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1
*
Division of Rheumatology and Immunology, Department of Internal Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston MA 02115; and
Pulmonary Center, Boston University School of Medicine, Boston, MA 02118
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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) apoptosis by a
TNF-
-dependent mechanism. The apoptotic response is postulated to be
a defense mechanism, limiting the growth of this intracellular
pathogen. Consistent with that model, recent studies showed that the
virulent MTB strain H37Rv induces substantially less AM apoptosis
than the attenuated strain H37Ra. We now report that AM infection
with either H37Rv or H37Ra induces comparable levels of TNF-
measured by ELISA but that TNF- bioactivity is reduced in
supernatants of H37Rv-infected AM. Differential release of soluble
TNFR2 (sTNFR2), with formation of inactive TNF--TNFR2 complexes
accounted for the difference in TNF- bioactivity in these cultures.
Release of sTNFR2 by H37Rv-infected AM was IL-10 dependent since it
was inhibited by neutralizing anti-IL-10 Ab. Thus, the effect of
TNF- produced by AM following infection can be modulated by
virulent MTB, using IL-10 as an upstream
mediator. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The primary route of infection with MTB is via the lung. In the
alveolus, AM are both the primary host cell for MTB and the first
line of defense for the infected individual. Following infection of
AM by MTB, a variety of cytokines are induced that orchestrate
containment of the infection. Among these cytokines, TNF- is
involved in the protective immune response in mice (3). Production of
TNF- is also required for the induction of AM apoptosis in
response to inoculation with MTB (4). Comparison in mice of different
MTB strains correlated resistance against tuberculosis in vivo with
susceptibility of infected M to apoptosis measured in vitro and in
vivo (5). Apoptosis of human monocytes was shown to limit the growth of
Mycobacterium bovis bacille Calmette-Guérin (BCG) (6)
and Mycobacterium avium (7) in vitro. The latter studies
shed light on the outcomes of host M apoptosis. First, apoptosis of
the infected cells contains the mycobacteria, likely preventing spread
of infection in vivo (8). Secondly, the process of host M apoptosis
prevents growth of the mycobacteria (7). Indeed, H37Rv, a
well-characterized pathogenic MTB strain, was found to induce
significantly less host M apoptosis than the closely related
attenuated strain H37Ra (4), suggesting that abrogation of host M
apoptosis might be a virulence-associated phenotype of MTB strains.
The present study was performed to delineate the mechanism by which
virulent MTB interferes with the host M apoptotic response to
infection. We identify inactivation of the cytokine TNF- as a key
event leading to decreased host M apoptosis. We also describe
proximal events: the induction of IL-10 production by virulent MTB
leading to release of soluble TNFR2 (sTNFR2) from the AM and
inactivation of TNF- by complex formation with sTNFR2. Together,
these events comprise an apparent virulence mechanism operative in
virulent and not in attenuated MTB.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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AM were obtained from bronchoalveolar lavage fluid of healthy
nonsmoking volunteers with their informed consent, at Boston University
Medical Center or Beth Israel-Deaconess Medical Center, under human
study protocols approved by the respective institutional review boards.
Lavage fluids and cells were filtrated through a single layer of
sterile gauze, centrifuged (450 x g, 100 min), and
the cell pellet was suspended in RPMI 1640 medium (Sigma, St. Louis,
MO) with 10% FCS, supplemented with cefotaxime (50 µg/ml, Sigma) or
penicillin and streptomycin (100 µg/ml each, Sigma). Cells were
plated on 24-well plates (Costar, Cambridge, MA) (5 x
105 cells/well) directly on the bottom of wells or on round
glass coverslips for staining purposes. Nonadherent cells were removed
by washing at 24 h, and fresh antibiotic-free medium was added.
Cell morphology and differential counts were determined with light
microscopy following cytocentrifugation and modified Giemsa staining
(Dif-Quik, Sigma). Viability of adherent alveolar macrophages was
examined in representative samples by trypan blue dye exclusion.
