Immune receptors amplify ‘invader’ signals by turning into mini-machines

When a receptor on the surface of a T cell — a sentry of the human immune system — senses a single particle from a harmful intruder, it immediately kicks the cell into action, launching a larger immune response. But exactly how the signal from a single receptor, among thousands on each T cell, can be amplified to affect a whole cell has puzzled immunologists for decades.