This study is exploring the best dose of CART-19 cells for treating a specific condition. CART-19 cells are special cells that are changed in a lab to help fight certain diseases. The study is divided into two parts. In the second part, subjects will receive the chosen dose of these cells over three days. The study is for people who have already had some response to these cells but have relapsed. Participants will be followed for at least 3 months after receiving the cells. If you are part of Stage 1, you might get a single dose, but if you were part of Stage 2, you will get the doses split over three days. If you qualify, you will be in the study for a few months and visit the clinic for your doses and follow-ups. This study does not provide details on age or other specific conditions for eligibility at this time.
- **Study Length**: At least 3 months of follow-up.
- **Visits**: Multiple visits for doses and follow-ups.
- **Purpose**: Testing different doses of CART-19 cells for effectiveness.