Tiny DNA nets to catch bacteria

Blood teems with wonders. The image above shows some of its lesser-known denizens in action.

When a certain kind of immune cells, known as neutrophils, are faced with a threatening pathogen they cannot overcome by their usual tactic of engulfment, they hurl out their own DNA as a molecular net in a last-ditch attempt to trap the invader. These DNA snares are called neutrophil extracellular traps, or NETs.

Here, Shigella flexneri bacteria – which can cause diarrhoea – are shown trapped in a NET. The meshlike structure of the NET can be seen between two intact neutrophils.