New research suggests one's environment plays a larger role in shaping their immune system than genetics do.
Advances in gene-sequencing technologies along with their declining costs have created a larger focus on genetics in health studies, but these new findings suggest genetics have less of an influence on the effectiveness of the immune system than we thought, Stanford University reported.
"Unlike inbred lab mice, people have broadly divergent genetic heritages," said Mark Davis, PhD, professor of microbiology and director of Stanford's Institute for Immunity, Transplantation and Infection. "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."
To make their findings the researchers compared sets of both identical and fraternal twins, which all share the same environment in the womb and usually through childhood as well. The study included 78 monozygotic-twin pairs (identical) and 27 pairs of dizygotic twins (fraternal) from an SRI International registry. Blood was drawn from each participant on three separate occasions, allowing for the measurement of 200 distinct immune-system components and activities.
The team found in three-quarters of the blood samples nonheritable influences such as: "previous microbial or toxic exposures, vaccinations, diet and dental hygiene" were more influential than inherited ones when it came to differences between the twins. These environmental influences were more pronounced in older sets of twins over the age of 60 than in those under 20.
The researchers observed significant environmental differences over the amount of antibodies a participants' body produced in twin pairs that had been vaccinated for influenza. The findings suggest the presence of a single chronic, viral infection could have a huge impact on immune system composition on responsiveness.
"Nonheritable influences, particularly microbes, seem to play a huge role in driving immune variation," Davis said. "At least for the first 20 or so years of your life, when your immune system is maturing, this amazing system appears able to adapt to wildly different environmental conditions. A healthy human immune system continually adapts to its encounters with hostile pathogens, friendly gut microbes, nutritional components and more, overshadowing the influences of most heritable factors."
The findings were published in a recent edition of the journal Cell.
