Every encounter between a T cell and a potential target—especially when that target is a developing tumor—begins with a rapid series of molecular decisions. Within seconds, the immune cell must determine whether to launch an attack or stand down. T cells are so potent, so potentially devastating, that misreading the situation can cause serious tissue injury.

But cancer cells come equipped with a bag of tricks that allows them to disarm these powerful warriors of the immune system. All of these activities, whether mediated by T cells or their targets, occur at split-second speed and unfold at the point of cell-to-cell contact.

Now, scientists have identified tiny nanoscale contact points where those decisions are made, revealing how activation and inhibitory signals are integrated at the first moments of a cell-to-cell encounter.