(University of Otago) An unexpected role for a white blood cell called the Natural Killer (NK) cell — a critical cell for ridding the body of infection and cancer, has been discovered by researchers t New Zealand’s University of Otago. The NK cell is a ‘vigilante’ killer — a white blood cell that destroys invaders and cancer cells through a process of ‘identity card’ checking.The researchers’ new work shows that violent vigilante NK cells act as helper cells to start up the immune response.