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dc.contributor.authorBohsali, Amro
dc.contributor.authorAbdalla, Hana
dc.contributor.authorVelmurugan, Kamalakannan
dc.contributor.authorBriken, Volker
dc.date.accessioned2013-01-10T21:20:10Z
dc.date.available2013-01-10T21:20:10Z
dc.date.issued2010-09-10
dc.identifier.citationBohsali et al. BMC Microbiology 2010, 10:237 http://www.biomedcentral.com/1471-2180/10/237en_US
dc.identifier.urihttp://hdl.handle.net/1903/13367
dc.description.abstractBackground: The HIV pandemic raised the potential for facultative-pathogenic mycobacterial species like, Mycobacterium kansasii, to cause disseminating disease in humans with immune deficiencies. In contrast, nonpathogenic mycobacterial species, like M. smegmatis, are not known to cause disseminating disease even in immunocompromised individuals. We hypothesized that this difference in phenotype could be explained by the strong induction of an innate immune response by the non-pathogenic mycobacterial species. Results: A comparison of two rapid-growing, non-pathogenic species (M. smegmatis and M. fortuitum) with two facultative-pathogenic species (M. kansasii and M. bovis BCG) demonstrated that only the non-pathogenic bacteria induced strong apoptosis in human THP-1 cells and murine bone marrow-derived macrophages (BMDM) and dendritic cells (BMDD). The phospho-myo-inositol modification of lipoarabinomannan (PI-LAM) isolated from nonpathogenic species may be one of the cell wall components responsible for the pro-inflammatory activity of the whole bacteria. Indeed, PI-LAM induces high levels of apoptosis and IL-12 expression compared to the mannosyl modification of LAM isolated from facultative-pathogenic mycobacteria. The apoptosis induced by non-pathogenic M. smegmatis was dependent upon caspase-3 activation and TNF secretion. Consistently, BALB/c BMDM responded by secreting large amounts of TNF upon infection with non-pathogenic but not facultative-pathogenic mycobacteria. Interestingly, C57Bl/6 BMDM do not undergo apoptosis upon infection with non-pathogenic mycobacteria despite the fact that they still induce an increase in TNF secretion. This suggests that the host cell signaling pathways are different between these two mouse genotypes and that TNF is necessary but not sufficient to induce host cell apoptosis. Conclusion: These results demonstrate a much stronger induction of the innate immune response by nonpathogenic versus facultative-pathogenic mycobacteria as measured by host cell apoptosis, IL-12 and TNF cytokine induction. These observations lend support to the hypothesis that the strong induction of the innate immune response is a major reason for the lack of pathogenicity in fast-growing mycobacteria.en_US
dc.language.isoen_USen_US
dc.subjectM. smegmatisen_US
dc.subjectM. fortuitumen_US
dc.subjectM. smegmatisen_US
dc.titleThe non-pathogenic mycobacteria M. smegmatis and M. fortuitum induce rapid host cell apoptosis via a caspase-3 and TNF dependent pathwayen_US
dc.typeArticleen_US
dc.relation.isAvailableAtCell Biology & Molecular Geneticsen_us
dc.relation.isAvailableAtDigital Repository at the University of Marylanden_us
dc.relation.isAvailableAtCollege of Computer, Mathematical & Natural Sciencesen_us
dc.relation.isAvailableAtUniversity of Maryland (College Park, MD)en_us


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