Infection of Mycobacterium leprae and Mycobacterium lepraemurium into a cloned macrophage like cell line

Abstract

Intracellular killing of Mycobacterium leprae and M. lepraemurium by cloned macropha- ge cell line was observed by direct staining with FDA/EB or in the spread subcutaneous tissue preparation with Ziehl-Neelsen stain. Clone 16, derived from J774, can produce superoxide anion (O2-) and H2O2 upon appropriate stimulation, while clone C3C, a variant in oxidative metabolism, defects in production of reactive oxygen intermediates. After both clones of the cells were infected with M. leprae or M. lepraemurium for three hours, and further incubat-ed in 5% CO2-air at 37°C, most of the bacteria of both species were stained green with FDA/EB staining. Under the microscopic observation of the spread subcutaneous tissue preparation, there was no difference in number of bacteria between clone 16 and C3C cells, but decreased number of bacteria was assessed in the cells of further incubation in 5% CO2-air at 37°C after one hour-infection than in the cells immediately after the one hour-infection periods. These results indicated that M. lepraemurium, and may be M. leprae, was partially killed or growth-inhibited by oxygen-independent killing mechanisms of macrophage cell line, rather than by reactive oxygen intermediates.