Different Innate Ability of I/St and A/Sn Mice To Combat VirulentMycobacterium tuberculosis: Phenotypes Expressed in Lung and Extrapulmonary Macrophages

Abstract

Mice of the I/St and A/Sn inbred strains display a severe and moderate course, respectively, of disease caused by Mycobacterium tuberculosis. Earlier, we showed that the response to mycobacterial antigens in I/St mice compared to that in A/Sn mice is shifted toward Th2-like reactivity and a higher proliferative activity and turnover of T cells. However, the physiologic basis for different expressions of tuberculosis severity in these mice remains largely unknown. Here, we extend our previous observations with evidence that I/St interstitial lung macrophages are defective in the ability to inhibit mycobacterial growth and to survive following in vitro infection with M. tuberculosis H37Rv. A unique feature of this phenotype is its exclusive expression in freshly isolated lung macrophages. The defect is not displayed in ex vivo macrophages obtained from the peritoneal cavity nor in macrophages developed in vitro from progenitors extracted from various organs, including the lung itself. In addition, we show that, in sharp contrast to peritoneal macrophages, the mycobactericidal capacity of lung macrophages is not elevated in the presence of exogenous gamma interferon. Our data suggest that the in vivo differentiation in a particular anatomical microenvironment determines the pattern of macrophage-mycobacterium interaction. Thus, caution should be exercised when conclusions based upon the results obtained in a particular in vitro system are generalized to the functions of all phagocytes during M. tuberculosis infection.The identification of genes and their alleles that confer resistance versus susceptibility to tuberculosis (TB) provides deep insight into basic mechanisms of immunity and pathology. Of utmost importance is establishing genotyping-based approaches for identifying the 10% of individuals who are at high risk of progression to clinical TB after primary infection (8). Although there is substantial evidence for the role of genetic factors in human susceptibility to TB (13,42,57), the identification of human TB susceptibility genes has been complicated by polygenic control of the trait (7,30,45,53) and inability to clearly delineate clinical phenotypes for stratified genetic analysis (5, 55). Unlike rare mutant alleles of the genes IFN␥R and IL-12R that determine extremely high susceptibility to mycobacterial infections in humans (2, 16, 31, 43)-resembling that in mice bearing disrupted genes for several key cytokines (14, 15, 25, 26)-genes with modest effects rarely produce clear phenotypes. Due to a limited power to detect such genes and to choose "major" genes among numerous candidates, little is known concerning the human genetics of TB control. Variations in NRAMP1 (1, 6) and/or NRAMP1-linked loci on the human chromosome 2q35 segment (28), as well as the class II HLA genes (10,27,40), have been shown to be linked to or associated with susceptibility to mycobacterial infections in humans. However, the overall effect of NRAMP1 and HLA genes on TB infection is acknowledged to be weak, and other genes are c...

A new coding mutation in the Tnf-α leader sequence in tuberculosis-sensitive I/St mice causes higher secretion levels of soluble TNF-α

“…29 The presence of a similar TNF-a secretion level from A/Sn and I/St cells, in a system with markedly higher stimulation of A/Sn compared to I/St cells, therefore, opens up the possibility for increased I/St TNF-a secretion from the inflammatory lung cell in a nonstimulated environment. The differences in TNF-a secretion between A/Sn and I/St lung macrophages reported by Majorov et al 26 might also have been affected by a possible difference in IL-12 activation.…”

“…However, the secretion level in vivo could be affected by other parameters, such as the additional variations found in the I/St Tnf-a gene. The TNF-a level from fresh lung macrophages has by Majorov et al 26 been positively correlated with resistance studying I/St and A/Sn mice. On the other hand, the TNF-a levels, produced by lung cell suspensions consisting of T cells, macrophages and dendritic cells from M. tuberculosis H37Rv intratracheally infected I/St and A/Sn mice, did not differ between the mouse strains within the first 3 weeks postchallenge despite a dramatic upregulation of IL-12 and IFN-g levels in A/Sn cells than in I/St cells.…”

“…38,39 It is suggested that enzyme inhibitors and the amount of soluble TNF-a present can affect the TNF-a expression and secretion in this cell system. 26 The HEK293A cell line was grown in DMEM containing sodium pyruvate, 1000 mg/l glucose and pyridoxine (Invitrogen, Carlsbad, CA, USA), supplemented with 10% FBS (Sigma-Aldrich, St Louis, MO, USA), 1% L-glutamine (100 Â ; Invitrogen) and 0.5% penicillin-streptomycin (10 000 U/ml penicillin G sodium and 10 000 mg/ml streptomycin sulfate in 0.85% saline; Invitrogen). Cells were grown as monolayers, in a 75 cm 2 culture flask (Sarstedt, Nü mbrecht, Germany) containing 30 ml cell medium, maintained in a humidified atmosphere of 5% CO 2 at 371C.…”

Virulence Factors and Pathogenicity of Mycobacterium

“…Primary murine bone marrow-derived macrophages (BMDMs) and human macrophages from peripheral blood monocytes (HMDMs) are the most common primary macrophages used, whereas the immortalized cell lines THP-1, J774 and MH-S cells have been widely used to study MTB-macrophage interactions. Data from both cell type should be interpreted with care because the response of MTB to intracellular environment can vary greatly depending on the cell type used [4]. In addition to evaluate the survival, replication and the intracellular bacillary load of MTB in the macrophages models, it is possible to study some of its mechanisms to counteract the macrophage microbicide ability, such as (1) the resistance to reactive oxygen/nitrogen intermediates (ROI/RNI), (2) the phagosome arresting and (3) the inhibition of apoptosis [1].…”

Efficacy of Isoniazid Therapy in Mice with Different Genetic Susceptibility to Infection

“…Our specific interest to the I/St mouse strain was dictated by the fact that these mice are extremely susceptible to TB challenge and this susceptibility is underlined by impaired mechanisms of both innate and acquired immunity: ineffective mycobacterial killing by lung macrophages [17] and impaired H2-dependent INF-γ production by CD4+ T-cells [15].…”