Researchers have found a reliable way to grow helper T cells from stem cells. This procedure solves a major challenge in the immunotherapy of cancer. Helper T cells act as coordinators of the immune system. They help other immune cells to fight cancer longer and more intensively. The team discovered how to precisely control a key signal. This signal determines which type of T cells are formed. Progress will enable the production of ready-made cell therapies. Such therapies will be cheaper, faster and more readily available.