Mycobacterium tuberculosis
Stock cultures of MTB H37Ra and H37Rv (ATCC 25177 and ATCC
25618; American Type Culture Collection (ATCC), Manassas, VA) were
stored frozen in 1-ml aliquots. Before inoculation of AM, the thawed
mycobacteria were vortexed, sonicated for 15 s at 500 W, and
allowed to stand for 10 min. The upper 500 µl of the solution were
used for experiments. Dilution of these dispersed mycobacterial
preparations were made to yield a multiplicity of infection 1 to 5
organisms/cell. For each experiment, the adequacy of dispersion and the
multiplicity of infection were checked by acid-fast staining of the
washed cells 4 h after inoculation. The rate of internalization
and intracellular growth during 5 days after infection was similar for
H37Ra and H37Rv as determined by electron microscopy, plate counting,
and BACTEC (9).
Reagents, Abs, and cytokines
Human rIL-10, polyclonal anti-human IL-10, and polyclonal
anti-human TNF- Abs were obtained from Endogen (Cambridge, MA).
Human rTNF- was purchased from Genzyme (Cambridge, MA). Human
rsTNFR2 and monoclonal anti-human sTNFR2 Ab were
purchased from R&D Systems (Minneapolis, MN).
Measurement of TNF-, IL-10, sTNFR, and TNF--sTNFR2 complexes
AM were cultured and challenged with MTB as described above,
in triplicate cultures. Supernatants were harvested at the times
indicated and passed through 0.22-µm pore-size filter (Costar). The
level of immunoreactive TNF- and IL-10 was determined by ELISA using
matched Ab pairs and cytokine standards (Genzyme and Endogen,
respectively). The amount of sTNFR was estimated using commercial ELISA
kits (R&D Systems) according to manufacturer’s instructions.
TNF bioactivity was assessed by measuring cytotoxicity on L929 cells
(10). In brief, L929 cell monolayers, cultured for 48 h on
flat-bottom 96-well plates (0.2 x 105 cells/well),
were overlaid with twofold serial dilutions of AM supernatants in
RPMI 1640 + 10% FCS supplemented with actinomycin D to a final
concentration of 1 µg/ml.
After incubation at 37°C for 24 h the cells were washed with
saline, stained with 0.05% crystal violet in 20% ethanol, and allowed
to dry overnight. The stain was eluted from the cells with 100%
methanol and read with a microtiter plate reader at an absorbance of
570 nm. Estimates of the concentrations of bioactive TNF in the
supernatants were obtained by comparison with calibration curves
established with a rTNF- standard. TNF bioactivity in selected AM
supernatant samples was inhibited by anti-TNF- Ab, but not by
control rabbit IgG, indicating that the cytotoxic activity in AM
supernatants represents TNF-.
TNF- bound to TNFR2 was detected in supernatants of MTB-infected
AM by a mixed Ab ELISA assay. The supernatants were added to 96-well
polystyrene microtiter plates coated with a murine monoclonal Ab
against sTNFR2 (part of TNFR2 ELISA; R&D Systems), and, after 2 h
at room temperature, the plates were washed and incubated for 1 h
at room temperature with biotinylated rabbit anti-human TNF- Ab
(0.2 µg/ml, Genzyme). After washing, peroxidase-labeled streptavidin
(Genzyme) was added. Peroxidase activity was determined by the addition
of 3,3',5,5'-tetramethylbenzidine (Vector Laboratories, Burlingame,
CA), and photospectrometry (450 nm) was performed using a microplate
reader. Since the stability of TNF--sTNFR2 complexes strongly
depends on the experimental conditions (11), calibrated dilutions of
rTNF- captured by immobilized anti-TNF- Ab were used as an
internal standard for the comparative measurements of TNFR2-bound
TNF-.
