Lysosomal breakdown of amyloid fibrils by macrophages

ABSTRACT

Mouse peritoneal macrophages incubated with isolated human amyloid fibrils for varying periods of time up to 24 hours were studies by electron microscopy, and by electron microscopic cytochemistry for demonstration of acid phosphatase activity. The sequential changes in cytoplasmatic vacuoles in macrophages containing the amyloid fibrils and related material were analyzed and compared with those in controls and with direct enzymatic digestion of amyloid fibrils. the results suggest that the lysosome into amorphous, granular or finely filamentous material and absorbed, leaving undigested material as membranous or myeling the lysosomal enzymes into the amyloid-phagosome or the amyloid-phagolysosome was studied and interpreted as showing (1) fusion of primary lysosome (s) with the phagocytic vacuole, (2) autophagy of primary lysosome(s) into the heterophagic vacuole, and (3) transport of the enzymes into the phagocytic vacuole durectly from the Golgi associated vesicles or smooth endoplasmatic reticulum.