Association of lysosomal enzymes in cultured fibroblasts with the intracellular growth of Mycobacterium lepraemurium.

An established line of rat fibroblasts (14pf), growing in either of two media, was infected with One of the media (equal parts of human cord serum and Hanks' balanced salt solution) supports active intracellular bacterial multiplication, whereas the other (10 per cent calf serum in Eagle's medium with added peptone) fails to do so. Within 1 week of infection, the cells were stained for acid phosphatase, aryl sulphatase and β-galactosidase activities and examined by light microscopy. Cells in equal parts of cord serum and Hanks' balanced salt solution showed an accumulation of all 3 enzymes around the bacteria whereas cells in 10 per cent calf serum in Eagle's medium showed only light, diffuse, general staining with little localization around the bacteria. Cells in the former medium also had greater lysosomal activity before infection with than cells in the latter medium, showing that the increased activity was not the result of intracellular multiplication of the bacteria. It is concluded that the failure to support mycobacterial growth by the cells growing in the medium containing calf serum must be unconnected with direct lysosomal action. A possible beneficial effect of lysosomal enzymes on the growth of these obligate intracellular mycobacteria is suggested.