Otago University researchers have found an unexpected role for the natural killer (NK) cell, which is critical for ridding the body of infection and cancer.
The NK, a 'vigilante', is a white blood cell that destroys invaders and cancer cells through a process of 'identity card' checking.
The researchers have now shown that it acts as a helper cell to start up the immune response.
Associate Professor Alex McLellan says NK cells patrol the body and destroy abnormal cells, especially infected or cancer cells.
They examine the surface of all cells and look for molecules that are present on healthy cells.
"Certain molecules act like identity cards, and NK cell are vigilantes, ready to respond if they don't see an ID card on cells," he said.
"During infections or with cancer, the absence of these molecules triggers the NK cells to destroy the cells."
The researchers, whose findings appear in the international Journal of Immunology, have identified a new way that NK cells act during infections or cancer.
"A few years ago, we showed that NK cells were required for the vaccination response against cancer," Assoc Prof McLellan said.
"The group has now recognised that NK cells enhance the ability of the immune system to recognise fragments of tumour cells released into the blood."
He said these fragments induced potent immune responses against cancer.
The new research showed that NK cells were critical for the immune activity of these fragments and also explained how such potent immune responses arose.
"This work also reveals new ways that NK cells help the immune system, aside from in their rather violent vigilante role," he said.
The group is looking at ways to improve NK cell function through living vaccines and growth factors to enhance the immune response to cancer.