| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
*
Institute of Microbiology and
Division of Infectious Diseases, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland; and
Ludwig Institute for Cancer Research, Lausanne Branch, Epalinges, Switzerland
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Protective immunity against the intracellular pathogen Mycobacterium tuberculosis is dependent on the activation of T cells (8). Initially, it was thought that Ag-specific helper T cells mediate their antimicrobial activity exclusively via the release of macrophage-activating cytokines (9). However, studies in mice and humans have demonstrated that mycobacteria, like other intracellular pathogens, induce Ag-specific, MHC-restricted CD4+ (10, 11, 12, 13, 14) and CD8+ (15) CTL. In humans, the bulk of M. tuberculosis-specific cytolytic activity is mediated by CD4+ CTL (16, 17), and the killing by CD4+ CTL clones of Mycobacterium-infected human macrophages has been shown, in some instances, to inhibit the growth of the bacilli (18), probably by destroying the intracellular habitat of the microorganisms (19). Since CD4+ CTL kill target cells via FasL-induced apoptosis (20), we analyzed whether the incubation with sFasL could kill macrophages infected with intracellular mycobacteria and possibly affect bacillary viability.
We show here that this is indeed the case. Moreover, we demonstrate
that another physiologic inducer of apoptosis, TNF-
, has the same
effect on infected macrophages, suggesting that apoptosis-related
reduction of bacterial viable counts in M.
tuberculosis-infected macrophages is not restricted to one
particular apoptosis induction pathway.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
M. tuberculosis H37Ra (attenuated strain) and H37Rv
(virulent strain) (American Type Culture Collection, Manassas, VA) were
obtained from Thomas Bodmer (Institute of Microbiology, Bern,
Switzerland). Mycobacterial strains were grown in 7H9 broth (Difco
Laboratories, Detroit, MI) containing 10% ADC supplement (Difco) and
0.05% Tween 80 (Difco), up to an OD600 of 1, corresponding
to a bacterial suspension of 
1 x 108 CFU/ml.
Reagents
Soluble recombinant Fas ligand (sFasL, 200 U/ml) was a gift from
Jürg Tschopp (Institute of Biochemistry, University of Lausanne,
Epalinges, Switzerland). sFasL was obtained by transfecting Neuro-2a
cells (5 x 106) with cloned human FasL cDNA, as
described (21). The activity of sFasL-containing supernatant was
determined by measuring the viability of A20 cells (22) exposed to
serial dilutions of sFasL. One unit of sFasL was defined as the amount
causing 75% cell death in 12 h. Anti-APO-1 IgG3 hybridoma
supernatant was a gift from Peter H. Krammer (Division of
Immunogenetics, German Cancer Research Center, Heidelberg, Germany).
TNF- (recombinant human (rhu) TNF-, Boehringer Ingelheim, Basel,
Switzerland), purified mouse IgG3 isotype control monoclonal Ab and
FITC-conjugated goat anti-mouse Ig antiserum (PharMingen, San
Diego, CA), cycloheximide (CHX, Sigma Chemical, St. Louis, MO), Annexin
V-FITC (Nexins Research BV, Hoeven, The Netherlands), Propidium iodide
(PI, Sigma), 4',6-Diamidino-2-phenylindole (Boehringer-Mannheim,
Mannheim, Germany) and Lympho-kwik reagent (One Lambda, Canoga Park,
CA) were obtained commercially.
Isolation of monocyte-derived macrophages
Human macrophages were derived from blood monocytes obtained from healthy volunteers and prepared by centrifugation over a Ficoll-Hypaque (Seromed, Biochrom, Berlin, Germany) gradient followed by a fibronectin adherence step (23). Monocytes were resuspended in RPMI 1640 (Life Technologies, Gaithersburg, MD) with 2 mM L-alanyl-L-glutamine (Life Technologies) and 5% heat-inactivated human AB+ serum (Sigma), plated at 4 x 105 cells/cm2 on 24-well Falcon Primaria plates (Becton Dickinson, Lincoln Park, NJ), and allowed to differentiate for 5 to 7 days at 37°C and 5% CO2, before infection. Cells obtained with this protocol gave rise to an even monolayer and were >95% esterase positive.
Infection of macrophages with M. tuberculosis
After four washings by centrifugation in RPMI 1640 to avoid any
LPS contamination from the bacterial culture medium, the bacterial
pellet was resuspended in RPMI 1640 containing 10% fresh human
AB+ serum and sonicated for 20 s in a 50-ml
conical polystyrene tube (Falcon) in a cup-horn transducer at maximum
output (400 W, Branson 450, Branson Ultrasonics, Danbury, CT). This
amount of sonication has been previously determined to be optimal for
dispersing bacteria without causing significant loss of viability.
