The goal of this prospective, open, single-arm clinical trial was to evaluate the safety and potential efficacy of CAR T cell therapy in children with refractory/recurrent lupus nephritis. The persistence and cell phenotype of CAR-T cells in vivo and CAR-T treatment-related inflammatory factors were evaluated after treatment. To explore new therapeutic methods, in order to reduce the side effects of traditional therapeutic drugs, increase curative effect, and finally make patients obtain long-term survival and improve survival quality.

Inclusion Criteria:

1. Age 6-18 years old (including critical value);

2. Diagnosed with SLE according to the 2019 EULAR/ACR SLE classification criteria;

3. According to the 2018 ISN/RPS LN standards diagnosed with active Class III or IV LN, with or without a membranous component and the biopsy must be performed within 6 months prior to screening;

4. SLEDAI-2000 score ≥8 points;

5. Meeting the diagnosis of refractory lupus nephritis,

   1. defined as treatment with two or more immunosuppressants (including glucocorticoids, cyclophosphamide, tacrolimus, mycophenolic acid analogues, leflunomide, and cyclosporine) for more than 6 months without inducing remission or relapse after remission,
   2. accompanied by proteinuria without remission;

6. Positive expression of CD19 in peripheral blood B cells determined by flow cytometry;

7. Participants had good venous access, no contraindications for cell collection;

8. Participants and their guardians sign the informed consent, understand the study procedures and participate in the clinical study voluntarily;

9. The functions of important organs are basically normal:

   1. Hematopoietic function (blood routine should meet):

      • Lymphocyte count ≥1×109/L,
      • White blood cell count ≥3×109/L,
      • Neutrophil count ≥1×109/L (no colony-stimulating factor treatment within 2 weeks prior to examination),
      • Hemoglobin ≥60g/L;

   2. Liver function:

      • ALT≤3×ULN (except elevated ALT caused by inflammatory myopathy),
      • AST≤3×ULN (except for elevated AST caused by inflammatory myopathy),
      • TBIL≤1.5×ULN (except Gilbert syndrome, total bilirubin ≤3.0×ULN);

   3. Renal function: eGFR ≥30 ml/(min.1.73m2) (Schwartz formula, except abnormal renal function by SLE);

   4. Coagulation function:

      • International standardized ratio (INR) ≤1.5×ULN,
      • prothrombin time (PT) ≤1.5×ULN;

   5. Heart function: hemodynamic stability;

10. Anti-nuclear antibody (ANA) ≥1:80;

11. Eastern Cancer Cooperation Group (ECOG) physical status score 0 to 2.

Exclusion Criteria:

1. Received kidney transplant previously;

2. Serious drug allergy history or allergy;

3. Presence or suspicion of fungal, bacterial, viral or other infections that cannot be controlled or require treatment;

4. Complicated with severe organ dysfunction of heart, liver, lung or coagulation dysfunction;

5. Complicated with congenital immunoglobulin deficiency;

6. Participants with infectious diseases:

   1. Hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBc Ab) positive and peripheral blood hepatitis B virus (HBV) DNA titer greater than the normal reference value range;
   2. Hepatitis C virus (HCV) antibody positive and peripheral blood hepatitis C virus (HCV) RNA titer greater than the normal reference value range;
   3. Human immunodeficiency virus (HIV) antibody positive;
   4. Syphilis positive;

7. Diagnosed with malignant tumors in the last five years.

8. Suffer from severe central nervous system disease, mental illness and severe cognitive dysfunction;

9. Participated in other clinical trials within 3 months before enrollment;

10. Received CAR-T therapy previously;

11. Other situations that the researcher considers unsuitable for inclusion.