PORTLAND, Ore. -- Medical science has known for years that people who drink moderate amounts of alcohol actually have a reduced risk of death. In general, they are healthier and have better cardiovascular function that those who don't drink alcohol at all.

Now, new research from Oregon Health & Science University adds a fascinating twist: moderate drinking may actually bolster our immune system and help it fight off infection.

The research, published Dec. 17 in the journal Vaccine, not only opens a new window into scientific understanding of the immune system, it also could help scientists find new ways to improve the human body's ability to respond to vaccines and infections.

The scientists did their research in rhesus macaques, which have an immune system very similar to humans. To conduct the study, the researchers trained a group of 12 rhesus macaques to consume alcohol -- a 4 percent ethanol mixture -- of their own accord.

Researchers vaccinated the monkeys against small pox as part of the study. They then separated the animals into two groups -- those with access to the 4 percent ethanol and those with access to sugar water. All of the animals had regular access to pure water, and to food.

The researchers then monitored the animals' daily ethanol consumption for 14 months. And the animals were vaccinated again, seven months after the experiment began.

"Like humans, rhesus macaques showed highly variable drinking behavior," said Ilhem Messaoudi, the lead author of the paper, a former assistant professor at the Vaccine and Gene Therapy Institute at OHSU and assistant scientist in the Division of Pathobiology and Immunology at the Oregon National Primate Research Center and now an associate professor of biomedical sciences at the University of California, Riverside. "Some animals drank large volumes of ethanol, while others drank in moderation."

The monkeys' voluntary ethanol consumption segregated them into two groups. One group was made up of heavy drinkers, those that had an average blood ethanol concentration greater than 0.08 percent -- the legal limit for humans to be able to drive a vehicle. The other group was made up of moderate drinkers, with an average blood ethanol concentration of 0.02 to 0.04 percent.

Prior to consuming the alcohol, all of the animals showed comparable responses to the vaccination. But after exposure to the alcohol, the two groups of monkeys responded in very different ways to the vaccination.

The heavy drinkers showed greatly diminished vaccine responses compared with the control group of monkeys who drank the sugar water. But the more surprising finding: the moderate-drinking monkeys displayed enhanced responses to the vaccine compared to the control group. Moderate drinking bolstered their bodies' immune systems.

"It seems that some of the benefits that we know of from moderate drinking might be related in some way to our immune system being boosted by that alcohol consumption," said Kathy Grant, Ph.D., senior author on the paper, a professor of behavioral neuroscience at OHSU and a senior scientist at the ONPRC.

The researchers stressed that excessive alcohol consumption was injurious to the monkeys' immune systems -- just as excessive alcohol consumption is bad for human bodies in many ways.

"If you have a family history of alcohol abuse, or are at risk, or have been an abuser in the past, we are not recommending you go out and drink to improve your immune system," Messaoudi said. "But for the average person who has, say, a glass of wine with dinner, it does seem in general to improve health and cardiovascular function. And now we can add the immune system to that list."

The next steps for the researchers will be to better understand why the immune system reacts as it does to moderate alcohol. That may lead to a pharmaceutical alternative that could provide the same benefits as the moderate alcohol consumption.

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The study was funded by the National Institutes of Health (grant #8P51 ODO11092-53) and the National Institute on Alcohol Abuse and Alcoholism within the NIH (grant # R21AA021947).

The study was carried out under strict accordance with the recommendations outlined in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health, the Office of Animal Welfare and the U.S. Department of Agriculture. The study also was approved by the Oregon National Primate Research Center Institutional Animal Care and Use Committee.

About ONPRC

The ONPRC is one of the eight National Primate Research Centers supported by NIH. ONPRC is a registered research institution, inspected regularly by the United States Department of Agriculture. It operates in compliance with the Animal Welfare Act and has an assurance of regulatory compliance on file with the National Institutes of Health. The ONPRC also participates in the voluntary accreditation program overseen by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC).

About OHSU

Oregon Health & Science University is a nationally prominent research university and Oregon's only public academic health center. It serves patients throughout the region with a Level 1 trauma center and nationally recognized Doernbecher Children's Hospital. OHSU operates dental, medical, nursing and pharmacy schools that rank high both in research funding and in meeting the university's social mission. OHSU's Knight Cancer Institute helped pioneer personalized medicine through a discovery that identified how to shut down cells that enable cancer to grow without harming healthy ones. OHSU Brain Institute scientists are nationally recognized for discoveries that have led to a better understanding of Alzheimer's disease and new treatments for Parkinson's disease, multiple sclerosis and stroke. OHSU's Casey Eye Institute is a global leader in ophthalmic imaging, and in clinical trials related to eye disease.