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* Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814;
Immunology Research Division, Department of Pathology, Brigham and Womens Hospital and Harvard Medical School, Boston, MA 02115; and
Nutrient Requirements and Functions Laboratory, Beltsville Human Nutrition Research Center, U.S. Department of Agriculture, Beltsville, MD 20705
| Abstract |
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| Introduction |
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Several studies have suggested that OX40/OX40L interactions may be particularly important in promoting the development of IL-4-producing T cells (7, 8, 9). In vivo administration of an anti-OX40L Ab decreased Th2 cytokine and Ab production during the primary immune response to Leishmania major with an increase in Th1 cytokine production associated with enhanced protection (4). However, more recent studies have demonstrated that protective immunity and the associated primary Th2 response to Nippostrongylus brasiliensis is not inhibited in OX40L-/- mice (10). As yet, the role of OX40L interactions in the development of the memory Th2 response during infectious disease has not been examined in vivo. Recent studies have suggested that OX40/OX40L interactions may be particularly important in sustaining T cell function at later stages of the primary immune response and during the memory response (8, 10, 11, 12, 13, 14, 15). Gramaglia et al. (15) demonstrated that T cells from OX40-deficient mice produce IL-2 and proliferate normally, but, as the response proceeds, T cell expansion and associated increased cytokine production is not sustained in vitro. Furthermore, Rogers et al. (16) demonstrated that reduced T cell survival in OX40-/- mice was due to decreased levels of the antiapoptotic proteins Bcl-xL and Bcl-2. In addition, the frequency of Ag-specific T cells was reduced in the absence of OX40 during both the primary and secondary immune responses to keyhole limpet hemocyanin (15).
In addition to regulating T cell survival, several studies suggest that OX40 signaling functions in the regulation of T cell homing within secondary lymphoid organs. In particular, CD28-dependent OX40 signaling has been correlated with the up-regulation of CXCR5 on CD4+ T cells, which results in homing of these T cells toward the B cell-rich follicles where they provide the necessary signals for germinal center (GC) formation (7, 17, 18). In a study by Brocker et al. (18), OX40L transgenic mice demonstrated an accumulation of activated CD4+OX40+ T cells in the B cell follicles of secondary lymphoid organs following antigenic stimulation.
To directly examine the role of OX40/OX40L interactions during in vivo primary and memory Th2 immune responses, we infected OX40L+/+ and OX40L-/- BALB/c mice with the murine gastrointestinal nematode parasite Heligmosomoides polygyrus. The parasite H. polygyrus is a useful model for studying development of primary and memory Th2 responses during infectious disease, because the primary host response is associated with chronic infection, while the memory immune response is a host-protective response characterized by CD4-dependent elevations in IL-4 production that effectively limit adult worm maturation and egg production (19). Although the mechanism of host protection is unclear, it appears to depend primarily on direct effects of IL-4 and/or IL-13 on intestinal tissue (19, 20). Infection with H. polygyrus is characterized by CD4-dependent increases in Th2 cytokines, serum IgE and IgG1, and GC formation in the mesenteric lymph node (MLN) (21, 22, 23). In these studies, we examined whether Th2 cells and the associated immune response could develop when OX40/OX40L interactions were inhibited during priming and challenge. Our results show an impairment in adult worm expulsion, associated with reduced production of IL-4, and decreases in total and Ag-specific serum IgE during the primary and challenge immune responses to H. polygyrus in OX40L-/- mice, as compared with OX40L+/+ mice. However, Ag-specific serum IgG1 levels and GC formation were comparable between OX40L+/+ and OX40L-/- mice inoculated with primary and challenge doses of H. polygyrus. In additional studies, CD4+ CFSE-labeled T cells from DO11.10 TCR transgenic OX40L+/+ mice were transferred to OX40L-/- mice to directly examine the role of OX40/OX40L interactions during the development and trafficking of Ag-specific T cells following primary inoculation with H. polygyrus. These studies demonstrated a reduction in Ag-specific IL-4 production, although Ag-specific T cell expansion, cell cycle progression, CXCR5 expression, and migration were comparable between OX40L+/+ and OX40L-/- mice primed with both H. polygyrus and OVA peptide. In summary, these studies suggest that the absence of OX40L does not impair the ability of Ag-specific T cells to proliferate and migrate toward the B cell follicles of secondary lymphoid organs, but does impair the ability of T cells to produce IL-4 and provide B cell help leading to increased IgE production and host protection.
