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* Microbiology Section, Department of Experimental Medicine and Biochemical Science, University of Perugia, Perugia, Italy;
Microbiology Section, Department of Experimental Medicine, University of Rome, Rome, Italy; and
Immunology Research Division, Department of Pathology, Brigham and Women’s Hospital, Boston, MA 02115
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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; and
required IL-10-producing, Candida hypha-activated
dendritic cells for generation. Adoptive transfer of
CD4+CD25+ T cells or IL-10-producing dendritic
cells restored resistance to reinfection and decreased inflammation in
B7-2-deficient mice. These results show that oral tolerance
induced by Candida hyphae is required for the occurrence
of long-lasting protective immunity after yeast priming. The
implication is that preventing reactivation rather than favoring
sterilizing immunity to ubiquitous fungal pathogens may represent the
ultimate expectation of vaccine-based
strategies. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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(1, 2), as
highlighted by the increased susceptibility to mucosal candidiasis
observed in patients with acquired (3) or genetic
(4) defects of cell-mediated immune responses. Early
studies implicated the balance of protective Th1 and pathogenic Th2
responses as major regulators of immunity to the fungus (1, 2). Indeed, both Th2 and Th1 cell responses were concomitantly
detected in mice with gastrointestinal candidiasis (5).
However, the detection of Th2 responses, such as high level production
of IL-4, IL-10, and IgE may or may not be observed in conditions of
susceptibility to C. albicans infection (1).
Paradoxically, some Th2 cytokines, such as IL-4 (6), IL-10
(7, 8), and TGF- (9), were found to be
required for the development and maintenance of protective Th1-mediated
antifungal immunity. Therefore, in addition to the Th1/Th2 balance,
other mechanisms seem to be involved in controlling and sustaining
Th1-dependent immune resistance to the fungus. Ultimately, regulation
appears to be an absolute requirement to ensure protective immunity in
the absence of immune pathology for a pathogen that also behave as a
commensal of the human gastrointestinal and vaginal tracts
(10). There is compelling evidence that regulatory T cells specialized in the attenuation of immune responses play a critical role in immune regulation (11, 12, 13, 14, 15, 16). Immune responses driven by Th1 and Th2 cells are also influenced by regulatory T cells the main function of which is counterregulation or suppression of immune responses mediated by Th1 and Th2. Different types of regulatory cells have been defined that are implicated in the control of organ-specific autoimmunity (17, 18, 19), transplantation tolerance (20), and inflammatory responses evoked by enteric organisms (21). Pathogen-specific regulatory T cells, with immunosuppressive activity, have also been described, such as those induced by chronic viral (22) or bacterial (23) infections.
Within the expanding family of costimulatory molecules (24), the B7/CD28 costimulatory pathway is a major regulatory pathway for the control of immune responses (25). Although with some overlap, each member of the B7/CD28 family has distinct functions. Engagement of CD28 on the surface of T cells by B7-1 (CD80) or B7-2 (CD86) expressed on APCs provides a potent costimulatory signal (26). CD28/B7 interactions lead to T cell proliferation, differentiation, and cytokine production. In contrast, engagement of CTLA-4 on activated T cells by B7-1 or B7-2 results in an inhibition of T cell responses (27). B7/CD28 costimulation is also required to maintain the survival of the regulatory CD4+CD25+CD62 ligandhigh T cells (28). In murine candidiasis, overexpression of B7-2, more than B7-1, correlated with enhanced Th1-mediated immune resistance to cutaneous infection with the fungus (29), although regulated expression of both costimulatory molecules was required for the development of protective anticandidal Th1 immunity (7, 30). However, whether each costimulatory molecule plays a distinct, nonoverlapping role in immunity to the fungus has yet to be defined.
To define the role of costimulatory molecules and cellular pathways
involved in regulation of Th1-mediated resistance to C.
albicans, in the present study mice deficient in B7-1, B7-2, and
CD28 costimulatory molecules were assessed for 1) pattern of resistance
or susceptibility to the disseminated or mucosal primary infection and
reinfection, 2) parameters of inflammatory and Th immune responses in
infections, and 3) the generation of T cells capable of regulating Th1
resistance to the fungus in vivo. A clear distinction was made between
wild-type or B7-1-deficient mice capable of both efficiently opposing
fungal infectivity and surviving reinfection and CD28- or
B7-2-deficient mice that did not survive reinfection. Lower fungal
growth, but signs of exaggerated inflammatory reaction, were observed
in the latter types of mice. Accordingly, regulatory T cells producing
IL-4, IL-10, and TGF-, induced on priming with IL-10-producing
dendritic cells (DC)3
pulsed with Candida hyphae and capable of preventing
excessive inflammatory and Th1 reactivity, were differently induced in
the course of the infection, being expanded in wild-type or
B7-1-deficient mice, but not in CD28- or B7-2-deficient mice.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Female BALB/c mice, 8–10 wk old, were purchased from Charles River (Calco, Italy). Homozygous, recombination-activating gene (RAG)-2-, IL-4-, CD28-, B7-1-, and B7-2-deficient mice on BALB/c background were bred under specific pathogen-free conditions in the Animal Facility, Perugia University (Perugia, Italy). Procedures involving animals and their care were conducted in conformity with national and international laws and policies.
C. albicans strains and infections
The origin and characteristics of the C. albicans virulent strain and the live vaccine strain used in this study have already been described in detail (6, 7). For disseminated infection, mice were injected i.v. with either 5 x 105/0.5 ml virulent strain delivered via the tail vein (acute disseminated infection) or 106 low virulence strain followed 14 days later by infection with the virulent strain (secondary disseminated infection). For gastrointestinal infection, 108 virulent Candida cells were injected intragastrically (i.g.), via an 18-gauge 4-cm-long plastic catheter, in a volume of 0.2 ml saline per mouse, as described elsewhere (5). Quantification of fungal growth in the organs of infected mice (4–6 mice per group) was performed by plating serial dilutions of homogenized organs in Sabouraud dextrose agar, and results (mean ± SE) were expressed as CFU per organ. Mice succumbing to fungal challenge were routinely necropsied for histopathological confirmation of candidiasis. For histology, tissues were excised and immediately fixed in formalin. Sections (3–4 µm) of paraffin-embedded tissues were stained with periodic acid-Schiff reagent and examined for histology as described (5).
