Clinical Study on the Safety and Efficacy of CD19-BCMA CAR-T Cell Therapy for Connective Tissue Diseases

Inclusion Criteria: 1. Good compliance: The patient or their guardian understands and voluntarily signs the informed consent form, and it is expected that all documents, procedures, follow-up examinations and treatments stipulated in the study can be completed. 2. Previously diagnosed with one of the following diseases and meeting the corresponding latest international classification/diagnostic criteria : 1. Systemic lupus erythematosus (SLE); 2. Rheumatoid arthritis (RA); 3. Systemic scleroderma (SSc) ; 4. Sjogren's Syndrome (SS); 5. Polymyositis/dermatomyositis (PM/DM); 6. Mixed connective tissue disease (MCTD). 3. Researchers determine that the disease is in an active stage; 4. At least one autoantibody is positive in the serum or plasma during the screening period; 5. Insufficient response, intolerance or recurrence to at least one standard treatment; 6. The pregnancy test of the female subjects was negative, and the subjects agreed to take effective contraceptive measures throughout the trial period. 7. The patient's major tissues and organs are functioning well. Exclusion Criteria: 1. Intracranial hypertension or confusion; 2. Symptomatic heart failure or severe arrhythmia; 3. Respiratory failure; 4. Accompanied by other types of malignant tumors; 5. Diffuse vascular coagulation; 6. Serum creatinine and/or urea nitrogen ≥ 1.5 times the normal value; 7. Sepsis or other difficult-to-control infections; 8. Uncontrollable diabetes; 9. Severe mental disorder; 10. Cranial magnetic resonance imaging (MRI) examination revealed obvious lesions in the intracranial cavity. 11. WHO physical status classification ≥ level 3; 12. Organ transplant recipients; 13. Pregnant and lactating women; 14. HIV+，HBV，HCV，EBV，CMV.