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* Emory Vaccine Center and Department of Pathology, Atlanta, GA 30329; and
Division of Basic and Clinical Immunology, University of California, Irvine, CA 92697-4096
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Abstract |
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84% identity at the amino acid level and can compensate for each other for most functions. Despite these features, ERK1 and ERK2 do serve different functions, but there is very little information on the contribution of individual forms of ERK on innate and adaptive immune responses. In this study, we describe that ERK1–/– mice display a bias toward Th1 type immune response. Consistent with this observation, dendritic cells from ERK1–/– mice show enhanced IL-12p70 and reduced IL-10 secretion in response to TLR stimulation. Furthermore, serum from ERK1–/– mice had 100-fold higher total IgG2b and 10-fold higher total IgG2a and IgG1 Ab isotype titers, and enhanced levels of Ag-specific IgG2b Ab titers, compared with wild-type mice. Consistent with this enhanced Th1 bias, ERK1–/– mice showed enhanced susceptibility to myelin oligodendrocyte glycoprotein (MOG)35–55 peptide-induced experimental autoimmune encephalomyelitis (EAE) and developed EAE earlier, and with increased severity, compared with wild-type mice. Importantly, there was a profound skewing toward Th1 responses in ERK1–/– mice, with higher IFN-
production and lower IL-5 production in MOG35–55-primed T cells, as well as an augmentation in the MOG-specific IgG2a and IgG2b Th1 Ab isotypes. Finally, increased infiltrating cells and myelin destruction was observed in the spinal cord of ERK1–/– mice. Taken together, our data suggest that deficiency of ERK1 biases the immune response toward Th1 resulting in increased susceptibility to EAE. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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Among these the ERK pathway is activated in response to growth factors and oxidative stress. Phosphorylation of ERK is thought to play a pivotal role in a wide range of cellular activities, including survival, proliferation, and differentiation (1, 2, 3). A number of recent studies have demonstrated a major role for the components of the MAPK pathway in the regulation of innate and adaptive immune responses including Th1/Th2 differentiation (4, 5, 6, 7, 8). For example, naive T cells from JNK1–/– mice preferentially differentiate into a Th2 phenotype on activation, whereas CD4+ T cells from JNK2–/– mice show impaired IFN- production and diminished Th1 responses. Similarly, p38 MAPK drives IL-12 production from macrophages inducing a Th1 response. Previous work from our laboratory has also shown that modulation of ERK in dendritic cells (DCs)3 gives rise to distinct Th responses. Selective inhibition of ERK in DCs has been shown to increase IL-12 production associated with concomitant decrease in IL-10 eliciting a Th1 response (5, 6). The inhibitors of the MAPK cascade, PD098059 and U0126, used in previous studies are quite selective in their inhibition of MEK but, unfortunately, do not differentiate between the two ERK isoforms. The two isoforms of ERK, 42 and 44 kDa, share an 84% identity at the amino acid level and can compensate for each other for most functions. However, the individual roles for the two isoforms of ERK have yet to be deciphered. The focus of the present study was to investigate the specific contribution of the ERK1 (p44) isoform of MAPK toward modulation of immune responses with particular emphasis on Th differentiation.
To determine whether ERK1 played a role in modulating Th1/Th2 bias, we examined the nature of cytokine secretion by DCs in ERK1–/– mice (9, 10) and found increased secretion of IL-12p70, a cytokine known to induce Th1 responses. Therefore we hypothesized that ERK1-deficient mice may be prone to autoimmune disease and enhanced Th1 responses. Thus we examined the effect of ERK1 deletion on the development and progression of experimental autoimmune encephalomyelitis (EAE), a prototypic Th1-mediated autoimmune disease of the CNS that is used as an animal model for multiple sclerosis, a human demyelinating disease (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21). The Th1 nature of the disease is reinforced by the fact that all encephalitogenic lines and clones express the Th1 phenotype (14). Mice, exhibiting an enhanced Th1 bias due to deletion of a given gene, also show increased susceptibility to EAE (13, 15, 16, 18, 19, 20). We therefore reasoned that EAE would serve as a good model to evaluate whether ERK1–/– mice displayed an enhanced Th1 bias. Furthermore, we used the Ag myelin oligodendrocyte glycoprotein (MOG)35–55 peptide, which is a well-characterized target Ag of encephalitogenic T cells in the mouse model of EAE (10, 12). Our data indicate that deletion of ERK1 isoform alone is sufficient to induce a Th1 bias, which is reflected by an increased IFN- production by MOG-specific T cells, and an early onset and increased susceptibility to EAE.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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ERK1–/– mice of 129S1sv/IMJ background were a gift from Dr. G. Landreth (Case Western Reserve University, Cleveland, OH). Wild-type (WT) 129S1sv/IMJ mice were purchased from The Jackson Laboratory. Mice 6–20 wk of age were maintained under standard pathogen-free housing conditions at the Emory Vaccine Center Vivarium (Atlanta, GA).
