This study is testing a new treatment for adults with Systemic Lupus Erythematosus (SLE), a disease where the body's defense system attacks its own tissues. The trial will use **Mesenchymal Stem Cells (MSCs)**, which are special cells taken from umbilical cords (part of a baby's birth cord). These cells will be compared to a placebo, which looks like the real treatment but doesn't have any active medicine.

Participants will receive one infusion (a way of putting fluids into the body) and will be monitored for safety. The study is *double-blind*, meaning neither the participants nor the doctors know who gets the MSCs or placebo. The trial is conducted at multiple locations and will assess if MSCs alongside usual care help more than usual care alone.

• **Duration & Visits:** It requires one IV infusion and ongoing monitoring.
• **Eligibility:** Adults 18-65 with SLE, not pregnant, and no major health issues.
• **Compensation & Risks:** Details on compensation and risks are provided during consent.