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September 15, 2008
Arteries from distinct body regions have unique alarm functions

By Quinn Eastman

Human arteries play distinct roles in the immune system depending on their anatomical location, Emory researchers have discovered.

Their findings explain why vascular diseases affect different parts of the arterial network and could help doctors fine-tune the treatment of such diseases as atherosclerosis and vasculitis. Atherosclerosis causes heart attacks and strokes because it occurs preferentially in arteries supplying the heart and the brain.

The results were published online Sept. 2 by the journal Circulation.

Cells embedded in the arterial walls called dendritic cells act like smoke-sensing fire alarms for the immune system, says immunologist Cornelia Weyand.

“All of our major arteries have this alarm system,” she says. “To our surprise, we found that the arteries of the neck, the arms, the abdomen and the legs are triggered by different infectious organisms.”

Some vascular diseases attack arteries only in the abdomen or in the neck and upper extremities, and this selectivity has puzzled doctors for years, Weyand said.

To probe the differences among arteries, Weyand and her colleagues examined the activity of genes that encode Toll-like receptors in blood vessels from human donors. Each type of artery had a different set of Toll-like receptor genes turned on.

Toll-like receptors are a cornerstone of the “innate” immune system. The capture of bacterial or viral fragments through Toll-like receptors alerts the immune system early during an infectious attack. Toll-like receptors can respond to whip-like antennas on bacteria called flagellae, parts of bacterial cell walls, or DNA and RNA that leaks from viruses or bacteria.

Weyand hypothesized that the dendritic cells in arteries are mainly performing a protective, calming function. For example, the reason cells in the iliac arteries, located in the vicinity of the gut, respond avidly to flagellae may be because of the abundant bacterial flora that inhabits the gut, she said.