Microbial stimuli and MOG peptide
Highly purified Escherichia coli LPS (strain 25922) was a gift from Dr. T. Van Dyke at Boston University (Boston, MA). Pam3Cys was obtained from G. Jung (Eberhard Karls Universität Tübingen, Tübingen, Germany) and reconstituted in endotoxin-free water. The MOG35–55 peptide used corresponds to amino acid residues 35–55 of the mouse sequence (MEVGWYRSPF SRVVHLYRNGK). The peptide was synthesized by Invitrogen Life Technologies and the purity was >97%.
DC purification and stimulation
CD11c+CD11b+ and CD11c+CD11b– DC subsets were purified from spleen cell suspensions from mice treated for 9 days with Flt-3 ligand as described before (5). Briefly, spleens from Flt-3 ligand-treated mice were dissected, cut into small fragments, and digested with collagenase and the resulting cells frozen until used. For DC subset preparation, thawed spleen cells were stained via allophycocyanin-conjugated CD11c (BD Pharmingen) and PE-conjugated CD11b (BD Pharmingen) and sorted into the CD11c+CD11b+ and CD11c+CD11b– DC subsets using a high speed modular flow cytometer (MoFlo; DakoCytomation). Total or sorted DCs from WT or ERK1–/– mice were cultured with E. coli LPS (1 µg/ml) and Pam3Cys (100 µg/ml) for 24 h in the presence of a fibroblast cell line expressing CD40L (5). Supernatant collected was assayed for IL-10 and IL-12p70 by ELISA kits (BD Pharmingen).
DC-naive CD4 T cell coculture
Magnetic bead purified CD11c+ DCs from ERK1–/– and WT mice were loaded with OVA peptide or LPS (1 µg/ml) and were cultured together with purified (flow sorted) naive CD4+CD62L+ T cells from OT-2 mice (transgenic for OVA Ag) for 5 days. At 5 days later, the T cells were restimulated with plate-bound anti-CD3 (10 µg/ml) and anti-CD28 (2 µg/ml) for an additional 3 days. Supernatants were collected before and after CD3 stimulation and assayed for IFN-, IL-2, IL-4, IL-5, IL-10, and TNF-
by ELISA kits (BD Biosciences). IL-17 was assayed with a kit from R&D Systems.
Dinitrophenol-conjugated keyhole limpet hemocyanin (DNP-KLH), DNP-Ficoll, and serum Ab isotyping
ERK1–/– and WT mice were immunized with 10 µg of DNP-KLH in alum. Blood was collected by retro-orbital puncture from ERK1–/– and WT mice on days 7 and 14 and allowed to clot overnight. Serum was separated by centrifugation. Dilutions of serum ranging from 1/100 to 1/100,000,000 were incubated on DNP-OVA-coated plates. Specific Ab detection was done using isotype specific HRP-conjugated anti-mouse Abs (Caltag Laboratories).
MOG Ab isotyping
ERK1–/– and WT mice were immunized with 200 µg of MOG peptide emulsified in CFA containing 5 µg/ml Mycobacterium tuberculosis. Serum was collected on days 14 and 28 after immunization. MOG-specific Ab titer was determined by ELISA using MOG-coated plates.
B cell proliferation
Spleen cells (5 x 105 cells/well) were stimulated in vitro with CD40, LPS, or IgM for 5 days. A total of 0.5 µCi of [3H]thymidine was added to each well, and plates harvested after an additional 16 h of culture. Supernatants were assayed for isotype-specific Abs using the isotyping kit (BD Biosciences).
