• Age between 18 and 65 years old (inclusive), regardless of gender.

• Positive expression of CD19 on peripheral blood B cells confirmed by flow cytometry.

• Functional requirements for major organs are as follows: 1) Bone marrow function must meet: A. Neutrophil count ≥ 1×109/L (no colony-stimulating factor treatment within 2 weeks before examination); B. Hemoglobin ≥ 60g/L; 2) Liver function: Alanine aminotransferase (ALT) ≤ 3×ULN (excluding ALT elevation due to inflammatory myopathy), aspartate aminotransferase (AST)≤3×Upper limit of normal (ULN) (excluding AST elevation due to inflammatory myopathy), TBIL≤1.5×ULN (or ≤ 3.0×ULN for subjects with Gilbert syndrome); 3) Renal function: creatinine clearance rate (CrCl) ≥ 30ml/minute (calculated by Cockcroft/Gault formula, acute CrCl decrease due to the target disease is excluded); 4) Coagulation function: International standardized ratio (INR) \<1.5×ULN, prothrombin time (PT) \<1.5×ULN; 5) Cardiac function: Stable hemodynamic.

• Female subjects of childbearing potential and male subjects with partners of childbearing potential must use medically approved contraception or abstinence during the study treatment period and for at least 6 months after the end of the study treatment; Female subjects of childbearing potential must have a negative Human chorionic gonadotropin (HCG) test within 7 days before study enrollment and not be lactating.

• Willing to participate in this clinical study, sign an informed consent form, have good compliance, and cooperate with follow-up.

⁃ Refractory/Relapsed SLE:

• SLE fulfilling the 2019 the American College of Rheumatology (ACR) /European League Against Rheumatism (EULAR) and classification criteria.

• Systemic lupus erythematosus disease activity index (SLEDAI)-2000 score ≥ 6 with at least one BILAG (British Isle Lupus Rating Group Index 2004) A or two BILAG B; or SLEDAI-2000 score ≥ 8.

• Definition of relapsed/refractory: Conventional treatment over 6 months remains ineffective, or disease recurrence after remission. Definition of conventional treatment: the use of glucocorticoids and cyclophosphamide, and any one or more of the following immunomodulatory drugs: antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics including belimumab, rituximab, and tocilizumab, etc.

⁃ Refractory/Relapsed Sjogren's syndrome:

• Primary Sjogren's syndrome fulfilling the 2002 AECG criteria or the 2016 ACR/EULAR classification criteria.

• EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) ≥ 6

• Positive anti-SSA/Ro antibodies

• Definition of relapsed/refractory: Conventional treatment over 6 months remains ineffective, or disease recurrence after remission. Definition of conventional treatment: the use of glucocorticoids and cyclophosphamide, and any one or more of the following immunomodulatory drugs: antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics including belimumab, rituximab, and tocilizumab, etc.

⁃ Refractory/Relapsed/Progressive Systemic Sclerosis:

• Scleroderma fulfilling the 2013 ACR classification criteria

• Positive scleroderma-related antibodies.

• Presence of diffuse cutaneous sclerosis or active interstitial lung disease (high-resolution computed tomography (HRCT) showing ground-glass opacities);

• Definition of relapsed/refractory: Conventional treatment over 6 months remains ineffective, or disease recurrence after remission. Definition of conventional treatment: the use of glucocorticoids and cyclophosphamide, and any one or more of the following immunomodulatory drugs: antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics including belimumab, rituximab, and tocilizumab, etc.

• Definition of progressive: Rapid skin progression (mRSS increase \> 25%); or progression of lung disease (forced vital capacity (FVC) decrease by 10%, or FVC decrease by more than 5% with diffusing capacity of the lung for carbon monoxide (DLCO) decrease by 15%).

⁃ Note: Meeting either criterion 4 or 5 is sufficient.

⁃ Refractory/Relapsed/Progressive Inflammatory Myopathy:

• Inflammatory myopathy fulfilling the 2017 EULAR/ACR classification criteria (including Dermatomyositis (DM), Polymyositis (PM), Anti-Synthetase Syndrome (ASS), and Necrotizing Myopathy (NM)).

• Positive myositis antibodies;

• Muscle involvement with Manual Muscle Testing-8 (MMT-8) score less than 142 and at least two abnormalities found among the following five core measurements (Physician Global Assessment (PhGA), Patient Global Assessment (PtGA), or extramuscular disease activity score ≥ 2; Health Assessment Questionnaire (HAQ) total score ≥ 0.25; muscle enzyme levels ≥ 1.5×ULN; or MMT-8 ≥ 142, but with active interstitial lung disease (HRCT showing ground-glass opacities);

• Definition of relapsed/refractory: Conventional treatment over 6 months remains ineffective, or disease recurrence after remission. Definition of conventional treatment: the use of glucocorticoids and cyclophosphamide, and any one or more of the following immunomodulatory drugs: antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics including belimumab, rituximab, and tocilizumab, etc.

• Definition of progressive: Rapid progression of interstitial lung disease within a short period.

⁃ Note: Meeting either criterion 4 or 5 is sufficient.

⁃ Refractory/Relapsed ANCA-Associated Vasculitis:

• ANCA-Associated Vasculitis fulfilling 2022 ACR/EULAR criteria, including microscopic polyangiitis, granulomatosis with polyangiitis, and eosinophilic granulomatosis with polyangiitis.

• Positive ANCA-associated antibodies (MPO-ANCA or PR3-ANCA positive).

• The Birmingham Vasculitis Activity Scale (BVAS) ≥ 15 points (a total score of 63 points), indicating active vasculitis.

• Definition of refractory/relapsed: Conventional treatment over 6 months remains ineffective, or disease recurrence after remission., or disease recurrence after remission. Definition of conventional treatment: the use of glucocorticoids and cyclophosphamide, and any one or more of the following immunomodulatory drugs: antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics including belimumab, rituximab, and tocilizumab, etc.

⁃ Refractory/Relapsed/Catastrophic Antiphospholipid Syndrome:

• Primary antiphospholipid syndrome fulfilling 2006 Sydney criteria.

• Positive phospholipid antibodies with medium to high titers (IgG/IgM for Lupus Anticoagulant (LA), Beta-2 Glycoprotein 1 (B2GP1), or Anticardiolipin (aCL), positive more than twice within 12 weeks).

• Definition of refractory/relapsed: Standard treatment with warfarin anticoagulation or alternative vitamin K antagonist therapy (maintaining treatment-required INR) or standard therapeutic dose of low molecular weight heparin (LMWH) and use of steroids and cyclophosphamide for recurrent thrombosis;

• Catastrophic antiphospholipid syndrome needs to meet the following four criteria: (1) involvement of three or more organs, systems, and/or tissues; (2) symptoms occurring within one week; (3) histological confirmation of small vessel occlusion in at least one organ or tissue; (4) positive aPL antibodies.

⁃ Note: Meeting either criterion 3 or 4 is sufficient.

• Completion of Step 1 and successful preparation of CAR-T cell product;

• Adequate organ function, defined as: 1) Creatinine clearance rate (Cockcroft and Gault) \>30 mL/min/1.73 m2, excluding acute decrease in CrCl due to the target disease; 2) ALT/AST ≤ 3×ULN (excluding liver enzyme elevation caused by inflammatory diseases); TBIL ≤ 1.5×ULN (Gilbert's syndrome allows TBIL ≤ 3×ULN).