Macrophages, microglia, and dendritic C

Celebrated as the decade of the brain, the ten years between 1990 and 2000 gave rise to an increased awareness of brain function in health and disease. At the cellular level, none other than the microglia emerged as stars of the decade despite being only 10% of the total brain cell population. The profiles of microglia overpower, in part, neurons (Streit et al., 1999). In this chapter, we provide an overview of the diverse functions of microglia including their ontogeny, immune functions, and the spectrum of their responses during neurodegeneration. Microglia are the brain's mononuclear phagocytes (MP) and are influenced by their microenvironment (Streit, 2006). Phagocytosis, killing, secretion of bioactive factors, and antigen presentation are function shared amongst all MP including microglia. Such roles in both health and disease are developed and discussed, in some detail, in this chapter.