T cell type and quantity
The phenotype and percentage of CD4+ and CD8+ T cells were determined by flow cytometry in nonimmunized ERK1–/– and WT mice by staining the total spleen cells with specific Abs (BD Biosciences). A total of 5 x 105 spleen cells were stimulated with CD3 (10 µg/ml) and CD28 (2 µg/ml) or Con A for 48 h, and proliferation determined by uptake of [3H]thymidine. Supernatants collected were assayed for IL-4, IL-5, and IFN- by ELISA.
MOG-specific T cell proliferation
Mice were immunized with MOG peptide (200 µg) and emulsified in CFA, containing 5 µg/ml M. tuberculosis, on days 0 and 7 s.c. in the hind flank. Popliteal and inguinal lymph nodes were harvested at days 7 and 14 or day 7 after boosting with MOG peptide. Lymphocytes (5 x 105cells/well) in 200 µl were incubated in 96-well flat-bottom plates with the indicated amounts of Ag in DMEM supplemented with 10% FCS (Mediatech) for 72 h. The 0.5 µCi of [3H]thymidine was added to each well, and plates harvested after an additional 16 h of culture. Cytokine estimation in the supernatant was by ELISA (BD Pharmingen).
EAE induction
EAE was induced by immunization of ERK1–/– and WT mice with 200 µg of MOG35–55 emulsified in CFA, containing 5 µg/ml M. tuberculosis, on days 0 and 7 s.c. in the hind flank. Mice also received 250–500 ng of pertussis toxin i.p. on days 0 and 2. Disease severity was monitored according to the following scale: 0, no disease; 1, flaccid tail; 2, hind limb weakness; 3, hind limb paralysis; 4, forelimb weakness; and 5, moribund.
Histology
WT and ERK1–/– mice were immunized with 200 µg of MOG35–55, as discussed earlier. Spinal cords were removed 22–24 days later at the peak of the disease, and fixed in 10% buffered Formalin (Sigma-Aldrich). Paraffin-embedded longitudinal sections (6-µm thick) were stained with either H&E or Luxol fast blue to assess cellular infiltration and demyelination, respectively.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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DCs are the most efficient APCs of the body that can modulate the nature and magnitude of T cell responses. Therefore, we first wanted to determine the effect of ERK1 deletion on the DC function. We did not find significant differences in either the numbers or phenotype of DCs from ERK1–/– and WT mice by flow cytometry (data not shown) but significant functional differences were observed. DCs in mouse can be further divided into CD11c+CD11b– and CD11c+CD11b+ subsets, which are capable of differentially priming Th responses (22, 23). CD11c+CD11b– DCs secrete copious amounts of IL-12p70 on stimulation with TLR ligands and thus induce Th1 responses, whereas CD11c+CD11b+ DCs induce a Th2 bias through secretion of IL-10 (22, 23). To investigate the effect of ERK1–/– deletion on the DC subsets, Flt-3-injected spleen cells from ERK1–/– and WT mice were sorted into CD11c+CD11b– and CD11c+CD11b+ populations. Sorted cells were stimulated with LPS and Pam3Cys, which are TLR ligands that induce Th1 and Th2 response, respectively, as previously described. IL-12p70 and IL-10 levels secreted were determined by ELISA. As shown in Fig. 1, IL-12p70 levels were significantly elevated in ERK1–/– mice in both LPS- and Pam3Cys-stimulated DC subsets. A 6- to 10-fold increase in IL-12 was observed in the CD11c+CD11b– DC subset stimulated with LPS and Pam3Cys. We have earlier reported an increase in IL-12p70 after ERK blockade, but what was remarkable was that this enhancement of IL-12p70 was evident even in the CD11c+CD11b+ DC subset, which is known to be more of a Th2 inducing subset of DCs (22, 23). A concomitant decrease in IL-10 was also observed in both groups compared with WT mice DCs. ERK1–/– thus seems to act as a negative regulator of IL-12 production through secretion of IL-10.
