| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
From the Department of Immunology,* University of Cape Town, Cape Town, South Africa; Centre National de la Recherche Scientifique (CNRS), GEM2358, Orleans, France; and the Institute for Medical Microbiology, Immunology and Hygiene, Technical University of Munich, Munich, Germany
 |
Abstract |
|---|
 Top Abstract Materials and MethodsResultsDiscussionReferences |
|---|
, tumor necrosis factor-
, and interleukin-12p40 as well as increased numbers of CD4+ and CD8+ cells. Furthermore, TLR2-deficient mice mounted elevated Ag-specific type 1 T-cell responses that were not protective because all deficient mice succumb to infection within 5 months. Taken together, the data suggests that TLR2 may function as a regulator of inflammation, and in its absence an exaggerated immune inflammatory response develops.
The discovery of the Toll-like receptor (TLR) protein family and its importance in mediating immune responses has provided novel insights into mechanisms linking innate and adaptive immunity. The number of members of human and mouse TLR thought to participate in innate immunity has grown, and evidence suggests a role for TLRs in the activation of immune cells by M. tuberculosis.3,4
M. tuberculosis-induced tumor necrosis factor (TNF)- production was found to be primarily TLR2-dependent, however, other TLRs can contribute to proinflammatory signaling.3-5
The immunostimulatory responses to M. tuberculosis 19-kd lipoprotein, lipoarabinomannan, and mannosylated phosphatidylinositol are mediated by TLR2,6-8
whereas a heat-labile factor associated with M. tuberculosis activates cells through TLR4.8
Direct anti-microbial activity has been shown to be TLR2-dependent as activation by 19-kd lipoprotein resulted in the killing of M. tuberculosis in both mouse and human macrophages.9
Although TLR2-dependent activation of murine macrophages led to nitric oxide-dependent growth inhibition of intracellular M. tuberculosis, human monocyte cultures displayed anti-microbial activity dependent on TLR2 but independent of both nitric oxide and TNF-. Additionally, maturation of dendritic cells is mediated by microbial lipopeptide signaling through TLR2,10,11
a process that results in the stimulation of naïve T cells and the development of an adaptive immune response. M. tuberculosis 19-kd protein mediates the inhibition of MHC class II expression and antigen processing through TLR2,12
a mechanism that may allow intracellular bacilli to evade immune surveillance, thereby promoting chronic infection. Abel and colleagues13
showed previously TLR4 dependence of macrophage activation and clearance of mycobacteria. By contrast, Reiling and colleagues14
suggested that TLR2 and TLR4 are redundant to control M. tuberculosis infection and only at extremely high infectious doses (2000 CFU) was reduced survival reported in TLR2-deficient (TLR2-/-) mice.
To determine whether TLR2 contributes to the host response to M. tuberculosis infection, we aerogenically infected TLR2-/- mice with the virulent strain M. tuberculosis H37Rv. We demonstrate a critical role for TLR2 in the host response to mycobacterial infection. TLR2-/- mice have up-regulated MHC class II expression, an increased proinflammatory response, and T-cell recruitment, but lack functional granulomas during the chronic stages of infection, and develop fatal chronic pneumonia.
|
Materials and Methods |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
TLR2-/-15 and TNF-/-16 mice backcrossed five times to C57BL/6 were obtained from the Institute Transgenose, Centre National de la Recherche Scientifique, Orleans, France. For experiments, adult (>7 weeks old) animals were housed in individually ventilated cages under specific pathogen-free conditions at the University of Cape Town (Cape Town, South Africa) animal facility, or after infection in individually ventilated cages in a biohazard level 3 physical containment facility. All experiments performed were in accordance with the guidelines of the Animal Research Ethics Board of the University of Cape Town.
Bacteria and Infections
M. tuberculosis H37Rv13 was grown in Middlebrook 7H9 broth (Difco, Detroit, MI) supplemented with Middlebrook oleic acid albumin dextrose catalase (OADC) enrichment medium (Life Technologies, Gaithersburg, MD), 0.002% glycerol, and 0.05% Tween 80. Pulmonary infection with M. tuberculosis H37Rv of either 100 or 500 live bacteria was performed using a Glas-Col inhalation exposure system, model A4224. Inoculum size was checked 24 hours after infection by determining the bacterial load in the lungs of infected mice.
