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You may have heard the phrase “nature versus nurture” before. This is the debate between whether a person’s behavior is shaped more by genetics (nature) or more by experiences and environmental influence (nurture). New research from Stanford University sought to resolve this debate and see whether differences in the human immune system could be attributed to genetics (heritable influences) or the environment (non-heritable influences).

To explore this question, researchers collected blood samples from 210 healthy twins between ages 8 and 82 who had no known immunological deficiencies. Of the 210 twins, 78 were monozygotic (identical twins) and 27 were dizygotic (fraternal twins). The differences in the two types of twins can be seen below. Identical twins develop from one fertilized egg that splits into two, while fraternal twins develop from two separate eggs fertilized by two different sperm cells.

The reason behind the use of twins in the study is that because identical twins share almost all of the same genes, any differences in the immune system between two identical twins can be said to have arisen due to non-heritable and environmental influences. If identical twins are much more similar than dizygotic twins (who share about half of the same genes), we can say that genes play a significant role in the similarity of whatever is being studied. The opposite can be said if identical twins are more different; the environment must play a significant role.

The body’s immune system can attack pathogens that enter the body and keep us from getting sick.

Image Source: Stone | Coneyl Jay

The researchers performed 204 different immune measurements to assess each person’s overall immune system health. Examples of some of the measurements recorded include the number of certain immune cells a person had, shown in the second image, and the immune cells’ response.

Results from these comparisons revealed that 77% of the 204 parameters measured are more significantly impacted by the environment than genes. In other words, non-heritable influences play a much larger role in differences in immunity than genetics. 58% of the 204 parameters were almost exclusively determined by environmental influence.

While there are aspects of our immunity that are inherited, the majority of what determines immunity was shown to be a result of the microorganisms our bodies are exposed to as we move through our lives. It may be hypothesized that those of us with stronger immune systems simply had greater environmental exposure. While there are some serious immunological diseases that are caused by genetic defects, the observation that children with diseases get better over time may be explained, the researchers hypothesize, by the fact that as time goes on, the children gain more exposure to the environment and their immune systems become stronger. This research presents the view that our immune systems are dynamic and constantly adapting.

Feature Image Source: Nature vs Nurture by San Sharma

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