This is an open-label, single-dose, prospective, monocenter, Phase I interventional study (not first-in-human) to assess the safety, tolerability, and preliminary efficacy of autologous anti-CD19 CAR-T cells as an advanced therapy medicinal product in adult patients; with severe and refractory systemic autoimmune rheumatic diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjogren's disease (SjD), systemic sclerosis (SSc) and idiopathic inflammatory myositis (IIM).

Inclusion Criteria:

• Adults aged 18-75 with ECOG PS 0-2 with written informed consent, valid health insurance, and eligibility for CAR T cell infusion are required may be included. Patients must have a treatment refractory systemic autoimmune rheumatic disease (RA, SLE, Sjögren's, SSc, or IIM) with severe, progressive activity with adequate renal function (creatinine clearance > 30 mL/min)

Exclusion Criteria:

• Patients with any significant active infection, including hepatitis B or C, HIV, or other opportunistic or recurrent infections, are excluded. Prior gene therapy, previous CAR T treatment, active cancer within 2 years, or any history of allogeneic stem cell or solid organ transplantation exclude participation. Inadequate organ function-renal, hepatic, cardiac (LVEF < 50%), or lung function requiring oxygen- and uncontrolled comorbidities prevents inclusion. Pregnancy, breastfeeding, or refusal to use highly effective contraception for 12 months post infusion