In situ DNA fragmentation analysis
DNA fragmentation was determined by the in situ TUNEL technique
(12). The method is based on the specific binding of terminal
deoxynucleotidyl transferase to 3'-OH ends of DNA. AM adherent to
glass coverslips were fixed with 4% formaldehyde in PBS, rinsed with
double distilled water, immersed in 0.5 U/µl of terminal transferase
and 1 mM Biotin-16-dUTP in reaction buffer (Boehringer Mannheim,
Indianapolis, IN) and incubated in a humid atmosphere at 37°C for 60
min. The reaction was terminated by transferring the coverslips to a
solution of 300 mM NaCl, 30 mM sodium citrate, pH 7.2, for 15 min at
room temperature. The coverslips were then rinsed with water, blocked
with 2% BSA in PBS for 10 min, rinsed again with water, immersed in
PBS for 5 min at room temperature, and immersed in avidin peroxidase
(1:10) for 30 min at 37°C. The cells were then stained with 1%
3-amino, 9-ethyl carbazole (Sigma) in dimethyl formamide (Sigma)
diluted 1:20 with 50 mM acetate buffer, pH 4.5, containing 0.018%
hydrogen peroxide for 20 min. Slides of experimental and control cells
subjected to in situ TUNEL were analyzed by light microscopy in a
blinded fashion. A total of 600 cells per slide were evaluated for the
presence of red-brown nuclear staining.
Statistical analysis
Results are expressed as mean ± SD. Statistical analysis
was performed employing SigmaStat Statistical Software (Jandel
Scientific, San Rafael, CA), using the ANOVA with correction for
multiple comparisons for analyses for multiple comparisons and paired
t test for analysis of the data on IL-10 production by
AM from individual donors.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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in AM cultures infected with virulent
MTB
Using AM from healthy donors, we measured TNF- levels by
ELISA in culture supernatants after infection with the virulent MTB
strain H37Rv or the attenuated strain H37Ra at 6 and 24 h. The
immunoreactive TNF- levels increased over time in both infections
and were not significantly different (Fig. 1
A). In contrast, TNF-
bioactivity measured at the same time by assessing L929 fibroblast
cytotoxicity was lower in H37Rv-infected AM cultures than in
H37Ra-infected AM cultures (Fig. 1B). Twenty- four
hours after infection, the level of TNF- bioactivity was 412 ±
75 pg/ml in supernatants from H37Rv-infected AM vs 1573 ± 189
pg/ml in supernatants from H37Ra-infected cells (n
= 3, p < 0.05). Control experiments confirmed that the
measurements of bioactivity reflected TNF- activity since the
addition of anti-TNF- Ab (5 µg/ml) completely inhibited L929
fibroblast cytotoxicity in both cultures, whereas irrelevant Ab had no
effect (data not shown). Consistent with the previous report that
apoptosis in MTB-infected AM resulted from TNF- signaling (4),
the level of AM apoptosis mirrored the pattern of TNF-
bioactivity (Fig. 1C). In contrast to the measurement of
TNF- by ELISA or by using a cytotoxicity assay, apoptosis was
determined at day 2 and 4 because optimal manifestation of apoptosis as
measured by the TUNEL technique (12) was found to occur several days
after inoculation of the M with mycobacteria (13). Together, these
data suggest that the reduced apoptotic response of AM to infection
by the virulent MTB strain H37Rv was due to the coinduction of a
TNF--neutralizing activity.
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in AM infected with virulent MTB
correlates with release of sTNFR2
To further dissect the events leading to attenuation of host M
apoptosis, we tested whether release of sTNFR occurred following MTB
infection as has been described in other systems (14, 15, 16, 17). Although
TNFR1 has been implicated as dominant in TNF--induced apoptosis
(18), levels of sTNFR1 measured by ELISA were not significantly
increased following MTB infection, and the levels did not differ with
infection by the attenuated or virulent strain (at 48 h:
n = 7, p = 0.75, Fig. 2). On the other hand, at 24 h the
increase in sTNFR2 concentration in supernatants of H37Rv-infected
AM was six times higher than in culture supernatants of AM
infected with H37Ra (Fig. 3B). The difference in the
TNFR2 levels was statistically significant at 6, 8, 24, 32, 48, and
96 h after infection (n = 3, p
< 0.05 for all time points).
