Low-dose Recombinant Human IL-2 for the Treatment of Relapsing Polychondritis

Inclusion Criteria: 1. Male or female ≥18 and ≤70 years 2. Meet the revised Michet criteria 3. Patients had an inadequate response to standard treatment for ≥ 4 weeks. The background treatment included corticosteroids (≤0.5 mg/ kg), immunosuppressants ( methotrexate, hydroxychloroquine, azathioprine, mycophenolate mofetil leflunomide, or cyclophosphamide) 4. Negative urine pregnancy test 5. Written informed consent form Exclusion Criteria: * Any subject who meets any of the following criteria shall be excluded: 1. Use rituximab or other monoclonal antibodies within 1.6 months. 2. 1 months after treatment with high dose glucocorticoid (\> 1 mg/kg/d). 3. Serious complications: heart failure (≥ New York Heart Association（NYHA） III grade), renal insufficiency (creatinine clearance rate ≤ 30 ml/min), liver function insufficiency (serum alanine transaminase or glutamic-pyruvic transaminaseT \> 3 times normal upper limit, or total bilirubin \> normal upper limit) 4. Other serious, progressive or uncontrollable hematological, gastrointestinal, endocrine, lung, heart, nerve, or brain diseases (including demyelination diseases, such as multiple sclerosis). 5. Known allergies, hyperresponsiveness or IL-2 or its excipients are intolerant. 6. Severe infections (including, but not limited to, hepatitis, pneumonia, bacteremia, pyelonephritis, Epstein-Barr virus, tuberculosis infection), hospitalization for infection, or intravenous antibiotics 2 months before the first dose of treatment. 7. Chest imaging showed abnormalities in malignant tumors or current active infections (including tuberculosis) within 3 months before the first use of the study. 8. Infected with HIV (HIV antibody positive serology) or hepatitis C (Hep C antibody positive serology). If seropositive, consult a doctor with expertise in the treatment of HIV or hepatitis C virus infection. 9. There has been any known malignant tumor or history of malignant tumor in the past 5 years (with the exception of non-melanoma skin cancer, non-melanoma skin cancer with no sign of recurrence or surgically cured cervical tumor within 3 months of use of the first study preparation). 10. There are uncontrolled mental or emotional disorders, including a history of drug and alcohol abuse over the past three years, which may hinder the successful completion of the study. 11. Within 3 months before the first injection of the research agent, during the study period or within 4 months after the last injection of the research agent, any live virus or bacterial vaccine is received or expected to be received. Bacillus Calmette-Guerin was vaccinated within 12 months after screening. 12. Pregnant and lactating women (WCBP) are reluctant to use medically approved contraceptives during and 12 months after treatment. 13. Men whose partners have fertility potential but do not want to use appropriate medically approved contraceptives during and within 12 months of treatment.