Enlarged and phagocytic, but not primed, interleukin-1 alpha-immunoreactive microglia increase with age in normal human brain
Abstract
Microglia-mediated inflammatory responses have been implicated in the pathogenesis of neuritic plaques in Alzheimer's disease. The strong age association of Alzheimer's disease incidence suggests that events in normal aging may promote such responses. We used immunohistochemistry and computerized image analysis to determine the numbers, size, activation state, and immunoreactive intensity of interleukin-1 alpha-immunoreactive (IL-1 alpha +) microglia in mesial temporal lobe of 20 neurologically normal individuals, 2-80 years of age. We also used Northern analysis to determine tissue levels of IL-1 alpha mRNA in an additional 11 neurologically normal individuals aged 1 day to 78 years. IL-1 alpha + microglia were characterized as primed, enlarged, or phagocytic (enlarged with heterogeneous cytoplasmic contents) based on morphology. These three microglial subtypes showed significant differences in size [27 +/- 1 58 +/- 2 114 +/- 6 (mean +/- SEM) micron 2/cell, respectively, P < 0.001 for each comparison] and in immunoreactive intensity [60 +/- 1 68 +/- 2 79 +/- 2 (arbitrary units), respectively, P < 0.001 or better for each comparison]. There were significant age-associated increases in the total numbers of activated IL-1 alpha +...Continue Reading
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