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To establish a causal relationship between levels of sTNFR2 and
TNF- bioactivity, we added recombinant sTNFR2 to cultures of AM
infected with the attenuated MTB strain H37Ra and measured the
bioactivity of TNF-. Bioactivity measured by the L929 cell
cytotoxicity assay was reduced by addition of exogenous
sTNFR2 in a dose-dependent manner, and the reduction of
cytotoxicity was statistically significant in cultures treated with 10
and 50 ng/ml of rTNFR2 compared with untreated controls
(n = 3, p < 0.05; a representative
experiment is shown in Fig. 4A). Apoptosis of host
AM measured in the same cultures was also inhibited by sTNFR2 (Fig. 4B), and the amount of apoptosis was comparable to the
level of TNF- bioactivity. Addition of an irrelevant protein (bovine
albumin) had no effect on either bioactivity.
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bound to sTNFR2 in supernatants of MTB-infected
AM cultures was examined by a mixed ELISA assay. The TNF--sTNFR2
complexes were captured by immobilized Abs to sTNFR2 and quantified
using Abs to TNF-. Detectable levels of TNF--sTNFR2 complexes
were found in cultures of AM infected with both MTB strains and were
not found in uninfected AM. The levels of complexes in supernatants
of AM infected with virulent H37Rv were about three times higher
than in M infected with the attenuated strain H37Ra (Fig. 5).
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apoptosis
Previous studies indicate that IL-10 has an anti-apoptotic
function (19, 20, 21) and induces the release of sTNFR2 from several cell
types (22, 23). To identify mechanisms regulating TNFR shedding from
MTB-infected AM, we tested the effects of exogenous IL-10 and of
neutralization of endogenous IL-10. Addition of anti-IL-10 Ab (10
µg/ml) to AM cultures infected with the virulent MTB strain H37Rv
significantly reduced the release of sTNFR2 (n = 3,
p < 0.05; Fig. 6A) and increased M
apoptosis (n = 6, p < 0.05, Fig. 6B). Conversely, addition of exogenous rIL-10 to AM
cultures infected with the attenuated H37Ra decreased apoptosis of the
host M in a dose-dependent manner (Fig. 6C).
Reduction of apoptosis was statistically significant after addition of
5, 10, and 20 ng/ml IL-10 (n = 6, p
< 0.05) to the infected cultures. Treatment of uninfected AM with
IL-10 (10 ng/ml) was also found to increase sTNFR2 shedding from
56 ± 8 pg/ml to 160 ± 26 pg/ml at 6 h, and from
121 ± 38 pg/ml to 248 ± 45 pg/ml at 48 h of culture,
and this difference was statistically significant
(n = 3, p < 0.05). These findings
indicate that the modulation of MTB-induced M apoptosis by sTNFR2
release may be regulated by IL-10 and suggest that the virulent strain
H37Rv and the attenuated strain H37Ra differ in the induction of
endogenous IL-10 secretion.
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apoptosis by virulent and attenuated MTB strains, we measured IL-10
levels by ELISA in supernatants of AM cultures inoculated with H37Rv
and H37Ra. Uninfected M from all donors produced negligible levels
of IL-10 (3 ± 1 pg/ml, n = 12). In contrast,
H37Ra induced 58 ± 11 pg/ml, and H37Rv 103 ± 18 pg/ml IL-10
(n = 12, p = 0.0092, Fig. 7). Thus, the decreased induction of
AM apoptosis by the virulent MTB strain H37Rv correlates directly
with increased induction of IL-10.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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are the first
line of defense against this infection, but mycobacteria can persist
and replicate within infected M. M respond to MTB by producing
TNF-, a pleiotropic cytokine critical for the protective immune
response to tuberculosis (3), which elicits a wide spectrum of cellular
responses including fever, tissue injury, and M activation (24).
