The human innate immune system is indispensable for protection against potentially invasive microbial and
viral pathogens, either neutralising them or containing their spread until effective mobilisation of the slower,
adaptive (specific), immune response. Until fairly recently, it was believed that the human innate immune
system possessed minimal discriminatory activity in the setting of a rather limited range of microbicidal or
virucidal mechanisms. However, recent discoveries have revealed that the innate immune system possesses
an array of novel pathogen recognition mechanisms, as well as a resourceful and effective alternative
mechanism of phagocyte (predominantly neutrophil)-mediated, anti-infective activity known as NETosis.
The process of NETosis involves an unusual type of programmed, purposeful cell death, resulting in the
extracellular release of a web of chromatin heavily impregnated with antimicrobial proteins. These structures,
known as neutrophil extracellular traps (NETs), immobilise and contribute to the eradication of microbial
pathogens, ensuring that the anti-infective potential of neutrophils is sustained beyond the lifespan of these
cells. The current review is focused on the mechanisms of NETosis and the role of this process in host
defence. Other topics reviewed include the potential threats to human health posed by poorly controlled,
excessive formation of NETs, specifically in relation to development of autoimmune and cardiovascular
diseases, as well as exacerbation of acute and chronic inflammatory disorders of the airways.