Many molecules in our bodies help our immune system keep us healthy without overreacting so much that our immune cells cause problems, such as autoimmune diseases. One molecule, called AIM2, is part of our innate immunity—a defense system established since birth—to fight pathogens and keep us healthy. But little was known about AIM2’s contribution to T cell adaptive immunity—defenses developed in response to particular pathogens and health problems we develop over the course of our lives.