Inclusion Criteria:
* Age ≥18 years (including 18 years), no gender restrictions.
* Confirmed by flow cytometry to express CD19 or BCMA antigen on the surface of peripheral blood B cells.
* Major organ function must meet the following requirements (excluding abnormalities related to active autoimmune disease):
* Bone marrow function: Neutrophil count ≥ 1 × 10\^9/L (no colony-stimulating factor therapy within 2 weeks prior to testing); Haemoglobin ≥ 60 g/L.
* Liver function: Alanine aminotransferase (ALT) ≤ 3 times the upper limit of normal (ULN) (excluding ALT elevation due to inflammatory myopathy) ; Aspartate Aminotransferase (AST) ≤ 3 times the upper limit of normal (ULN) (excluding AST elevation due to inflammatory myopathy); Total Bilirubin (TBIL) ≤ 2 times ULN (may be relaxed to ≤ 3.0 times ULN for subjects with Gilbert's syndrome).
* Renal function: Creatinine clearance (CrCl) ≥ 30 ml/min (calculated using the Cockcroft-Gault formula, excluding acute CrCl decline due to target disease; lupus nephritis (LN) patients excluded).
* Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2.
* Female subjects of childbearing potential and male subjects with partners of childbearing potential must use medically approved contraception or abstain from sexual intercourse for at least 6 months during study treatment and for at least 6 months after study treatment completion.
* Voluntary participation in this clinical study, signing of informed consent, good compliance, and ability to complete follow-up.
Disease-specific inclusion criteria:
* Relapsed/refractory systemic lupus erythematosus
* Diagnosis of systemic lupus erythematosus (SLE) meeting the 2019 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria.
* Systemic Lupus Erythematosus Disease Activity Index (SLEDAI-2000) ≥ 8 points; or significant organ involvement, such as lupus nephritis (histologically confirmed active nephritis of type III or IV, with or without type V involvement; National Institutes of Health \[NIH\] activity score \> 2 points; evidence of elevated chronicity index; urine protein/creatinine ratio \> 1.0 g/g, or 24-hour urine protein quantification \> 1.0 g).
* Refractory or recurrent disease is defined as: no response after more than 6 months of conventional therapy, or recurrence of disease activity following remission. Conventional therapy is defined as: glucocorticoids combined with one or more of the following immunomodulatory agents: cyclophosphamide, antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics such as rituximab, belimumab, or tatalimab.
* Refractory/Recurrent/Progressive Systemic Sclerosis
* Scleroderma diagnosis conforms to the 2013 ACR（American College of Rheumatology） classification criteria.
* Positive for scleroderma-associated antibodies.
* Presence of diffuse cutaneous sclerosis or active interstitial lung disease (high-resolution computed tomography (HRCT) showing ground-glass opacities).
* Definition of recurrent/refractory: No response to conventional therapy for over 6 months, or recurrence following remission. Conventional therapy defined as: Glucocorticoids combined with any one or more of the following immunomodulators: cyclophosphamide, antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics such as belimumab, rituximab, or tocilizumab.
* Progressive definition: Rapid progression of cutaneous lesions (Modified Rodnan Skin Score (mRSS) increase \> 25%); or progression of pulmonary lesions (Forced Vital Capacity (FVC) decline ≥10%, or FVC decline ≥5% accompanied by Diffusion Capacity for Carbon Monoxide (DLCO) decline ≥15%).
Note: Fulfilment of either criterion 4 or 5 is sufficient.
* Refractory/Recurrent/Progressive Inflammatory Myopathies
* Diagnosis of inflammatory myopathy conforms to the 2017 EULAR（European Alliance of Associations for Rheumatology）/ACR classification criteria (including dermatomyositis (DM), polymyositis (PM), anti-synthetase syndrome (ASS), and necrotising myopathy (NM)).
