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and Nitric Oxide-Dependent Mechanism
*
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115; and
Neose Technologies, Horsham, PA 19044
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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dependent, as addition of inhibitors
of inducible NO synthase
(NG-monomethyl-L-arginine), as
well as anti-IFN- Abs, restored the ability of CD4+
T cells to proliferate in vitro. Depletion of the F4/80+
subset of Gr1+ cells eliminated the suppressive activity of
peritoneal exudate cells showing that these cells were macrophages.
Thus, LNFPIII-dextran rapidly expands the Gr1+ suppressor
macrophage population in the peritoneal cavities of otherwise naive
mice. These Gr1+ cells suppress proliferation of naive
CD4+ T cells in an NO-dependent mechanism, and may play a
regulatory role in the switching of Th1- to Th2-type
responses. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, or TNF-
as well as pro-inflammatory chemokines (3). In contrast to
Th1-type pro-inflammatory responses, chronic helminth infection leads
to polarized Th2-type responses, and little is known about innate
immune responses during acute helminth infection. However, it has been
shown that soon after exposure to schistosome egg Ags, mice produce Th1
pro-inflammatory responses, which then switch to polarized Th2-type
responses (4). The mechanisms that enable the immune
response to switch from Th1 to Th2 type are not known, but likely
involve one or more types of innate interactions. In this regard,
recent studies have described an innate response that leads to
expansion of suppressor macrophage populations (5, 6, 7, 8).
These immunoregulatory cells, termed natural suppressor
(NS)2 cells, originate
from granulocyte-monocyte progenitors, express Gr1, CD11b, and/or F4/80
surface markers, and are capable of inhibiting proliferative responses
of naive or activated T and B cells. That helminth infection may
involve NS cells was suggested in a study where peritoneal implantation
of larval filarial parasites in mice expanded the resident NS
population (9, 10, 11).
All suppressor macrophages resemble one another phenotypically and
share a similar suppressor function. Despite these similarities,
mechanistically there are two different subpopulations of suppressor
macrophages: 1) classically activated (CA) macrophages, which are
IFN- dependent (12, 13, 14, 15); and 2) alternatively activated
(AA) macrophages, which are IL-4 dependent (3, 16, 17, 18, 19).
IFN--dependent Gr1+ suppressors are found in
the bone marrow and peripheral lymphoid organs in cancer patients or
tumor-bearing mice, and during viral infection (12, 13, 14).
AA macrophages are found in the peritoneal cavity (PC) of mice in
response to the filarial nematode Brugia malayi as well as
in other cases (3, 9, 10, 11, 20, 21).
In schistosome infection of mice or humans, parasite carbohydrates have
been shown to play a role in driving Th2-type and/or
anti-inflammatory responses (22). Two immunoregulatory
oligosaccharides expressed on schistosomes have been described
(23, 24, 25). Therefore, we examined early immune responses to
the schistosome-expressed immunoregulatory oligosaccharide
lacto-N-fucopentaose III (LNFPIII) in an attempt to
elucidate how this oligosaccharide may contribute to T helper biasing.
We examined phenotypically and functionally the peritoneal cell
response in mice injected with a glycoconjugate composed of LNFPIII
conjugated to dextran (LNFPIII-dex) and found that a single injection
of LNFPIII-dex rapidly expanded the peritoneal
CD11b+/Gr1+/F4/80+
population in a T cell-independent manner. These cells suppressed the
proliferation of naive CD4+ T cells, and the
process of inhibition was found to be NO- and IFN--dependent.
Depletion of Gr1+/F4/80+
cells from the peritoneal exudate cells (PECs) of LNFPIII-dex-injected
mice eliminated their ability to suppress proliferation of naive T
cells. In addition, injection of the structurally related
glycoconjugate lacto-N-neotetraose-dextran (LNnT-dex) has
also been shown to expand suppressor cells in the PCs of otherwise
naive mice.3 The ability of these
helminth-expressed oligosaccharides to rapidly expand this particular
suppressor population may be one mechanism that schistosomes use to
modulate the host response and induce immune anergy.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Female BALB/c and SCID:SCID mice between 6 and 8 wk of age were used in these studies and were purchased from Taconic Farms (Germantown, NY) and The Jackson Laboratory (Bar Harbor, ME).
