Scientists have found a way to turn the body’s immune system against one of the most common forms of pediatric cancer.

A panel of experts has recommended the Food and Drug Administration approve the use of a genetic therapy for acute lymphoblastic leukemia, a blood cancer that affects kids and young adults. The therapy involves genetically reprogramming key immune system cells to recognize and attack cancer cells.

Here’s how it works: Blood is drawn from the body, and immune system cells called T cells are sifted out and frozen. The frozen cells are shipped to a special facility for genetic tweaking. By inserting a new gene, scientists can give the T cells a special protein molecule on the outside of the cell. This molecule, called a receptor, is chemically drawn to cancer cells.Once the genetic tweaking is done, more killer T cells are grown. They are frozen again and sent back to the hospital, where the modified cells are thawed and transferred back into the body. With multitudes of T cells ready to find and destroy cancer, patients have a powerful new weapon against leukemia. Small trials have shown high rates of remission for patients within a few months of undergoing this one-time therapy.

Researchers noted there are short-term side effects, such as fever and hallucinations once the amped-up immune system turns against the cancer cells. Long-term side effects are not known, and it’s also unclear whether the cancer will go into remission and possibly return.

Still, scientists are optimistic about what they say will be a pioneering use of gene therapy. One expert hailed it as a major advance that is ushering in a new era of cancer treatment.