Colony Enumeration Assay
Bacterial loads in the lung, liver, and spleen of infected mice were evaluated at different time points after infection with M. tuberculosis H37Rv. Organs were weighed and defined aliquots were homogenized in 0.04% Tween 80 saline. Tenfold serial dilutions of organ homogenates were plated in duplicates onto Middlebrook 7H10 agar plates containing 10% OADC and incubated at 37°C for 19 to 21 days. Colonies on plates were enumerated and results are expressed as log10 CFU per organ.
Microscopic Investigation of the Lungs
For analysis, mice were sacrificed by carbon dioxide inhalation. Organs were weighed and fixed in 4% phosphate-buffered formalin and paraffin-embedded. Sections (2 to 3 µm) were stained with hematoxylin and eosin and a modified Ziehl-Nielsen method as described.17 Microscopic alterations such as thickening of alveolar septae, alveolar exudates, granulomas, bronchitis, and pleuritis were graded semiquantitatively using a score from 0 to 3 (no difference, moderate, distinct/severe lesions). The remaining ventilated airspace was assessed using a simplified morphometric test and expressed as a percentage of the total lung cross-section. For the immunostaining formalin-fixed paraffin-embedded sections were deparaffinized and rehydrated and stained with rabbit anti-mouse antibody specific for inducible nitric oxide synthase (iNOS) as described.18 The sections were then washed in phosphate-buffered saline (PBS) and incubated for 30 minutes at room temperature with the biotinylated secondary antibody. The sections were incubated with avidin-biotin complexes (ABC vector kit) for 30 minutes, washed, and incubated with diaminobenzidine substrate (DAKO, Glostrup, Denmark).
Lung Homogenate Preparations and Fluorescence-Activated Cell Sorting Analysis of Cell Surface Markers
Whole lungs were removed from infected mice at different time points and were homogenized in 1 ml of 0.04% Tween 80 saline and supernatants were collected after low-speed centrifugation, aliquoted, and frozen at -80°C. Isolated lung cells were obtained by collagenase and DNase treatment as described previously.19 The cells were counted and incubated with antibodies against CD3 (anti-CD3 PE, clone 145. 2C11), CD4 (anti-CD4 FITC, clone H129.19), CD8 (anti-CD8 FITC, clone 53–6.7), CD11a (anti-CD11a PE, clone M17/4), CD44 (anti-CD44 PE, clone IM7), CD11c (anti-CD11c FITC, clone HL3), Ly-6G (anti-Ly6G FITC, clone RB6-8C5), I-A/I-E (anti-I-A/I-E PE, clone M5/114.15.2), CD16/32 (clone 2.4G2). All staining procedures were performed in PBS containing 0.1% bovine serum albumin and 0.1% sodium azide (fluorescence-activated cell-sorting buffer) for 20 minutes at 4°C. All antibodies were used at 0.2 µg/106 cells and obtained from BD PharMingen (San Diego, CA). Cells were fixed with 4% paraformaldehyde for at least 1 hour and analyzed by flow cytometry. Cells were gated on the lymphocyte or monocyte population by forward and side scatter, and the data analyzed using CellQuest software (BD Systems, San Jose, CA).
Preparation of Elicited Peritoneal Macrophages
Mice were injected with 1 ml of 4% thioglycolate (Difco). Five days later, peritoneal exudate cells were isolated from the peritoneal cavity by washing with ice-cold Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal calf serum (FCS) (Life Technologies). Cells were cultured overnight and washed with DMEM/10% FCS to remove nonadherent cells. Adherent monolayer cells were used as peritoneal macrophages. Peritoneal macrophages (5 x 105cells/ml) were cultured in DMEM/10% FCS and stimulated with either lipopolysaccharide (LPS) (Escherichia coli, serotype O111:B4, 100 ng/ml; Sigma) or M. tuberculosis H37Rv (multiplicity of infection, 2:1). Supernatants were harvested after 4 hours.
