Journal of Immunology. 2007 Aug 15;179(4):2509-19.
Division of Infectious Diseases, Department of Medicine, New York University School of Medicine, New York, NY 10016, USA.
Wolf AJ, Linas B, Trevejo-Nuņez GJ, Kincaid E, Tamura T, Takatsu K, Ernst JD.
Significance:
Since 1925, it has been widely believed that macrophages are the cells that harbor the bacteria in tuberculosis. This paper used a strain of Mycobacterium tuberculosis engineered to express a fluorescent protein, together with a new method for flow cytometry, to discover that, in addition to macrophages, dendritic cells are also infected with M. tuberculosis in the lungs and lymph nodes of mice.
Dendritic cells are crucial to initiating cellular immune responses, and this work provides the basis for new approaches to understanding the immune response in tuberculosis, and to understanding how M. tuberculosis avoids being eliminated by the immune response.
Abstract:
Mycobacterium tuberculosis (Mtb) is thought to reside in macrophages, although infected dendritic cells (DCs) have been observed. Thus, although cellular associations have been made, global characterization of the cells harboring Mtb is lacking.
We have performed temporal and quantitative characterization of the cells harboring Mtb following aerosol infection of mice by using GFP-expressing bacteria and flow cytometry.
We discovered that Mtb infects phagocytic cells of diverse phenotypes, that the predominant infected cell populations change with time, and that myeloid DCs are the major cell population infected with Mtb in the lungs and lymph nodes.
We also found that the bacteria in the lung-draining lymph node are transported there from the lungs by a CCL19/21-dependent mechanism and that the transport of bacteria to the lymph node is a transient phenomenon despite chronic infection.
In addition, we found that the lymph node cell subsets that are most efficacious in stimulating Mtb-specific, TCR-transgenic CD4(+) T lymphocytes are not infected with the bacteria and are scarce or absent from the lungs of infected mice.
Finally, we found that the lung cell populations that are infected with Mtb at high frequency are relatively ineffective at stimulating Ag-specific CD4(+) T lymphocytes, and we have obtained evidence that live Mtb can inhibit MHC class II Ag presentation without a decrease in the surface expression of MHC class II. These results indicate that Mtb targets DC migration and Ag presentation in vivo to promote persistent infection.
PMID: 17675513
