Microglia
Research has discovered dystrophic (defective development) human microglia. "These cells are characterized by abnormalities in their cytoplasmic structure, such as deramified, atrophic, fragmented or unusually tortuous processes, frequently bearing spheroidal or bulbous swellings." The incidence of dystrophic microglia increases with aging. Microglial degeneration and death have been reported in research on Prion disease, Schizophrenia and Alzheimer's disease, indicating that microglial deterioration might be involved in neurodegenerative diseases. A complication of this theory is the fact that it is difficult to distinguish between "activated" and "dystrophic" microglia in the human brain.
Role of microglia in disease
One discrepancy in HAD is the limited number of HIV-1 infected microglia in comparison to the many CNS abnormalities that occur. This suggests that chemical factors that are released from microglial cells are contributing to neuronal loss. "It has become more and more apparent that HIV-1 infected microglial cells actively secrete both endogenous neurotoxins such as TNF-α, IL-1β, CXCL8/IL-8, glutamate, quinolinic acid, platelet activating factor, eicosanoids, and NO as well as the neurotoxic viral proteins Tat, gp120, and gp41."