Study shows how STAT5 optimizes function of CD4+ T cells to drive antitumor immunity Cancer immunotherapy using "designer" immune cells has revolutionized cancer treatment in recent years. In this type of therapy, T cells, a type of white blood cell, are collected from a patient's blood and subjected to genetic engineering to produce T cells carrying a synthetic molecule termed chimeric antigen receptor (CAR) that is designed to enable T cells to recognize and destroy cancer cells. Then these genetically modified CAR T cells are expanded to large quantities and infused back to the patient. CAR T cell-based immunotherapies have seen remarkable outcomes in some patients with certain types of cancer, but more work is needed to improve the persistence and function of CAR T cells so that more patients can benefit from this type of therapy.