| Materials and Methods |
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All experiments were performed using BALB/c mice genetically deficient for OX40L (OX40L-/-) or normal BALB/c controls; four to five mice were used per treatment group. Breeding pairs of BALB/c OX40L-/- mice and BALB/c DO11.10 TCR transgenic mice were obtained from Dr. A. Sharpe (Brigham and Womens Hospital and Harvard Medical School), while the BALB/c controls were obtained from The Jackson Laboratory (Bar Harbor, ME). T cells from DO11.10 transgenic mice express a receptor specific for class II MHC-restricted chicken OVA peptide (323339); this TCR is uniquely recognized by the KJ1-26 anticlonotypic mAb (24). All mice were maintained in a specific pathogen-free, virus Ab-free facility administered by the Laboratory of Animal Medicine, Uniformed Services University of the Health Sciences, which is an Association for the Assessment and Accreditation of Laboratory Animal Care-accredited institution. The experiments in this study were conducted according to the principles set forth in the Guide for the Care and Use of Laboratory Animals (Institute of Animal Resources, National Research Council, Department of Health, Education and Welfare (National Institutes of Health) 86-23).
Parasites and OVA inoculation
Mice were inoculated per os with 200 infective third-stage H. polygyrus larvae using a rounded gavage tube, and adult worm numbers and egg production were quantitated as described previously (25). An antihelminthic, pyrantel pamoate (12 mg) was administered orally to expulse H. polygyrus adults from the gut after primary infection and before secondary challenge infection (25). Alternatively, DO11.10 T cell-recipient mice were inoculated intracutaneously (in the ear) with 300 infective third-stage H. polygyrus larvae and/or 30 µg of OVA peptide. HPLC-purified OVA peptide 323339 with the sequence I-S-Q-A-V-H-A-A-H-A-E-I-N-E-A-G-R-COOH was synthesized by the Biomedical Instrumentation Center at the Uniformed Services University of the Health Sciences.
DO11.10 adoptive cell transfer
Peripheral lymph nodes and the spleen were harvested from
DO11.10 TCR transgenic mice that were age- and sex-matched to adoptive
transfer recipients, and single-cell suspensions were prepared by
gently pressing the tissue through a nylon strainer (BD Biosciences
Discovery Labware, Bedford, MA). DO11.10
CD4+ T cells were purified by incubation with
anti-CD4 beads and by passage through an LS+
column (Miltenyi Biotec, Auburn, CA); purity was
99%, as determined
by FACS. Purified CD4+ DO11.10 T cells were then
resuspended at 5 x 107 cells/ml in PBS plus
0.1% BSA, and labeled with 10 µM CFSE (Molecular Probes, Eugene, OR)
for 10 min at 37°C; labeling was terminated by washing in cold RPMI
plus 10% FCS (Life Technologies, Grand Island, NY). Single-cell
suspensions (5 x 106) of OVA-specific
KJ1-26+CD4+ T cells were
then injected i.v. into recipient mice.
Quantitation of serum Igs
Total serum IgG1, IgG2a, and IgE levels were quantitated by ELISA (26). Ag-specific Ab levels were measured using a modified ELISA as described previously (27).