Media and reagents
LNFPIII-dex and dextran were obtained from Neose Technologies (Horsham, PA). The glycoconjugate consisted of 12 LNFPIII molecules conjugated to a 10-kDa molecule of dextran. We tested for the presence of endotoxin in LNFPIII-dextran using a RAW murine macrophage bioassay for the production of NO and IL-10. RAW cells were stimulated with LPS (5 µg/ml) or LNFPIII-dextran (25 and 50 µg/ml) for 24, 48, or 72 h after which supernatants were collected and NO and IL-10 levels were determined by Griess reagent or ELISA. Both IL-10 and NO were produced in response to LPS, whereas neither was detected in supernatants from LNFPIII-dextran-stimulated cells. RPMI 1640 medium was supplemented with 10% FBS (HyClone Laboratories, Logan, UT), 100 U/mg penicillin, 100 µg/ml streptomycin, 0.05 mM 2-ME, and 2 mM glutamine (Sigma, St. Louis, MO). L-nMMA (NG-monomethyl-L-arginine) and MnTBAP (manganese [III] tetrakis [4-benzoic acid] porphyrin) were obtained from Calbiochem (La Jolla, CA).
Monoclonal Abs
Purified anti-mouse CD3e (clone 145-2C11),
anti-CD28, anti-mouse IFN-, CD11b-FITC, Gr-1-PE (RB6-8C5),
CD4-PE, purified rat IgG1, and IgG2a isotype control IgG were purchased
from BD PharMingen (San Diego, CA). Rat anti-mouse F4/80-Cy5 mAb
was purchased from Serotec (Raleigh, NC). Anti-FITC and anti-PE
microbeads were obtained from Miltenyi Biotec (Auburn, CA).
Cell preparation
Mice were injected i.p. with 50 µg of LNFPIII-dex or dextran in HBSS (Life Technologies, Rockville, MD). Approximately 20 h postinjection, mice were euthanized by CO2 inhalation, and PECs were obtained by lavage under sterile conditions by injection of 5 ml of HBSS into the PC. In some experiments, Gr1+ and F4/80+ cells were separated from PECs of LNFPIII-dex- or dextran-injected mice. PECs were incubated for 30 min at 4°C with anti-F4/80-FITC and anti-Gr1-PE Abs. Cells were washed to remove unbound Abs then incubated with anti-FITC and/or anti-PE microbeads for 20 min at 4°C. Positive and negative cell populations were then separated on a MACS column according to the manufacturer’s instructions. Purity of the various populations was determined via FACScan.
T cell activation and proliferation assay
Spleen cell preparations were prepared from naive mice.
Following lysis of RBC with Boyle’s solution, splenocytes were washed
and resuspended at 5–10 x 106/ml in PBS.
CFSE (Molecular Probes, Eugene, OR) was added to a final concentration
of 5 µM and incubated at room temperature for 8 min. Next, FBS was
added to a final concentration of 20%. Cells were washed three times
in cold RPMI 1640/10% FBS and plated. CFSE-labeled splenocytes
(at a concentration of 1 x 106/ml and a
volume of 0.5 ml) were plated in 48-well plates coated with 1 µg/ml
anti-CD3 and 5 µg/ml anti-CD28 mAbs. Splenocytes were
cultured for 3 h on Ab-coated plates, then 0.5 ml of PECs was
added such that the ratios of PECs to splenocytes/T cells were 1:2,
1:4, 1:8, and 1:16. The cocultures were incubated for 72 h, then
harvested and analyzed by flow cytometry. In some experiments,
L-nMMA, MnTBAP, or anti-IFN- mAbs (final
concentrations 0.5 mM, 10 µM, and 10 µg/ml, respectively) were
added to coculture of splenocytes and PECs. In the same experiments,
cocultured supernatants were harvested and levels of NO measured by
mixing equal volumes of culture supernatants (50 µl) and Greiss
reagent. After a 5-min incubation at room temperature, the absorbance
was read at 550 nm using a Spectramax plate reader (Molecular Devices,
Sunnyvale, CA). Nitrite concentrations were determined by comparing
absorbance values of the test samples to a standard curve generated by
serial dilution of 62.5 µM sodium nitrite.