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DCs are capable of modulating the T cell response toward Th1 or Th2 through the cytokines secreted by them. To determine whether indeed the ERK1–/– DCs induce enhanced Th1 differentiation, CD11c+ splenic DCs were isolated from ERK1–/– and WT mice injected with Flt-3 ligand, pulsed with class II-restricted OVA peptide, or OVA peptide plus LPS, and cultured together with purified (FACS sorted) naive CD4+CD62L+ T cells from OT-2 mice (TCR transgenic mice, which express a TCR that is specific for OVA (5)). Five days later, supernatants were assayed for IFN-, IL-2, IL-4, IL-5, IL-17, and TNF- by ELISA. In addition, the T cells were restimulated with plate-bound anti-CD3 and anti-CD28 for an additional 3 days. Supernatants were collected before and after CD3 stimulation and assayed for IFN-, IL-2, IL-4, IL-5, IL-17, and TNF- by ELISA. As indicated in Fig. 2A, 5 days of stimulation with OVA-pulsed WT DCs induced significant levels of IL-2, TNF-, and IL-17, but did not result in detectable production of IFN-, IL-4, or IL-5. In contrast, stimulation with ERK1–/– DCs did result in significant induction of IFN-, but no IL-4, IL-5 nor any enhancement of IL-2, TNF-, or IL-17. Importantly, the induction of similar levels of IL-2 in T cells by WT DCs, and ERK1–/– DCs, suggests that both types of DCs induce equivalent activation of T cells. After restimulation of the T cells with anti-CD3 and anti-CD28, there is a noticeable enhancement in the induction of IL-2, IFN-, TNF-, and IL-17 (Fig. 2B), although not IL-4 or IL-5 (data not shown). In particular, ERK1–/– DCs pulsed with OVA, either in the presence of absence of LPS, results in a significant enhancement (p < 0.05) of IFN- relative to wild-type DCs (Fig. 2B). There was no significant difference in the levels of IL-17 and TNF- secreted between the WT and ERK1–/–. IL-2 levels were similar and IL-4 and IL-5 were undetectable (data not shown). ERK1–/– DCs thus prime the naive T cell responses toward a Th1 type immune response.
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We then determined the influence of ERK1–/– on B cell development and function. Again no significant differences were observed in the percentages, or absolute number of B cells in the spleen, bone marrow, and peritoneal cavity as analyzed by flow cytometry (data not shown). Proliferation of B cells in response to IgM cross-linking, CD40 or LPS was also similar in ERK1–/– and WT mice (Fig. 3A). However, when we determined the Ab in the culture supernatant after stimulation with CD40, we observed significant differences in the isotype of Ab secreted between ERK1–/– and WT mice B cells (Fig. 3B). The level of IgG2b was 3-fold higher in ERK1–/– B cells compared with WT (p < 0.005) (Fig. 3B). IgG3 levels were found to be different but the difference was not statistically significant (p > 0.05). The molecular mechanism resulting in this preferential enhancement of the IgG2b isotype is at present unclear.
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We next tested the ability of ERK1–/– to respond to T cell-independent and T cell-dependent Ags (24). For this purpose ERK1–/– and WT mice were immunized with DNP-Ficoll and DNP-KLH in alum, and serum Ab titer was determined at various time points. As shown in Fig. 3D, a 10-fold increase in DNP IgG2b-specific Ab titer was observed in ERK1–/– mice immunized with DNP-KLH over Ab titers in WT mice (p < 0.05). Immunization with T cell-independent Ag DNP-Ficoll did not result in a significant difference in titers of IgM and IgG3 between ERK1–/– mice and controls (data not shown).
Taken together, these data suggest that although the ERK1–/– deficiency is dispensable for B cell development, it affects the nature of T cell-dependent Ab response, resulting particularly in the enhancement of IgG2b secretion (25, 26). Why the deficiency of ERK1–/– results in significant enhancement of IgG2b Ab secretion in the supernatants (Fig. 3B), at the basal level in nonimmunized mice (Fig. 3C), and in the DNP-KLH group (Fig. 3D) is not clear to us at this point. TGF-
is considered one of the factors responsible for isotype switching to IgG2b; however, we did not observe significant differences in the level of TGF- between the serum of ERK1–/– and WT mice (data not shown).