Antigen-Specific Interferon (IFN)- Production
For measuring antigen-specific production of IFN-, single-cell suspension of splenocytes were prepared from wild-type and TLR2-/- mice 4 weeks after infection with 500 CFU M. tuberculosis H37Rv. Cells were resuspended in DMEM supplemented with 10% FCS, penicillin, and streptomycin (100 U/ml and 100 µg/ml; Life Technologies). Splenocytes were cultured at 5 x 105 cells/well in 96-well round-bottom microplates (Nunc, Naperville, IL), and stimulated with either 5 µg/ml Con A (Sigma) or live M. tuberculosis H37Rv (multiplicity of infection, 2:1) at 37°C and 5% CO2. Supernatants were harvested after 3 days.
CD4+ and CD8+ T-Cell Enrichment
Peripheral lymph nodes were obtained 4 weeks after infection with 500 CFU M. tuberculosis H37Rv. Single-cell suspensions were prepared in DMEM supplemented with 10% FCS, and penicillin and streptomycin (100 U/ml and 100 µg/ml; Life Technologies). Enrichment of CD4+ and CD8+ T cells was performed by negative selection with magnetic mouse anti-B220-specific Dynabeads (Dynal; Robbins-Scientific, Mountain View, CA). Negatively enriched CD3+ T-cell suspensions contained >90% CD3 cells, as determined by flow cytometry analysis.20
Functional CD4+ and CD8+ T-Cell Assay
In vitro responses to mycobacterial Ag were measured as described previously,21
with slight modifications: 4 x 105 CD3 -enriched lymph node cells obtained from C57BL/6-infected mice were cultured with 2 x 104 peritoneal macrophages pulsed with 2 x 105 M. tuberculosis H37Rv or 1 µg of PPD for 4 hours in antibiotic-free DMEM. Resident peritoneal macrophages were obtained 1 day before the experiment from peritoneal lavages of uninfected C57BL/6 and TLR2-/- mice and incubated in 96-well round-bottom microplates (Nunc) in complete DMEM. CD3+ T cells and pulsed macrophages were incubated for 96 hours at 37°C and 5% CO2. To determine mycobacterial Ag-specific IFN- production, 100 µl of supernatants from cultures were taken and kept frozen at -80°C.
Cytokine Enzyme-Linked Immunosorbent Assay
Supernatants were harvested and assayed for cytokine content using commercially available enzyme-linked immunosorbent assay reagents for TNF-, IFN-, and interleukin (IL)-12p40 (R&D Systems, Abingdon, UK, and BD PharMingen, San Diego, CA).
Nitrite Measurements
Nitrite concentrations in freshly obtained lung homogenate supernatants were determined using the Griess reagent (3% phosphoric acid, 1% p-aminobenzene-sulfonamide, 1% n-1-napthylethylenediamide) as described.22
Statistical Analysis
Data were analyzed by comparison of C57BL/6 and TLR2-/- mice at each time point, with four to six mice per time point. Analysis was performed using Student’s t-tests and values of P 
0.05 were considered significant. Each experiment was repeated at least once to ensure reproducibility.