Flow cytometry
FITC- or PE-labeled positive and negative populations of Gr1 and F4/80 PECs, isolated as described in Cell preparation, or CFSE-labeled cocultured cells (2–5 x 105) were transferred to 12 x 75-mm polystyrene tubes and washed with FACS buffer (PBS containing 0.1% BSA and 0.1% sodium azide). Cocultured cells or freshly isolated PECs were stained with various combinations of mAbs for 30 min on ice in the dark and washed twice in FACS buffer. Acquisition of cells was performed using a FACSCalibur flow cytometer (BD Biosciences, San Jose, CA). A minimum of 20,000 events was required for analysis. Cell populations were analyzed using CellQuest software (BD Biosciences).
Statistical analysis
Statistical significance of difference in values among groups was determined by Student’s t test. All data are expressed as the mean ± SE.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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BALB/c mice were used to study the expansion and function
of PEC subpopulations within 20 h postinjection of 50 µg of
LNFPIII-dex or dextran alone. As shown in Fig. 1
A, PECs from
LNFPIII-dex-injected mice contained higher numbers of
Gr1+/CD11b+ cells than
control (uninjected and dextran-injected) mice. The presence of
Gr1+/F4/80+ PECs in
LNFPIII-dex-injected mice is shown in Fig. 1B. Analysis of
double-positive cells from sugar-injected mice showed two
subpopulations characterized as Gr1+ high or low
(Fig. 1, arrows). Both Gr1+ subpopulations
express CD11b and F4/80 surface markers. To study the expression of Gr1
by macrophages, we gated double-positive CD11b/F4/80 cells (Fig. 1C, left panel). The results, showing Gr1-positive cells,
are given in the histogram in Fig. 1C (right
panel).
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. Injection of
LNFPIII-dex resulted in a significant (p <
0.001) increase in the percentage of
CD11b+/F4/80+ macrophages
expressing the Gr1+ marker (75.55 ± 2.1%)
compared with control (uninjected and dex-injected mice, 18.48 ±
1.83 and 18.39 ± 1.88%, respectively). It is clear that not only
the percentage but also the absolute number of
Gr1+ macrophages was dramatically increased in
mice injected with LNFPIII-dex.
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In several reports, Gr1+ CD11b- and/or
F4/80-positive populations suppressed naive T cell proliferation to
mitogen or costimulatory signaling. Here we performed experiments to
determine whether Gr1+,
F4/80+ PECs from LNFPIII-dex-injected mice were
able to suppress proliferation of naive splenocytes. Naive splenocytes
were stained with the proliferation marker CFSE before stimulation with
anti-CD3 and anti-CD28 Abs (26). CFSE-labeled
splenocytes were incubated in 48-well plates coated with
anti-CD3/CD28 mAbs for 3 h, then mixed with varying numbers of
PECs from uninjected, dex-injected, or LNFPIII-dex-injected mice. In
the current study, we gated CD4+ T cells and
analyzed their proliferation. Fig. 2
shows data from a representative experiment where PECs from mice
injected with LNFPIII-dex, at ratios of 1:4 and 1:8 (PECs to
splenocytes), significantly suppressed CD4+ T
cell proliferation compared with PECs from control mice at the same
ratios.
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Activated macrophages often suppress T cell activity via NO
production. Measurement of NO production in supernatants of cocultured
PECs and naive splenocytes is shown in Table II. In all experiments, at all ratios of
PECs to splenocytes, slightly higher nitrite levels were detected in
coculture supernatants containing PECs from LNFPIII-injected mice.
Neither PECs nor splenocytes alone generated NO (data not shown).
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A). NO
production in supernatants obtained from the same cocultures is shown
in Fig. 3B. The concentration of NO was dependent on the
numbers of PECs in coculture with naive splenocytes.
L-nMMA decreased NO in cell cultures to
background levels.
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-dependent mechanism of inhibition of T cell
proliferation in vitro
NS macrophages suppress via IFN-- or IL-4-dependent
mechanisms. In addition, NO production by suppressor cells has
been linked with an IFN--dependent mechanism (5). To
further define the suppressive mechanism used by LNFPIII-dex PECs, we
performed coculture experiments with neutralizing Abs to IFN-
or IL-4.
