The proposed research will develop the technology needed to supply commercially produced cultures of human microglia and specialized media for them to the biomedical research community. Microglia are the only type of immune cell found in the central nervous system in significant numbers. They are normally present in a quiescent state, but in response to injury or infection, they rapidly convert to ameboid macrophage-like cells that can release inflammatory cytokines and reactive oxygen species and are also capable of phagocytosis. Recent studies suggest that insufficiently regulated microglial responses may contribute to a variety of brain pathologies, including the neurodegeneration associated with Alzheimer's disease and the infectious spongioform encephalopathies, as well as delayed nerve loss after cerebral ischemia (stroke). Microglia are also the principal site for HIV infection in the brain, and are believed to be the cell type primarily responsible for HIV encephalitis. Phase I will determine the proliferative potential of normal human microglia and identify the best combinations of existing nutrient media and supplements for culturing them. During phase II, all components of the culture medium and other aspects of the culture system will be optimized and adapted as needed for commercial production. A reliable and consistent source of cultured human microglia will greatly facilitate future research on human brain function and pathology. PROPOSED COMMERCIAL APPLICATION: Clonetics will market the microglia with the accompanying medium. These products will allow basic biochemical and pharmaceutical studies on neurodegerative diseases and other diseases involving the activation of microglia during brain injury.