In vivo analysis and treatments
Total and differential white blood cell counts were done by hemocytometry and by staining blood smears from transplanted mice with May-Grünwald-Giemsa reagents (Sigma-Aldrich, St. Louis, MO) before analysis. Treatments with B7-1- or B7-2-neutralizing mAbs (BD PharMingen, San Diego, CA) were done on days 0, 1, and 2 after the acute disseminated infection or on days 1, 3, and 5 after the gastrointestinal infection. Control mice were injected with an unrelated, isotype-matched Ab. Anti-IL-10R mAb (1B1.3) (31) was given i.p. at a total dose of 500 µg on days 1, 3, and 7 after the gastrointestinal infection. Control mice received an equivalent amount of purified GL.113 mAb.
Candidacidal activity
For the candidacidal assay, peripheral blood neutrophils, obtained by Ficoll-Hypaque (Pharmacia, Peapack, NJ) density gradient centrifugation, were plated (1 x 106/100 µl/well) in 96-well flat-bottom microtiter plates and incubated with 1 x 105/100 µl/well C. albicans yeasts for 1 h, as described (6, 7, 8, 9) The percent of CFU inhibition (mean ± SE) was determined as a percentage of colony formation inhibition = 100 - (CFU experimental group/CFU control cultures) x 100.
Flow cytometry
For analysis of costimulatory molecule surface expression, cells
were sequentially reacted with 10 µg/ml FITC-conjugated anti-B7-1
(16-10A1) or PE-conjugated anti-B7-2 (GL1) mAbs (BD PharMingen).
For lymphocyte analysis, cells were reacted with FITC-conjugated
anti-CD4 (RM4-5), or anti-CD8
(53-6.7) mAbs (BD PharMingen).
For double staining, splenocytes were sequentially reacted with
saturating amounts of FITC-conjugated anti-CD4 mAb and
PE-conjugated anti-CD25 (PC61; BD PharMingen). Before staining with
the relevant mAb, cells were incubated at room temperature with 5 µg
of anti-FcR mAb (2.4G2; BD PharMingen). Cells were analyzed with
a FACScan flow cytofluorometer (BD Biosciences, San Jose, CA).
Nonviable cells were excluded from analysis by accepted procedures
involving propidium iodide and narrow forward-angle light scatter
gating. Control staining of cells with irrelevant Ab was used to obtain
background fluorescence values. Data are expressed as a percent of
positive cells over total cells analyzed.
Isolation of CD4+CD25+ cells and Peyer’s patches (PP) DC
CD4+ T cells were purified from the mesenteric lymph nodes (MLN) or thymuses of mice by panning procedures, as described (6). CD4+CD25+ cells were separated by magnetic separation of CD4+ cells reacted with biotin-conjugated anti-CD25 (10 µg/108 cells) on ice for 30 min, followed by streptavidin MicroBeads (Miltenyi Biotec, Bergisch Gladbach, Germany). DC were purified from PP (PP-DC) by magnetic cell sorting with MicroBeads (Miltenyi Biotec, Germany) conjugated to hamster anti-mouse CD11c mAbs (clone N-418), as described (32). Consistent with previous reports (32), myeloid, lymphoid, and double-negative DC were present in the PP-DC on FACS analysis (data not shown).
Adoptive transfer of cells
RAG-2- or B7-2-deficient mice injected with C.
albicans i.g. 1 wk before received 106/0.5
ml of PBS of CD4+CD25+ or
CD4+CD25- cells given i.v.
or 3 x 105/20 µl of PBS of
Candida-pulsed DC given s.c. T cells were from MLN of
different strains of mice at 1 wk after the gastrointestinal infection.
PP-DC were from uninfected BALB/c mice. One week after the adoptive
transfer, mice were assessed for resistance to reinfection, fungal
growth in the stomach, and number of IFN--producing
CD4+ T cells in the MLN.
CFSE labeling
Purified CD4+CD25+
and CD4+CD25- cells from
MLN or thymuses were labeled with CFSE (Molecular Probes, Eugene, OR)
(33). Cells were suspended in complete medium (RPMI
containing 10% FCS, 50 mM 2-ME, 1 mM sodium pyruvate, 10 mM HEPES, and
50 µg/ml gentamicin) at 106/ml, and the CFSE
was added at the final concentration of 1 µM. The cells were
incubated on anti-CD3
-coated plates (clone 145-2C11; BD
PharMingen) in the presence of 1 µg/ml soluble anti-CD28 mAb
(clone 37.51; BD PharMingen). Coating was accomplished by pre-exposure
of individual wells to 10 µg/ml murine anti-CD3 mAb in
bicarbonate buffer (pH 9.6) overnight at 4°C. After 72 h, the
labeling was terminated by the addition of cold RPMI, and the cells
were analyzed by flow cytometry.
Pulsing of PP-DC and culture of cells
For pulsing, 106 PP-DC were exposed to
live unopsonized yeasts or hyphae (at DC:fungi ratio of 1:1 and 1:10,
respectively) for 2 h before addition of 2.5 µg/ml amphotericin
B (Sigma-Aldrich) to prevent Candida overgrowth, as
described (34). After pulsing, the cells were left for an
additional 22 h in culture before measurement of cytokine in the
supernatants and adoptive transfer into recipient mice. Unfractionated
cells (106/ml) from MLN were cultured in complete
medium in flat-bottom 96-well plates in the presence of inactivated
Candida cells, as described (6, 7, 8, 9). After
48 h of culture, the levels of IFN-, IL-4 and IL-10 production
in culture supernatants were assayed by ELISA. For IL-12 p70
production, cells were stimulated with IFN- and LPS for 24 h,
as described (6).
Cytokine and ELISPOT assays
The levels of IFN-, IL-4, IL-10, and IL-12 p70 were
determined by commercially available specific ELISAs (from BD
PharMingen and R&D Systems, Minneapolis, MN) using paired
anti-cytokine mAbs, as described elsewhere (6, 7, 8).
