29 March 2019
Vol 363, Issue 6434

About The Cover

Cover image expansion

COVER T cells (specialized immune cells that can destroy tumors) may lose functionality during development, depicted here as balls rolling down sloped tracks. High levels of potassium (orange) preserve T cells in a "stem-like" state that maintains their ability to persist, divide, and fight tumors. The presence of tumor-specific T cells with stem cell–like properties helps to explain the effectiveness of cancer immunotherapies and guides the design of improved treatments. See pages 1395 and 1417.
Illustration: V. Altounian/Science