Study: Environment trumps genetics in shaping immune system

WASHINGTON — New research shows that how your immune system does its job seems to depend more on your environment and the germs you encounter than on your genes.

Scientists know there is tremendous variation in how the immune systems of healthy people function. Stanford University researchers compared identical and fraternal twins to ask if that's more a matter of nature or nurture. Traits shared by identical twins are more likely to be hereditary.

In most cases, the researchers found little genetic influence. Such differences as how the twins responded to flu shots were more likely explained by environmental factors including previous infections or vaccinations. And the older the twins became, the more experience mattered.

The study was published Thursday in the journal Cell.