People whose immune system produces too much of a certain molecule are up to four times more likely to die a premature death compared to those without it, according to a new study.

Researchers said that people whose immune system makes too much of an antibody molecule called a free light chain are significantly more likely to die of life-threatening illnesses like cancer, diabetes and cardiac and respiratory disease, compared to those whose bodies make normal levels.

Investigators analyzed blood samples from nearly 16,000 people aged 50 and older and found that the top 10 percent of those whose blood samples contained the highest level of free light chains were about four times more at risk of dying than those with lower levels.

Even after scientists controlled for age, gender and kidney function, the risk of death was still twice as high.

The latest findings, published in the June 7 issue of Mayo Clinic Proceedings, suggest that high levels of free light chains are indicators of increased immune system response to infection, inflammation or some other serious disorders, according to lead researcher Dr. Vincent Rajkumar of the Mayo Clinic.

Past studies have linked high levels of free light chains to a greater likelihood of death among patients with plasma disorders, such as lymphomas and other blood cancers, but the latest study is the first to link high levels of light chains with increased mortality in the general population.

Researchers said that levels of free light chain can be measured by a serum free light chain assay blood test, which is often used to monitor light chain levels in patients with plasma disorders and to determine how well patients are responding to treatment.

However, Rajkumar warned against taking the simple blood test with the intent of evaluating one’s risk of death.

"We do not recommend this test as a screening test, because it will only cause alarm," Rajkumar said in a statement. "We do not know why this marker is associated with higher rates of death. We do not have a way of turning things around. Therefore, I would urge caution in using this test until we figure out what to do about it and what these results mean."

White blood cells or plasma cells in the blood produce large amounts of antibodies and are important in fighting infections. Researchers explain that the antibodies are made up of two different types of molecules that are tightly connected to each other: heavy chains and light chains.

Most people produce a marginally excess amount of light chains that can be detected in the blood in the "free" state, meaning they are unbound to heavy chains.

While free light chains are generally not hazardous to health, production in excess levels can indicate underlying immune system stimulation, kidney failure or plasma cell disorders like myeloma.

Researchers plan on identifying the precise biological mechanisms that link excess free light chains to a higher likelihood of death, and determining whether specific diagnostic or treatment options gauging free light chains should be pursued.