T cells from ERK1–/– mice show reduced proliferation
Next, we determined the effect of ERK1 deletion on peripheral T cells. No significant difference was observed in the number and percentage of CD4+ and CD8+ T cells in spleen and lymph node between ERK1–/– and control mice (Fig. 4A). However, ERK1–/– T cells exhibited significantly lower proliferation when stimulated through TCR or mitogenic stimuli such as Con A (Fig. 4B). This phenomenon was similar to that observed in an earlier study with ERK1–/– mice in which research showed reduced T cell proliferation of the thymic T cells (26). Interestingly, IFN-, IL-4, and IL-5 levels were not significantly different between ERK1–/– and WT T cells (Fig. 4C).
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Next, we examined the effect of ERK1–/– gene disruption on the development of EAE, which is considered a prototypic Th1-mediated disease (9, 14, 18). EAE was induced in ERK1–/– and WT mice following active immunization with MOG35–55. As shown in Fig. 5, both the onset and severity of disease was enhanced in ERK1–/– mice compared with their WT littermates. The development of severe paralytic symptoms was apparent in ERK1–/– mice by day 20 with the maximal disease severity score of 3.6 being observed by day 21–22. In the WT mice, the mean day of onset of severe paralysis was on day 23, and a maximal severity score never crossed 2.5. Although all mice in both groups succumbed to the disease, there was no mortality associated with the acute attack. It is possible that ERK2 compensated to a certain extent for ERK1 preventing the development of fatal disease. Unfortunately, ERK2 deletion is fatal to mice, thus we were unable to use ERK2–/– mice to determine its effects. Nevertheless these results clearly suggest that the ERK1 deletion alone results in the exacerbation of progression and severity of EAE.
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To further confirm that the clinical severity observed in ERK1–/– mice correlated with increased pathological inflammation and demyelination in the CNS, longitudinal spinal cord sections from ERK1–/– mice and their WT littermates were analyzed for myelin loss (demyelination) and infiltration of mononuclear cells (inflammation) after staining with Luxol fast blue and H&E (11, 27). Areas of demyelination and inflammation were more extensively widespread in ERK1–/– compared with WT mice (Fig. 6, A and B). Although the WT mice showed 42% demyelination (Fig. 6C), the ERK1–/– showed 73% (1.5-fold increase). Similarly the inflammation was also increased from 33% to 69.2% in ERK1–/– mice. These observations showed a close association between the development of paralysis and the pathological severity of the disease.
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To further understand the mechanistic basis of exacerbated EAE observed in ERK1–/– mice, we examined whether MOG-specific T cells generated in mice deficient in ERK1 respond to MOG peptide in a manner similar to T cells generated in WT. First, a kinetic study was done in which WT or ERK1–/– mice were immunized s.c. with MOG peptide, and lymph node cells were collected at 7 or 14 days later. In addition, a separate group of mice was immunized with MOG peptide and given a secondary boost at day 28, and draining lymph node cells were harvested 7 days after the boost. The lymph node cells were cultured in vitro with MOG peptide for 72 h, then [3H]thymidine uptake assayed, and the culture supernatants assayed for cytokines by ELISA. The results indicated that ERK1–/– T cells proliferated to a moderately lower extent than their WT counterparts (Fig. 7A), consistent with what was observed after mitogenic stimulation with Con A (Fig. 4B). However, increased secretion of IFN- was observed in the ERK-deficient MOG-primed T cells at day 14, and after boosting compared with WT cells. IFN- secretion increased with time and this difference became significant (p < 0.05) after boosting. There was an increase of nearly 4-fold in the ERK1–/– mice compared with WT mice at higher concentrations. Similar to Nekrasova et al. (27), we did not observe a difference at earlier time points such as day 7. It is possible that an amplification of the response in the form of boosting was required for the difference to be visible. We also determined the level of IL-17 and TNF-. We were unable to detect IL-17 or IL-4 reproducibly, and IL-10 and TNF- levels were similar, although 7 days after primary immunization there was slightly higher levels of IL-10 in ERK1–/– mice (data not shown). These results suggest that ERK1–/– mice developed augmented Th1 response to neuronal Ag MOG, contributing to the increased susceptibility of these mice to EAE. T cells are thought to play a key role in initiating and perpetuating the disruptive inflammatory process associated with EAE, which is regarded as a Th1 MHC class II-restricted CD4+ T cell-mediated disease of the CNS.