ELISPOT
The frequency of IL-4-producing cells was determined by an ELISPOT assay as previously described (26, 28). Alternatively, the ELISPOT assay was modified to include the capability to quantitate IL-4-producing cells following in vitro restimulation with OVA peptide. Briefly, lymph node cells were first cultured for 3 days on anti-IL-4-coated plates with, or without, 10 µg/ml OVA peptide. The OVA peptide was then washed away with PBS and PBS plus Tween 20 before addition of the secondary anti-IL-4 Ab diluted (4 µg/ml) in PBS plus 0.05% Tween plus 5% FCS, and added at 100 µl/well. Following an overnight incubation at 4°C, plates were washed, and a 1/2000 dilution of streptavidin-alkaline phosphatase (Jackson ImmunoResearch Laboratories, West Grove, PA) was added. Plates were then developed, and results were counted as previously described (26, 28).
Cell labeling and FACS analysis
The draining cervical lymph nodes were removed from individual mice, and single-cell suspensions were pooled within a treatment group. Lymph node cells were washed and 1 x 106 cells were blocked with Fc Block (BD PharMingen, San Diego, CA) before incubation with the following fluorescent Abs: CyChrome-anti-CD4 (BD PharMingen), PE-anti-CD69 (BD PharMingen), KJ1-26-PE (Caltag Laboratories, Burlingame, CA), KJ1-26-Tri-Color (Caltag Laboratories), and rabbit-anti-CXCR5 (polyclonal; a kind gift from Dr. J. Cyster (Department of Microbiology and Immunology, University of California, San Francisco, CA)), which was followed by PE-anti-rabbit-Ig (Serotec, Raleigh, NC). After washes, cells were fixed with 1% paraformaldehyde (Fisher Scientific, Pittsburgh, PA) and analyzed by flow cytometry using an EPICS XL-MCL (Beckman Coulter, Fullerton, CA). Twenty thousand events were collected and analysis of activation marker expression was performed by gating on the CD4+ population. The total number of KJ1-26+ cells per draining lymph node was determined as the percentage of KJ1-26+CD4+ cells multiplied by the total number of cells per lymph node. For CFSE-labeled cells, anti-CD4-CyChrome and KJ1-26-PE were used to distinguish the DO11.10 T cells. Cell cycle progression was monitored by measuring sequential reductions in CFSE fluorescence (29) of KJ1-26+CD4+ cells using ModFit (Verity Software House, Topsham, ME) software.
Immunohistological analysis
Immunohistological staining and GC quantitation of the MLN were performed as described previously (22, 30). In other experiments, the draining cervical lymph nodes were harvested from individual mice and frozen in liquid nitrogen, and 8-µm tissue sections were obtained from near the center of the cervical lymph node using a HM505E cryostat (Richard-Allan Scientific, Kalamazoo, MI). Tissue sections were allowed to dry at room temperature for 30 min, fixed in cold acetone for 10 min, and stored at -80°C. Cervical lymph node tissue sections were then dual-stained with PE-KJ1-26 (Caltag Laboratories) and biotinylated-anti-B220 (RA3-6B2; BD PharMingen), followed by streptavidin Alexa-647 (Molecular Probes, Eugene, OR), and coverslipped using FlouromountG (Southern Biotechnology Associates, Birmingham, AL). The surface of the entire cervical lymph node section was mapped using scanning software designed by Jozsef Czege in the Biomedical Instrumentation Center at the Uniformed Services University of the Health Sciences. Mapped regions of the lymph node were then individually photographed at x20 magnification using a SPOT2 cooled CCD camera (Diagnostic Instruments, Sterling Heights, MI) mounted on a Leica DMRXA (Leica Microsystems, Bannockburn, IL) computerized fluorescence microscope, and using SPOTAdvance software (Diagnostic Instruments). Each fluorescent channel was photographed separately, and the three sets of x20 images were merged using TIFFany3 software (Caffeine Software, Santa Clara, CA) to create the final picture of the whole cervical lymph node section.
Cytokine gene expression by RT-PCR
Total RNA was prepared from tissues and reverse transcribed, as previously described (26). Real-time PCR commercial kits (Applied Biosystems, Foster City, CA) specific for different cytokines or rRNA were used and all data were normalized to constitutive rRNA values. The Applied Biosystems 7700 sequence detector (PE Applied Biosystems) was used for amplification of target mRNA and quantitation of differences between treatment groups was calculated according to the manufacturers instructions.