|
Results |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
TNF- and IL-12 play important roles in the control of local immune responses to intracellular organisms such as M. tuberculosis. We therefore investigated the ability of elicited TLR2-/- peritoneal macrophages to secrete TNF- and IL-12p40 in response to infection with M. tuberculosis in vitro. The concentrations of both TNF- and IL-12p40 in the supernatant secreted by TLR2-/- macrophages were significantly lower compared to wild-type controls (Figure 1, a and b)
, whereas TNF- and IL-12p40 secretion in response to LPS stimulation was comparable for wild-type and TLR2-/- macrophages. In view of the reduced production of proinflammatory cytokines, we predicted that TLR2-/- mice would have reduced resistance to M. tuberculosis infections, as described for TNF-/- mice.23
|
TLR2-/- mice infected with a standard dose (100 CFU/mouse) of virulent M. tuberculosis experienced no change in clinical status and survived the duration of the 6-month experimental period (Figure 2a)
, although they exhibited 1 log10 higher bacterial loads in the lungs compared to wild-type controls at 5 months after infection (Figure 2b)
. The heightened pulmonary infection was accompanied by bacterial dissemination into the liver and spleen (Figure 2, c and d)
. To exacerbate the clinical consequences of the defective bacterial control, TLR2-/- mice were infected with a higher dose (500 CFU/mouse) of M. tuberculosis. Infected TLR2-/- mice appeared healthy at 4 weeks, but became morbid and emaciated with initial deaths occurring between weeks 7 and 11. At 15 weeks after infection, 50% of TLR2-/- mice succumbed to infection and all mice were dead by week 22 (Figure 2e)
. Wild-type mice controlled the same infectious dose and appeared healthy at 10 months after infection at which point the experiment was terminated. TNF-/- mice used as a positive control strain for susceptibility in both standard and high-dose experiments succumbed to infection within 1 month after infection (Figure 2, a and e)
. The number of viable mycobacteria recovered from the lungs of TLR2-/- was 1 log10 higher at 8 weeks after infection, and persisted through to week 13 when compared to wild-type mice (Figure 2f)
. An increased pulmonary load of viable mycobacteria in the TLR2-/- mice was associated with concomitant dissemination of bacilli into the liver at week 8 (Figure 2g)
and the spleen at week 14 (Figure 2h)
.
|
Macroscopically the lungs of TLR2-/- mice were swollen, displayed pleural adhesions, and were significantly increased in weight within 8 weeks after 500 CFU infection (see Figure 7a
). The lungs of both wild-type and TLR2-/- mice were examined histologically to assess the pattern of cellular responses and to assess the progression of the disease. Microscopically, both wild-type and TLR2-/- mice infected with 500 CFU M. tuberculosis exhibited comparable thickening of alveolar septae, with no discernable granulomatous structures at 2 weeks after infection (Figure 3, a and b)
. At 4 weeks after infection, wild-type mice had developed typical granulomatous lesions characterized by epithelioid macrophages accompanied by lymphocytic perivascular and peribronchiolar cuffing (Figure 3c)
. TLR2-/- mice exhibited a diffuse recruitment of inflammatory cells with thickening of the alveolar septae and interstitial pneumonia (Figure 3d)
. Strikingly, markedly different lesions were visible at 8 weeks after infection. Although wild-type mice displayed dense infiltration of lymphocytes within compact epithelioid granulomas (Figure 3e)
, TLR2-/- mice showed massive coalescent inflammatory lesions, substantial perivascular cuffing accompanied by a few granulomatous structures, focal necrosis, and diffuse foamy macrophages (Figure 3f)
. At the late stages of infection, moribund TLR2-/- mice displayed chronic pneumonia, increased neutrophil infiltration, and pleuritis (Figure 3h)
. An identical pulmonary pathology was found in TLR2-/- mice infected with a standard dose of M. tuberculosis (100 CFU/mouse), albeit at a later stage. Here, chronic inflammation prevailed in TLR2-/- mice at 5 months after infection and was comparable to the high-dose pathology seen at 8 weeks (data not shown). Analysis of the number of granulomas and free airspace in the TLR2-/- mouse lungs revealed lower numbers of granulomas and dramatically reduced alveolar spaces when compared to the wild-type controls (Figure 4, a and b
, respectively). Additionally, the induction and production of nitric oxide and related nitrogen intermediates (RNI) by macrophages is a major effector mechanism responsible for the anti-mycobacterial activity of IFN- and TNF-.1
We therefore investigated the extent of pulmonary macrophage activation in wild-type and TLR2-/- mice by iNOS immunostaining (Figure 4, c and d
, respectively). Although iNOS was highly expressed in typical granulomas in the wild-type mice, a few scattered, but clearly iNOS-expressing macrophages were found in TLR2-/- mice.
