Inside or outside the phagosome? The controversy of the intracellular localization of Mycobacterium tuberculosis - 21/02/12

Doi : 10.1016/j.tube.2011.09.009

Amanda Welin ^a,^c , Maria Lerm ^a,^b,^⁎
^a Medical Microbiology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, SE-58185 Linköping, Sweden
^b Center for Infectious Medicine, Department of Medicine, Karolinska Institute, SE-17177 Stockholm, Sweden
^c Phagocyte Research Laboratory, Department of Rheumatology and Inflammation Research, Sahlgrenska Academy, University of Gothenburg, SE-41346, Gothenburg, Sweden

Corresponding author. Medical Microbiology, Linköping University, SE-58185 Linköping, Sweden. Tel.: +46 101034779; fax: +46 101034789.

Summary

The localization of Mycobacterium tuberculosis (Mtb) inside the macrophage has been a matter of debate in recent years. Upon inhalation, the bacterium is taken up into macrophage phagosomes, which are manipulated by the bacterium. Subsequent translocation of the bacilli into the cytosol has been observed by several groups, while others fail to observe this phenomenon. Here, we review the available literature in favour of and against this idea, and scrutinize the existing data on how human macrophages control Mtb infection, relating this to the robustness of the host cell. We conclude that both phagosomal maturation inhibition and escape from the phagosome are part of the greater infection strategy of Mtb. The balance between the host cell and the infecting bacterium is an important factor in determining the outcome of infection as well as whether phagosomal escape occurs and can be captured.

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Keywords : Mycobacterium tuberculosis, Macrophage, Cytoplasm, Escape, Translocation, Phagosomal maturation