Yale researchers have made an unexpected discovery—turncoat T cells that help a tumor evade other cancer-fighting immune T cells—in a study of patients living with advanced melanoma.

The study by Yale Cancer Center (YCC) researchers at Yale School of Medicine (YSM) discovered that not all CD8⁺ T cells are allies in a body’s fight against cancer cells. Patients living with severe melanoma who had increased levels of suppressor, regulatory CD8⁺ T cells had worse survival outcomes.

The study is published in the journal Nature Immunology.