Phagocytosis of Mycobacterium leprae and M. avium by armadillo lung fibroblasts and kidney epithelial cells.

In vitro cell cultures of lung fibroblasts and kidney epithelial cells were established from a freshly killed armadillo and were inoculated with Mycobacterium leprae. Lung fibroblasts were also inoculated with M. avium. Phagocytosis was allowed for 6 h at an input of about 50 bacilli/cell, and the ultrastructure was then studied at 24 and 48 hours, and 4, 7 and 10 days. Following observations were made: 1. Armadillo cells could be maintained for nearly 3 months. 2. Both lung fibroblasts and kidney epithelial cells phagocytized M. leprae at a high rate. 3. Lung fibroblasts also phagocytized M. avium but with a rate much slower than M. leprae. 4. Both in M. leprae and M. avium, an electron-translucent halo surrounded the ingested bacteria within hours of phagocytosis, and this halo appeared to lessen the diffusion of lysosomal enzymes towards the bacterium. 5. M. leprae was often phagocytized in clumps of 3 to 5 bacilli, which separated inside the cell resulting into small individual phagosomes with a single bacterium. 6. In our experimental conditions, there was no evidence of multiplication for both M. leprae and M. avium. 7. The phagocytized bacilli slowly degraded with longer incubation periods, however, the undigested cell bodies remained inside the phagosomes.