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The Inconstant Gardener

Microglia, the same immune cells that help sculpt the developing brain, may do damage later in life

Like the cavalry in old Western movies, certain immune cells in the brain rush to answer distress calls and save the day. If a nerve cell is injured or a toxin attacks the brain, these microglia ride to the rescue, moving to the injury site and destroying any bad guys they encounter.

But even in the movies the cavalry, mistakenly or intentionally, sometimes mows down innocent bystanders. A similar scenario may be playing out in the brain with processes that normally limit damage: Microglia may be improperly activated late in life and play a role in neurodegenerative disease.

Take Alzheimer’s as an example. People with Alzheimer’s disease lose millions of nerve cells in brain areas crucial for memory. As the losses grow, the brain also becomes cluttered with clumps of plaque containing a protein fragment called amyloid-beta, or A-beta. Where these plaques emerge, microglia appear as well.

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