Cytokine titers were calculated by reference to standardcurves,
constructed with known amounts of recombinant cytokines (BD PharMingen
and, for IL-12p70, R&D Systems). Cytokine-producing cells were
enumerated by ELISPOT as described (33). Briefly, purified
cells from MLN and thymuses were cultured (1 x
102–1 x 105
cells/well) in complete medium for 18 h in 96-well plates using
pairs of mAbs as described (35). ELISPOT for TGF- was
done using coating and blocking mAbs from Promega (Promega Italia,
Milan, Italy). The enzyme was avidin-alkaline phosphatase conjugate
(Vector Laboratories, Burlingame, CA), and the substrate was
5-bromo-4-chloro-3-indolyl phosphate-p-toluidine salt (Life
Technologies, Gaithersburg, MD). Results were expressed as the mean
number of cytokine-producing cells (±SE) per 104
cells, calculated using replicates of serial 2-fold dilutions of
cells.
Statistical analysis
Survival data were analyzed using the Mann-Whitney U test. Student’s t test was used to determine significance of values among experimental groups. Significance was defined as p < 0.05. The data reported are either from one representative experiment of three independent experiments (FACS analysis) or pooled from three to five experiments, otherwise. The in vivo groups consisted of six to eight mice per group.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To assess whether parameters of innate or adaptive immunity to the
fungus were influenced by costimulatory molecules, we resorted to
different experimental models of infection, in which the relative
contribution of the innate and the adaptive immunity is clearly defined
(36). To evaluate parameters of innate resistance, each
type of mouse was injected i.v. with virulent Candida cells
and assessed for fungal growth, recruitment, and effector activity of
peripheral polymorphonuclear cells. No differences were observed in the
handling of the fungus by the innate cells from the different types of
mice (Table I
). All mice succumbed to the
infection, had a comparable fungal growth in the kidney, and did
not show differences in the ability to recruit polymorphonuclear cells
or to exhibit fungicidal activity. Similarly, no differences were
observed on administration of anti-B7-1 or anti-B7-2 mAbs to
wild-type mice. Therefore, these results would suggest a limited role,
if any, of costimulatory molecules in the innate immune response to the
fungus.
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A). In some
experiments, the latter groups did not survive the primary infection
(data not shown). Paradoxically, the ability of CD28- or B7-2-deficient
mice to restrict the fungal growth in the kidneys was even higher than
that of wild-type or B7-1-deficient mice (Fig. 1B). In
addition, in gastrointestinally infected mice, the fungal growth in the
stomach was different among the different types of mice and paralleled
that observed on reinfection: it was higher in wild-type and
B7-1-deficient mice than in CD28- or B7-2-deficient mice (Fig. 1C). Interestingly, treatment of wild-type (Fig. 1D) or CD28-deficient (Fig. 1E) mice with
anti-B7-1 or anti-B7-2 mAbs significantly increased or
decreased, respectively, the fungal growth in the stomach on
the primary gastrointestinal infection. The fungal growth was also
decreased in the stomach of B7-1-deficient mice on treatment with
anti-B7-2 mAb (Fig. 1F) but not in the stomach of
B7-2-deficient mice on treatment with anti-B7-1 mAb (Fig. 1G). Similar to what was observed in the disseminated
infection, wild-type and B7-1-deficient mice were capable of resistance
to reinfection (data not shown). Altogether, these results would
suggest that CD28 or B7-2 deficiency, but not B7-1 deficiency, impairs
immune resistance to C. albicans, as revealed by the
susceptibility to reinfection and failure to control the mucosal
infection. Intriguingly, however, the failure to survive reinfection
did not correlate with an excessive fungal growth in the relevant
organs, as occurs in conditions of Th2 activation (1).
Histopathological examination of the stomachs of infected mice revealed
the presence of Candida cells present in the keratinized
layer, at the cardial-atrium fold level, with a limited inflammatory
reaction in wild-type and B7-1-deficient mice (Fig. 2, A and B). In
contrast, fewer Candida cells with signs of exaggerated
inflammatory reactions, such as acanthosis, parakeratosis, and abundant
inflammatory cells were present in the stomach of CD28- or
B7-2-deficient mice (Fig. 2, C and D). Therefore,
although capable of efficiently controlling the fungal growth, CD28- or
B7-2-deficient mice were not able to fully oppose fungal infectivity
and apparently experienced an excessive inflammatory reaction.
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Because susceptibility or resistance to mucosal candidiasis is
considered to reflect the pattern of locally induced Th reactivity
(1, 5, 36), we measured levels of IFN-, IL-4, IL-10,
and IL-12 in culture supernatants of Ag-activated cells from MLN after
gastrointestinal infection. We found that levels of IFN- and IL-12
were elevated in each type of mouse on the infection, although the
levels of IFN- were significantly higher in B7-2-deficient mice than
in the other types of mice. The levels of IL-4 and IL-10 were instead
significantly higher in B7-1-deficient and significantly lower in CD28-
or B7-2-deficient than wild-type mice (Fig. 3A). Similar results were
obtained in the spleens of mice after reinfection (data not shown).
ELISPOT confirms these results by showing that the number of
CD4+ T cells producing IFN- was significantly
lower and that producing IL-4/IL-10 significantly higher in BALB/c and
B7-1-deficient mice than in CD28- or B7-2-deficient mice (Fig. 3B). Analysis of cytokine gene expression on purified
CD4+ T lymphocytes revealed that messages of
IFN-, IL-4, and IL-10 were present in wild-type and B7-1-deficient
mice, as opposed to the strong expression of the IFN- message only
in CD28- or B7-2-deficient mice (data not shown). These data are
reminiscent of our previous findings on patterns of cytokine production
in gastrointestinal candidiasis (5), because they show
that both Th1 and Th2 cytokines are present in the MLN of
wild-type-infected mice. However, the balance between Th1 and Th2
cytokines is shifted toward the Th1 pattern in CD28- or B7-2-deficient
mice and to the Th2 pattern in B7-1-deficient mice. Moreover, the data
show that the occurrence of Th1 responses to the fungus is relatively
independent from the B7/CD28 costimulatory pathway.
