MS: Why Our Immune System Gets It Wrong

The story of multiple sclerosis (MS) starts with our genes and ends in a modern kitchen. Some scientists say that the very DNA that makes us strong against bugs also makes us prone to MS. They call this “antagonistic pleiotropy. ” Other researchers point out that we used to live with tiny worms and other microbes that kept our immune system calm. When those helpers disappeared because of cleaner homes, the immune system began to overreact. That idea is called the “Old Friends” hypothesis. Recent DNA scans from ancient people have added a new twist.

People who moved across Eurasia during the Bronze Age came from the Pontic‑Caspian Steppe. Their hunter‑gatherer and early farmer lifestyle exposed them to many animal diseases, pushing their immune system toward a strong inflammatory response. At the same time they probably had plenty of worm infections that kept the inflammation in check. This balance meant fewer auto‑immune problems back then. Today, our cleaner lives mean fewer worms and more “clean” environments. The immune system that was once balanced now flares too much, leading to higher rates of MS—especially in northern Europe where the Steppe ancestry is common. So, the mix of ancient genetics and modern hygiene may explain why MS is on the rise.

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