Descartes-08 for Children, Adolescents, and Young Adults With Autoimmune Disorders

Inclusion Criteria: * At least age 12 * definitive diagnosis of childhood-onset systemic lupus erythematous, juvenile Myasthenie gravis, juvenile dermatomyositis and AAV * Signs and symptoms of moderate disease * History of systemic treatment * Parent/Guardian/Patient must be able to give written informed consent Exclusion Criteria: * Major chronic illness that is not well managed at the time of study entry and in the opinion of the investigator may increase the risk to the patient; * Abnormal PT/INR or PTT increased \> 1.5-fold or patient is on anticoagulation therapy (except in cases of elevated PTT with documented lupus anticoagulant; or in patients who have been on stable doses of anticoagulation therapy for more than 6 months of VTE diagnosis; or in patients on stable doses of anticoagulation therapy for at least 8 weeks of atrial fibrillation diagnosis; these conditions will not be exclusionary unless, in the investigator's opinion, they make participation in the study unsafe); * ANC \< 1000 cells/microliter ; * Hemoglobin \< 8.0 g/dL ; * Platelets \< 50,000/mm3 (NOTE: platelet transfusions are permissible); * ALT and/or AST with GGT ≥ 3× upper limit of normal * Creatine Clearance less than 30mL/min /1.73 m2; * History of primary immunodeficiency, organ, or allogeneic bone marrow transplant; * Patients must be seronegative for hepatitis B surface antigen; * Patients must be seronegative for hepatitis C antibody. If hepatitis C antibody test is positive, then patients must be tested for the presence of viremia by RT-PCR and must be HCV RNA negative; * History of positive HIV or positive HIV at screening; * Active tuberculosis or positive QuantiFERON test at screening; * Any other laboratory abnormality that, in the opinion of the investigator, may jeopardize the subject's ability to participate in the study; 23. Any active significant cardiac or pulmonary disease not related to the primary indication as determined by principal investigator and medical monitor Note: Patients with asthma and COPD controlled with inhaled medications are allowed; 24. Any arterial or venous thromboembolic events in the past 3 months; 25. History of malignancy that required treatment in the past 3 years except for successfully-treated squamous cell and/or basal cell carcinoma of the skin and/or breast or colon cancer that is surgically removed and did not require adjuvant chemotherapy or radiotherapy; 26. Treatment with any investigational agent within 4 weeks of screening or 5 half-lives of the investigational drug (whichever is longer); 27. Receipt of a live vaccination within 4 weeks prior to baseline (Day 1) or intent to receive live vaccination during the study (Note: mRNA-based vaccines such as those against SARS-CoV-2 are not considered live; likewise, the Janssen Covid-19 vaccine is not live); 28. History of significant recurrent infections or any active infection that may interfere with the patient's participation in the opinion of the investigator; 29. Any known psychiatric illness that may interfere with the patient's participation in the study in the opinion of the investigator.