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Multiple studies have documented the importance of anti-MOG Abs in the pathogenesis of EAE. Increased levels of Abs directed to proteolipid protein and MOG correlate with relapse and demyelination (28, 29, 30, 31, 32). Injection of anti-MOG mAb at the onset of acute EAE exacerbated clinical neurological disease and induced demyelination in the CNS (31). Therefore we investigated the effect of ERK1 deletion on the MOG-specific Ab response. The results were similar to what we observed with DNP-KLH immunization. As shown in Fig. 8, a 4-fold increase in MOG-specific IgG2a and IgG2b Ab titers was observed at day 14, which increased to 16-fold at day 28 in ERK1–/– mice immunized with MOG over the increase in WT mice (p < 0.05). Total MOG IgG Ab titer was also significantly higher in the ERK1–/– mice compared with WT mice.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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Interestingly, one difference between our data and those of Nekrasova et al. (27) concerns the role of ERK1 in the effector functions of peripheral T cells. Although our data suggest that immunization of ERK1–/– mice with MOG35–55 in CFA results in a significant enhancement of IFN-, and diminution of IL-5 (Fig. 7), this study by Nekrasova et al. (27) suggests that there is no difference in the Th1/Th2 balance. The reason for this discrepancy is not apparent, but may reside in the effects caused by environmental differences in the housing conditions of the two mouse colonies.
With respect to the relative roles played by IFN--secreting prototypic "Th1" cells vs IL-17-secreting "Th17" cells in the pathogenesis of EAE, there is presently some debate. Numerous previous studies have addressed the role of so-called "Th1" vs "Th2" in EAE and multiple sclerosis, with IL-12 and Th1 responses shown to play critical roles in mediating the pathogenesis of disease (e.g., 16, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47). However, some recent studies have demonstrated that IL-23, rather than IL-12, is the critical cytokine for the establishment and persistence of inflammatory lesions in EAE (48, 49, 50, 51). IL-17 is a crucial effector cytokine that is associated with many inflammatory diseases, including EAE, and is specifically induced by IL-23 (52, 53, 54, 55). Given that current thinking favors a dominant role for IL-23-induced "Th17" cells in the pathogenesis of EAE, we investigated the possibility that DCs from ERK1–/– mice produce greater levels of IL-23, which might result in enhanced IL-17. However, we failed to detect any significant difference in the secretion of IL-23 protein DCs from WT and ERK1–/– mice, stimulated in vitro, with TLR4 or TLR2 ligands (data not shown). Furthermore, as observed in Fig. 2, we could not detect any enhanced secretion of IL-17 by OT-2 cells stimulated in vitro by ERK1–/– DCs vs WT DCs. Thus, our data suggests that although ERK1 plays a critical role in regulating the Th1/Th2 balance by modulating IL-12 and IL-10 in DCs, it does not exert any significant effect on IL-23 production by DCs. These data might explain the disconnect between the significant effects of ERK1 deficiency on the induction of IL-12 and IL-10 in DCs (Fig. 1), and the consequences of this result for T cell responses (Figs. 2 and 7) and the more modest effects on EAE pathogenesis (Fig. 5).
Finally, regarding the role of MAPKs in EAE, there is little information (56, 57, 58). The recent study by Nekrasova et al. (27), consistent with our study, suggests that ERK1-deficient mice show somewhat enhanced susceptibility to EAE. Our present studies, however, do not allow us to clearly delineate the functions of the two isoforms of ERK. ERK2 might be acting in a synergistic fashion along with ERK1 in the regulation of the Th1 immune response because both become activated through a similar signaling pathway. To what extent it compensates or differs from ERK1 is to be determined in future studies. Nevertheless our data clearly show the role ERK1 in modulating the balance of IL-12 and IL-10 in DCs, and the consequences of this role for the Th1/Th2 balance and the regulation of autoimmune disorders.