Statistical analysis
Statistical differences (significance level of p < 0.05) between groups were assessed using ANOVA and Tukeys t test for pairwise comparisons. The software program SigmaStat (Jandel Scientific Software, San Rafael, CA) was used for all statistical analyses.
| Results |
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Initial infection with H. polygyrus stimulates a chronic Th2 CD4-dependent immune response, which can be completely cleared by administration of an antihelminthic drug. Subsequent exposure to H. polygyrus results in a strong IL-4 dominant memory response, which impairs adult worm development resulting in reduced fecundity (19). Previous studies have suggested that, although B7 blockade inhibits the primary response, administration of the B7 antagonist, CTLA4Ig, at the time of challenge does not impair the memory response (22, 23, 31). More recent studies have demonstrated that the development of memory T cells in response to H. polygyrus (27) or lymphocytic choriomeningitis virus (32) does not require B7-1/B7-2 or CD28 interactions, suggesting that other costimulatory molecules may play a role in the development of memory T cells. In particular, several studies have suggested that OX40/OX40L interactions may function in the development of memory T cells (8, 15, 16, 33, 34, 35). To examine the role of OX40/OX40L interactions in the primary and memory Th2 immune responses to H. polygyrus, BALB/c OX40L+/+ and BALB/c OX40L-/- mice were orally inoculated with 200 third-stage H. polygyrus larvae. All mice were treated with the antihelminthic pyrantel pamoate at 23 wk postinfection to expulse all parasites before a challenge oral dose of H. polygyrus given 56 wk after primary inoculation. Two additional control groups of OX40L+/+ and OX40L-/- mice received an initial inoculum of H. polygyrus at the time of challenge, allowing direct comparison between the primary and secondary immune responses to H. polygyrus. At day 12 following H. polygyrus challenge inoculation, all treatment groups were sacrificed, and various immune parameters were assessed.
Previous studies have demonstrated that
CD4+TCR-
+ cells are
the primary source of IL-4 production during the primary (21, 22, 25) and challenge (23, 25) immune responses to
H. polygyus. This cell population directly mediates host
protection during the challenge response (25), resulting
in an inhospitable enteric environment in which egg production by adult
worms is inhibited and, in some cases, worms are expulsed (23, 25). At day 12 following H. polygyrus challenge, the
total number of eggs and adult worms per mouse were determined, as
previously described (25). As seen in Fig. 1
A, the number of adult worms
was significantly (p < 0.01) reduced in the
H. polygyrus-challenged OX40L+/+ mice,
as compared with OX40L+/+ mice that received only
a primary H. polygyrus inoculation. However, comparable
numbers of adult worms were observed in
OX40L-/- mice during both the primary and
memory immune responses to H. polygyrus, indicating that
adult worm expulsion was blocked in the H.
polygyrus-challenged OX40L-/- mice.
Although H. polygyrus-challenged
OX40L+/+ and
OX40L-/- mice demonstrated a significant
(p < 0.05) reduction in adult worm egg
production, as compared with OX40L+/+ and
OX40L-/- mice given only a primary dose of
H. polygyrus, egg production was significantly
(p < 0.05) greater in H.
polygyrus-challenged OX40L-/- mice, as
compared with H. polygyrus-challenged
OX40L+/+ mice (Fig. 1
B). These
findings suggested that the H. polygyrus memory response
that developed in the OX40L-deficient mice was unable to mediate
effective adult worm expulsion, while partially limiting adult worm egg
production.