Recent studies showed that TNF- induces also apoptosis (25). Host
cell apoptosis is a defense strategy to limit the growth of certain
intracellular pathogens, including viruses (26, 27). In the case of
mycobacterial infection, this response has been shown to sequester
bacilli within apoptotic cells and to restrict their replication
directly (6), and by activation of uninfected M (7).
To investigate the possibility that virulent MTB might suppress host
M apoptosis, we performed in vitro infection of normal human AM
with a virulent and an attenuated strain of MTB. Our data show that
inactivation of TNF- and subsequent attenuation of apoptosis by the
virulent strain H37Rv occurs by a unique mechanism. Compared with the
attenuated strain H37Ra, H37Rv induces a quantitatively greater release
of IL-10 from infected M. The enhanced IL-10 response causes
increased accumulation of sTNFR2 in the supernatants, resulting in the
inactivation of TNF- by soluble receptor-ligand complex formation.
sTNFR2 was found to inactivate TNF-, since we showed that
TNF--dependent cytotoxicity and apoptosis are significantly reduced
by addition of rTNFR2 to H37Ra-infected AM cultures (Fig. 4
). We
have also attempted to demonstrate neutralization of endogenous sTNFR2
with anti-TNFR2 Abs and subsequent enhancement of apoptosis. In
these experiments 10 µg/ml anti-TNFR2 Abs were added to AM
cultures at the time of inoculation with H37Rv. H37Rv-infected AM
cultures to which no anti-TNFR2 Abs were added showed 39 ±
5% apoptosis at day 4 of culture in comparison with uninfected
cultures (9 ± 1% apoptosis, p < 0.05). In contrast,
in the presence of anti-TNFR2 Abs, 49 ± 3% apoptosis
(n = 3, p < 0.05) was observed.
These experiments suggest that endogenous sTNFR2 is able to neutralize
TNF-, but do not rule out a stimulatory effect of these Abs on
cell-associated TNFR2 and are therefore difficult to interpret.
Furthermore, another way to prove involvement of sTNFR2 in TNF-
neutralization, specific blocking of TNFR2 release by metalloproteinase
inhibitors, cannot be performed, because such inhibitors also affect
processing of TNF- (28).
The release of TNFR2 from the AM, which differs significantly in
H37Rv- and H37Ra-infected AM, comprises an apparent virulence
mechanism operative in pathogenic MTB.
This study indicates that a virulent MTB strain can modulate TNF-
activity by IL-10-dependent TNFR2 shedding. IL-10 has also been
reported to prevent apoptosis of M during Salmonella
infection (19), to prevent apoptosis of T cells in infectious
mononucleosis (21), and to prevent apoptosis of germinal center
B cells (20). In addition to attenuating apoptosis by increasing the
release of sTNFR2, IL-10 might also down-regulate apoptosis by
inhibiting IFN-
and TNF- production (29), and by down-regulating
surface TNFR expression (23).
sTNFR2 release from the AM caused by IL-10 has been found to depend
on the action of metalloproteinases (28). IL-10 has been found to
down-regulate (30), to activate (31), and to have no effect (32) on the
activity of metalloproteinases. In future studies we will examine the
role of proteolytic enzymes in the IL-10-dependent release of TNFR2
from AM.
The cytokine responses of primary human AM to a MTB challenge
typically demonstrate a high degree of individual variation, and a high
IL-10 response might represent a host susceptibility factor to
tuberculosis. On the other hand, the two individuals (of 12
individuals) whose AM did not respond to H37Rv inoculation with
increased IL-10 levels (Fig. 7) might be part of a population with
innate resistance to MTB. We are currently investigating this
possibility.
