PT134 · S3 · Q17 Science writer: The deterioration

The author is presenting two parallel causal ideas: Alzheimer's → protein BA buildup + Microglia attacks → destroys → mental protein BA buildup healthy deterioration with poisons cells This answer is saying low microglia levels → protein BA buildup The author doesn't need that to be true, and it doesn't really fit his story well. Since he expects microglia activity to be present in a patient with protein buildup, he wouldn't expect that protein buildups go hand-in-hand with low levels of microglia.

The author thinks microglia causes the mental deterioration of Alzheimer's through the behavior of attacking protein buildup with poisons. If they attack the protein deposits in the brain, one would think that their activity results in a decreases of protein deposits. So this answer seems to explicitly state something that we already knew / took for granted. Ultimately, for the author's causal story to work, it's less important whether microglia successfully get rid of protein deposits and more important just that the poisons microglia release in an attempt to get rid of protein deposits kill enough healthy brain cells to cause mental deterioration.

This poses an alternate cause for the mental deterioration of Alzheimer's: the protein buildup itself causes it.

Since microglia are the brain's immune cells, we'd expect them to be involved in other brain diseases. But that tells us nothing about whether microglia cause the mental deterioration associated with Alzheimer's.