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expression were detected in H. polygyrus-inoculated
OX40L-/- mice as measured by RT-PCR (data not
shown). Elevations in total and Ag-specific serum IgE levels are reduced, while elevations in Ag-specific serum IgG1 levels and GC formation are comparable between OX40L-/- and OX40L+/+ mice primed or challenged with H. polygyrus
Previous studies with H. polygyrus have demonstrated
that production of serum IgG1 and IgE is dependent on the presence of
CD4+ T cells (38), while IgE, but
not IgG1, is dependent on IL-4 (39, 40). Furthermore,
CD4+ T cells are required for the production of
IgE and IgG1 during both the primary (38) and secondary
(25) immune responses to H. polygyrus. To
determine whether the humoral immune response was impaired in the
absence of OX40/OX40L interactions due to reduced levels of IL-4, total
and Ag-specific serum Ig levels were measured by ELISA at day 12
following H. polygyrus challenge inoculation of
OX40L+/+ and OX40L-/-
mice. As seen in Fig. 2
A,
elevations in total serum IgE levels were significantly
(p < 0.01) increased in H.
polygyrus-challenged OX40L+/+ and
OX40L-/- mice, as compared with
OX40L+/+ and OX40L-/-
mice given a primary inoculation of H. polygyrus. However,
elevations in total serum IgE levels were significantly
(p < 0.01) reduced during both the primary and
secondary immune response to H. polygyrus in
OX40L-/- mice, as compared with
OX40L+/+ mice inoculated with H.
polygyrus (Fig. 2
A). Elevations in Ag-specific serum
IgE levels were also significantly (p < 0.01)
reduced in H. polygyrus-challenged
OX40L-/- mice, as compared with H.
polygyrus-challenged OX40L+/+ mice (Figs. 2
B). Total serum IgG1 levels were significantly
(p < 0.01) increased in H.
polygyrus-challenged OX40L+/+ and
OX40L-/- mice as compared with
OX40L+/+ and OX40L-/-
mice given only a primary dose of H. polygyrus (Fig. 2
C), while elevations in Ag-specific serum IgG1 levels were
comparable between H. polygyrus-challenged
OX40L+/+ and H. polygyrus-challenged
OX40L-/- mice (Fig. 2
D). Similar
results were obtained in an independent experiment. These data
suggested that, in the absence of OX40/OX40L interactions, the humoral
response, particularly with respect to IL-4-dependent class-switching
to IgE, was impaired during both the primary and secondary immune
responses to H. polygyrus.
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The previous studies demonstrated impaired production of IL-4 and IgE during both the primary and memory immune responses to H. polygyrus in OX40L-deficient mice, suggesting a preferential role for OX40L in development of IL-4-producing T cells. To directly examine the development and trafficking of Ag-specific T cells in the absence of OX40L, OVA-specific DO11.10 T cell-recipient mice were immunized intracutaneously in the ear with OVA plus H. polygyrus. This approach, where OVA is the peptide Ag and H. polygyrus acts as the adjuvant for the OVA-specific DO11.10 T cells, provides a useful model system to examine the requirements for OX40/OX40L costimulation during the development of Ag-specific T cells.
CD4+ T cells were purified from BALB/c DO11.10
TCR transgenic mice, and labeled with CFSE before transfer into BALB/c
OX40L+/+ and BALB/c
OX40L-/- recipient mice. Two days later,
recipient OX40L+/+ and
OX40L-/- mice were inoculated in the ear with
OVA peptide alone, H. polygyrus alone, or a combination of
OVA peptide and H. polygyrus. At day 7 after inoculation
with OVA and H. polygyrus (day 9 following DO11.10 T cell
transfer), all mice were sacrificed, and the draining cervical lymph
node was removed for analysis. Previous studies have shown marked
increases in IL-4, but not IFN-
, mRNA in the cervical draining lymph
node following intracutaneous immunization with H. polygyrus
in the ear (data not shown). To assess IL-4 production by Ag-specific T
cells, the draining cervical lymph nodes were removed from individual
mice and single-cell suspensions were cultured for 3 days with or
without OVA peptide restimulation; an ELISPOT assay was then performed
using the cultured cells. The OVA peptide restimulation allowed
measurement of IL-4 produced in response to Ag-specific stimulation. As
shown in Fig. 3
A,
OX40L+/+ and OX40L-/-
mice given either OVA peptide alone or H. polygyrus alone
demonstrated minimal IL-4 production when cultured in either medium
alone or with OVA peptide. In contrast, OX40L+/+
and OX40L-/- mice inoculated with both OVA and
H. polygyrus demonstrated a marked increase in IL-4 protein
production when cultured with OVA peptide, although levels were
significantly (p < 0.01) reduced in the
OX40L-/- mice, as compared with the
OX40L+/+ mice. These findings suggested that
H. polygyrus was able to act as a potent adjuvant that, in
combination with OVA peptide, induced a strong Ag-specific primary
DO11.10 T cell IL-4 response in both OX40L+/+ and
OX40L-/- mice. However, OX40/OX40L interactions
were required for optimal production of Ag-specific-induced IL-4
following inoculation with OVA and H. polygyrus.
