Endocellular parasitism of Mycobacterium avium in rabbit liver. A morphological study.

Yersin's type of experimental tuberculosis was induced in rabbits by intravenous administration of Mycobacterium avium and was studied in situ in the liver. Mycobacteria were only found in Kupffer-cell phagosomes and, at the later stages of the disease, in the phagosomes of the multinuclear giant cells. Ultrastructural changes in Kupffer's cells amounted to an increase in cytoplasm volume and corresponding increase in the number of ribosomes, endoplasmic reticulum and mitochondria. As compared with control animals, Kupffer's cells were more frequent in the experimental rabbits, clustering around sinusoid capillaries. Characteristic changes in mycobacterium ultrastructure were cytoplasmic vacuolisation in some individuals and an almost regular presence of high-density polymorphous structures. The microbial cell walls remained intact.