Inclusion Criteria:
1. Voluntarily sign an informed consent form.
2. Male or female aged ≥18 and ≤65 years.
3. Medical history indicating the fulfillment of at least 4 out of the 11 SLE classification criteria recommended by the American College of Rheumatology (ACR) in 1997, with a Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score of ≥6.
4. Previous receipt of induction therapy (combination of steroids with immunosuppressants, biologics, or two or more treatments), as determined by the investigator, and the participant demonstrated intolerance to or lack of response to this treatment.
5. Confirmed diagnosis of class III or class IV lupus nephritis according to the ISN/RPS classification criteria (Class III(A), Class III(A+C), Class IV(A), or Class IV(A+C)), with the possibility of being combined with Class V or isolated Class V (including activity and chronicity indices).
6. Laboratory examination showing a urinary protein-to-creatinine ratio (UPCR) \> 1000 mg/g or 100 mg/mmol or \> 1.0.
7. During the trial and for at least 1 year after injection administration, the participant has no plans for pregnancy and voluntarily agrees to use effective contraception with their partner (see Appendix 1) and has no plans for sperm or egg donation.
Exclusion Criteria:
1. Severe liver dysfunction with any of the following abnormalities: total bilirubin \> 2 times the upper limit of normal (ULN); ALT or AST \> 2 times the ULN.
2. Severe kidney dysfunction with eGFR \< 30 mL/min/1.73m² or serum creatinine \> 265.2 µmol/L.
3. Kidney biopsy pathology indicating ≥50% glomerulosclerosis.
4. Blood system abnormalities with any of the following abnormalities: white blood cell count \< 2000/µL (2×10\^9/L), hemoglobin \< 6g/dL (60g/L), platelet count \< 30000/µL (30×10\^9/L), neutrophils \< 1000/µL (1×10\^9/L).
5. Severe and uncontrolled cardiovascular diseases, neurological disorders, pulmonary diseases (including obstructive lung disease and interstitial lung disease), liver diseases, endocrine disorders (including uncontrolled diabetes), and gastrointestinal diseases, including but not limited to:
* Patients with uncontrolled severe hypertension (≥160/100 mmHg).
* Patients with uncorrected heart failure or severe heart dysfunction (NYHA class ≥III).
* Patients with a history of myocardial infarction within the previous 6 months or meet the diagnostic criteria for acute myocardial infarction at screening.
* Patients with a history of acute stroke within the previous 6 months or at risk of acute cerebrovascular events at screening.
* Patients with a history of severe pulmonary hypertension.
* Patients with severe arrhythmias (e.g., rapid atrial fibrillation, atrial flutter, paroxysmal ventricular tachycardia).
6. Patients with a history of IgA deficiency (IgA \< 10 mg/dL).
7. Patients with other autoimmune diseases except for SLE, including dermatomyositis/polymyositis, mixed connective tissue disease, systemic sclerosis, rheumatoid arthritis, etc., should be excluded. However, patients with secondary Sjögren's syndrome are allowed to participate in this trial.
8. Received live vaccines or attenuated live vaccines within the previous 12 weeks or expect to receive/require live vaccines during the trial.
9. Underwent plasmapheresis or immunoadsorption therapy within the previous 24 weeks or received intravenous immunoglobulin (IVIG) therapy within the previous 4 weeks.
10. Used other investigational drugs within the previous 12 weeks.
11. Tested positive for human immunodeficiency virus antibodies (anti-HIV-Ab) during screening, active syphilis, active hepatitis C (positive for hepatitis C antibodies, and HCV-RNA higher than the lower limit of detection), or positive for hepatitis B surface antigen (HBsAg) and hepatitis B virus DNA (HBV-DNA ≥500 IU/ml).
History of severe active or recurrent bacterial, viral, fungal, parasitic, or other infections during the screening period.
12. History of malignant tumors within the past 5 years, including solid tumors, hematological malignancies, or in situ cancers (except for surgically removed or cured basal cell carcinoma of the skin).
13. Underwent any major surgery within the previous 12 weeks or anticipated to undergo major surgery during the trial, which is considered to pose an unacceptable risk to the participant by the investigator.
14. Intolerance or contraindication to the treatment protocol of this trial, including any of the following conditions:
* History of allergies to allogeneic mesenchymal stem cells or excipients (including human albumin).
* Intolerance or contraindication to oral or intravenous corticosteroids.
* Absence of peripheral venous access.
15. Pregnant or lactating women.
16. Within the previous 12 months or during the screening period, there is evidence of smoking, alcohol misuse, or drug abuse, defined as follows:
* Smoking defined as an average daily smoking of ≥5 cigarettes within the previous 3 months.
* Alcohol misuse defined as consuming more than 14 units of alcohol per week within the previous 3 months (1 unit of alcohol = 350 ml of beer, or 45 ml of spirits, or 150 ml of wine).
* Drug abuse defined as a positive result in urine drug screening or having a history of drug abuse.
17. Participants judged by the investigator as not suitable for participation in this trial will be excluded.