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To examine the ability of OX40L-deficient T cells to undergo cell cycle
progression, single-cell suspensions from the draining cervical lymph
nodes were pooled and analyzed for DO11.10 T cell CFSE fluorescence as
described in Materials and Methods. As seen in Fig. 4
A,
OX40L+/+ and OX40L-/-
mice that received only DO11.10 CFSE-labeled T cells demonstrated
minimal cell cycling, with >90% of the transferred cells remaining in
the parent generation. OX40L+/+ and
OX40L-/- mice inoculated with either H.
polygyrus alone (Fig. 4
B) or OVA peptide alone (data
not shown) also demonstrated minimal cell cycling. However,
OX40L+/+ and OX40L-/-
mice inoculated with both OVA peptide and H. polygyrus
demonstrated markedly increased, and comparable, cell cycling;
40%
(i.e., percentage of events shifted to the left) of the transferred
DO11.10 T cells underwent at least nine cell divisions (Fig. 4
C). Similar results were obtained in an independent
experiment as late as 12 days after inoculation, with markedly
increased, and comparable, cell cycle progression occurring in DO11.10
T-cell recipient OX40L+/+ and
OX40L-/- mice inoculated with both OVA peptide
and H. polygyrus (data not shown). These data suggested that
OX40/OX40L interactions were not required to sustain DO11.10 T cell
cycling, even at later time points after priming with OVA and H.
polygyrus; therefore, OX40/OX40L interactions were not required
for either Ag-specific T cell proliferation or expansion during the
primary response, although the ability of CD4+ T
cells to specifically produce IL-4 was impaired in the absence of
OX40/OX40L interactions.
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Although Ag-specific T cells were able to expand and proliferate
normally during the primary response in the absence of OX40/OX40L
interactions, it was possible that they were unable to provide optimal
cognate B cell help due to impaired migration. Several studies have
suggested that OX40/OX40L interactions are required to up-regulate
expression of the chemokine receptor CXCR5 (BLR-1) on
CD4+ T cells, which mediates their migration to
the T:B cell zone where they provide cognate help to B cells (7, 11, 17, 41). To examine the role of OX40/OX40L interactions in
the up-regulation of CXCR5 expression on Ag-specific Th2 cells, the
draining cervical lymph nodes were removed from
OX40L+/+ and OX40L-/-
mice at day 7 postinoculation, and CXCR5 expression on
KJ1-26+CFSE+ cells was
analyzed by FACS. As shown in Fig. 5
, CXCR5 expression was comparable in OX40L+/+ and
OX40L-/- mice inoculated with a combination of
OVA and H. polygyrus, and furthermore, CXCR5 was expressed
in a cell cycle-dependent manner. CXCR5 expression in
OX40L+/+ and OX40L-/-
mice that received only DO11.10 CFSE-labeled T cells was greatly
reduced and similar to that observed in OX40L+/+
and OX40L-/- mice inoculated with either OVA
peptide alone or H. polygyrus alone (Fig. 5
and data not
shown). These findings suggested that Ag-specific T cells were able to
up-regulate CXCR5 expression during an in vivo primary Th2 response in
the absence of OX40L interactions.
