The T cells first need to be taught by dendritic cells, which are rare immune cells that are hard to obtain from cancer patients. The UCSF method gets around this by making dendritic cells from induced pluripotent stem cells (iPSCs), which can be grown in large quantities in the laboratory.

Since typical iPSCs would be rejected by the immune system, the scientists first strip them of identifying information, then prompt them to mature into dendritic cells. Finally, they “dress” the dendritic cells with tiny membrane bubbles made from tumor cells. These give the dendritic cells many different signs of the cancer to show to T cells.