Which of the following is associated with ependy¬mal cells rather than microglial cells?

Ependymal cells line the cerebral ventricles and have blepharoplasts that are visible with special stains. They are useful histologic markers that document the epen­dymal origin of a brain tumor. Microglial cells are derived from macrophages and are the phagocytic cells of the central nervous system. When activated, microg­lial cells are called gitter cells and have a foamy appear­ance. Neuronophagia (e.g., viral encephalitis, poliomy­elitis) occurs when microglial cells phagocytize breakdown products of the neuron. Rod-like microg­lial cells are seen in neurosyphilis. Macrophages are primarily responsible for carrying HIV into the central nervous system and are the reservoir cell for the virus.