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Acknowledgments |
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Disclosures |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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Footnotes |
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1 This work was supported by National Institutes of Health Grants DK0 57665, AI48638, AI056499, U19 AI05726601, and Regional Centers of Excellence Grants U54 AI057157 and AI056947. 
2 Address correspondence and reprint requests to Dr. Bali Pulendran, Emory Vaccine Center, 954 Gatewood Road, Atlanta, GA 30329. E-mail address: bpulend{at}rmy.emory.edu
3 Abbreviations used in the paper: DC, dendritic cell; EAE, experimental autoimmune encephalomyelitis; WT, wild type; MOG, myelin oligodendrocyte glycoprotein; DNP-KLH, dinitrophenol-conjugated keyhole limpet hemocyanin.
Received for publication November 18, 2005. Accepted for publication February 27, 2006.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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expression of encephalitogenic T cells. Eur. J. Immunol. 25: 1951-1959. [Medline]+ and CD8– subclasses of dendritic cells direct the development of distinct T helper cells in vivo. J. Exp. Med. 189: 587-592. agonists inhibit experimental allergic encephalomyelitis by blocking IL-12 production, IL-12 signaling and Th1 differentiation. Genes Immun. 3: 59-70. [Medline] and Gadd45 are critical for regulating autoimmunity. J. Exp. Med. 202: 1341-1347. This article has been cited by other articles:
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 C. F. Brereton, C. E. Sutton, S. J. Lalor, E. C. Lavelle, and K. H. G. Mills Inhibition of ERK MAPK Suppresses IL-23- and IL-1-Driven IL-17 Production and Attenuates Autoimmune Disease J. Immunol., August 1, 2009; 183(3): 1715 - 1723. [Abstract] [Full Text] [PDF]
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W. N. D'Souza, C.-F. Chang, A. M. Fischer, M. Li, and S. M. Hedrick The Erk2 MAPK Regulates CD8 T Cell Proliferation and Survival J. Immunol., December 1, 2008; 181(11): 7617 - 7629. [Abstract] [Full Text] [PDF]
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A. Reijerkerk, G. Kooij, S. M. A. van der Pol, T. Leyen, B. van het Hof, P.-O. Couraud, D. Vivien, C. D. Dijkstra, and H. E. de Vries Tissue-Type Plasminogen Activator Is a Regulator of Monocyte Diapedesis through the Brain Endothelial Barrier J. Immunol., September 1, 2008; 181(5): 3567 - 3574. [Abstract] [Full Text] [PDF]
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P. R. Kroening, T. W. Barnes, L. Pease, A. Limper, H. Kita, and R. Vassallo Cigarette Smoke-Induced Oxidative Stress Suppresses Generation of Dendritic Cell IL-12 and IL-23 through ERK-Dependent Pathways J. Immunol., July 15, 2008; 181(2): 1536 - 1547. [Abstract] [Full Text] [PDF]
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B. Liang, C. Workman, J. Lee, C. Chew, B. M. Dale, L. Colonna, M. Flores, N. Li, E. Schweighoffer, S. Greenberg, et al. Regulatory T Cells Inhibit Dendritic Cells by Lymphocyte Activation Gene-3 Engagement of MHC Class II J. Immunol., May 1, 2008; 180(9): 5916 - 5926. [Abstract] [Full Text] [PDF]
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 A. C. Schnitzler, J. M. Burke, and L. M. Wetzler Induction of Cell Signaling Events by the Cholera Toxin B Subunit in Antigen-Presenting Cells Infect. Immun., June 1, 2007; 75(6): 3150 - 3159. [Abstract] [Full Text] [PDF]
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 S. M. Shin, Y. H. Kim, B. K. Choi, P. M. Kwon, H.-W. Lee, and B. S. Kwon 4-1BB triggers IL-13 production from T cells to limit the polarized, Th1-mediated inflammation J. Leukoc. Biol., June 1, 2007; 81(6): 1455 - 1465. [Abstract] [Full Text] [PDF]
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) and WT mice (
) are indicated. At day 28, significant difference (**, p < 0.005; *, p < 0.05) in Ab titers in ERK1–/– mice immunized with MOG over the increase in WT mice were present. Data represent mean of five to seven individual mice. Total IgG is represented as T-IgG.