This study is a single-arm, intervention, dose-escalation clinical trial to evaluate the safety of allogeneic CD19/BCMA-targeted CAR-γδT cell in the treatment of relapsed/refractory autoimmune diseases

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.
• 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.

Access to the data underlying this study can be obtained from the corresponding author upon reasonable request and subject to any required ethical approvals.