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To understand whether the patterns of cytokine production observed
in the different strains of mice could be associated with the expansion
of distinct cellular phenotypes, we assessed levels of CD4 and CD8 Ag
expression in the MLN of mice with candidiasis. Although B7
costimulation regulates CD4/CD8 T cell homeostasis (37),
no significant differences were observed in terms of the number of
CD4+ and CD8+ cells among
the different types of mice, neither uninfected nor infected (the
percent of CD4+ and CD8+
cells were 23, 24, 30, and 22 and 14, 13, 14, and 10 in wild-type,
CD28-, B7-1-, and B7-2-deficient mice, respectively). Interestingly,
levels of CD4+CD25+ cells
were instead different among mice (Fig. 4A). These cells were expanded
in wild-type and B7-1-, but not in B7-2-, deficient mice 1 wk after the
infection. An increase was also observed in CD28-deficient mice,
although the number of
CD4+CD25+ cells was far
below that observed in wild-type or B7-1-deficient mice. At 2 wk after
infection, the number of
CD4+CD25+ cells declined in
wild-type mice but remained high in B7-1-deficient mice.
CD4+CD25+ cells from each
type of mice also stained positive for the CD45RB and CD69 Ags,
although to a variable degree (data not shown).
CD4+CD25+ were also
expanded in the thymuses, but not in the PP or spleens (data not
shown). On assessing levels of local costimulatory Ag expression, we
found that B7-2 expression increased in wild-type and B7-1-deficient
mice, but not in CD28- or B7-2-deficient mice, 1 wk after infection and
decline thereafter (Fig. 4B). B7-1 expression was instead
promptly increased in B7-2-deficient mice soon after infection as
opposed to wild-type and, of course, B7-1-deficient mice. At 2 wk after
the infection, B7-1 expression continued to be elevated in
B7-2-deficient mice and to increase in wild-type or, to a lesser
extent, in CD28-deficient mice (Fig. 4B). Therefore, it
appears that CD4+CD25+
cells are expanded 1 wk after infection, at the time when B7-2
expression predominates over that of B7-1. In contrast, they are not
expanded under conditions in which B7-1 expression predominates over
that of B7-2, such as in B7-2-deficient mice or, later in infection, in
wild-type mice. Moreover, these cells were not expanded in double B7-1-
and B7-2-deficient mice (data not shown). The expansion of
CD4+CD25+ cells also
occurred in mice with the disseminated infection. However, the
expansion was not observed in the spleens (data nor shown) but in the
thymuses (Fig. 4C). Here again,
CD4+CD25+ cells were
expanded in wild-type and B7-1-deficient mice, but not in CD28- or
B7-2-deficient mice.
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To functionally characterize the
CD4+CD25+ population
expanded in mice with gastrointestinal or disseminated candidiasis,
CD4+CD25+ cells were
purified from MLN or thymuses of the different mice and assessed for
the ability to proliferate in response to anti-CD3 plus
anti-CD28 mAbs and for number of cells producing IFN-, IL-4,
IL-10, and TGF-. It was found that proliferation of
CD4+CD25+ cells was
minimal, as compared with that of
CD4+CD25- cells, for
BALB/c and B7-1-deficient mice. Proliferation, albeit small, was
instead observed with
CD4+CD25+ cells from CD28-
or B7-2-deficient mice (Fig. 5A). This finding would
suggest the existence of functionally different types of cells within
the CD4+CD25+ population
from the different mice. Moreover, in terms of frequency of cells
producing cytokines within the
CD4+CD25+ population, we
found that the number of cells producing IFN- was low in each type
of mice and that of cells producing IL-4, IL-10, or TGF- was high.
Interestingly, differences could be observed among the different types
of mice, being the number of cells producing IL-4, IL-10, and TGF-
higher in wild-type and B7-1-deficient mice than in CD28- or
B7-2-deficient mice, in both the MLN and thymuses (Fig. 5B).
The number of IFN--producing cells was elevated within the
CD4+CD25- population (data
not shown).
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To define whether IL-4 or IL-10 production was associated with the
activation of CD4+CD25+
cells, we evaluated the presence of these cells in the MLN of
gastrointestinally infected IL-4-deficient mice or wild-type mice
treated with a anti-IL-10R-neutralizing mAb. The results show that
CD4+CD25+ cells were not
expanded in mice treated with the IL-10R-neutralizing mAb. These cells
were present in IL-4-deficient mice, although to a lesser extent than
wild-type mice (Fig. 6A), a
finding indicating that they were not IL-4-dependent Th2 cells. We have
shown that splenic myeloid DC phagocytose yeasts and hyphae of
Candida discriminate between the two forms of the fungus in
terms of production of IL-12 (in response to yeasts) or IL-4 (in
response to hyphae) (34). To find out whether DC also
discriminate between the two forms of the fungus at the mucosal site,
we exposed PP-DC from BALB/c mice to unopsonized yeasts and hyphae and
measured levels of cytokines in culture supernatants. We found that
levels of IL-12 were elevated during yeast phagocytosis, whereas levels
of IL-10, more than those of IL-4, were elevated during the
phagocytosis of hyphae (Fig. 6B). IL-10 was also observed on
exposure to hyphae of PP-DC from IL-4-deficient mice (data not shown).
To directly assess whether IL-10-producing DC were required for the
activation of CD4+CD25+ T
cells, PP-DC from wild-type mice were pulsed with Candida
yeasts or hyphae and adoptively transferred into recipient
B7-2-deficient mice with gastrointestinal candidiasis. After 1 wk, mice
were assessed for the presence of
CD4+CD25+ T cells in MLN.
