ≥3.0×10^9/L, and lymphocyte count ≥ 0.5× 10^9/L and CD20 (or CD19)≥1/ul;
5. No cyclophosphamide or rituximab induction therapy was used before enrollment;
6. Informed consent form is signed by the guardian and children over 8 years old;
7. In the active stage of the disease, the 24-hour urine protein quantification ≥25mg/kg, or the urine protein/creatinine ≥1.0mg/mg;
8. Estimated GFR≥60ml/min/1.73m^2 (improved Swchartz formula).

Exclusion Criteria:

1. Patients with lupus encephalopathy;
2. Estimated GFR<60ml/min/1.73m^2(Swchartz formula);
3. HBV-antigen positive, HCV or HIV antibody positive;
4. Severe infection (including chronic hepatitis, EB virus or cytomegalovirus infection) and tuberculosis;
5. Allergic to the active ingredients or any auxiliary materials in rituximab, mycophenolate mofetil or cyclophosphamide;
6. Severe heart failure and liver function damage;
7. Patients who is not suitable to participate in this study judged by the researchers.