Joan Plant, tracing family tree.
For a disease-causing microorganism to infect the human body there must be a gateway or portal through which it enters into human cells. The plague bacterium works this way, hijacking the white blood cells sent to eliminate it. Traveling inside the white blood cells to the lymph nodes, the bacteria break out and attack the focal point of the human immune system. Dr. Stephen O'Brien felt that the mutated CCR5 gene, delta 32, may have prevented the plague from being able to enter its host's white blood cells.
Eyam provided O'Brien an ideal opportunity to test this theory. Specifically, Eyam was an isolated population known to have survived a plague epidemic. Everyone in the town would have been exposed to the bacterium, so it's likely that any life-saving genetic trait would have been possessed by each of these survivors. "Like a Xerox machine," says O'Brien, "their gene frequencies have been replicated for several generations without a lot of infusion from outside," thus providing a viable pool of survivor-descendents who would have inherited such a trait.
Dr. Bill Paxton examines Steve Crohn's DNA. | |
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