CAR-T-19 Injection in the Treatment of CD19-positive Relapsed/Refractory B-ALL

This study is testing a type of immunotherapy called CAR-T cell therapy for children and young adults with B-cell acute lymphoblastic leukemia (B-ALL) — a blood cancer that has come back or stopped responding to treatment. CAR-T cells are made from the patient's own immune cells, reprogrammed to attack cancer cells that carry a protein called CD19. **You may be eligible if...** - You are 25 years old or younger - You have been diagnosed with B-cell leukemia (CD19-positive) that has relapsed (come back) or is not responding to current treatments - You are in reasonably good health despite your leukemia - You or a legal guardian can provide informed consent **You may NOT be eligible if...** - Your leukemia cells do not have the CD19 marker - You have active, uncontrolled infections (including active HIV or hepatitis) - You have severe organ problems (heart, liver, kidney, or lung) - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.