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| Discussion |
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A number of studies have suggested that OX40/OX40L interactions influence T cell differentiation downstream of B7-1/B7-2 costimulation. In particular, several studies have suggested that OX40L interactions may be required for CD4+ T cell up-regulation of CXCR5 and consequent migration from the T cell-rich region of the lymph node to the T:B cell zone, where T cell help leading to Ig class switching and plasma cell differentiation is initiated (7, 11, 17, 18, 41). Our studies did find pronounced decreases in serum IgE elevations and CD4+ T cell IL-4 production in H. polygyrus-primed OX40L-/- mice, although elevations in serum IgG1 and GC formation were sustained. This is in contrast to findings in OX40-/- mice immunized with the intestinal nematode parasite, N. brasiliensis, where both IL-4 production and serum IgE levels were comparable to those observed in N. brasiliensis-inoculated OX40+/+ mice (10). We also observed little difference in these parameters in N. brasiliensis-inoculated OX40L-/- mice (data not shown), indicating a difference in OX40L costimulatory molecule requirements for Th2 cell differentiation in the immune response to these two pathogens. Interestingly, the primary immune responses to these two gastrointestinal nematode parasites also differ in B7-1/B7-2 costimulatory molecule requirements: the primary immune response to N. brasiliensis is B7 independent (42), while the primary immune response to H. polygyrus is B7 dependent (22, 31). Although these parasites are both intestinal nematodes, the life cycles and Th2 immune responses to N. brasiliensis and H. polygyrus are actually quite different. N. brasiliensis is inoculated s.c. and migrates to the lung and finally to the gut, while H. polygyrus is orally inoculated and is a strictly enteric parasite (19, 43, 44). Thus, additional APC populations may mediate T cell activation during the N. brasiliensis immune response. Furthermore, N. brasiliensis triggers an acute host-protective primary Th2 response while H. polygyrus infection results in a chronic primary Th2 response and host-protective secondary response. Our findings with H. polygyrus are more consistent with those of Akiba et al. (4) who showed that administration of anti-OX40L Ab partially inhibited the development of the B7-dependent Th2 immune response to Leishmania major in BALB/c mice, resulting in suppression of IL-4 and total serum IgE.
To address the possibility that reduced serum IgE, and perhaps also T cell IL-4 production was a consequence of impaired migration to the T:B cell zone, DO11.10 adoptively transferred T cells were examined in the context of the primary Th2 response to H. polygyrus. Our findings showed that, in the absence of OX40L interactions, Ag-specific Th2 cells up-regulated CXCR5 and migrated to the B cell zone, indicating that this chemokine-mediated migration pathway is intact in vivo, and comparable, in H. polygyrus-inoculated OX40L-/- and OX40L+/+ mice during the primary response.
Other studies involving in vitro restimulation have indicated that OX40L interactions are required to sustain T effector cell survival and cell cycle progression (8, 15, 16, 45). We directly examined this possibility in vivo by comparing cell cycle progression of Ag-specific T cells inoculated with H. polygyrus and OVA and found no difference between OX40L-/- and OX40L+/+ mice as late as 12 days after primary immunization. There were also no differences in the total number of DO11.10 T cells in the draining cervical lymph nodes. These studies suggest that, in the context of the immune response to an infectious pathogen that triggers a Th2 response, sustained T cell survival and expansion is not impaired by an absence of OX40L interactions during the primary response. The regulation of IL-4 expression by OX40L interactions in the H. polygyrus system is thus not directly related to T cell cycling or expansion. Other studies have also suggested that Th2 cell development is not directly linked to cell division (46, 47). Our studies suggest that other factors are important in regulating the acquisition of competence to produce optimal IL-4, independent of cell cycle progression. One possibility is that optimal IL-4 receptor expression or signaling, as well as optimal IL-4 expression, may require OX40/OX40L interactions.