PP-DC pulsed with Candida hyphae, but not yeasts, induced
the expansion of CD4+CD25+
cells (Fig. 6C), and this correlates with an increased
resistance to reinfection (median survival time on reinfection was 28,
4, and 4.5 days in mice receiving DC pulsed with hyphae, pulsed with
yeasts, or not receiving DC, respectively). Because PP-DC from
IL-4-deficient mice also increased resistance to reinfection (data not
shown), these data suggest that IL-10-producing DC are required to
induce the activation of regulatory T cells and that signaling through
IL-10 appears to dominate over that of IL-4
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To evaluate the effect of the adoptive transfer of
CD4+CD25+ cells in mice
with candidiasis, B7-2-deficient mice were infected i.g. and 1 wk later
received purified CD4+CD25+
cells from MLN of wild-type, B7-1-, CD28-, or IL-4-deficient infected
mice. We also assessed the effect of the adoptive transfer of
CD4+CD25+ cells from
thymuses or CD4+CD25-
cells. The adoptive transfer of
CD4+CD25- T cells from
each type of mice did not induce resistance to reinfection, although
the local fungal burden in the stomach was significantly decreased, a
finding confirming the activation of anticandidal Th1 cells in these
mice. In contrast, the adoptive transfer of
CD4+CD25+ cells from MLN or
thymuses of wild-type or B7-1-deficient mice increased resistance to
reinfection, as measured by the increased survival (Table II). The primary fungal burden in the
stomach was also increased (Table II), but no signs of excessive
inflammatory pathology were present (data not shown). These effects
were not observed with cells from CD28- or IL-4-deficient mice,
although the former slightly increased the fungal burden in the
stomach. CD4+CD25+ cells
did not modify the fungal growth in RAG-2-deficient as in wild-type
mice, a finding implicating that recipient T cells are required for the
regulatory activity of the transferred cells. Accordingly, protection
always correlated with a decreased number of IFN--producing cells in
the MLN (Table II). All together,
CD4+CD25+ cells, induced by
Candida hypha-activated DC, are expanded in mice with
candidiasis and appear to function by limiting antifungal Th1
reactivity and the associated opposing effects.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and capable of limiting Th1 cell reactivity is
strictly dependent on levels of costimulatory Ag expression, presumably
on IL-10-producing DC. Thus, rather than having opposite functions,
B7-1 and B7-2 appear to determine the magnitude and the quality of the
immune Th1 reactivity to the fungus, i.e., the induction of an
efficient antifungal Th1 response without its opposing effects.
The importance of the role of CD28-mediated costimulation has been
demonstrated in a variety of model systems. The absence of CD28
function results in a greatly reduced ability to respond to protein
Ags, parasites (38, 39), and microbes (40, 41). However, many pathogens are able to trigger immune
responses that are largely independent of CD28 costimulation
(42, 43, 44). The alternative costimulatory molecule,
inducible costimulatory protein, that can be induced in the absence of
CD28, was found to regulate both CD28-dependent and CD28-independent
CD4+ Th responses in vivo (45, 46).
Here we show that CD28 is not required for either the early control of
the infection by the innate immune system or the
CD4+ Th1 cell activation. Early resistance to the
infection as well as the production of IL-12 and IFN- were not
different from those of wild-type mice. Because similar findings were
observed in B7-2- or B7-1-deficient mice, this suggests that the
activation of anticandidal Th1 cells is relatively independent on the
B7/CD28 costimulatory pathway.
The pattern of susceptibility and resistance to the infection seen in the different types of mice did not reveal an overt immunodeviation, given that both Th1 and Th2 cytokines were present in each type of mouse and no evidence of extensive fungal growth typically associated with Th2 cell activation (1, 2) was observed in susceptible mice. However, the Th1:Th2 cytokine ratio was different among mice and, paradoxically, Th1 cytokines predominate over Th2 cytokines in mice capable of efficiently restricting the fungal growth, yet succumbing to reinfection, such as the CD28- or B7-2-deficient mice. In contrast, Th2 cytokines predominate over Th1 cytokines in B7-1-deficient mice, which were nevertheless capable of controlling the infection and fully resisting reinfection. Therefore, at variance with pathogenic antifungal Th2 cells, the cells expanded in B7-1-deficient mice appear to be an essential component of the protective host immunity to the fungus.
A recent study showed that regulatory T cells may overexpress a subset
of Th2 gene transcripts (47). Therefore, although the
implication of the CD28/B7 interactions in the generation and
maintenance of T cell memory is still controversial (41, 48, 49, 50), our findings point to the existence of cellular pathways
dependent on the B7/CD28 interactions and involving IL-4, IL-10, and
TGF-, regulating the anticandidal Th1 immune reactivity. This would
be consistent with a series of previous studies suggesting that IL-4
(6), IL-10 (7), and TGF- (9)
are all required for maintaining a long-lasting Th1 immunity to the
fungus, yet inhibiting its activation in the inductive phase. The data
of the present study show that
CD4+CD25+ cells producing
IL-4, IL-10, and TGF- are differently expanded in mice with
candidiasis and may account for the different ability of mice to
maintain a sustained protective immune response. These cells were not
expanded in conditions of B7-2, CD28, or IL-10 deficiencies,
concomitantly with heightened antifungal Th1 reactivity and the ensuing
opposing effects. In contrast, they were expanded in wild-type and
B7-1-deficient mice and were associated with a relatively
impaired ability to restrict the local fungal growth but with
resistance to reinfection. In wild-type mice, the kinetics of
appearance of CD4+CD25+ T
cells parallels that of B7-2, given that these cells expanded at the
time when B7-2 was maximally up-regulated. Later in infection, both
B7-2 expression and expansion of
CD4+CD25+ T cells were
reduced. Thus, the kinetics of appearance of regulatory T cells
parallels that of B7-2. Concomitantly, B7-1 expression was low or high
in conditions of maximal expansion or restriction of
CD4+CD25+ cells. Therefore,
it appears that levels of costimulatory molecule expression at the
local sites may determine the extent to which
CD4+CD25+ cells will be
locally expanded. In accordance with other studies (28),
the costimulatory pathway of B7-2/CD28 is associated with the expansion
of regulatory T cells.
It is known that a subset of regulatory T cells are CTLA-4+ and CTLA-4 might be involved in the activity of these cells (28, 51, 52), because blocking CTLA-4 reversed the activity of CD4+CD25+ T cells in vivo (53). However, CTLA-4 ligation also triggers apoptosis of T cells (54). We found that CTLA-4 expression was slightly increased in concomitance with the expansion of CD4+CD25+ T cells in both the MLN and thymuses of infected mice (data not shown). Structural data indicate that a key function of B7-1 is to generate particularly stable complexes with CTLA-4 (55), a finding that along with the timing of B7-1 and CTLA-4 expression further points to the concept that inhibitory signals delivered by the B7-1/CTLA-4 interaction may terminate T cell activation (56, 57). Whether B7-1 molecules negatively regulate the expansion of CD4+CD25+ regulatory T cells, as our study would suggest, is presently unknown.
Different subsets of regulatory cells have been described
(11, 12, 13, 14, 15, 16). The subsets may differ in the mode of generation
and mechanism of action, although evidence for similarities between the
different regulatory T cells has also been shown (11, 12, 13, 14, 15, 16).
