White cells and the formation of plaque.

T-cells, a type of immune cell that helps defend the body against disease, may play a villain's role in the drama of atherosclerosis, the buildup of plaque that clogs arteries and causes heart attacks.

That's the surprising conclusion reported last week at the American Heart Association's 65th scientific sessions by Augusto E. Villa and William E. Braun of the Cleveland (Ohio) Clinic Foundation.

The researchers' interest in the immune system and atherosclerosis began several years ago, when Braun made an intriguing observation while conducting a study of kidney transplant patients. He discovered that patients with very serious atherosclerosis had significantly fewer white cells circulating in their bloodstream than did patients with clear vessels.

Braun, Villa, and their colleagues designed a study specifically to test that preliminary finding. They recruited 20 middle-aged men and women with coronary artery disease and 20 middle-aged men and women without diseased arteries, who served as a control group. None of the participants had other conditions, such as AIDS, that would alter the white cells found in their blood, Villa says.

All the recruits had undergone angiography, an X-ray examination of the blood vessels that can reveal plaque blocking the arteries. The team noted that 11 of the 20 patients had the most severe type of coronary artery disease, in which two or three arteries supplying the heart with blood are clogged. The researchers took blood samples and measured the number of white cells in the bloodstream.

Compared to the controls, the 11 people with the most severe heart disease had 35 percent fewer T4 lymphocytes, a particular type of T-cell, in their blood, the researchers concluded. And these patients also showed a 25 to 30 percent decrease in a specialized T4 lymphocyte called T4 helper-inducer cells, Villa reported at the meeting in New Orleans.

Villa points out that people with severe atherosclerosis have fewer circulating T4 lymphocytes because these white cells are buried within the plaque clogging their arteries. Scientists believe that fatty lipids such as cholesterol first stick to the inner lining of the artery and then attract T4 lymphocytes (SN: 10/5/91, p.220). The lymphocytes then secrete powerful substances called lymphokines, which may speed up the progression of atherosclerosis, Villa speculates.

The findings may eventually lead to a cheaper way of identifying people with very severe atherosclerosis, Villa says. Rather than sending everyone with symptoms of coronary artery disease to get an expensive angiogram, doctors may be able to pick out high-risk patients with an inexpensive white-cell test. To confirm the suspicion of disease, people with significantly decreased T4 lymphocytes would then go on to receive an angiogram, he adds.

A blood test for T4 lymphocytes could reduce the number of angiograms performed in the United States, Villa points out. A study by Thomas B. Graboys of the Lown Cardiovascular Center in Brookline, Mass., and his colleagues in the Nov. 11 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION suggests that an estimated 50 percent of all angiograms are unnecessary.

The Cleveland study raises questions about how the T4 lymphocytes (and in particular the T4 helper-inducer cells) aid and abet plaque buildup. If researchers can find out how these immune cells accelerate the disease process, they may be able to design new treatments aimed at slowing down or preventing atherosclerosis, Villa adds.