HD6 Cobwebs Shield the Human Gut from Unwanted Invaders

HD6 Cobwebs Shield the Human Gut from Unwanted Invaders

Just like spiders, we weave webs – microscopic ones that capture and prevent microbes from irritating the lining of the small intestine. This discovery could help with the development of treatments for inflammatory bowel disease.

We think their major function is to defend against fungi, bacteria and other pathogens says Charles Bevins, head of the team at the University of California, Davis, that discovered the webs.

HD6 Cobwebs Shield the Human Gut

The protein that makes this intestinal web – human alpha defensin 6 (HD6) – has been a mystery for decades.

HD6 was thought to kill invaders directly, by punching holes in the walls of bacteria, for example, because that is how other defensins such as HD5 work.

Yet when Bevin’s team tested HD6 against bacteria, it didn’t seem to kill them. Then, three years ago, one of his graduate students, Hiutung Chu, noticed that a white web-like haze formed when she added HD6 to a solution containing fungi. “That was the eureka moment, when the penny dropped with what was going on,” says Bevins.

Caught in a trap

Further investigation showed how, in the right environment, HD6 molecules bind to each other to form a fibrous web after they have ensnared individual bacterial or fungal cells. This web prevents trespassers from infiltrating intestinal crypts – recesses that lie at the bottom of villi that line the small intestine.

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