T cells are white blood cells that play an essential role in the immune system to clear infections and kill tumor cells. As a result, promoting the recovery of T cell immunity is an important therapeutic strategy in numerous clinical settings, such as following stem cell transplantation. In addition, T cells are increasingly exploited in the battle against cancer. In this setting, T cells from the patient are isolated, subsequently genetically modified so that they can specifically recognize the tumor cells, and finally refused into the patient. Unfortunately, this approach is very expensive due to its patient-specific nature and, moreover, it takes a long time before the actual treatment can start. We discovered a mechanism that allows to generate precursor T cells in a more efficient manner. This approach should allow to more rapidly and cost-effectively generate T cells, also tumor specific T cells, that are applicable to a broad group of patients as off-the-shelf cell therapy products.