How the Bubonic Plague Shaped Autoimmune Diseases
By Craig Lammert, M.D. AIHA Executive Director
The Black Death and Its Unexpected Legacy
The bubonic plague often brings to mind flea bites and swollen lymph nodes. However, should we also connect the Black Death with autoimmune diseases?
Throughout history, humans have battled countless infections. These diseases shaped our immune systems into what they are today. They may have even contributed to our current risk for autoimmune conditions.
During the second pandemic of the bubonic plague, caused by Yersinia pestis, up to half of Europe’s population died. Those who survived likely carried genes that offered protection. They passed these traits to future generations, changing our genetic landscape.
Searching for Genetic Clues in History
Recently, researchers from several academic medical centers studied how the plague may have changed human DNA. They compared genetic material from people who died before, during, and after the outbreak in London and Denmark.
Their work revealed major differences in immune system–related genes between those who lived before and after the plague.
Key Genetic Findings
The study found that the plague may have “selected” certain immune traits. This means some genes became more common because they helped people survive.
The Role of the ERAP2 Gene
One of the most striking findings involved the ERAP2 gene. This gene influenced how the immune system fought Yersinia pestis. People with the “plague-selected” form of ERAP2 were about 40% more likely to survive infection.
Today, researchers know that ERAP2 responds to many infections. It helps control inflammation in the immune system. Interestingly, the same ERAP2 variant that once protected people from the plague now increases the risk for Crohn’s disease. This connection suggests that natural selection from ancient pandemics may contribute to modern autoimmune diseases.
The CTLA4 Gene Connection
Scientists also found changes in another immune-related gene, CTLA4. This gene plays a role in regulating immune responses. Variations in CTLA4 are now linked to rheumatoid arthritis and lupus. These findings further connect historic infections to autoimmune diseases seen today.
What It Means for Autoimmune Diseases Today
Our genes and immune systems continue to evolve as we face new environmental pressures. The rise in autoimmune conditions may partly result from these ancient genetic adaptations. In other words, the same genes that once saved lives might now make us more vulnerable to autoimmune disease.
A Legacy That Lives On
The next time you wonder how you or a loved one developed an autoimmune disease, remember history’s role. Those plague-infected fleas of the 14th century may have left a lasting mark on our genes.
You can read more in the original article here.
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