Neutrophil extracellular traps (NETs) are web-like structures that immune cells called neutrophils use to trap and kill microbes such as bacteria or fungi. NETs are shown as DNA (blue) forming a complex with neutrophil granule protein elastase (red). Normally, NETs are released in response to invading pathogens, but have also been associated with autoimmune diseases. For this image, NETs were induced by levamisole, a drug that can promote autoimmunity.