Environment Affects Your Immunity



How many times have you heard that growing up? Humans are born with an immune system that protects our bodies from bacteria, viruses and other environmental factors. But not everyone’s immune system is the same, even in identical twins. Why does one twin get sick from the flu and the other does not?

Doing a Double Take

To understand the environmental and genetic influences that shape our immune system, scientists turned to the ever-reliable twin study. They recruited 210 identical and fraternal twins between eight and 82 years old and studied how they responded to pathogens. Identical twins possess almost exactly the same DNA and, therefore, should possess identical innate immune systems. So, scientists looked at 95 immune cells and 51 kinds of proteins and found enough variation to rule out genetics as the cause. Furthermore, scientist studied the twins’ individual responses to identical pathogens, in this case: influenza. With identical genetic immune systems, their response should be…identical. It was not.


Nature Versus Nurture

As it turns out, your environment and previous exposure to pathogens play a major role in the development of your immune system. As your body is exposed to antigens from those pathogens, it produces target-specific antibodies to destroy them. Once exposed, your body remembers the specific pathogen and what antibodies it needs to destroy it. Vaccines work by exposing your body to an attenuated virus, producing antibodies and activating your immune system’s ‘memory.’ The next time you are exposed to the pathogen…you won’t get sick!

The immune system is complex and involves many different factors. Genetics and the environment determine our resistance to pathogens. It seems that scientists have found strong evidence that environment and exposure have the greatest impact on when and why you get sick.  

In the future, we should probably tell our kids: “Don't stop. Eat that dirt!”

Extension Questions

  • Why do we give vaccines? Why was this year’s influenza vaccine ineffective in some cases (est. 60 percent)?
  • What can you do to strengthen your body’s immune system?