Cells in the gut send secret messages to the immune system. Thanks to new research from La Jolla Institute for Immunology (LJI) scientists, we can finally get a look at what they’re saying.

A new study in Science Immunology reveals how the barrier cells that line the intestines send messages to the patrolling T cells that reside there. These cells communicate by expressing a protein called HVEM, which prompts T cells to survive longer and move more to stop potential infections.

“The research shows how barrier cells in the intestine, structural elements of the tissue, and resident immune cells communicate to provide host defense,” says LJI Professor and Chief Scientific Officer Mitchell Kronenberg, Ph.D., senior author of the new study.

Barrier cells, or “epithelial” cells, form a one-cell thick layer that lines the gut. One can picture these cells lining up like a busy queue outside a nightclub. The epithelial cells squish together. They jostle each other and chat. Meanwhile, T cell security guards circulate around the line, looking up and down the block for signs of trouble. “These T cells move around the epithelial cells as if they are truly patrolling,” says Kronenberg.

But what keeps these T cells in the epithelium to do their job?

“We’ve got some insight on what gets T cells to the gut, but we need to understand what keeps them there,” says Kronenberg. In fact, a lot of immune cells reside long-term in specific tissues. By understanding the signals that keep T cells in certain tissues, Kronenberg hopes to shed light on conditions like inflammatory bowel disease, where far too many inflammatory T cells gather in the bowel.

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