Scientists Discover The Real Reason Some People Get Sick More Than Others
You may have wondered why a seasonal bug puts you outside for a week while your partner gets the sniffles, or why COVID-19 infects some healthy adults while others remain asymptomatic.
For years, the answer was unclear whether it had to do with genetics or luck. However, breakthrough research has finally provided a concrete explanation: your history of infections and environmental exposures physically rewrites your immune system’s workbook.
Researchers at the Salk Institute for Biological Studies in California have found a way to explain this discrepancy. In a study published in the scientific journal Nature Genetics, scientists found that your past experiences – including previous infections and vaccinations – leave “epigenetic fingerprints” on your immune cells.
These markers significantly change the way your body reacts to future threats. It turns out that your immune response isn’t just a product of your inherited genes; a cumulative record of what your body has endured.
The findings challenge the traditional view that physical fitness is primarily static or genetic. Instead, the research highlights the role of the “epigenome” – chemical changes in your DNA that don’t change the gene sequence itself but determine which genes are turned on or off. The research team found that while some aspects of the immune system are hardwired into your DNA, a large part of your immune system’s diversity is determined by these experience-driven changes.
To reach this conclusion, the researchers analyzed immune cells from 110 donors with an extensive medical history, including exposure to influenza, HIV, MRSA, and SARS-CoV-2, as well as those who had received anthrax vaccines. By examining these samples at the single-cell level, the team separated epigenetic changes linked to ancestry (which they called gDMRs) from those linked to life history (eDMRs).
The analysis revealed surprising differences in where these markers reside in your genome. Immune genes tend to cluster around stable genetic regions—basically the structure of your immune system. In contrast, changes caused by life experiences were concentrated in adaptive, regulatory regions.
These “switches” allow your immune system to quickly adapt to new challenges. The findings provide a molecular explanation for a long-standing medical mystery: why genetically identical twins can ultimately develop very different immune responses as lifestyles diverge.
The implications of this discovery are important for the future of personalized medicine. Currently, doctors often cannot predict how a patient will react to a particular pathogen until they are already sick.
This research suggests a future where blood tests can read a patient’s epigenetic history to predict their susceptibility to serious illness before it is revealed. This may allow for precise prevention strategies, tailored vaccinations or prophylactic treatments for individuals based on the unique “fingerprints” left by their past battles with disease.
This research successfully paves the way for understanding the “why” behind immune system diversity. It ensures that every cold, flu, or exposure a survivor has contributed to a unique biological signature – one that dictates how well he or she will weather the next storm.