AM apoptosis is induced by the action of TNF-. TNF- elicits
cellular responses through its interaction with two distinct receptors,
the 55-kDa TNFR1 and the 75-kDa TNFR2 (33). A distinctive difference
between these two TNFR, which are both members of the TNF receptor
superfamily including CD30, CD40, CD27, and Fas (34), is the presence
of a death domain (DED) in TNFR1. Stimulation of TNFR1 results in
activation of the apoptotic protease cascade (35, 36) leading to
apoptosis. Inactivation of TNF- by formation of a complex with
sTNFR2 abrogates the induction of apoptosis upstream of the
death-signaling cascade by elimination of the inducing cytokine signal.
Related strategies are used by human herpes virus 4, which encodes a
viral IL-10 homologue (37), parainfluenza virus, which induces IL-10
(38), and pox virus, which encodes a sTNFR1-like molecule (39).
sTNFR are naturally occurring inhibitors of TNF-, which are normally
present in the blood and urine (14, 15, 16, 17). Serum concentrations of sTNFR
increase significantly in a variety of disease states including
tuberculosis and HIV-1 infection (40, 41). sTNFR2 were
reported to be more prone to being released from AM than TNFR1 (42, 43), which is in agreement with our finding that MTB infection
induced shedding of TNFR2, but not TNFR1, from AM. sTNFR2 are also
more abundant than TNFR1 in the serum of patients with cancer and in
the serum and synovial fluid of patients with rheumatoid arthritis (44, 45). This evidence suggests that sTNFR2 may be an important regulator
of TNF- activity in vivo. Our present investigations indicate that a
virulent MTB strain can modulate TNF- activity by IL-10-dependent
shedding of sTNFR2.
The mycobacterial determinants that effect the unique capacity of
virulent MTB to manipulate host TNF- responses have yet to be
defined. Identifying the basis of this multistep mechanism should
provide further insight to the pathogenesis of human tuberculosis and
may suggest novel approaches to therapy.
Note. A study describing reduction of TNF- biological
activity in supernatants from murine M infected with virulent
M. avium strains with a possible role for sTNFR2 has
recently come to our attention (46).
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Heinz G. Remold, Division of Rheumatology and Immunology, Department of Internal Medicine, Brigham and Women’s Hospital and Harvard Medical School, Smith Building, Room 526B, 75 Francis Street, Boston MA, 02115.
3 Abbreviations used in this paper: MTB, Mycobacterium tuberculosis; AM, alveolar macrophages; sTNFR, soluble TNFR; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling.
Received for publication December 17, 1997. Accepted for publication April 30, 1998.
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quantification by ELISA and bioassay: effects of TNF -soluble TNF receptor (p55) complex dissociation during assay incubations. J. Immunol. Methods 177:191.[Medline]
on murine macrophages infected with Mycobacterium avium. Infect. Immun. 65:2100.[Abstract]
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H. M. S. Algood, P. L. Lin, D. Yankura, A. Jones, J. Chan, and J. L. Flynn TNF Influences Chemokine Expression of Macrophages In Vitro and That of CD11b+ Cells In Vivo during Mycobacterium tuberculosis Infection J. Immunol., June 1, 2004; 172(11): 6846 - 6857. [Abstract] [Full Text] [PDF]
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 R. B. Day, Y. Wang, K. S. Knox, R. Pasula, W. J. Martin II, and H. L. Twigg III Alveolar Macrophages from HIV-Infected Subjects are Resistant to Mycobacterium tuberculosis In Vitro Am. J. Respir. Cell Mol. Biol., March 1, 2004; 30(3): 403 - 410. [Abstract] [Full Text] [PDF]
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A. Luhrmann, N. Mauder, T. Sydor, E. Fernandez-Mora, J. Schulze-Luehrmann, S. Takai, and A. Haas Necrotic Death of Rhodococcus equi-Infected Macrophages Is Regulated by Virulence-Associated Plasmids Infect. Immun., February 1, 2004; 72(2): 853 - 862. [Abstract] [Full Text] [PDF]
