CD19 CAR-T Therapy for Refractory Childhood-Onset Systemic Lupus Erythematosus

Inclusion Criteria: 1. Participants must be 25 years of age or younger at the time of SNUH-CD19-CAR-T infusion. 2. Participants must have a diagnosis of systemic lupus erythematosus and meet the 2019 European Alliance of Associations for Rheumatology/American College of Rheumatology classification criteria for systemic lupus erythematosus. 3. Participants must be currently receiving or have previously received at least three of the following therapies, including corticosteroids: hydroxychloroquine, methotrexate, cyclophosphamide, mycophenolate mofetil, cyclosporine, tacrolimus, rituximab, or belimumab. 4. Participants must have involvement of at least one of the following major organ systems: * Kidney: class II-V lupus nephritis confirmed by biopsy or proteinuria greater than 0.5 g/day * Heart: pericarditis, myocarditis, conduction abnormality, or valvular disease * Lung: pleuritis, interstitial lung disease, or pulmonary arterial hypertension * Hematologic system: platelet count below 50,000/μL or hemolytic anemia 5. Participants must have uncontrolled active disease, defined as a Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score of 10 or higher. Exclusion Criteria: 1. Severe active central nervous system lupus requiring current treatment, including uncontrolled seizures, psychotic symptoms, or cognitive impairment. 2. Inability to obtain an adequate leukapheresis product suitable for the manufacture of SNUH-CD19-CAR-T cells. 3. Known human immunodeficiency virus infection. 4. Uncontrolled active infection, as determined by the investigator. An infection will be considered controlled if appropriate treatment has been administered and there is no evidence of progression at enrollment. Persistent fever without other signs or symptoms of infection will not, by itself, be considered evidence of progressive infection. 5. Pregnancy or breastfeeding. 6. Any medical or other condition that, in the investigator's clinical judgment, makes participation in the study inappropriate.