“…Three major APP protein forms of 695 [3], 751 [41, and 770 amino acids [5], respectively, are derived from an alternatively spliced hn mRNA. APP is synthesized in the brain as well as m several other organs and tissues of healthy individuals (for reviews, see [6,7]), Until now, only cortical and hippocampal neurons, astrocytes, and endothelial cells have been reported to be cortical sites of APP synthesis [5, 8-151. Although numerous reactiv~ microglia are consistently found in and around AD senile plaques [16][17][18][19] and although amyloid was found to beass0ciated with them [17,18,20] nothing is known so far as to whether this cell population of the brain may synthesize APP and thus may contribute to ,6A4 deposits, The question remained open whether the material was synthesized by the ceils themselves or whether it had been phagocytosed. Our intention was to obtain evidence whether or not human microglia might be able to express APP and how it may be regulated, We applied a previously described special cultivation system to obtain terminally Correspondettce address: J, Bauer', Psychiatrische Universit~tsklinik, Hauptstrasse 5, I3-7800 Freiburg, Germany.…”