A tenuous connection has emerged between stress, the immune system, and cancer, with a surprising new insight that is changing the direction of research: it now appears that cancer cells make proteins that actually tell the immune system to let them alone and even to help them grow.

One immediate consequence of this line of thinking is a new idea for treatment: scientists could seal off the cancer cells’ proteins that block the immune system and enable white blood cells to kill the tumor. Or they could make the immune system more aggressive. To do that, they can block a molecule on the surface of T cells, CTLA-4, that tends to dampen the immune response.