Salmonella invading an immune cellWIKIMEDIA, NIAIDA person’s gut is full of microbes—some beneficial, some not. Friend or foe, these bacteria must be prevented from accessing the rest of the body, where they could cause harm. In a paper published in Science today (November 12), researchers describe a barrier in mice between the intestine and the adjacent blood vessels that restricts the size of particles that can pass through. The team also shows, however, that Salmonella bacteria can suppress a chemical pathway critical to barrier function, enabling the bugs to invade.
“First of all, [the authors] are really defining and showing the existence of this barrier and in what way it resembles the brain [barrier],” said immunologist Bana Jabri of the University of Chicago who was not involved in the study. “Then they show a pathogen that apparently has evolved to modulate that barrier to its own favor.”
The intestine is lined with epithelial cells covered in mucus. These cells provide both a physical barrier against microbial intrusion—they are tightly packed together—as well as biochemical one—they secrete antimicrobial proteins. In addition, the mucus itself “acts like a rip tide,” continuously washing the bacteria away from the epithelial shore, said gastroenterologist and immunologist Andrew Macpherson of the University of Bern in Switzerland who also did not participate ...
