MICROGLIAL EXPRESSION OF MHC CLASS-II INCREASES IN NORMAL AGING OF NONHUMAN-PRIMATES

The search for factors that influence age-related behavioral and cogni tive slowing is ongoing. Because microglia are involved in many neurol ogical disorders, they may also contribute to changes in normal aging. To assess increases in microglial activity, we used an antibody again st MHC class II to label microglia in three groups of brains from fema le Macaca nemestrina: juvenile (2-5 years), young adult (5-11 years), and mature (11-19 years). Image analysis was completed on four white m atter and three gray matter regions in a single coronal plane. Microgl ial expression of MHC class II increased with age, and was highest in the white matter regions of the mature, or middle-aged, monkeys. The h igher expression of this antigen map indicate that the cells will more easily respond to stimulation. Their location in the white matter sug gest that they may influence myelin loss and the eventual cognitive de cline in aged human and nonhuman primates. (C) 1998 Elsevier Science i nc.