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J.-z. Zhang, M. Sinha, B. A. Luxon, and X.-j. Yu Survival Strategy of Obligately Intracellular Ehrlichia chaffeensis: Novel Modulation of Immune Response and Host Cell Cycles Infect. Immun., January 1, 2004; 72(1): 498 - 507. [Abstract] [Full Text] [PDF]
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 D. A. Lewinsohn, A. S. Heinzel, J. M. Gardner, L. Zhu, M. R. Alderson, and D. M. Lewinsohn Mycobacterium tuberculosis-specific CD8+ T Cells Preferentially Recognize Heavily Infected Cells Am. J. Respir. Crit. Care Med., December 1, 2003; 168(11): 1346 - 1352. [Abstract] [Full Text] [PDF]
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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]
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A. L. K. Hestvik, Z. Hmama, and Y. Av-Gay Kinome Analysis of Host Response to Mycobacterial Infection: a Novel Technique in Proteomics Infect. Immun., October 1, 2003; 71(10): 5514 - 5522. [Abstract] [Full Text] [PDF]
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 I. Smith Mycobacterium tuberculosis Pathogenesis and Molecular Determinants of Virulence Clin. Microbiol. Rev., July 1, 2003; 16(3): 463 - 496. [Abstract] [Full Text] [PDF]
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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]
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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]
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C. J. Riendeau and H. Kornfeld THP-1 Cell Apoptosis in Response to Mycobacterial Infection Infect. Immun., January 1, 2003; 71(1): 254 - 259. [Abstract] [Full Text] [PDF]
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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]
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C. G. Feng, M. C. Kullberg, D. Jankovic, A. W. Cheever, P. Caspar, R. L. Coffman, and A. Sher Transgenic Mice Expressing Human Interleukin-10 in the Antigen-Presenting Cell Compartment Show Increased Susceptibility to Infection with Mycobacterium avium Associated with Decreased Macrophage Effector Function and Apoptosis Infect. Immun., December 1, 2002; 70(12): 6672 - 6679. [Abstract] [Full Text] [PDF]
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M.-K. Kim, S.-Y. Seong, J.-Y. Seoh, T.-H. Han, H.-J. Song, J.-E. Lee, J.-H. Shin, B.-U. Lim, and J.-S. Kang Orientia tsutsugamushi Inhibits Apoptosis of Macrophages by Retarding Intracellular Calcium Release Infect. Immun., August 1, 2002; 70(8): 4692 - 4696. [Abstract] [Full Text] [PDF]
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Y. Qiao, S. Prabhakar, E. M. Coccia, M. Weiden, A. Canova, E. Giacomini, and R. Pine Host Defense Responses to Infection by Mycobacterium tuberculosis. INDUCTION OF IRF-1 AND A SERINE PROTEASE INHIBITOR J. Biol. Chem., June 14, 2002; 277(25): 22377 - 22385. [Abstract] [Full Text] [PDF]
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S. K. Roach and J. S. Schorey Differential Regulation of the Mitogen-Activated Protein Kinases by Pathogenic and Nonpathogenic Mycobacteria Infect. Immun., June 1, 2002; 70(6): 3040 - 3052. [Abstract] [Full Text] [PDF]
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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]
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J. A. Gutierrez-Pabello, D. N. McMurray, and L. G. Adams Upregulation of Thymosin {beta}-10 by Mycobacterium bovis Infection of Bovine Macrophages Is Associated with Apoptosis Infect. Immun., April 1, 2002; 70(4): 2121 - 2127. [Abstract] [Full Text] [PDF]
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 S B Gordon and R C Read Macrophage defences against respiratory tract infections: The immunology of childhood respiratory infections Br. Med. Bull., March 1, 2002; 61(1): 45 - 61. [Abstract] [Full Text] [PDF]
