Lysosomes and the "toxicity" of Rickettsiales. IV. Ultrastructural studies of macrophages infected with a cytopathic L cell-grown C. psittaci 6BC strain

Abstract

Mouse macrophages in vitro inoculated with a low dose of a cytopathic L cell-grown C. psittaci 6BC strain were harvested at times when a delayed cytopathic effect (CPE) was observed by light microscopy and when a cytochemical test for acid phosphatase revealed lysosomal enzyme release. An array of different lysosomal types was revealed by ultrastructural studies such as digestive vesicles with single or double outer membranes and whorls of membranes, dense residual bodies, aggregated and single scattered ferritin-like granules, and fragments of membranes. Enlargement of cysternae of endoplasmic reticulum, disintegration of cytoplasmic organelles, and thinning of ground cytoplasm were also observed. Cytoplasmic degeneration has been observed both within membrane-limited structures and in wider areas not limited by recognizable membranes.A high concentration of the agent resulted in an early toxic effect; this was accompanied by a rapid vacuolization of the cytoplasm of the macrophages which showed a poorly developed ultrastructure, and absence of mitochondria and cytoplasmic organelles. Cytochemical tests indicated that these alterations correlated with release of lysosomal acid phosphatase and disintegration of neutral red stained granules. Ultrastructural studies support the view that disintegration of lysosomes may be considered an important contributory factor in the pathology of chlamydial infection.