Interactions between naive and infected macrophages reduce Mycobacterium tuberculosis viability
UMass Chan AffiliationsDepartment of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine
Document TypeJournal Article
Green Fluorescent Proteins
Lysosome-Associated Membrane Glycoproteins
Mice, Inbred C57BL
Nitric Oxide Synthase Type II
Receptors, Purinergic P2X7
Immunology and Infectious Disease
Medicine and Health Sciences
MetadataShow full item record
AbstractA high intracellular bacillary load of Mycobacterium tuberculosis in macrophages induces an atypical lysosomal cell death with early features of apoptosis that progress to necrosis within hours. Unlike classical apoptosis, this cell death mode does not appear to diminish M. tuberculosis viability. We previously reported that culturing heavily infected macrophages with naive macrophages produced an antimicrobial effect, but only if naive macrophages were added during the pre-necrotic phase of M. tuberculosis-induced cell death. In the present study we investigated the mechanism of antimicrobial activity in co-cultures, anticipating that efferocytosis of bacilli in apoptotic bodies would be required. Confocal microscopy revealed frustrated phagocytosis of M. tuberculosis-infected macrophages with no evidence that significant numbers of bacilli were transferred to the naive macrophages. The antimicrobial effect of naive macrophages was retained when they were separated from infected macrophages in transwells, and conditioned co-culture supernatants transferred antimicrobial activity to cultures of infected macrophages alone. Antimicrobial activity in macrophage co-cultures was abrogated when the naive population was deficient in IL-1 receptor or when the infected population was deficient in inducible nitric oxide synthase. The participation of nitric oxide suggested a conventional antimicrobial mechanism requiring delivery of bacilli to a late endosomal compartment. Using macrophages expressing GFP-LC3 we observed the induction of autophagy specifically by a high intracellular load of M. tuberculosis. Bacilli were identified in LC3-positive compartments and LC3-positive compartments were confirmed to be acidified and LAMP1 positive. Thus, the antimicrobial effect of naive macrophages acting on M. tuberculosis in heavily-infected macrophages is contact-independent. Interleukin-1 provides an afferent signal that induces an as yet unidentified small molecule which promotes nitric oxide-dependent antimicrobial activity against bacilli in autolysosomes of heavily infected macrophages. This cooperative, innate antimicrobial interaction may limit the maximal growth rate of M. tuberculosis prior to the expression of adaptive immunity in pulmonary tuberculosis.
SourceHartman ML, Kornfeld H (2011) Interactions between Naïve and Infected Macrophages Reduce Mycobacterium tuberculosis Viability. PLoS ONE 6(11): e27972. doi:10.1371/journal.pone.0027972. Link to article on publisher's site
Permanent Link to this Itemhttp://hdl.handle.net/20.500.14038/39556
Related ResourcesLink to Article in PubMed
RightsCopyright: © 2011 Hartman, Kornfeld. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.