The purpose of this study is to find out if the study drug, Anifrolumab, is effective and safe for pediatric participants with moderate to severe active systemic lupus erythematosus (SLE) while on background standard of care therapy. Researchers will also be testing how the body processes a drug by measuring how quickly the drug is absorbed by the body, how quickly it is broken down by the body, and how long it remains in the body (pharmacokinetics). Subjects will be asked to come into the Rheumatology clinic for blood, hepatitis/HIV, urine, and pregnancy testing, physical exam, an electrocardiogram (ECG), questionnaire completion, medical record review, corticosteroid use, and administration of study drug. Anifrolumab is administered as an infusion every 4 weeks over the course of the study.

The purpose of this study is to find out what dose of CABA-201 ("study drug") can be safely administered to patients with Systemic Lupus Erythematosus and Lupus Nephritis. CABA-201 is a CAR T cell therapy drug, which uses your own T cells (immune cells), and modifies them in order to find and remove other immune cells (B cells) that cause this disease.

The cells will be collected through a process called leukapheresis, then modified in a lab. This modified version will be infused into the body.

The purpose of this study is to evaluate the safety and tolerability of CABA-201, an experimental form of therapy, in participants with active Idiopathic Inflammatory Myopathies (IIM) and Juvenile Idiopathic Inflammatory Myopathies (JIIM). CABA-201 is a CAR therapy drug, which uses T- cells (immune cells) and modifies them to find and remove the other immune cells (B cells) involved in causing this disease. The cells will be collected through a process called leukapheresis, then modified in a lab, the modified version will be infused into the body.

The purpose of this study is to find out how well surveys can measure disease activity in kids with lower back arthritis. The study will last for either 3 or 6 months and take 2 or 3 visits. Each visit will last between 30 minutes and 2 hours and have either an MRI plus a survey or just a survey.

The purpose of this research study is to learn more about the normal function of blood vessels in healthy children and adolescents. This will help us discover differences between healthy individuals and children with lupus. Healthy control participants will be asked to make 1 visit to CHOP to complete a brief survey, a fasting blood draw and a test to measure the blood pressure in your fingers.