Immune cells do more than just fend off infections. When cholesterol starts building up in arteries, scavenger white blood cells known as macrophages report to the scene to start trying to digest it. These little cells, though, don't always manage to clear the site and often end up as part of the blockade themselves. These building plaques can restrict blood flow in the artery—a precursor to a heart attack—or dislodge and wind up in the brain—leading to stroke.

Another kind of immune cell, however, seems to ward off atherosclerosis (a.k.a. hardening arteries). Dendritic cells, so-named for their long, spindly arms, coordinate immune responses, and new research shows that one subtype, known as Flt3 signaling-dependent dendritic cells, might actually be helping to cut down on the arterial buildup.

These cells, for instance, were far less prevalent in mice that had been genetically programmed to have atherosclerosis than in the hearts of healthier mice, according to the new findings, published online Thursday in Immunity. The discovery suggests that these specialized dendritic cells are helping to protect against the condition. The senior study author, Ralph Steinman of Rockefeller University, described dendritic cells in the 1970s, work for which he received the 2011 Nobel Prize in Physiology or Medicine (but died just days before the October announcement).

The findings suggest a far more complex role for the immune system in this common cardiovascular disease, "with one subset of [dendritic cells] providing a protective edge," Steinman and his colleagues wrote. This preliminary research should pave the way for new possibilities for treating atherosclerosis.