Inclusion Criteria:  Male or female adults, ≥ 18 years of age at time of informed consent; Written informed consent; Diagnosed with retroperitoneal fibrosis and normal level of Serum IgG4; Higher level of ESR and CRP than normal; Pathologic results show fibrosis and IgG4/IgG <50%.  Exclusion Criteria:  Combined with other connective tissue disease. Known immunodeficiency disorder. Active malignancy or history of malignancy that was active within the last 10 years. Pregnancy, lactation, or planning to become pregnant within 6 months of the test. Positive test for, or prior treatment for, hepatitis B or HIV infection. A positive test for hepatitis B is detection of hepatitis B surface antigen (HBsAg) or HBV-DNA. Evidence of active tuberculosis (TB), including Chest X-ray and PPD. Severe abnormal liver function or cardiac insufficiency. Any reason the investigator think that should not attend this trial.