* Muscle involvement present, Manual Muscle Test - 8 (MMT-8) score \< 142 points, and at least 2 abnormalities in the following 5 core indicators: Physician Global Assessment (PhGA), Patient Global Assessment (PtGA) or extra-muscular disease activity score ≥ 2 points; Health Assessment Questionnaire (HAQ) total score ≥ 0.25 points; Muscle enzyme levels ≥1.5 times the upper limit of normal.
* Definition of recurrent/refractory: No response to conventional therapy for over 6 months, or relapse following remission. Conventional therapy defined as: Glucocorticoids combined with any one or more of the following immunomodulators: cyclophosphamide, antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics such as belimumab, rituximab, or tocilizumab.
* Definition of progressive disease: Rapid progression of interstitial lung disease within a short timeframe.
Note: Meeting any one criterion from either section 4 or 5 suffices.
* Refractory/Recurrent Anti-Neutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis
* Diagnosis of ANCA-associated vasculitis conforms to the 2022 ACR/EULAR criteria, encompassing microscopic polyangiitis, granulomatous polyangiitis, and eosinophilic granulomatous polyangiitis.
* ANCA-associated antibody testing is positive (myeloperoxidase antibody \[MPO-ANCA\] or proteinase 3 antibody \[PR3-ANCA\] positive).
* Birmingham Vasculitis Activity Score (BVAS) ≥15 points (out of 63 total points), indicating active vasculitis.
* Refractory/recurrent definition: Failure to respond to conventional therapy for over 6 months, or recurrence following remission. Conventional therapy is defined as:Use of glucocorticoids in combination with any one or more of the following immunomodulatory agents: cyclophosphamide, antimalarials, azathioprine, mycophenolate mofetil, methotrexate, leflunomide, tacrolimus, cyclosporine, and biologics such as belimumab, rituximab, or tocilizumab.
* Refractory/Recurrent Connective Tissue Disease-Associated Thrombocytopenia
* Diagnosis of connective tissue disease conforming to the latest classification criteria, including but not limited to systemic lupus erythematosus, primary Sjögren's syndrome, antiphospholipid syndrome, and undifferentiated connective tissue disease.
* Diagnosed with connective tissue disease-associated thrombocytopenia, with platelet count \< 30 × 10⁹/L, or platelet count \< 50 × 10⁹/L accompanied by bleeding tendency.
* Bone marrow morphology consistent with features of immune thrombocytopenia.
* Previous treatment with at least one course of glucocorticoid pulse therapy, or high-dose glucocorticoids combined with one or more immunosuppressants (including biologics) for at least three months, failing to achieve partial remission or unable to maintain efficacy during glucocorticoid tapering.
Exclusion Criteria:
* -Individuals with a history of severe drug allergies or an allergic constitution.
* Presence or suspected presence of uncontrolled or treatable fungal, bacterial, viral, or other infections.
* Active, severe central nervous system disorders caused by autoimmune or non-autoimmune diseases (including epilepsy, psychosis, organic brain syndrome, cerebrovascular accident, encephalitis, central nervous system vasculitis).
* Patients with cardiac insufficiency.
* Patients with congenital immunoglobulin deficiency.
* History of malignant tumours within the past five years.
* End-stage renal disease (excluding lupus nephritis (LN) patients).
* Hepatitis B surface antigen (HBsAg) positive or hepatitis B core antibody (HBcAb) positive with peripheral blood hepatitis B virus (HBV) DNA \> upper limit of normal; hepatitis C virus (HCV) antibody positive with peripheral blood hepatitis C virus (HCV) RNA positive; human immunodeficiency virus (HIV) antibody positive; positive syphilis test.
* Individuals with psychiatric disorders or severe cognitive impairment.
* Individuals who have previously received CAR-T therapy.
* Participants who have been enrolled in another clinical trial within the three months preceding study entry.
* Individuals who have received immunosuppressive agents or biological agents for therapeutic indications within five half-lives prior to study entry.
* Pregnant women or women planning pregnancy.
* Individuals deemed by the investigator to have other conditions rendering them unsuitable for inclusion in this study.