|
|
|
.), a factor that may have contributed to the fatal outcome of infection. A poorly controlled pulmonary infection merited analysis of the local inflammatory cytokine response as well as the T cell activation status.
|
Down-regulation of cell surface expression of MHC class II molecules is one mechanism by which M. tuberculosis might inhibit recognition of macrophages by CD4+ T cells. Recently, TLR2 has been implicated in inhibition of macrophage MHC class II expression by M. tuberculosis 19-kd lipoprotein,12
thereby decreasing Ag recognition by T cells. Here, we examined whether the absence of TLR2 signaling affected the MHC class II surface expression of lung CD11c+ and Ly-6G+ cells, as such alterations might influence the outcome of CD4+ T-cell differentiation.24
At 2 weeks after infection, flow cytometric analysis of pulmonary CD11c+ and Ly-6G+ cells showed a significant increase in the expression levels of MHC class II in M. tuberculosis-infected TLR2-/- mice (Figure 5b)
. This was accompanied by significantly increased numbers of CD4+ and CD8+ cells in TLR2-/- mice at 4 and 8 weeks after infection (Figure 6, a and b)
. Additionally, increased numbers of activated CD4+ and CD8+ cells were recruited to the lungs of TLR2-/- mice at weeks 4 and 8 after infection (Figure 6
; c to f).
|
|
and IL-12p40 production using in vitro infected macrophages, pulmonary IFN-, TNF-, and IL-12p40 levels were elevated in TLR2-/- mice after infection, which preceded the increase in bacterial burden. The absolute amount of IFN-, TNF-, and IL-12p40 detected in lung homogenates of TLR2-/- mice was significantly elevated when compared to congenic control mice (Figure 7
; b to d). Strikingly, pulmonary levels of IFN-, TNF-, and IL-12p40 were elevated in TLR2-/- mice while no significant difference in lung mass was observed during the first 4 weeks when compared to wild-type controls. The elevated levels of IFN- observed in the lungs of TLR2-/- mice at 2 and 4 weeks after infection suggested an enhanced capacity to mount a mycobacterial Ag-specific T-cell response. Thus, the pathology and elevated bacterial burden observed in the lungs of TLR2-/- mice appears to be associated with an increased proinflammatory cytokine response. Increased Antigen-Specific T-Cell Response in M. tuberculosis-Infected TLR2-/- Mice
The increased pulmonary IFN- production suggests an enhanced type 1 cell-mediated immune response in TLR2-/- mice. To confirm the immune competence of the TLR2-/- mice, their ability to mount comparable mycobacterial Ag-specific T-cell responses after aerosol M. tuberculosis infection was examined. Restimulation of TLR2-/- splenocytes with live M. tuberculosis showed significantly higher levels of IFN- production when compared to control mice (Figure 8a)
. To confirm that T cells were responsible for IFN- production in the in vitro splenocyte assay, T cells were purified from mediastinal lymph nodes of wild-type mice at 4 weeks after infection and co-cultured with either TLR2-/- or wild-type peritoneal macrophages. TLR2-/- peritoneal macrophages pulsed with either PPD or M. tuberculosis restimulated the wild-type T cells more efficiently than the congenic wild-type macrophages (Figure 8b)
. These results demonstrate an enhanced Ag-specific T-cell response in the absence of TLR2.
|
|
Discussion |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
production was found to be primarily dependent on TLR signaling,26
and subsequently TLR2 activation has been directly linked to killing of intracellular M. tuberculosis in vitro.9
Here we examined the relative in vivo contribution of TLR2 to the generation of a protective immune response against M. tuberculosis. Our results demonstrate that TLR2-/- mice 1) are susceptible to M. tuberculosis infection and have reduced bacterial clearance, 2) develop a chronic pneumonia despite enhanced cell mediated immunity, 3) have an augmented production of proinflammatory cytokines, and 4) are unable to form mycobactericidal granulomas.