Fig. 4 demonstrates that addition of
anti-IFN- Abs to cocultures completely restored the
proliferative activity of naive CD4+ T cells
activated with anti-CD3/CD28 mAbs. In contrast,
CD4+ T cells in cocultures containing
anti-IL-4, anti-IL-10 (data not shown), or isotype control Abs
did not restore proliferation, demonstrating that LNFPIII-dex expanded
suppressor macrophages were functioning via an IFN--, but not an
IL-4- or IL-10-dependent mechanism. NO production of cocultured PECs
and splenocytes was reduced to 2.5 µM at all concentrations of PECs
in wells where anti-IFN- was added. Thus, IFN- is a critical
factor for development of LNFPIII-dex-induced PEC suppressor
activity.
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Previous studies have shown that suppression of T cell
proliferation is linked to the presence of Gr1+
cells, which also express CD11b and/or F4/80 (13, 14). To
identify whether suppression was due to Gr1+
macrophages, we used positively selected Gr1/F4/80 cells. In these
experiments, PECs were separated into
Gr1+/- and
F4/80+/- populations as
described in Materials and Methods. FACS staining (Fig. 5A) confirmed the efficiency
of the selection. The Gr1+ subpopulation
contained 99.7% positive cells (data not shown). The ability of
Gr1+/F4/80+ and the various
depleted subpopulations to suppress naive splenocytes was tested in
coculture experiments. The population that was depleted of
F4/80+/Gr1high cells still
contained Gr1+ cells, although the overall
fluorescence intensity was low (Fig. 5A, right panel). In
coculture experiments we found that the Gr1high,
F4/80+ purified subpopulation was responsible for
suppression. The representative pattern in Fig. 5B shows
that double-positive cells blocked T cell proliferation even at a ratio
of 1:16 (PECs to splenocytes). In contrast, the PEC population that
contained Gr1low/F4/80-
cells did not inhibit splenocyte proliferation, nor did the
F4/80+/Gr1low
population.
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-dependent, as
anti-IFN- mAbs completely abrogated suppression at all ratios of
suppressor/responder (Fig. 5
C). Supernatants from
cocultures of Gr1-/F4/80-
PECs with splenocytes contained small amounts of NO products, as
opposed to cocultures of splenocytes and
Gr1+/F4/80+ PECs, which
contained high amounts of NO (data not shown). Thus,
F4/80+/Gr1+ double-positive
macrophages are responsible for the observed suppressive activity of
PECs from LNFPIII-dex-injected mice. Mechanism of PEC suppression is T cell-independent
In normal mice, resident PECs include macrophages, neutrophils,
and NK cells, as well as T and B cells. We injected LNFPIII-dex
or dextran into SCID mice to determine whether the
LNFPIII-dex-induced accumulation of Gr1+
macrophages was dependent on the presence of T cells in the PEC
population. Table III compares the
Gr1+ cells of the
CD11b+/F4/80+ population in
both SCID and BALB/c mice 20 h after LNFPIII-dex or dex
injection. In LNFPIII-dex-injected SCID mice, 92.5 ± 2.5% of the
CD11b+/F4/80+ cells were
Gr1+ vs 75.6 ± 2.1% in BALB/c, although
absolute numbers of PECs from SCID mice were substantially less than
those from BALB/c (data not shown). The greater percentage of
Gr1+ cells seen in SCID mice compared with BALB/c
mice may be due to immuno-compensatory mechanisms in SCID
mice.
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. The
degree of suppression was higher than in wild-type mice, even when
the ratio of PECs to splenocytes was 1:16, and inhibition was also NO
dependent, as addition of L-nMMA to cocultures completely
restored proliferation of CD4+ T cells at all
ratios of suppressor-responder. For both strains of mice, the amount of
NO products present was found to be dependent on the number of PECs in
culture, although the difference in the amount of NO products between
control and SCID mice was not significant (data not shown). This may be
due to the existence of a "ceiling" concentration of NO products.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Because expansion of NS cell populations in helminth-infected or tumor-bearing mice has been reported to take days to weeks, this phenomenon has not been considered an innate response. However, in contrast to these studies, we demonstrated that injection of LNFPIII-dex significantly expanded the peritoneal suppressor macrophage population within 20 h. This observation, coupled with the results from a study showing that suppressor macrophage populations could be increased within 48 h by injection of superantigen, suggests that expansion of this cell type may occur through an innate immune response triggered by ligation of pattern recognition receptors (14).
