The study found higher blood levels of an antibody called IgG were linked to lower risk of heart attack in a group of people with high blood pressure.
The study, from Imperial College London in the United Kingdom, is published in the journal EbioMedicine. It describes how the team discovered a link between blood levels of Immunoglobulin G (IgG) antibodies and reduced chances of having a heart attack.
Lead investigator Dr. Ramzi Khamis, a consultant cardiologist and clinical research fellow, says:
"Linking a stronger, more robust immune system to protection from heart attacks is a really exciting finding. As well as improving the way we tell who is at the highest risk of a heart attack so that we can give them appropriate treatments, we now have a new avenue to follow in future work."
Coronary artery disease is the most common type of heart disease, and is caused by atherosclerosis, an inflammatory disease where plaque - deposits of cholesterol and other substances - builds up in the walls of the arteries that supply blood to the heart.
As the plaque builds up, the blood supply to the heart lessens and weakens the heart muscle, raising the risk of a heart attack or other cardiac event. Every year, about 735,000 Americans have a heart attack.
Various studies have shown that the immune system is involved in atherosclerosis, playing both helpful and unhelpful roles. IgG is the most abundant antibody in the immune system. It protects the body against infection by bacteria and viruses.
IgG independently linked to lower heart attack risk
For their study, Dr. Khamis and colleagues compared patients who took part in the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) with matched controls. The ASCOT study involved over 19,000 patients in the U.K., Ireland, and Nordic regions who had high blood pressure and were at high risk of a cardiovascular event.
The researchers analyzed blood levels of total IgG and another antibody called Immunoglobulin M (IgM). They also examined blood levels of antibodies against oxLDL - an oxidized form of low-density lipoprotein (LDL) cholesterol, or "bad" cholesterol, that is known to promote atherosclerosis.
The results showed participants with higher levels of general antibodies and anti-oxLDL antibodies had a lower risk of heart attack.
The team was surprised to find the strongest link to reduced heart attack risk was to higher levels of IgG, and this was independent of other risk factors, such as cholesterol and blood pressure.
The study focused on people with high blood pressure. The team now wants to find out if the link exists in other at-risk groups.
The researchers note that measuring blood levels of IgG is simple and cheap, and subject to further investigation, their finding could lead to an easier way for doctors to determine their patients' risk of heart attack.
"We hope that we can use this new finding to study the factors that lead some people to have an immune system that helps protect from heart attacks, while others don't. We also hope to explore ways of strengthening the immune system to aid in protecting from heart disease."
Dr. Ramzi Khamis