Diffuse microglial proliferation after global ischemia in a patient with aplastic bone marrow.

Abundant proliferation of cells having the histologic and tinctorial features of microglia, were seen in the brain of 34-year old man who suffered cardiac arrest 10 days before death and whose bone marrow was nearly totally depleted of white-blood-cell precursors. It is suggested, that in adult human brains there are native microglial precursors which can take on a phagocytic function. Therefore, brain macrophages do not have to originate from circulating monocytes, as suggested by some animal studies.