Gut immune cells help prevent severe salmonella infections

Widely recognized as the face of food poisoning, salmonella bacteria lurk in raw meat and poultry, on pets and in unpasteurized dairy products. If untreated, extreme cases can lead to full-body infections, like Typhoid fever. 

UIC researcher Kiwook Kim asked why some salmonella infections remain in the intestine, causing uncomfortable but nonfatal symptoms like vomiting and diarrhea, while others evolve into life-threatening infections. 

In a new study, he and his team of researchers found that immune cells in a portion of the abdominal cavity, called the mesentery, play a critical role in suppressing - or exacerbating - salmonella infection. The study appears in the Journal of Experimental Medicine. 

The mesentery is a 6-foot, spiral-shaped organ curled up at the back of our abdominal cavity. It's physically linked to the liver, spleen, pancreas and intestines. 

Although the gut mesentery anatomically connects to small and large intestines, its exact function is mysterious. Researchers believe it structurally supports our internal organs, with which it shares blood vessels, lymph nodes and nerves." 

Kiwook Kim, professor of pharmacology and regenerative medicine, College of Medicine, UIC

Many types of immune cells reside within the gut mesentery. Macrophages, immune cells that live in tissues and are everywhere in the body, find and remove germs and damaged or sick cells. Monocytes, similar in function, circulate in the bloodstream and attend to infected areas when needed. 

In a series of tests conducted with mice, the researchers found that the interactions between macrophages and monocytes in the mesentery helped stop salmonella infection from spreading throughout the body.

Further, the researchers noticed that when the mesentery's resident macrophages were removed during salmonella infection, monocytes from the bloodstream flooded the organ. This suggested to the researchers that macrophages help mediate the presence monocytes in the mesentery, kind of like bouncers in a nightclub: Too many immune cells can damage the tissue, so only a regulated amount can pass through the velvet rope. 

"Understanding the relationship between macrophages and monocytes in this portion of the gut can help us manipulate immune cells and develop therapies to treat gastrointestinal infections," Kim said.

Jiseon Kim, a postdoctoral research associate in the College of Medicine, is the study's first author. Kiwook Kim is an affiliate of the University of Illinois Cancer Center.