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M. Engele, K. Castiglione, N. Schwerdtner, M. Wagner, P. Bolcskei, M. Rollinghoff, and S. Stenger Induction of TNF in Human Alveolar Macrophages As a Potential Evasion Mechanism of Virulent Mycobacterium tuberculosis J. Immunol., February 1, 2002; 168(3): 1328 - 1337. [Abstract] [Full Text] [PDF]
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E. Zuniga, A. Gruppi, J. Hirabayashi, K. I. Kasai, and G. A. Rabinovich Regulated Expression and Effect of Galectin-1 on Trypanosoma cruzi-Infected Macrophages: Modulation of Microbicidal Activity and Survival Infect. Immun., November 1, 2001; 69(11): 6804 - 6812. [Abstract] [Full Text] [PDF]
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D. J. Kusner and J. A. Barton ATP Stimulates Human Macrophages to Kill Intracellular Virulent Mycobacterium tuberculosis Via Calcium-Dependent Phagosome-Lysosome Fusion J. Immunol., September 15, 2001; 167(6): 3308 - 3315. [Abstract] [Full Text] [PDF]
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G. T. Seah and G. A. W. Rook IL-4 Influences Apoptosis of Mycobacterium-Reactive Lymphocytes in the Presence of TNF-{alpha} J. Immunol., August 1, 2001; 167(3): 1230 - 1237. [Abstract] [Full Text] [PDF]
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 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]
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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]
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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]
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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]
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 D. V. Havlir, F. J. Torriani, R. D. Schrier, J. Y. Huang, M. M. Lederman, K. A. Chervenak, and W. H. Boom Serum Interleukin-6 (IL-6), IL-10, Tumor Necrosis Factor (TNF) Alpha, Soluble Type II TNF Receptor, and Transforming Growth Factor Beta Levels in Human Immunodeficiency Virus Type 1-Infected Individuals with Mycobacterium avium Complex Disease J. Clin. Microbiol., January 1, 2001; 39(1): 298 - 303. [Abstract] [Full Text]
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 C. Fratazzi, N. Manjunath, R. D. Arbeit, C. Carini, T. A. Gerken, B. Ardman, E. Remold-O'Donnell, and H. G. Remold A Macrophage Invasion Mechanism for Mycobacteria Implicating the Extracellular Domain of Cd43 J. Exp. Med., July 17, 2000; 192(2): 183 - 192. [Abstract] [Full Text] [PDF]
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D. Fortsch, M. Rollinghoff, and S. Stenger IL-10 Converts Human Dendritic Cells into Macrophage-Like Cells with Increased Antibacterial Activity Against Virulent Mycobacterium tuberculosis J. Immunol., July 15, 2000; 165(2): 978 - 987. [Abstract] [Full Text] [PDF]
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 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]
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Y. Geng, R. B. Shane, K. Berencsi, E. Gonczol, M. H. Zaki, D. J. Margolis, G. Trinchieri, and A. H. Rook Chlamydia pneumoniae Inhibits Apoptosis in Human Peripheral Blood Mononuclear Cells Through Induction of IL-10 J. Immunol., May 15, 2000; 164(10): 5522 - 5529. [Abstract] [Full Text] [PDF]
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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]
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D. J. Kusner and J. Adams ATP-Induced Killing of Virulent Mycobacterium tuberculosis Within Human Macrophages Requires Phospholipase D J. Immunol., January 1, 2000; 164(1): 379 - 388. [Abstract] [Full Text] [PDF]
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M. Rojas, M. Olivier, P. Gros, L. F. Barrera, and L. F. Garcia TNF-{alpha} and IL-10 Modulate the Induction of Apoptosis by Virulent Mycobacterium tuberculosis in Murine Macrophages J. Immunol., May 15, 1999; 162(10): 6122 - 6131. [Abstract] [Full Text] [PDF]
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