Now, scientists have discovered that certain immune cells depend on these molecules to activate and destroy cancer cells and that tumors exploit this dependency by releasing natural antioxidants to shut down the immune attack.

The findings, published today in Science, could help improve the effectiveness of cancer immunotherapies.

Our immune system keeps us healthy by hunting down and destroying harmful material, including invading bacteria and viruses, as well as cancer cells. It does so by deploying a number of different types of immune cells, including specialized cells known as T cells. These T cells hunt down and destroy tumor cells, but they need small amounts of reactive oxygen species to activate and switch on their killing ability.