Certain types of regulatory T cells are preferentially induced at
mucosal surfaces (58, 59, 60), where they may limit the
excessive inflammatory response to microorganisms and mediate oral
tolerance. Others develops in the thymus and are associated with
protection from a number of autoimmune processes (61). One
form of T cell regulation is mediated by secretion of IL-10 (type 1 T
regulatory cells) and/or TGF- (Th3) after Ag-specific triggering
(16, 62). In several experimental systems,
CD4+CD25+ T cells are
regulatory T cells present in the thymus but also induced at mucosal
surfaces (60, 61). Their mechanism of action is dependent
on cell-to-cell contact, although the involvement of the suppressive
IL-10 and TGF- has also been described (60). We found
that CD4+CD25+ cells
producing IL-10, IL-4, and TGF- were expanded in the MLN and
thymuses of mice after gastrointestinal infection or in the thymuses of
mice with disseminated infection. Both types of
CD4+CD25+ cells appear to
have a similar function, given that they poorly proliferate in vitro;
contain cells producing IL-4, IL-10, and TGF-; and inhibited Th1
cells in vivo. This finding suggests that the generation of regulatory
cells occurs both in the thymus and in the periphery, although the
reciprocal relationship between the two cell populations is not
presently known. CD4+CD25+
cells were not generated in conditions of IL-10 deficiency, a finding
that may be explained with the notion that IL-10-producing DC have been
implicated in the induction of regulatory T cells (58, 63). We found that PP-DC produced IL-10 in response to
Candida hyphae but not yeasts. Accordingly, the former, and
not the latter, were able to induce the activation of
CD4+CD25+ T cells on
adoptive transfer into mice otherwise incapable of activating
regulatory T cells.
CD4+CD25+ T cells were
detected in IL-4-deficient mice, albeit at low level. However, they
were not as effective as
CD4+CD25+ T cells from
wild-type mice in increasing Th1 resistance on adoptive transfer, a
finding suggesting that IL-4 may be required for the effector activity
of regulatory T cells. In this regard, we have already shown that IL-4
produced late in infection served to promote a sustained IL-12
production (6). However, a dysregulated expression of
costimulatory molecules in the absence of IL-4 cannot be excluded.
Nevertheless, it appears that local levels of B7-2 expression along
with the ability of DC to produce IL-10 in response to the fungus are
both required for the generation of regulatory T cells during C.
albicans infection. The finding that DC produce either IL-4
(34) or IL-10 (this study) on exposure to
Candida hyphae agrees with the recent observations that the
type of receptors engaged on DC by the fungus will ultimately dictate
the pattern of both cytokine production and Th reactivity
(64). The pattern of receptors involved in the recognition
of yeasts and hyphae of the fungus by subsets of DC at different body
sites is presently under investigation.
Much remains to be learned about the generation, Ag specificity, and mechanisms of action of regulatory T cells in mice with candidiasis. In terms of generation, preliminary observations suggest that regulatory T cells are induced in mice of different haplotypes (our unpublished observations). Ag persistence seems to be required, as already suggested by others (62), or could be a consequence of otherwise activated regulatory T cells. Self-Ag-reactive regulatory cells capable of inhibiting development of colitis triggered by enteric organisms have been described (21). In this regard, it is worth mentioning that immunological cross-reactivity between C. albicans and human tissues (65) as well as the association of chronic mucocutaneous candidiasis with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (66) have been described. Interestingly, in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, the mutated gene has been shown to be involved in the ontogeny of regulatory CD25+ T cells (67). Although these hypotheses are not mutually exclusive, the findings that a sustained colonization with Candida was required for the induction of a long-lasting protective immunity to the fungus (68) and that hypha-pulsed DC activate regulatory T cells in vivo suggest that epitopes from Candida exist which are endowed with the ability to activate regulatory T cells. In this regard, it has long been known that the ability of C. albicans to establish an infection involves multiple components of this fungal pathogen, but its ability to persist in host tissue may involve primarily the immunosuppressive property of a major cell wall glycoprotein, mannan (69). Mannan and oligosaccharide fragments of mannan are potent inhibitors of cell-mediated immunity and appear to reproduce the immune deficit of patients with the mucocutaneous form of candidiasis (70).
Pathogen-specific regulatory T cells have been demonstrated in viral (22) and bacterial (23) infections. Here we show that regulatory T cells, the specificity of which is yet to be defined, are also induced in a fungal infection. It is likely that immunoregulation is one key component of the complex dynamic of the host-fungus interaction that may operate from commensalism and/or exposure to fungi to severe infections. In the case of C. albicans, it appears that oral tolerance induced by hyphae appears to be as protective as yeast priming in the occurrence of antifungal protective immunity; this would be consistent with a number of clinical observations indicating that, although a commensal, either the recovery of the fungus from the gastrointestinal tract as well as the detection of the underlying Th1 reactivity, such as delayed-type hypersensitivity and lymphoproliferation, may fluctuate in healthy subjects and in infection (10, 71). In chronic mucocutaneous candidiasis, both anergy and active lymphoproliferation and variable delayed-type hypersensitivity reactivity to the fungus are indeed observed (71, 72). It is conceivable that these cells, by dampening Th1-mediated antifungal resistance, will oppose inflammatory pathology at the expenses of fungal persistence. It is indeed clear that regulation of antifungal immunity occurs at the levels of T cells, given that the ability of CD4+CD25+ T cells to affect antifungal resistance was impaired in T cell-deficient mice. A corollary to these findings would be that conditions or vaccination strategies favoring a sterilizing immunity to the fungus may limit the activation of regulatory cells and thus negatively affect the generation of memory immunity. The importance of Ag persistence in the generation of memory immunity to pathogens has recently been reported (73, 74).
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Luigina Romani, Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Via del Giochetto, 06122 Perugia, Italy. E-mail address: lromani{at}unipg.it
3 Abbreviations used in this paper: DC, dendritic cells; MLN, mesenteric lymph node; PP, Peyer’s patches; PP-DC, DC purified from PP; i.g., intragastrically; RAG, recombination-activating gene.
