HUMAN MUSCLE MACROPHAGES EXPRESS BETA-AMYLOID PRECURSOR AND PRION PROTEINS AND THEIR MESSENGER-RNAS

WELL-CHARACTERIZED antibodies against beta-amyloid precursor protein ( beta APP) and prion protein (PrP), and specific cRNA probes, were used to localize beta APP and PrP and their mRNAs in human muscle macropha ges. Macrophages present in muscle biopsies of 51 patients with variou s neuromuscular disorders showed accumulation of beta APP and PrP, and strongly expressed beta APP and PrP mRNAs. These were present in all muscle macrophages unrelated to their localization within the muscle t issue or diagnosis. Our study provides the first demonstration that hu man muscle resident macrophages synthesize and accumulate beta APP and PrP. We suggest that those proteins play a role in biology of muscle macrophages, including their participation in inflammatory and immune responses.