Although all suppressor macrophages described to date have
similar/identical surface markers, two distinct subpopulations of
suppressors have been characterized. CA suppressor macrophages are NO-
and IFN--dependent (13, 14), whereas AA macrophages are
IL-4-dependent (11, 16, 18, 19, 21, 27, 28). CA
macrophages have been reported in mice injected with superantigens,
tumors, viruses, cyclophosphamide, and other Ags (13, 14, 15, 32). The Gr1+ suppressor macrophage
population we described in this study falls into the CA category. The
cell population expanded by injection of LNFPIII-dex-suppressed T cell
proliferation via an NO- and IFN--dependent mechanism, as
demonstrated by addition of L-nMMA or anti-IFN-
mAbs, respectively. Furthermore, although addition of anti-IFN-
mAbs completely abrogated suppression, addition of Abs to IL-4 had no
effect. That LNFPIII-dex expands peritoneal cells, which suppress naive
T cells in an NO- and IFN--dependent mechanism, is nearly identical
with that reported for the structurally similar schistosome
oligosaccharide, LNnT-dex.3 The results with both
glycoconjugates are consistent with several studies including that of
Angulo and coworkers (15), who showed that
Gr1+/CD11b+/CD31+
cells from cyclophosphamide-treated mice inhibited mitogen-induced
splenic T cell responses through an NO-dependent mechanism, which was
IFN--dependent. The study of Brooks and Hoskin (32)
also demonstrated that CD11b+
cyclophosphamide-treated spleen cells were dependent on the presence of
IFN- for expression of inhibitory activity. Additionally, IFN-
has been suggested as an inducible NO synthase inducer in NS cells
(5). Although the study reported here and those of Angulo
et al. (5) and Brooks and Hoskin (32)
demonstrated that the suppressive mechanism was NO-and
IFN--dependent, other signals that we did not examine, such as
TNF-, CD40, and LPS, may be required for successful NO production
(5, 15).
Macrophages respond to Ag exposure by producing IL-12 and TNF-,
activating CD4, CD8, and NK cells for IFN- release
(33, 34, 35, 36, 37). IFN- has been shown to stimulate NO
production by macrophages (38, 39, 40) and induce apoptosis of
activated CD4 T cells and macrophages in vitro during bacillus
Calmette-Guérin infection, a mechanism that involves NO
(41). It was previously reported that NO, or products of
the L-arginine pathway of reactive nitrogen intermediates,
mediated bone marrow-derived NS activity (5, 15). The data
presented here are consistent with these earlier studies, as we
demonstrated that NS activity was greatly inhibited by
L-nMMA, a competitive inhibitor of arginine-dependent NO
synthase (42, 43). The mechanism by which NO might act in
this manner is still unclear. Although our data show an important role
of NO in Gr1+ PEC suppression of T cell
proliferation, they do not formally demonstrate this agent as the
ultimate suppressor molecule. The involvement of NO as a
suppressive factor for proliferative responses of lymphocytes has
already been shown for peritoneal macrophages in another
parasite-infected mouse model (44).
The rapid expansion of suppressor macrophages observed here, following
injection of LNFPIII-dex, has not previously been observed. Twenty
hours after injection of LNFPIII-dex, the percentage of
Gr1+ cells as a subpopulation of
F4/80+/CD11b+ PECs was
expanded >4-fold, to 75%, compared with 18% in uninjected or
dex-injected mice. Using methods similar to those reported by
Kusmartsev (13), we demonstrated that these cells were
functional suppressors, as they inhibited the proliferation of
anti-CD3/CD28-stimulated naive T cells in vitro at ratios of 1:4
and 1:8 (PECs-splenocytes), whereas PECs from control mice did not.