Finally, the inoculum was filtered through a 5-µm pore size
polyvinylidene difluoride Millex filter membrane (Millipore, Bedford,
MA) to produce a strictly single-cell suspension. The bacterial density
of the final suspension was estimated by phase contrast microscopy and
adjusted to 107 bacilli/ml. The viable counts of the
inoculum were then checked by serial dilution and plating on 7H10 agar
with 10% Middlebrook OADC supplement (Difco, Detroit, MI). Monolayers
of macrophages were infected by replacing the culture medium with the
M. tuberculosis inoculum for 2 h. The cells were then
washed three times with RPMI 1640 and cultured in RPMI 1640 with 10%
FCS (PAA, Linz, Austria). To obtain a morphologic assessment of the
infection, macrophages differentiated and infected in parallel on slide
chambers (Nunc, Naperville, IL) were fixed and stained by the Kinyoun
method.
Induction of apoptosis in human macrophages
Uninfected and infected macrophages (5 x
105 cells) were incubated for 6 to 18 h in RPMI
1640 with 10% FCS containing recombinant sFasL (final concentration,
40 U/ml) or rhuTNF (10 ng/ml). All samples, including controls, were
treated with 1 µg/ml CHX. At the end of the incubation time, cells
were incubated with PBS containing 5 mM EDTA and detached by gentle
scraping. After detachment, the viability of control macrophages was
>90% as assessed by trypan blue exclusion.
Quantification of macrophages undergoing apoptosis by annexin V-FITC assay
The binding of annexin V-FITC was used as a sensitive measurement of macrophage apoptosis and performed by modification of a previously described method (24). Cells were incubated in 100 µl of binding buffer (HEPES-buffered saline solution with 2 mM CaCl2, pH 7.5) containing 1/500 dilution of annexin V-FITC for 30 min at 4°C and then with propidium iodide (PI) (2 µg/ml). Macrophages were immediately analyzed, without fixation, on a FACScan flow cytometer (Becton Dickinson, Mountain View, CA). After gating on the basis of forward vs side scatter to exclude cell debris, macrophage apoptosis was quantitatively evaluated by measuring the proportion of annexin V-FITC, excluding or not PI-positive cells. Macrophages infected with H37Rv strain were stained with annexin V-FITC only and fixed before analysis with 1% paraformaldehyde (Sigma) dissolved in HEPES buffer with 2 mM Ca2+, pH 7.5.
Assessment of macrophage apoptosis by TUNEL
Cells undergoing DNA fragmentation were detected in situ with the TUNEL method (terminal deoxyribonucleotidyl transferase labeling of DNA strand breaks with dUTP, Boehringer-Mannheim), according to the manufacturer’s instructions. Stained cells were analyzed under light microscopy.
Assessment of bacillary viability in human macrophages
To evaluate bacillary viability, monolayers of 5 x 105 M. tuberculosis-infected macrophages differentiated in 24-well plates were used in triplicates. Culture medium was removed and replaced with 200 µl of 0.1% saponin (Sigma) in RPMI 1640, and the adherent cells were incubated at 37°C for 20 min. The supernatant of each well was also lysed separately by adding saponin to the supernatant to a final concentration of 0.1%, so that no colony forming unit could escape detection due to cell detachment or lysis. After gentle mixing, the supernatant and cell lysates were collected and sonicated for 20 s to disperse the residual clumps of bacilli. Serial 10-fold dilutions were made in 7H9 broth and plated on 7H10 agar plates. Plates were sealed in plastic, kept at 37°C, and counted after 11 to 13 days, with the aid of a dissecting microscope. The bacterial counts were calculated based on the counting of colonies from a dilution containing at least 20 colonies and expressed as the number of CFU per well of both adherent cell and supernatant lysate. In every experiment, >95% of the CFU counts were cell associated.
Induction of cell lysis in infected macrophages
Cell lysis was induced by incubating macrophages for 18 h with mAbs against nonlymphoid leukocytes and complement (Lympho-kwik reagent) and was assessed by phase contrast microscopy.
