Exploratory Study of Anti-BCMA-CD19 CAR-T Cell Therapy in Relapsed or Refractory IgG4-Related Disease

Inclusion Criteria: To participate, subjects must meet all of the following criteria: 1. Aged 18 to 75 years, inclusive, regardless of sex. 2. Meet the 2019 ACR/EULAR classification criteria for IgG4-related disease. 3. Involvement of two or more important systems/sites (including but not limited to the pancreas, bile ducts, kidneys and dura mater). 4. Relapsed or refractory IgG4-RD: The disease either remains active after 3 months of glucocorticoid and/or rituximab therapy or relapses within 6 months post-treatment. 5. Important organ function meeting the following conditions: * Bone marrow: (i) neutrophil count ≥1×10\^9/L (excluding disease-related neutropenia); (ii) hemoglobin ≥60 g/L. * Hepatic function: ALT≤3×ULN (elevation caused by disease may be excluded); AST≤3×ULN (elevation caused by disease may be excluded); TBIL≤1.5×ULN (elevation caused by disease may be excluded). * Renal function: creatinine clearance (Cockcroft-Gault formula) ≥30 ml/min (excluding acute decline due to disease). * Coagulation: international normalized ratio (INR) ≤ 1.5×ULN, prothrombin time (PT) ≤ 1.5×ULN * Cardiac function: stable hemodynamics. 6. Women of childbearing potential and male subjects with partners of childbearing potential must use medically accepted contraception or abstain during study treatment and for at least 12 months after the end of treatment. Women of childbearing potential must have a negative serum HCG test within 7 days before enrollment and must not be breastfeeding. 7. Voluntary participation in this clinical study with signed informed consent and willingness to comply with study procedures and follow-up. 8. Patent superficial peripheral veins adequate for intravenous infusion. Exclusion Criteria: Subjects will be excluded if any of the following criteria are met: 1. History of severe drug allergy or allergic constitution. 2. Current or suspected uncontrollable or treatment-requiring fungal, bacterial, viral or other infections. 3. Central nervous system disease (excluding disease-related epilepsy, psychosis, organic brain syndrome, cerebrovascular accident, encephalitis or central nervous system vasculitis). 4. Cardiac insufficiency that precludes participation. 5. Congenital immunoglobulin deficiency. 6. Congenital malformation or nutritional disorder causing severe organ impairment. 7. History of malignancy within the past five years. 8. End-stage renal failure. 9. Positive hepatitis B surface antigen and hepatitis B core antibody with HBV-DNA titers above the assay limit of detection; positive hepatitis C antibody with HCV-RNA positivity; positive human immunodeficiency virus antibody; positive syphilis serology. 10. Psychiatric disorders or severe cognitive impairment. 11. Participation in other clinical trials within three months before enrollment. 12. Receipt of any investigational drug within 12 weeks before screening or within five half-lives of the agent (whichever is longer). 13. Pregnant or intending to become pregnant. 14. Any other reason deemed by the investigator to preclude enrollment.