Our initial experiments revealed that in a standard-dose model of infection (100 CFU/mouse), TLR2-/- mice develop chronic pneumonia and have a reduced capacity to clear a mycobacterial infection, but survived the duration of the chronic infection for 6 months. Subsequent challenge with a higher dose (500 CFU/mouse) accelerated the progression of the disease development. Here TLR2-/- mice developed fatal chronic pneumonia with all of the animals succumbing to the infection within 5 months (Figure 2e)
. TLR2 therefore appears to play a crucial role in the host response to M. tuberculosis infection.
Conflicting data exists describing the role TLR4 may have in the development of an optimum immune response to M. tuberculosis,13,14,26,27
while mycobacterial antigens have been reported to interact with TLR2 and a combination of additional TLRs including TLR1 and TLR6.28,29
The critical role of TLRs in effecting an initial innate immune response has been shown in several disease models.30-35
The fact that TLR2 has been directly implicated in effector responses of macrophages against M. tuberculosis expands its potential role beyond sensing and signaling. Subsequently, work done by Noss and colleagues12
reported that M. tuberculosis inhibits MHC class II Ag processing of M. tuberculosis 19-kd lipoprotein via TLR2. Here, the TLR2-depedent down-regulation of MHC class II expression might be a mechanism used by M. tuberculosis to evade immune surveillance, thereby promoting chronic infection. Expanding on this observation we postulated that MHC class II expression could be elevated in the absence of TLR2. Analysis of MHC class II expression levels on CD11c+ and Ly-6G+ cells isolated from the lungs of TLR2-/- mice after an M. tuberculosis infection showed this to be the case (Figure 5b)
. This was accompanied by increased numbers of CD4+, CD8+, activated CD4+, and activated CD8+ cells in the lungs of TLR2-/- mice at 4 and 8 weeks after infection (Figure 6)
. An elevated type 1 cellular immune response was also observed after restimulation of TLR2-/- splenocytes (Figure 8a)
. Additionally, co-culturing purified T cells with M. tuberculosis-pulsed TLR2-/- peritoneal macrophages confirmed that T cells were responsible for the IFN- produced in the in vitro splenocyte assay (Figure 8b)
. Whether the elevated MHC class II expression levels present on TLR2-/- CD11c+ cells is responsible for the increased numbers of CD4+ and CD8+ cells remains to be determined. However, locally, T cells recruited to the site of infection appear to be stimulated more by TLR2-deficient cells than T cells stimulated by their wild-type counterparts.
Although the contribution made by CD4+ and CD8+ cells and cytokines such as IFN- are critically important in the control of M. tuberculosis infection, TNF- expression at the site of infection is also considered critical for determining the course of disease. TNF- is essential for the control of murine tuberculosis in vitro36-38
and in vivo.23,39-41
Our in vitro results show that induction of TNF- and IL-12p40 by peritoneal macrophages after infection with live M. tuberculosis is TLR2-dependent (Figure 1)
, and corroborates earlier reports in transfected cells.8,26
Conversely, pulmonary levels of IFN-, TNF-, and IL-12p40 were elevated in TLR2-/- mice infected with M. tuberculosis (Figure 7
; b to d), not only during the chronic phase of infection but within the first 4 weeks as well. Thus, secretion of cytokines by resident macrophages cannot account for the elevated levels of TNF- and IL-12p40 because their secretion by macrophages after M. tuberculosis-induced activation is TLR2-dependent. An alternative is that resident macrophages stimulate recruited T cells to produce more IFN-, as was shown to be the case in vitro (Figure 8b)
, whereas elevated TNF- levels could be attributed to enhanced T-cell activation. Nevertheless, TNF- has been associated with host pathology to M. tuberculosis infection and is a major factor in host-mediated destruction of lung tissue.42,43
Recently Moreira and colleagues44
showed that increased levels of pulmonary TNF- resulted in increased pathology because of destructive inflammation. Although the bacillary load remained the same, an increase in the granuloma size in the lungs was observed. In human alveolar macrophages, induction of TNF- has been shown to support bacterial multiplication,45
thereby providing a mechanism for intracellular pathogens to contribute to virulence and the progression of infection.
