March 14, 2012

‘Nature’ publishes key ‘goblet cell’ research study

by Tim Crosby

CARBONDALE, ILL. -- When someone with food allergies eats the wrong kind of food, the person’s body declares full-scale war, attacking the food protein with everything it has in a desperate attempt to protect the body from what it perceives as a dire threat.

And in the process, unfortunately, instead of the protecting the body this response sometimes ends up gravely harming or even killing it.

A researcher at Southern Illinois University Carbondale, however, has helped make some recent discoveries that might lead to new vaccines or targeted drug therapies that would prevent food allergies from causing such harm.  And her research, which centers on a new technique for studying the cells in the intestines of living mice and observations using this technique, will be shared with the scientific world community this week when it is published in the journal, “Nature.”

Vjollca Konjufca, assistant professor of microbiology in the College of Science, is one of the authors of the paper titled “Goblet cells deliver luminal antigen to CD103+ dendritic cells in the small intestine.” The paper is set for publication in “Nature” on Thursday, March 15.

Konjufca, who arrived at SIU Carbondale in 2010, pioneered the technique for imaging the intestinal tract in living animals while working at Washington University in St. Louis.  While working there, she discovered how to use two-photon microscopy to study the interaction of cells in the small intestine of living mice. Konjufca used a chemical to temporarily halt the peristaltic squeezing muscle action in the mouse’s intestines in order to bring the powerful, laser-based microscope to bear.

The microscope works by using a laser to excite fluorescent proteins in the living mouse.  The fluorescent proteins (or small probes) can be either injected into the blood flow of the mouse or fed to the mice.  In addition, mice used in this type of research have been engineered to express fluorescent proteins in certain cells. The use of different fluorescent colors expressed in cells and antigens injected or fed to the mouse, enables one to keep track of the different teams on the field, so to speak.

The microscope has the ability to peer relatively “deep” into the living organism -- up to 500 microns  -- and allows the researchers to observe cells, protein antigens or bacteria that cause infection interacting in the mouse’s gut.  The microscope views the action in “slices” of progressive depth that, when assembled by computer software, provide a fascinating peek at life on a microscopic level.

It was after developing this technique that Konjufca began making observations that would eventually lead to new discoveries about the so-called “goblet cells” lining the intestinal tract. While tracking one set of fluorescent antigens working its way thrqough the mouse gut, she observed them being taken in at certain points in the intestine’s villi (finger-like structures), and being passed deeper into dendritic cells within the villi.

“I started wondering how the substance was coming in at those selected spaces, what was the entry point?” she said.  “I noticed these little conduit-like structures that penetrated the villi, leaving little tracks and was seeing the antigen enter those.” 

After some theorizing and further experimentation, Konjufca found that these “channels” were not a part of lymphatics and that neither Salmonella nor Norovirus infection altered the appearance of these structures.    However, when she introduced a fluorescent egg protein into the gut, she saw the same reaction. 

The distribution of the conduit-like structures caused her to theorize that goblet cells were providing the pathway for antigen entry into the deeper dendritic cells, but she left for SIU Carbondale before having a chance to prove it.

Colleagues at Washington University eventually ran the experiments that confirmed Konjufca’s suspicions.  And it turned out to be quite a discovery.

Goblet cells, which get their name from their flared, goblet-like conical shape, are known to supply the mucus that lines the inside of the intestinal tract, protecting the epithelial lining.  Finding out that they may also act as an inlet for antigens, however, is a potentially important discovery.

“It will help us better understand the mechanisms of soluble antigen uptake from the intestinal lumen and induction of immune tolerance to these antigens.  It will also open the possibilities of new vaccine designs and drug-targeted therapies,” Konjufca said.

One of those, for instance, might target those who suffer from severe food allergies. As the goblet cells allow such food antigens into the dendritic cells, the body must decide whether to tolerate the foreign substance or mount a campaign against it.  One particular dendritic cell, known as CD103-positive dendritic cell, helps the body tolerate such foreign matter instead of mounting an immune reaction.

“We know the intake is happening through goblet cells and we know dendritic cells that are important for helping us tolerate antigens are picking up the antigens, so we’ve taken it that far,” she said.  “Oral tolerance is an immune response that tells the body not to react to innocuous food antigens.”

People with peanut allergies, for example, have an immune reaction to the peanut protein instead of tolerating it.  That’s why they react so strongly.  So one could develop a vaccine or therapy for them.  But first, scientists must characterize the immune responses that are induced to the antigens that enter the body through goblet cells.

“We’ve discovered a novel way that the body takes up antigens from the lumen of the gut,” she said.  “So now, the outcome of this antigen uptake is the topic of more research.”

The other authors of the paper include Jeremiah R. McDole, Leroy W. Wheeler, Keely G. McDonald, Baomei Wang, Kathryn A. Knoop, Rodney D. Newberry and Mark J. Miller, all of Washington University School of Medicine.