Detection of Fas expression on human macrophages
Cell surface Fas expression was quantitated on human macrophages by flow cytometry. Uninfected and infected adherent human macrophages were detached with 5 mM PBS-EDTA and gentle scraping. Viability was >90% as determined by trypan blue exclusion. Cells (5 x 105) were incubated with 100 µl of anti-APO-1 IgG3 hybridoma supernatant (5 µg/ml) in PBS-5% FCS for 45 min at 4°C and then with a 1:100 dilution of FITC-conjugated goat anti-mouse Ig (PharMingen, San Diego, CA). Macrophages were also stained with goat anti-mouse FITC alone (negative control) or purified mouse IgG3 plus goat anti-mouse FITC (isotype control). Cells were then analyzed on a FACScan flow cytometer.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Apoptosis of human macrophages was analyzed by cytofluorometric
detection of annexin V and PI staining. In living cells,
phosphatidylserine is stringently located in the membrane leaflet that
faces the cytosol. The surface expression of phosphatidylserine is an
early feature of apoptosis and occurs before the loss of membrane
integrity (25). Early apoptotic cells bind annexin V, a
Ca2+-dependent phospholipid-binding protein with high
affinity for phosphatidylserine, but exclude PI and can therefore be
specifically detected and quantified by FACS analysis (26). Recent
studies have shown that CHX blocks the synthesis of proteins that
prevent cell death and thus enhances the killing mediated by death
factors of the TNF family, including FasL (27) and TNF- (28).
Incubation of macrophages with sFasL (40 U/ml), in combination with CHX
(1 µg/ml), led to a substantial increase in the percentage of cells
undergoing apoptosis (Fig. 1
), showing
that human macrophages are indeed susceptible to FasL-induced killing.
The induction of apoptosis by sFasL was dose dependent from 20 to 200
U/ml and time dependent from 6 to 24 h (data not shown). When the
analysis was restricted to PI-negative cells, representing cells that
have maintained their membrane integrity, the percentage of early
apoptotic annexin V-positive cells significantly increased in
FasL-treated cells. A similar increase in the percentage of annexin
V-positive cells was observed among the total cell population. In all
additional experiments, the analysis of apoptotic cells was
specifically restricted to PI-negative macrophages, which represented
>70% of the total cell population. Macrophage apoptosis was shown to
be specifically FasL dependent in all our experiments, as the
incubation of cells with supernatant of mock-transfected Neuro-2a
cells, CHX, or both did not induce any significant increase in
apoptosis (data not shown). The occurrence of apoptosis in
sFasL-treated macrophages was further confirmed by the observation of
chromatin condensation, a hallmark of apoptosis, using
4',6-diamidino-2-phenylindole nuclear staining (data not shown), as
well as by the in situ observation of DNA fragmentation using the TUNEL
assay (Fig. 2,
B–E).
|
|
There are potential caveats when evaluating the intracellular
survival and growth of M. tuberculosis in macrophages; high
density inocula, and in particular bacterial clumps, lead to an
overload of the macrophages with concomitant cytotoxicity and early
macrophage lysis (29) (our unpublished results). It is therefore
crucial to prepare a strictly single-cell suspension, such that the
vast majority of macrophages are infected with 5 to 10 isolated bacilli
each. Monolayers of adherent human macrophages were infected 5 to 7
days after isolation with a single-cell suspension of M.
tuberculosis. With this procedure, the infection of >95% of the
macrophages was routinely achieved (see, e.g., H37Ra-infected
macrophages in Fig. 2
A). Similar results were
observed using H37Rv). After 2 h of infection, cells were washed
three times to eliminate bacteria that were not cell associated and
incubated with sFasL. To investigate whether apoptosis affected the
viability of M. tuberculosis, measurements of annexin V
binding and bacterial colony counts were performed after 18 h in
macrophages infected with the attenuated H37Ra strain. M.
tuberculosis-infected macrophages were susceptible to FasL-induced
apoptosis (Fig. 3A, sFasL).
Bacillary viability was determined in parallel by CFU counting.
FasL-induced apoptosis of macrophages infected with the attenuated
H37Ra strain was associated with a 63 ± 7% reduction in
bacterial colony counts after 18 h (sFasL), compared with the
colony counts immediately after infection (T0). During the same time
interval, no change in mycobacterial viability was observed in control
cells treated with supernatant of mock-transfected Neuro-2a cells and
CHX (Fig. 3B, CTRL). The separate culture of cell and
supernatant lysates confirmed that the decreased bacterial counts in
macrophages undergoing FasL-induced apoptosis were not accompanied by
increased bacterial counts in the supernatant (data not shown). This
excludes cell detachment or cell lysis with release of bacteria as the
cause for the reduced bacterial viable counts in adherent macrophages.
Neither the addition of sFasL nor that of CHX alone to the bacterial
inoculum suspension prepared in RPMI medium affected mycobacterial
viability (data not shown). Furthermore, when infected macrophages were
completely resistant to FasL-induced apoptosis, as observed in one of
the donors tested (see below), no reduction of mycobacterial viability
was observed (data not shown).
|
induces apoptosis by activating the same
cascade of cellular proteases as FasL (3). Indeed, like sFasL,
rhuTNF- (10 ng/ml) induced apoptosis in infected macrophages (Fig. 3A, TNF) when associated with cycloheximide. TNF-induced
apoptosis of M. tuberculosis-infected human macrophages was
associated with a comparable reduction in mycobacterial viability as
sFasL-induced apoptosis. (Fig. 3B, TNF). Macrophages treated
with rhuTNF- alone did not undergo noticeable apoptosis, and there
was no reduction in bacterial counts (data not shown).