Received for publication April 15, 2002. Accepted for publication September 17, 2002.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
is important in determining the in vivo patterns of susceptibility or resistance in mice infected with Candida albicans infection. J. Immunol. 155:1349.[Abstract]
-secreting Th3 regulatory cells. Immunol. Rev. 182:207.[Medline]
double-deficient mice infected with Candida albicans. Int. Immunol. 10:37.This article has been cited by other articles:
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|
  S. P. Dudhgaonkar, S. B. Janardhanam, K. N. Kodumudi, and M. Srinivasan CD80 Blockade Enhance Glucocorticoid-Induced Leucine Zipper Expression and Suppress Experimental Autoimmune Encephalomyelitis J. Immunol., December 1, 2009; 183(11): 7505 - 7513. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. A. Da Silva, C. Chalouni, A. Williams, D. Hartl, C. G. Lee, and J. A. Elias Chitin Is a Size-Dependent Regulator of Macrophage TNF and IL-10 Production J. Immunol., March 15, 2009; 182(6): 3573 - 3582. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Ji and M. W. Cloyd HIV-1 binding to CD4 on CD4+CD25+ regulatory T cells enhances their suppressive function and induces them to home to, and accumulate in, peripheral and mucosal lymphoid tissues: an additional mechanism of immunosuppression Int. Immunol., March 1, 2009; 21(3): 283 - 294. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. N. Couper, D. G. Blount, and E. M. Riley IL-10: The Master Regulator of Immunity to Infection J. Immunol., May 1, 2008; 180(9): 5771 - 5777. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Razmara, B. Hilliard, A. K. Ziarani, Y. H. Chen, and M. L. Tykocinski CTLA-4{middle dot}Ig converts naive CD4+CD25- T cells into CD4+CD25+ regulatory T cells Int. Immunol., April 1, 2008; 20(4): 471 - 483. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Bozza, T. Zelante, S. Moretti, P. Bonifazi, A. DeLuca, C. D'Angelo, G. Giovannini, C. Garlanda, L. Boon, F. Bistoni, et al. Lack of Toll IL-1R8 Exacerbates Th17 Cell Responses in Fungal Infection J. Immunol., March 15, 2008; 180(6): 4022 - 4031. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. De Luca, C. Montagnoli, T. Zelante, P. Bonifazi, S. Bozza, S. Moretti, C. D'Angelo, C. Vacca, L. Boon, F. Bistoni, et al. Functional yet Balanced Reactivity to Candida albicans Requires TRIF, MyD88, and IDO-Dependent Inhibition of Rorc J. Immunol., November 1, 2007; 179(9): 5999 - 6008. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Merlo, C. Calcaterra, S. Menard, and A. Balsari Cross-talk between Toll-like receptors 5 and 9 on activation of human immune responses J. Leukoc. Biol., September 1, 2007; 82(3): 509 - 518. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Q. Nie, N. J. Bernard, L. Schofield, and D. S. Hansen CD4+ CD25+ Regulatory T Cells Suppress CD4+ T-Cell Function and Inhibit the Development of Plasmodium berghei-Specific TH1 Responses Involved in Cerebral Malaria Pathogenesis Infect. Immun., May 1, 2007; 75(5): 2275 - 2282. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Zhan, D. Bourges, J. A. Dromey, L. C. Harrison, and A. M. Lew The origin of thymic CD4+CD25+ regulatory T cells and their co-stimulatory requirements are determined after elimination of recirculating peripheral CD4+ cells Int. Immunol., April 1, 2007; 19(4): 455 - 463. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. F. May Jr., X. Chang, H. Zhang, K. D. Lute, P. Zhou, E. Kocak, P. Zheng, and Y. Liu B7-Deficient Autoreactive T Cells Are Highly Susceptible to Suppression by CD4+CD25+ Regulatory T Cells J. Immunol., February 1, 2007; 178(3): 1542 - 1552. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. A. Cavassani, A. P. Campanelli, A. P. Moreira, J. O. Vancim, L. H. Vitali, R. C. Mamede, R. Martinez, and J. S. Silva Systemic and Local Characterization of Regulatory T Cells in a Chronic Fungal Infection in Humans J. Immunol., November 1, 2006; 177(9): 5811 - 5818. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Romani, F. Bistoni, K. Perruccio, C. Montagnoli, R. Gaziano, S. Bozza, P. Bonifazi, G. Bistoni, G. Rasi, A. Velardi, et al. Thymosin {alpha}1 activates dendritic cell tryptophan catabolism and establishes a regulatory environment for balance of inflammation and tolerance Blood, October 1, 2006; 108(7): 2265 - 2274. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. De Bernardis, R. Lucciarini, M. Boccanera, C. Amantini, S. Arancia, S. Morrone, M. Mosca, A. Cassone, and G. Santoni Phenotypic and Functional Characterization of Vaginal Dendritic Cells in a Rat Model of Candida albicans Vaginitis Infect. Immun., July 1, 2006; 74(7): 4282 - 4294. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Vojdani and J. Erde Regulatory T Cells, a Potent Immunoregulatory Target for CAM Researchers: Modulating Allergic and Infectious Disease Pathology (II) Evid. Based Complement. Altern. Med., June 1, 2006; 3(2): 209 - 215. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Kosonen, A. Rantala, C. H. Little, P. Lintu, P.-R. Harjamaki, G. M. Georgiou, R. E. Cone, and J. Savolainen Increased Levels of Candida albicans Mannan-Specific T-Cell-Derived Antigen Binding Molecules in Patients with Invasive Candidiasis Clin. Vaccine Immunol., April 1, 2006; 13(4): 467 - 474. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Montagnoli, F. Fallarino, R. Gaziano, S. Bozza, S. Bellocchio, T. Zelante, W. P. Kurup, L. Pitzurra, P. Puccetti, and L. Romani Immunity and Tolerance to Aspergillus Involve Functionally Distinct Regulatory T Cells and Tryptophan Catabolism J. Immunol., February 1, 2006; 176(3): 1712 - 1723. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Sanchez-Fueyo, S. Sandner, A. Habicht, C. Mariat, J. Kenny, N. Degauque, X. X. Zheng, T. B. Strom, L. A. Turka, and M. H. Sayegh Specificity of CD4+CD25+ Regulatory T Cell Function in Alloimmunity J. Immunol., January 1, 2006; 176(1): 329 - 334. