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
The infection of mononuclear phagocytes with HIV-1 is an important element in the development of HIV-associated dementia complex (HAD). The only brain cell type that is "productively" infected with the virus are microglial cells. It has also become clear that neurotoxic mediators released from brain microglia play an important role in the pathogenesis of HIV-1.