Similar data were obtained using the structurally related
glycoconjugate LNnT-dex.3 These data are also
consistent with the results of Cauley and coworkers (14),
who showed that Gr1+ splenocytes from mice given
soluble egg Ag completely inhibited the proliferative response of
CD4+ T cells at a ratio of 1:8. This same study
also demonstrated that Gr1+ cells from control
mice had the ability to suppress naive T cells when they were
cocultured at a ratio of 1:2 (PECs-T cells). The suppressor population
described in our study suppressed via NO and was IFN--dependent and
IL-4-independent. Thus, in comparison to the studies that generated
IL-4-dependent, AA suppressor populations including those examining
suppressor cells from filaria-harboring mice (11),
injection of LNFPIII-dex led to expansion of CA, IFN--dependent
suppressors. A simple explanation for the presence of CA NS
cells following injection of LNFPIII-dex, vs AA PECs following
implantation of filarial parasites, may be because LNFPIII is not found
on filaria (45). Furthermore, LNFPIII is found on a subset
of tumors in addition to schistosomes (23, 25, 46, 47, 48).
The difference may also due to something as simple as differences
between injection of the glycoconjugate vs implantation of several
living metazoan parasites.
In addition to demonstrating that the mechanism of suppression was NO-
and IFN--dependent, we also demonstrated that
Gr1+/F4/80+ PECs depleted
of Gr1+ cells were no longer able to suppress
naive T cells, functionally showing that the Gr1+
macrophages are the suppressors and that
Gr1low/F4/80- cells are
not. Injection of LNFPIII-dex gave rise to two populations of
Gr1+ cells, which we termed high and low. This
observation on two Gr1+ populations is similar to
that reported for Gr1+ populations described in
the spleens of superantigen-treated mice, which were shown to express
high levels of CD11b and LFA-1 (14). Salvadory and
coworkers (8) also found two populations of
Gr1+ cells in splenocytes from naive and
tumor-bearing mice. In the tumor-bearing host, the majority of
Gr1+ cells stained brightly for Gr1
(Gr1high), with very few
Gr1low cells. In our study, depletion of either
Gr1high or
F4/80+/Gr1+ cells from PEC
populations of LNFPIII-dex-injected mice eliminated the ability of the
PECs to suppress naive T cell proliferation.
The last experiments we performed on suppressor macrophages were to
determine whether T cells were required for their expansion and/or
function as suppressors. Considering the rapid time frame in which the
suppressor population expanded following LNFPIII-dex injection, we felt
it was unlikely that these cells required other cell populations, and
that they likely directly interacted with the LNFPIII-dex conjugate,
leading to up-regulation of Gr1. We did inject LNFPIII-dex into SCID
mice and found similar kinetics of the PEC suppressor population,
showing that this phase was T cell-independent. Furthermore,
Gr1+ suppressor cells from SCID mice were
functional suppressors, and the mechanism of suppression was also
NO-dependent. The findings on NO production are similar to earlier
studies demonstrating that macrophages from SCID spleens produced large
amounts of NO when incubated with heat-killed Listeria
monocytogenes, but only in the presence of IFN-
(49). This T cell-independent response relied on the
presence of both macrophages and NK cells, and was modulated by the
addition of mAbs against F4/80 (2). In the current study
we demonstrated that increased numbers of
Gr1+/F4/80+ cells were
accompanied by strong suppression and NO production during coculture of
PECs and naive splenocytes, and the effects of suppression and NO
production were abrogated by addition of an inhibitor of NO synthase
(L-nMMA).
Taken together, injection of the S. mansoni expressed
immunoregulatory oligosaccharide as the neo-glycoconjugate LNFPIII-dex
rapidly expanded a peritoneal suppressor macrophage population that
phenotypically and mechanistically resembles the CA suppressor
macrophages defined in viral, tumor-, and superantigen-exposed murine
systems (12, 13, 14, 15). The kinetics of expansion of the
suppressor macrophages reported here are the most rapid observed to
date, and suggest an innate response. Indeed, we have shown using the
structurally related, nonfucosylated homologue LNnT-dex conjugate, that
suppressor macrophages are expanded as rapidly as 2 h
postinjection.3 How the generation of such a
suppressor population might alter immune responses during schistosome
infection is currently being investigated. One can speculate that
suppressor cells, if they are actually expanded during infection, would
dampen cell-mediated responses, and possibly help bias the ensuing
response to Th2-type. The latter point is based on the observation that
suppressor PECs obtained from mice injected with LNnT-dex produce lower
levels of Th1 cytokines and enhanced levels of IL-10 and
TGF-
.3 In this regard, we have observed the
appearance of Gr1+ suppressors in the PCs of
schistosome-infected mice at 6 wk postinfection, which is the earliest
we have looked (data not shown). Experiments where this population is
eliminated from infected animals should help define a role for
suppressor macrophages during natural infection.