Finally, we tested in parallel the effect of apoptosis on the viability
of the attenuated (Ra) and the virulent (Rv) strains. FasL treatment
induced a similar increase of the percentage of annexin V-binding cells
(data not shown) and a comparable reduction of viable counts with
either strain (Fig. 4).
|
To test whether the reduction in mycobacterial counts was
specifically related to FasL-induced killing of infected macrophages,
cells were killed by complement-mediated cell lysis, using a mix of Abs
directed against nonlymphoid leukocytes and complement. Cell lysis, as
assessed by phase contrast microscopy, was complete after 30 min, with
only macrophage ghosts remaining. M. tuberculosis viability
was determined after 18 h by CFU assay in cultures of infected
macrophages treated with complement and compared with parallel cultures
of untreated and sFasL-treated macrophages. As shown in Figure 5, complement-mediated lysis of infected
macrophages had no effect on bacillary viability, whereas FasL-induced
apoptosis was coupled with a significant reduction in cell-associated
bacillary counts. In contrast to apoptotic death, cell lysis resulted
in threefold increased bacterial numbers in the culture supernatant
(data not shown).
|
With sFasL treatment, the proportion of apoptotic cells in
infected macrophages was diminished, to a variable extent, compared
with that of uninfected cells from the same donor (Fig. 6). The decreased proportion of apoptotic
cell death in M. tuberculosis-infected macrophages was
observed whether the analysis was restricted to PI-negative cells or
extended to the total cell population, including live and dead cells.
This suggests that intracellular M. tuberculosis was able to
prevent its host macrophage from FasL-induced apoptosis. These
observations led us to ask whether the intracellular M.
tuberculosis infection might modulate the expression of Fas on
human macrophages. Using FACS analysis, we could demonstrate that Fas
expression was substantially down-regulated on M.
tuberculosis-infected cells (Fig. 7), potentially explaining the reduced
susceptibility of infected macrophages to FasL-induced apoptosis.
|
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
.
A specific relationship between apoptosis and diminished viable
counts is supported by the following observations. Bacterial counts
were not reduced when FasL-induced apoptosis was completely inhibited
by M. tuberculosis infection as observed in one experiment.
TNF- has been claimed to act as a macrophage-arming factor for
M. tuberculosis (30, 31). In our experiments, however, a
reduction in bacterial counts was observed only when TNF- was
associated with cycloheximide to induce apoptosis in infected
macrophages, while TNF- alone did not affect bacterial viability.
Finally, nonapoptotic cell death induced by complement-mediated lysis
had no effect on bacillary viability, suggesting that only apoptotic
cell death may reduce bacterial viability inside human macrophages.
Molloy et al. (32) recently showed that the induction of apoptosis by chemical agents such as ATP in Mycobacterium bovis bacillus Calmette-Guérin-infected macrophages was accompanied by a reduction of intracellular bacterial viable counts. Others have observed that the apoptosis of Mycobacterium avium-infected macrophages favored the adherence of freshly added uninfected macrophages and that this process was accompanied by a reduction of M. avium viable counts without promoting the release of extracellular bacteria (33). While this reduction in the bacterial counts was specifically associated with the apoptosis of infected macrophages, the exact relationship between these observations in a complex system and our data awaits further understanding of the relationship between macrophage apoptosis and bacterial loss of viability.
In the present study, we now demonstrate a similar effect using physiologic apoptosis-inducing agents that are relevant to the immune system. In addition, the observation that FasL-induced apoptosis of macrophages infected with the virulent H37Rv M. tuberculosis strain was also coupled with a reduction in bacterial viability extend these findings to a pathogenic strain of greater clinical relevance.
M. tuberculosis has been shown to inhibit phagosome-lysosome fusion in human macrophages (34) and to reside in a compartment with endosomal characteristics (35), thereby avoiding the hostile environment of the phagolysosome. Conceivably, the induction of apoptosis via the FasL system might reverse the block imposed by M. tuberculosis to phagosome-lysosome fusion. In addition, M. tuberculosis-containing phagosomes fail to acidify by exclusion of the vesicular proton-ATPase (36). Recent observations showed that FasL-induced apoptosis of Jurkat cells is accompanied by cytoplasmic acidification at a relatively early stage (37). Whether this would result in a reduced pH in Mycobacterium-containing phagosomes remains to be determined.