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Skinner, M. R. Pilione, H. Shen, E. T. Harvill, and M. H. Yuk Bordetella Type III Secretion Modulates Dendritic Cell Migration Resulting in Immunosuppression and Bacterial Persistence J. Immunol., October 1, 2005; 175(7): 4647 - 4652. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. T. Nardelli, J. P. Cloute, K. H. K. Luk, J. Torrealba, T. F. Warner, S. M. Callister, and R. F. Schell CD4+ CD25+ T Cells Prevent Arthritis Associated with Borrelia Vaccination and Infection Clin. Vaccine Immunol., June 1, 2005; 12(6): 786 - 792. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. D. Taylor, L. LeGoff, A. Harris, E. Malone, J. E. Allen, and R. M. Maizels Removal of Regulatory T Cell Activity Reverses Hyporesponsiveness and Leads to Filarial Parasite Clearance In Vivo J. Immunol., April 15, 2005; 174(8): 4924 - 4933. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. M. Haeryfar, R. J. DiPaolo, D. C. Tscharke, J. R. Bennink, and J. W. Yewdell Regulatory T Cells Suppress CD8+ T Cell Responses Induced by Direct Priming and Cross-Priming and Moderate Immunodominance Disparities J. Immunol., March 15, 2005; 174(6): 3344 - 3351. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Bozza, F. Fallarino, L. Pitzurra, T. Zelante, C. Montagnoli, S. Bellocchio, P. Mosci, C. Vacca, P. Puccetti, and L. Romani A Crucial Role for Tryptophan Catabolism at the Host/Candida albicans Interface J. Immunol., March 1, 2005; 174(5): 2910 - 2918. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. M. Freeman, B.-C. Chiu, V. R. Stolberg, J. Hu, K. Zeibecoglou, N. W. Lukacs, S. A. Lira, S. L. Kunkel, and S. W. Chensue CCR8 Is Expressed by Antigen-Elicited, IL-10-Producing CD4+CD25+ T Cells, Which Regulate Th2-Mediated Granuloma Formation in Mice J. Immunol., February 15, 2005; 174(4): 1962 - 1970. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Yadav, V. Judkowski, M. Flodstrom-Tullberg, L. Sterling, W. L. Redmond, L. Sherman, and N. Sarvetnick B7-2 (CD86) Controls the Priming of Autoreactive CD4 T Cell Response against Pancreatic Islets J. Immunol., September 15, 2004; 173(6): 3631 - 3639. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. T. Rouse and S. Suvas Regulatory Cells and Infectious Agents: Detentes Cordiale and Contraire J. Immunol., August 15, 2004; 173(4): 2211 - 2215. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. L. Kinter, M. Hennessey, A. Bell, S. Kern, Y. Lin, M. Daucher, M. Planta, M. McGlaughlin, R. Jackson, S. F. Ziegler, et al. CD25+CD4+ Regulatory T Cells from the Peripheral Blood of Asymptomatic HIV-infected Individuals Regulate CD4+ and CD8+ HIV-specific T Cell Immune Responses In Vitro and Are Associated with Favorable Clinical Markers of Disease Status J. Exp. Med., August 2, 2004; 200(3): 331 - 343. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. K. Choi, J. S. Bae, E. M. Choi, W. J. Kang, S. Sakaguchi, D. S. Vinay, and B. S. Kwon 4-1BB-dependent inhibition of immunosuppression by activated CD4+CD25+ T cells J. Leukoc. Biol., May 1, 2004; 75(5): 785 - 791. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. W. Vahlenkamp, M. B. Tompkins, and W. A. F. Tompkins Feline Immunodeficiency Virus Infection Phenotypically and Functionally Activates Immunosuppressive CD4+CD25+ T Regulatory Cells J. Immunol., April 15, 2004; 172(8): 4752 - 4761. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. G. Netea, R. Sutmuller, C. Hermann, C. A. A. Van der Graaf, J. W. M. Van der Meer, J. H. van Krieken, T. Hartung, G. Adema, and B. J. Kullberg Toll-Like Receptor 2 Suppresses Immunity against Candida albicans through Induction of IL-10 and Regulatory T Cells J. Immunol., March 15, 2004; 172(6): 3712 - 3718. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Bellocchio, C. Montagnoli, S. Bozza, R. Gaziano, G. Rossi, S. S. Mambula, A. Vecchi, A. Mantovani, S. M. Levitz, and L. Romani The Contribution of the Toll-Like/IL-1 Receptor Superfamily to Innate and Adaptive Immunity to Fungal Pathogens In Vivo J. Immunol., March 1, 2004; 172(5): 3059 - 3069. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Romani, C. Montagnoli, S. Bozza, K. Perruccio, A. Spreca, P. Allavena, S. Verbeek, R. A. Calderone, F. Bistoni, and P. Puccetti The exploitation of distinct recognition receptors in dendritic cells determines the full range of host immune relationships with Candida albicans Int. Immunol., January 1, 2004; 16(1): 149 - 161. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Romagnoli, R. Nisini, P. Chiani, S. Mariotti, R. Teloni, A. Cassone, and A. Torosantucci The interaction of human dendritic cells with yeast and germ-tube forms of Candida albicans leads to efficient fungal processing, dendritic cell maturation, and acquisition of a Th1 response-promoting function J. Leukoc. Biol., January 1, 2004; 75(1): 117 - 126. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Cavani, F. Nasorri, C. Ottaviani, S. Sebastiani, O. De Pita, and G. Girolomoni Human CD25+ Regulatory T Cells Maintain Immune Tolerance to Nickel in Healthy, Nonallergic Individuals J. Immunol., December 1, 2003; 171(11): 5760 - 5768. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Bozza, K. Perruccio, C. Montagnoli, R. Gaziano, S. Bellocchio, E. Burchielli, G. Nkwanyuo, L. Pitzurra, A. Velardi, and L. Romani A dendritic cell vaccine against invasive aspergillosis in allogeneic hematopoietic transplantation Blood, November 15, 2003; 102(10): 3807 - 3814. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Spellberg, D. Johnston, Q. T. Phan, J. E. Edwards Jr., S. W. French, A. S. Ibrahim, and S. G. Filler Parenchymal Organ, and Not Splenic, Immunity Correlates with Host Survival during Disseminated Candidiasis Infect. Immun., October 1, 2003; 71(10): 5756 - 5764. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Sakaguchi Control of Immune Responses by Naturally Arising CD4+ Regulatory T Cells That Express Toll-like Receptors J. Exp. Med., February 17, 2003; 197(4): 397 - 401. [Full Text] [PDF]
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