DNA lasso

In 2004 a new white blood cell defence mechanism was discovered: the cells extrude DNA threads like nets or lassos to trap and neutralise harmful bacteria.

Neutrophil eating MRSA bacteria
National Institutes of Health (NIH), Public domain, via Wikimedia Commons

White blood cells are the body’s first line of defence against bacteria. Neutrophils are the front line of that first line of defence. Whenever the body detects harmful bacteria, the neutrophils swarm directly toward them, engulf them, and basically eat them. The picture above is a neutrophil ingesting MRSA bacteria. It’s kind of like an amoeba, oozing around on pseudopods, surrounding tasty microbes, and destroying them.

We’ve known about this immune response mechanism for a long time now. In 2004, however, scientists discovered a new white blood cell defence mechanism: neutrophil extracellular traps (NETs). And they are a doozy.

The neutrophil white blood cells take long strands of DNA, plus a few other proteins, and push them out of the cell membrane itself. As in, the neutrophil literally extrudes its DNA through the cell wall like an octopus tentacle. These tendrils are basically DNA nets, or DNA lassos. Their target: dangerous bacteria.

The bacteria hone in on that alluring DNA waving loose and undefended outside the cells’ walls. But it’s a trap! The lassos rope the bacteria before they get as far as the white blood cell proper. And those proteins on the lassos that were coming along for the ride? They’re anti-microbial, and engulf and destroy the trapped bacteria.

Research into this weird mechanism continues today. Some promising lines of inquiry link malfunctioning NETs to lupus, pre-eclampsia, and some cancers. I am just delighted that such an exotic biological function was undetected until recently – the body continues to amaze and surprise.

[Thanks to Cristina G.]

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