FasL can induce apoptosis in vitro as a membrane-bound molecule or in a soluble form (21), and it has been shown that the supernatant of cultured activated T cells contains FasL and triggers apoptosis in vitro (38). In our experiments, we induced apoptosis using a soluble form of FasL. Other investigators have examined the ability of CD4+ CTL to induce lysis of Mycobacterium-infected macrophages. In some experiments, a concomitant decrease of bacterial viable counts was observed (18), while no such effect was detected in other studies (39). It is possible that differences in the mechanism of cell death involved in individual experimental systems, the different M. tuberculosis strains used, and the differential susceptibility of infected cells to apoptosis may explain these discordant results. Recently, Stenger et al. (40) derived CD-1-restricted human T cell lines of two distinct phenotypes that were able to lyse efficiently M. tuberculosis-infected macrophages. Interestingly, CD4-CD8- T cells lysed macrophages in a Fas-FasL-dependent manner without effect on bacterial viability. In contrast, CD8+ T cells lysed macrophages in a granule-dependent mechanism that resulted in killing of bacteria (40). While these data are difficult to reconcile with ours, it should be noted that macrophages presenting mycobacterial antigens in a CD-1-restricted manner were obtained through a differentiation procedure involving GM-CSF and IL-4 quite different from our preparation of adherent macrophages (40).
Few data are available concerning the role of CTL-induced apoptosis on the outcome of intracellular pathogen infections in vivo. In humans, the lack of CD4+-restricted cytolytic activity against mycobacteria correlate with high bacillary load and a disseminated disease in tuberculous and leprosy patients (17, 41) suggesting that CD4+CTL could have a protective role against mycobacterial infections in vivo. This seems to be further confirmed by the experiments conducted in vivo with spontaneous mutants gld mice. These mice lack functional FasL on mature T cells and have a strikingly reduced CD4+-restricted cytolytic activity (42). Recent results have shown that gld mice, which fail to eliminate Leishmania major, are indeed able to clear cutaneous lesions after the in situ injection of soluble FasL (47), suggesting a direct implication of the FasL-induced apoptotic cell death pathway in the protection against intracellular pathogens. Laochumroonvorapong et al. (43) recently reported that in Fas receptor-defective lpr mice the course of primary M. bovis bacillus Calmette-Guérin infection was not altered. However, Kägi et al. (44) have demonstrated that while CTL have no effect on the course of Listeria monocytogenes primary infection in mice, they do affect the bacterial load in the organs once these animals have mounted a specific immune response. Therefore, additional studies are needed to test whether the FasL system is implicated in the host defenses against M. tuberculosis, beyond the time of the primary infection.
We also show that M. tuberculosis-infected macrophages display a reduced susceptibility to FasL-induced apoptosis, together with reduced levels of surface Fas expression. The modulation in macrophages of cell surface molecules expression by intracellular mycobacteria is not unprecedented. M. tuberculosis infection has been shown to reduce the expression of the costimulatory molecule B7 on murine macrophages (45) and of HLA-DR on human macrophages (46), allowing the bacteria to dampen the immune response by interfering with antigen presentation.
In summary, M. tuberculosis has developed the capacity to
escape killing mechanisms in human macrophages. Our results suggest
that M. tuberculosis-specific CD4+ CTL might
induce in vivo FasL-dependent macrophage apoptosis, not only depriving
mycobacteria from their growth environment but also reducing viable
bacterial counts during the apoptotic processus. In so doing, CTL may
complement the effector functions of IFN-
-secreting effector cells
by the specific killing of infected cells. An advantage of such a
mechanism would be that mycobacteria inside apoptotic macrophages would
remain intracellular and prone to phagocytosis in apoptotic debris by
freshly attracted monocytes, thus preventing bacterial dissemination.
In turn, the capacity of M. tuberculosis to modulate the Fas
expression and the susceptibility of infected macrophages to
FasL-induced killing might appear as another escape mechanism of
M. tuberculosis to evade immune control.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Pascal R. A. Meylan, Institute of Microbiology, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland. E-mail address:
3 Abbreviations used in this paper: FasL, Fas ligand; CHX, cycloheximide; sFasL, soluble recombinant Fas ligand; PI, propidium iodide; rhu, recombinant human.
