Environment More Important than Genes for Immune System

By Jane Farrell

Environment may be a stronger factor than genes in shaping the human immune system, according to a new study.

Research conducted by investigators from the Stanford University School of Medicine also found that the role of environment grows stronger with age.

“The idea in some circles has been that if you sequence someone’s genome, you can tell what diseases they’re going to have 50 years later,” said Mark Davis, PhD, professor of microbiology and director of Stanford’s Institute for Immunity, Transplantation and Infection. But, he emphasized, the immune system has to “think on its feet” – i.e. adapt to unforeseen episodes of infection, injury and tumors.

“Unlike inbred lab mice, people have broadly divergent genetic heritages,” said Davis. “And when you examine people’s immune systems, you often find tremendous differences between them. So we wondered whether this reflects underlying genetic differences or something else. But what we found was that in most cases, including the reaction to a standard influenza vaccine and other types of immune responsiveness, there is little or no genetic influence at work, and most likely the environment and your exposure to innumerable microbes is the major driver.”

In the study, which was published in the journal Cell, Davis and his colleagues compared 78 pairs of identical twins and 27 pairs of fraternal twins. Identical twins have the same genome, while fraternal twins share only 50 percent of their genes on average.

Using blood samples, they found that “nonheritable influences” such as diet and dental hygiene proved more important than genes in determining immune-system response.  The environmental influence was stronger in identical twins who were older than 60.