The role of OX40L interactions in the memory Th2 response during infectious disease has not previously been examined. However, Ab production was impaired during the secondary immune response to the T-dependent Ag trinitrophenyl-keyhole limpet hemocyanin when OX40/OX40L interactions were inhibited with blocking Abs administered during both the primary and secondary immune responses (48). The H. polygyrus memory Th2 immune response also showed impaired Ab production in OX40L-/- mice. However, only IgE was markedly reduced, while serum IgG1 levels and GC formation remained pronounced. The reduced levels of serum IgE were probably a result of the reduced IL-4 levels also detected in the memory response. Previous studies have shown that CD4+ T cell-dependent IgE, but not IgG1 elevations, are IL-4-dependent during the H. polygyrus immune response (39, 40). Worm expulsion and decreases in adult worm fecundity, which are dependent on Th2 cytokines and occur primarily during the memory response (19), were also impaired. This is in contrast to studies of the CD4+ T cell-dependent memory response to H. polygyrus in B7-1/B7-2-/- mice, where decreases in adult worm fecundity and increases in T cell IL-4 production were not reduced (27). These findings suggest a preferential role for OX40/OX40L costimulatory molecules during the Th2 memory response. However, further studies are required to specifically determine whether OX40 interactions are required for the initial development of memory cells, the maintenance of memory cells, or the activation of memory cells during challenge.
Taken together, these studies suggest an important role for OX40/OX40L interactions in specifically promoting IL-4 production, as well as associated IgE elevations and host protection, during the Th2 response to H. polygyrus. However, other aspects of the Th2 immune response remain intact in the absence of OX40/OX40L costimulation.
| Acknowledgments |
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| Footnotes |
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2 The opinions or assertions contained within are the private views of the authors and should not be construed as official or necessarily reflecting the views of the Uniformed Services University of the Health Sciences, Department of Defense, or the U. S. Department of Agriculture. ![]()
3 Address correspondence and reprint requests to Dr. William C. Gause, Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814. E-mail address: wgause{at}usuhs.mil ![]()
4 Abbreviations used in this paper: OX40L, OX40 ligand; GC, germinal center; MLN, mesenteric lymph node. ![]()
Received for publication August 6, 2002. Accepted for publication October 21, 2002.
| References |
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OX-40 with
CTLA-4. J. Immunol. 167:6804.
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J. T. Pesce, Z. Liu, H. Hamed, F. Alem, J. Whitmire, H. Lin, Q. Liu, J. F. Urban Jr., and W. C. Gause Neutrophils Clear Bacteria Associated with Parasitic Nematodes Augmenting the Development of an Effective Th2-Type Response J. Immunol., January 1, 2008; 180(1): 464 - 474. [Abstract] [Full Text] [PDF] |
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S. J. Jenkins, G. Perona-Wright, A. G. F. Worsley, N. Ishii, and A. S. MacDonald Dendritic Cell Expression of OX40 Ligand Acts as a Costimulatory, Not Polarizing, Signal for Optimal Th2 Priming and Memory Induction In Vivo J. Immunol., September 15, 2007; 179(6): 3515 - 3523. [Abstract] [Full Text] [PDF] |
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W. G. Shreffler, R. R. Castro, Z. Y. Kucuk, Z. Charlop-Powers, G. Grishina, S. Yoo, A. W. Burks, and H. A. Sampson The Major Glycoprotein Allergen from Arachis hypogaea, Ara h 1, Is a Ligand of Dendritic Cell-Specific ICAM-Grabbing Nonintegrin and Acts as a Th2 Adjuvant In Vitro J. Immunol., September 15, 2006; 177(6): 3677 - 3685. [Abstract] [Full Text] [PDF] |
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T. So, J. Song, K. Sugie, A. Altman, and M. Croft Signals from OX40 regulate nuclear factor of activated T cells c1 and T cell helper 2 lineage commitment PNAS, March 7, 2006; 103(10): 3740 - 3745. [Abstract] [Full Text] [PDF] |