Received for publication May 15, 1997. Accepted for publication January 30, 1998.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
RIII and acquire annexin V binding sites during apoptosis in vitro. Blood 85:532.-mediated growth inhibition of Mycobacterium tuberculosis by human alveolar macrophages. J. Immunol. 152:743.[Abstract]
This article has been cited by other articles:
|
|
 |
|
  J. Day, A. Friedman, and L. S. Schlesinger Modeling the immune rheostat of macrophages in the lung in response to infection PNAS, July 7, 2009; 106(27): 11246 - 11251. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. R. Patel, K. Swan, X. Li, S. D. Tachado, and H. Koziel Impaired M. tuberculosis-mediated apoptosis in alveolar macrophages from HIV+ persons: potential role of IL-10 and BCL-3 J. Leukoc. Biol., July 1, 2009; 86(1): 53 - 60. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. S. Woodworth, Y. Wu, and S. M. Behar Mycobacterium tuberculosis-Specific CD8+ T Cells Require Perforin to Kill Target Cells and Provide Protection In Vivo J. Immunol., December 15, 2008; 181(12): 8595 - 8603. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A S-Y Leong, P Wannakrairot, and T Y-M Leong Apoptosis is a major cause of so-called "caseous necrosis" in mycobacterial granulomas in HIV-infected patients J. Clin. Pathol., March 1, 2008; 61(3): 366 - 372. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. M. Kelly, A. M. C. ten Bokum, S. M. O'Leary, M. P. O'Sullivan, and J. Keane Bystander Macrophage Apoptosis after Mycobacterium tuberculosis H37Ra Infection Infect. Immun., January 1, 2008; 76(1): 351 - 360. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. R. Patel, J. Zhu, S. D. Tachado, J. Zhang, Z. Wan, J. Saukkonen, and H. Koziel HIV Impairs TNF-{alpha} Mediated Macrophage Apoptotic Response to Mycobacterium tuberculosis J. Immunol., November 15, 2007; 179(10): 6973 - 6980. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y.-M. Lai, K. A. Mohammed, N. Nasreen, A. Baumuratov, B. F. Bellew, and V. B. Antony Induction of cell cycle arrest and apoptosis by BCG infection in cultured human bronchial airway epithelial cells Am J Physiol Lung Cell Mol Physiol, August 1, 2007; 293(2): L393 - L401. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. P. O'Sullivan, S. O'Leary, D. M. Kelly, and J. Keane A Caspase-Independent Pathway Mediates Macrophage Cell Death in Response to Mycobacterium tuberculosis Infection Infect. Immun., April 1, 2007; 75(4): 1984 - 1993. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Loeuillet, F. Martinon, C. Perez, M. Munoz, M. Thome, and P. R. Meylan Mycobacterium tuberculosis Subverts Innate Immunity to Evade Specific Effectors J. Immunol., November 1, 2006; 177(9): 6245 - 6255. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. V. Pichugin, S. N. Petrovskaya, and A. S. Apt H2 complex controls CD4/CD8 ratio, recurrent responsiveness to repeated stimulations, and resistance to activation-induced apoptosis during T cell response to mycobacterial antigens J. Leukoc. Biol., April 1, 2006; 79(4): 739 - 746. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Lee, H. G. Remold, M. H. Ieong, and H. Kornfeld Macrophage Apoptosis in Response to High Intracellular Burden of Mycobacterium tuberculosis Is Mediated by a Novel Caspase-Independent Pathway J. Immunol., April 1, 2006; 176(7): 4267 - 4274. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Sud, C. Bigbee, J. L. Flynn, and D. E. Kirschner Contribution of CD8+ T Cells to Control of Mycobacterium tuberculosis Infection J. Immunol., April 1, 2006; 176(7): 4296 - 4314. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S Stenger Immunological control of tuberculosis: role of tumour necrosis factor and more Ann Rheum Dis, November 1, 2005; 64(suppl_4): iv24 - iv28. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Ordway, M. Henao-Tamayo, I. M. Orme, and M. Gonzalez-Juarrero Foamy Macrophages within Lung Granulomas of Mice Infected with Mycobacterium tuberculosis Express Molecules Characteristic of Dendritic Cells and Antiapoptotic Markers of the TNF Receptor-Associated Factor Family J. Immunol., September 15, 2005; 175(6): 3873 - 3881. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Oddo, T. Calandra, R. Bucala, and P. R. A. Meylan Macrophage Migration Inhibitory Factor Reduces the Growth of Virulent Mycobacterium tuberculosis in Human Macrophages Infect. Immun., June 1, 2005; 73(6): 3783 - 3786. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. F. Pais and R. Appelberg Induction of Mycobacterium avium growth restriction and inhibition of phagosome-endosome interactions during macrophage activation and apoptosis induction by picolinic acid plus IFN{gamma} Microbiology, May 1, 2004; 150(5): 1507 - 1518. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Kim, W. J. McAuliffe, L. S. Zaritskaya, P. A. Moore, L. Zhang, and B. Nardelli Selective Induction of Tumor Necrosis Receptor Factor 6/Decoy Receptor 3 Release by Bacterial Antigens in Human Monocytes and Myeloid Dendritic Cells Infect. Immun., January 1, 2004; 72(1): 89 - 93. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Kaplan, F. A. Post, A. L. Moreira, H. Wainwright, B. N. Kreiswirth, M. Tanverdi, B. Mathema, S. V. Ramaswamy, G. Walther, L. M. Steyn, et al. Mycobacterium tuberculosis Growth at the Cavity Surface: a Microenvironment with Failed Immunity Infect. Immun., December 1, 2003; 71(12): 7099 - 7108. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. H. Dockrell, H. M. Marriott, L. R. Prince, V. C. Ridger, P. G. Ince, P. G. Hellewell, and M. K. B. Whyte Alveolar Macrophage Apoptosis Contributes to Pneumococcal Clearance in a Resolving Model of Pulmonary Infection J. Immunol., November 15, 2003; 171(10): 5380 - 5388. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Fukui, R. Imamura, M. Umemura, T. Kawabe, and T. Suda Pathogen-Associated Molecular Patterns Sensitize Macrophages to Fas Ligand-Induced Apoptosis and IL-1{beta} Release J. Immunol., August 15, 2003; 171(4): 1868 - 1874. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Villarreal-Ramos, M. McAulay, V. Chance, M. Martin, J. Morgan, and C. J. Howard Investigation of the Role of CD8+ T Cells in Bovine Tuberculosis In Vivo Infect. Immun., August 1, 2003; 71(8): 4297 - 4303. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Bhattacharyya, S. Pathak, C. Basak, S. Law, M. Kundu, and J. Basu Execution of Macrophage Apoptosis by Mycobacterium avium through Apoptosis Signal-regulating Kinase 1/p38 Mitogen-activated Protein Kinase Signaling and Caspase 8 Activation J. Biol. Chem., July 11, 2003; 278(29): 26517 - 26525. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Worku and D. F. Hoft Differential Effects of Control and Antigen-Specific T Cells on Intracellular Mycobacterial Growth Infect. Immun., April 1, 2003; 71(4): 1763 - 1773. [Abstract] [Full Text]
|
|
|
|
|
|
M. Lopez, L. M. Sly, Y. Luu, D. Young, H. Cooper, and N. E. Reiner The 19-kDa Mycobacterium tuberculosis Protein Induces Macrophage Apoptosis Through Toll-Like Receptor-2 J. Immunol., March 1, 2003; 170(5): 2409 - 2416. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. C. Turner, R. J. Basaraba, and I. M. Orme Immunopathogenesis of Pulmonary Granulomas in the Guinea Pig after Infection with Mycobacterium tuberculosis Infect. Immun., February 1, 2003; 71(2): 864 - 871. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. M. Sly, S. M. Hingley-Wilson, N. E. Reiner, and W. R. McMaster Survival of Mycobacterium tuberculosis in Host Macrophages Involves Resistance to Apoptosis Dependent upon Induction of Antiapoptotic Bcl-2 Family Member Mcl-1 J. Immunol., January 1, 2003; 170(1): 430 - 437. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. L. Jones, A. S. Day, H. Jennings, P. T. Shannon, E. Galindo-Mata, and P. M. Sherman Enhanced Disease Severity in Helicobacter pylori-Infected Mice Deficient in Fas Signaling Infect. Immun., May 1, 2002; 70(5): 2591 - 2597. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. van Crevel, T. H. M. Ottenhoff, and J. W. M. van der Meer Innate Immunity to Mycobacterium tuberculosis Clin. Microbiol. Rev., April 1, 2002; 15(2): 294 - 309. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. M. EDWARDS, M. H. CYNAMON, R. K. R. VOLADRI, C. C. HAGER, M. S. DESTEFANO, K. T. THAM, D. L. LAKEY, M. R. BOCHAN, and D. S. KERNODLE Iron-cofactored Superoxide Dismutase Inhibits Host Responses to Mycobacterium tuberculosis Am. J. Respir. Crit. Care Med., December 15, 2001; 164(12): 2213 - 2219. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Aoshiba, J. Tamaoki, and A. Nagai Acute cigarette smoke exposure induces apoptosis of alveolar macrophages Am J Physiol Lung Cell Mol Physiol, December 1, 2001; 281(6): L1392 - L1401. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Merlo, D. Saverino, C. Tenca, C. E. Grossi, S. Bruno, and E. Ciccone CD85/LIR-1/ILT2 and CD152 (Cytotoxic T Lymphocyte Antigen 4) Inhibitory Molecules Down-Regulate the Cytolytic Activity of Human CD4+ T-Cell Clones Specific for Mycobacterium tuberculosis Infect. Immun., October 1, 2001; 69(10): 6022 - 6029. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. H. Canaday, R. J. Wilkinson, Q. Li, C. V. Harding, R. F. Silver, and W. H. Boom CD4+ and CD8+ T Cells Kill Intracellular Mycobacterium tuberculosis by a Perforin and Fas/Fas Ligand-Independent Mechanism J. Immunol., September 1, 2001; 167(5): 2734 - 2742. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. M. Borges, H. Falcao, J. H. Leite-Junior, L. Alvim, G. P. Teixeira, M. Russo, A. F. Nobrega, M. F. Lopes, P. M. Rocco, W. F. Davidson, et al. FAS Ligand Triggers Pulmonary Silicosis J. Exp. Med., July 16, 2001; 194(2): 155 - 164. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. C. Leemans, N. P. Juffermans, S. Florquin, N. van Rooijen, M. J. Vervoordeldonk, A. Verbon, S. J. H. van Deventer, and T. van der Poll Depletion of Alveolar Macrophages Exerts Protective Effects in Pulmonary Tuberculosis in Mice J. Immunol., April 1, 2001; 166(7): 4604 - 4611. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. E. Cocco and D. S. Ucker Distinct Modes of Macrophage Recognition for Apoptotic and Necrotic Cells Are Not Specified Exclusively by Phosphatidylserine Exposure Mol. Biol. Cell, April 1, 2001; 12(4): 919 - 930. [Abstract] [Full Text]
|
|
|
|
 |
|
 G.A.W. Rook, G. Seah, and A. Ustianowski M. tuberculosis: immunology and vaccination Eur. Respir. J., March 1, 2001; 17(3): 537 - 557. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. J. Brill, Q. Li, R. Larkin, D. H. Canaday, D. R. Kaplan, W. H. Boom, and R. F. Silver Human Natural Killer Cells Mediate Killing of Intracellular Mycobacterium tuberculosis H37Rv via Granule-Independent Mechanisms Infect. Immun., March 1, 2001; 69(3): 1755 - 1765. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. P. Mohan, C. A. Scanga, K. Yu, H. M. Scott, K. E. Tanaka, E. Tsang, M. C. Tsai, J. L. Flynn, and J. Chan Effects of Tumor Necrosis Factor Alpha on Host Immune Response in Chronic Persistent Tuberculosis: Possible Role for Limiting Pathology Infect. Immun., March 1, 2001; 69(3): 1847 - 1855. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Wigginton and D. Kirschner A Model to Predict Cell-Mediated Immune Regulatory Mechanisms During Human Infection with Mycobacterium tuberculosis J. Immunol., February 1, 2001; 166(3): 1951 - 1967. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Thoma-Uszynski, S. Stenger, and R. L. Modlin CTL-Mediated Killing of Intracellular Mycobacterium tuberculosis Is Independent of Target Cell Nuclear Apoptosis J. Immunol., November 15, 2000; 165(10): 5773 - 5779. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Lewinsohn, A. L. Briden, S. G. Reed, K. H. Grabstein, and M. R. Alderson Mycobacterium tuberculosis-Reactive CD8+ T Lymphocytes: The Relative Contribution of Classical Versus Nonclassical HLA Restriction J. Immunol., July 15, 2000; 165(2): 925 - 930. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. L. Silva and D. B. Lowrie Identification and Characterization of Murine Cytotoxic T Cells That Kill Mycobacterium tuberculosis Infect. Immun., June 1, 2000; 68(6): 3269 - 3274. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Behnia, K. A. Robertson, and W. J. Martin II Lung Infections : Role of Apoptosis in Host Defense and Pathogenesis of Disease Chest, June 1, 2000; 117(6): 1771 - 1777. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Keane, H. G. Remold, and H. Kornfeld Virulent Mycobacterium tuberculosis Strains Evade Apoptosis of Infected Alveolar Macrophages J. Immunol., February 15, 2000; 164(4): 2016 - 2020. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. F. Pais and R. Appelberg Macrophage Control of Mycobacterial Growth Induced by Picolinic Acid Is Dependent on Host Cell Apoptosis J. Immunol., January 1, 2000; 164(1): 389 - 397. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Loyer, P. Fontaine, S. Pion, F. Hetu, D.-C. Roy, and C. Perreault The In Vivo Fate of APCs Displaying Minor H Antigen and/or MHC Differences Is Regulated by CTLs Specific for Immunodominant Class I-Associated Epitopes J. Immunol., December 15, 1999; 163(12): 6462 - 6467. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