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Acknowledgments |
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Footnotes |
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2 Abbreviations used in this paper; NS, natural suppressor; LNFPIII, lacto-N-fucopentaose III; PEC, peritoneal exudate cell; PC, peritoneal cavity; CA, classically activated; AA, alternatively activated; L-nMMA, NG-monomethyl-L-arginine; LNFPII-dex, LNFPIII conjugated to dextran; LNnT-dex, lacto-N-neotetraose-dextran; MnTBAP, manganese [III] tetrakis [4-benzoic acid] porphyrin.
3 L. Terrazas, K. Walsh, D. Piskorska, E. McGuire, and D. Harn. Lacto-N-neotetrose expands Gr-1+ suppressor cells that secrete anti-inflammatory cytokines and inhibit proliferation of nave CD4+ cells: a potential mechanism for immune polarization in helminth infections. Submitted for publication.
Received for publication April 3, 2001. Accepted for publication August 16, 2001.
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P. Smith, N. E. Mangan, C. M. Walsh, R. E. Fallon, A. N. J. McKenzie, N. van Rooijen, and P. G. Fallon Infection with a Helminth Parasite Prevents Experimental Colitis via a Macrophage-Mediated Mechanism J. Immunol., April 1, 2007; 178(7): 4557 - 4566. [Abstract] [Full Text] [PDF]
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X. Song, Y. Krelin, T. Dvorkin, O. Bjorkdahl, S. Segal, C. A. Dinarello, E. Voronov, and R. N. Apte CD11b+/Gr-1+ Immature Myeloid Cells Mediate Suppression of T Cells in Mice Bearing Tumors of IL-1{beta}-Secreting Cells J. Immunol., December 15, 2005; 175(12): 8200 - 8208. [Abstract] [Full Text] [PDF]
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 O. Atochina and D. Harn LNFPIII/LeX-Stimulated Macrophages Activate Natural Killer Cells via CD40-CD40L Interaction Clin. Vaccine Immunol., September 1, 2005; 12(9): 1041 - 1049. [Abstract] [Full Text] [PDF]
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 B. Sawitzki, C. I. Kingsley, V. Oliveira, M. Karim, M. Herber, and K. J. Wood IFN-{gamma} production by alloantigen-reactive regulatory T cells is important for their regulatory function in vivo J. Exp. Med., June 20, 2005; 201(12): 1925 - 1935. [Abstract] [Full Text] [PDF]
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L. Brys, A. Beschin, G. Raes, G. H. Ghassabeh, W. Noel, J. Brandt, F. Brombacher, and P. D. Baetselier Reactive Oxygen Species and 12/15-Lipoxygenase Contribute to the Antiproliferative Capacity of Alternatively Activated Myeloid Cells Elicited during Helminth Infection J. Immunol., May 15, 2005; 174(10): 6095 - 6104. [Abstract] [Full Text] [PDF]
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S. P. Zehntner, C. Brickman, L. Bourbonniere, L. Remington, M. Caruso, and T. Owens Neutrophils That Infiltrate the Central Nervous System Regulate T Cell Responses J. Immunol., April 15, 2005; 174(8): 5124 - 5131. [Abstract] [Full Text] [PDF]
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 G. Borkow and Z. Bentwich Chronic Immune Activation Associated with Chronic Helminthic and Human Immunodeficiency Virus Infections: Role of Hyporesponsiveness and Anergy Clin. Microbiol. Rev., October 1, 2004; 17(4): 1012 - 1030. [Abstract] [Full Text] [PDF]
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 M.-B. Voisin, D. Buzoni-Gatel, D. Bout, and F. Velge-Roussel Both Expansion of Regulatory GR1+ CD11b+ Myeloid Cells and Anergy of T Lymphocytes Participate in Hyporesponsiveness of |