Recently it was shown that TLR2 is not required to confer resistance to natural M. tuberculosis infection.14 Our initial standard-dose aerosol infection revealed significantly elevated bacterial loads in TLR2-/- mice at 5 months after infection, a time point not reported on by Reiling and colleagues.14 In terms of a high-dose M. tuberculosis aerosol infection, our results and those published by Reiling and colleagues show increased susceptibility in the absence of TLR2. Here, pathology was only apparent once the mycobacterial load increased in the TLR2-/- mice, a result observed by us in both standard and high-dose experiments.
In summary, the recognition of mycobacterial ligands by TLR2 facilitates the activation of antigen-presenting cells46 and induction of accessory signals necessary for the optimum activation of T cells. Because of redundancy within the innate immune system’s pattern recognition receptors (PRRs), it is probable that mycobacterial bacilli engage a multiligand activation pattern resulting in the differential activation of anti-bacterial effector pathways. To date, TLR2 has been shown to form heterodimers with TLR1 and TLR6, although the in vivo contribution of TLR1 and TLR6 required for optimal immunity of mice to M. tuberculosis remains to be determined. Whether TLR2 forms a heterodimer with other TLRs or forms a large receptor complex consisting of TLR1, TLR2, and TLR6 remains to be determined. Nevertheless, the present data demonstrate that TLR2 appears to play a more critical role in immunity to tuberculosis when compared to other members of the mammalian TLR family investigated thus far.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
Supported by the Wellcome trust, Medical Research Council (MRC), National Health Laboratory Services (NHLS), National Research Foundation (NRF), the Harry Crossley Fund (grant 435873), Cape Town, and the Fondation de la Recherche Medicale of France.
Accepted for publication September 10, 2003.
|
References |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
-interferon receptor or inducible nitric-oxide synthase. Infect Immun 1998, 66:1208-1215 is required in the protective immune response against M. tuberculosis in mice. Immunity 1995, 2:561-572[Medline]
This article has been cited by other articles:
 |
|
 |
|
  D. N. Wedlock, M. Denis, G. F. Painter, G. D. Ainge, H. M. Vordermeier, R. G. Hewinson, and B. M. Buddle Enhanced Protection against Bovine Tuberculosis after Coadministration of Mycobacterium bovis BCG with a Mycobacterial Protein Vaccine-Adjuvant Combination but Not after Coadministration of Adjuvant Alone Clin. Vaccine Immunol., May 1, 2008; 15(5): 765 - 772. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Mendez-Samperio, A. Trejo, and A. Perez Mycobacterium bovis Bacillus Calmette-Guerin Induces CCL5 Secretion via the Toll-Like Receptor 2-NF-{kappa}B and -Jun N-Terminal Kinase Signaling Pathways Clin. Vaccine Immunol., February 1, 2008; 15(2): 277 - 283. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. S. ADAMS, P. T. LIU, R. CHUN, R. L. MODLIN, and M. HEWISON Vitamin D in Defense of the Human Immune Response Ann. N.Y. Acad. Sci., November 1, 2007; 1117(1): 94 - 105. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Gandotra, S. Jang, P. J. Murray, P. Salgame, and S. Ehrt Nucleotide-Binding Oligomerization Domain Protein 2-Deficient Mice Control Infection with Mycobacterium tuberculosis Infect. Immun., November 1, 2007; 75(11): 5127 - 5134. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Doz, S. Rose, J. Nigou, M. Gilleron, G. Puzo, F. Erard, B. Ryffel, and V. F. J. Quesniaux Acylation Determines the Toll-like receptor (TLR)-dependent Positive Versus TLR2-, Mannose Receptor-, and SIGNR1-independent Negative Regulation of Pro-inflammatory Cytokines by Mycobacterial Lipomannan J. Biol. Chem., September 7, 2007; 282(36): 26014 - 26025. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Z. Kincaid, A. J. Wolf, L. Desvignes, S. Mahapatra, D. C. Crick, P. J. Brennan, M. S. Pavelka Jr., and J. D. Ernst Codominance of TLR2-Dependent and TLR2-Independent Modulation of MHC Class II in Mycobacterium tuberculosis Infection In Vivo J. Immunol., September 1, 2007; 179(5): 3187 - 3195. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. M. Fremond, D. Togbe, E. Doz, S. Rose, V. Vasseur, I. Maillet, M. Jacobs, B. Ryffel, and V. F. J. Quesniaux IL-1 Receptor-Mediated Signal Is an Essential Component of MyD88-Dependent Innate Response to Mycobacterium tuberculosis Infection J. Immunol., July 15, 2007; 179(2): 1178 - 1189. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Basu, S. K. Pathak, A. Banerjee, S. Pathak, A. Bhattacharyya, Z. Yang, S. Talarico, M. Kundu, and J. Basu Execution of Macrophage Apoptosis by PE_PGRS33 of Mycobacterium tuberculosis Is Mediated by Toll-like Receptor 2-dependent Release of Tumor Necrosis Factor-{alpha} J. Biol. Chem., January 12, 2007; 282(2): 1039 - 1050. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.R BORNSTEIN, C.G ZIEGLER, A.W KRUG, W KANCZKOWSKI, V RETTORI, S.M MCCANN, M WIRTH, and K ZACHAROWSKI The Role of Toll-like Receptors in the Immune-Adrenal Crosstalk Ann. N.Y. Acad. Sci., November 1, 2006; 1088(1): 307 - 318. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Togbe, S. Schnyder-Candrian, B. Schnyder, I. Couillin, I. Maillet, F. Bihl, D. Malo, B. Ryffel, and V. F. J. Quesniaux TLR4 gene dosage contributes to endotoxin-induced acute respiratory inflammation J. Leukoc. Biol., September 1, 2006; 80(3): 451 - 457. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-S. Chang, J. F. Huggett, K. Dheda, L. U. Kim, A. Zumla, and G. A. W. Rook Myobacterium tuberculosis Induces Selective Up-Regulation of TLRs in the Mononuclear Leukocytes of Patients with Active Pulmonary Tuberculosis. J. Immunol., March 1, 2006; 176(5): 3010 - 3018. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Bafica, C. A. Scanga, C. G. Feng, C. Leifer, A. Cheever, and A. Sher TLR9 regulates Th1 responses and cooperates with TLR2 in mediating optimal resistance to Mycobacterium tuberculosis J. Exp. Med., December 19, 2005; 202(12): 1715 - 1724. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. B. Su, P. B. Silver, R. S. Grajewski, R. K. Agarwal, J. Tang, C.-C. Chan, and R. R. Caspi Essential Role of the MyD88 Pathway, but Nonessential Roles of TLRs 2, 4, and 9, in the Adjuvant Effect Promoting Th1-Mediated Autoimmunity J. Immunol., November 15, 2005; 175(10): 6303 - 6310. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Kielian, A. Haney, P. M. Mayes, S. Garg, and N. Esen Toll-Like Receptor 2 Modulates the Proinflammatory Milieu in Staphylococcus aureus-Induced Brain Abscess Infect. Immun., November 1, 2005; 73(11): 7428 - 7435. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
|
), TLR2-/- (
), and TNF-/- (
) mice were aerogenically infected with a standard (a–d; 100 CFU/mouse) and high dose (e–h; 500 CFU/mouse) of M. tuberculosis. C57BL/6, TLR2-/-, and TNF-/- mice (a and e; 10 mice per group) were monitored for survival. Moribund mice were sacrificed. Survival rates of C57BL/6 and TLR2-/- mice were significantly different (e; P < 0.0001). CFU counts were determined at days 35 and 155 after infection (b–d), as well as days 14, 28, 56, and 98 after infection (f–h). Lungs (b and f), livers (c and g), and spleens (d and h) were taken from C57BL/6 and TLR2-/- mice. Data represent the means ± SD of four mice. One experiment representative of two performed is shown. *, P 
