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*
Department of Neurology, University of Pennsylvania, Philadelphia, PA 19104;
The Wistar Institute of Anatomy and Biology, Philadelphia, PA 19104; and
Department of Pathology and Laboratory Medicine, Division of Neuropathology, University of Pennsylvania, Philadelphia, PA 19104
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and TNF and promoting
cell-mediated immunity). These cells preferentially use the Vß8 TCR
in Lewis rats and H2u mice (1). The superantigen (SAG)
staphyloccocal enterotoxin (SE) B (SEB) is a potent T cell activator
stimulating a large proportion of Vß8 T cells and has been postulated
to trigger autoimmunity by stimulating autoreactive T cells (2). SEB
induces relapsing paralysis in PL/J (3, 4) and (PL/J x
SJL/J)F1 mice (3) that have recovered from the first acute
EAE attack. This property of SEB has been attributed to its ability to
activate Vß8 T cells and has given rise to analogies with the
frequent precipitation of MS relapses by infectious events (5). (PL/J x SJL/J)F1 mice, when immunized with whole MBP, also have a high incidence of spontaneous relapses (6). These typically occur between days 23 and 32 after immunization, (7–10 days after recovery from the initial EAE episode) (6) (C.S.C. and A.R., unpublished observations). Thus, spontaneous relapses in (PL/J x SJL/J)F1 mice are distinguishable from the SEB-induced relapses (3), which occur within 1 to 3 days after SEB administration. Interestingly, staphyloccocal enterotoxin A (SEA), a SAG that does not activate Vß8 T cells, can induce similar relapses (3, 4), suggesting that the mechanisms of SAG-induced relapses are not strictly Vß8-dependent.
Staphylococcal SAG bind the MHC class II molecule of the APC outside of
the binding groove and, subsequently, as a binary complex bind to the
Vß region of the TCR (2). This process induces cytokines both in the
T cell and in the APC (7). SAG binding to the MHC class II molecule on
the APC induces signaling (8), cytokine gene transcription (9) and
secretion (10), and nitrite production (11). Staphylococcal SAG
preferentially induce Th1 cytokines (12, 13, 14). SAG binding is enhanced
by IFN-, suggesting that cooperation of T cells and MHC class
II-positive APC is needed for optimal SAG-induced responses (15).
An important cytokine produced by activated APC is IL-12. This
heterodimeric cytokine, consisting of the p35 and p40 subunits, induces
IFN- production by T and NK cells (16, 17) and is pivotal in
Th1-type immune response development (18, 19). IL-12 is involved in the
induction of the acute phase of EAE, as demonstrated by the ability of
a neutralizing anti-IL-12 Ab to prevent both actively induced EAE
(C.S.C. and A.R., unpublished observations) and adoptively transferred
EAE (20), and by the increased encephalitogenicity of
neuroantigen-reactive T cells stimulated with IL-12 (20, 21). In
addition, exogenous IL-12 induces relapses in an otherwise typically
monophasic form of EAE in Lewis rats (22). Thus, it is of interest to
determine whether endogenous IL-12 plays a role in EAE relapse,
characterized in our mouse model by both spontaneous and SAG-induced
relapses. Moreover, because SAG, including staphylococcal SAG, can
induce IL-12 production by APC in vitro (23, 24, 25), it is interesting to
determine this ability in vivo (particularly because SAG may have
different effects in vitro and in vivo) and to investigate whether this
induction plays a role in the relapsing paralysis of EAE.
Staphylococcus aureus is a potent inducer of IL-12 (26). Moreover, recent evidence indicates that the ability of several bacteria-derived substances, including staphylococcal products, to overcome resistance to EAE is mediated through IL-12 induction (27). S. aureus SAG also synergize with IL-12 (28). In this study, we investigated the role of IL-12 in relapsing EAE in (PL/J x SJL/J)F1 mice. We analyzed the p40 subunit (the inducible component of IL-12) and the p70 heterodimer (generally p40 correlates well with the biologically active p70) (16, 26). We showed that SE induce IL-12 in splenocytes in vitro and in vivo. We also demonstrated that neutralizing anti-IL-12 Abs prevent SE-induced relapses. Further, spontaneous relapses are prevented by anti-IL-12 Abs. IL-12 administration mimics SE in inducing spontaneous relapses and enhancing the severity and frequency of spontaneous relapses.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Male or female (PL/J x SJL/J)F1 mice were purchased from The Jackson Laboratory (Bar Harbor, ME). The animals were sex and age matched within each experiment. Previous studies in our laboratory and others’ (6) showed no differences between male and female mice of this strain in terms of EAE susceptibility and frequency of relapses.
Reagents and Ag
MBP was prepared from guinea pig spinal cord (Rockland,
Gilbertsville, PA) (29), lyophilized, and stored at -20°C until use.
SEA and SEB were purchased from Sigma (St. Louis, MO). Recombinant
murine IL-12 was a generous gift of Dr. Maurice Gately (Hoffmann-La
Roche, Nutley, NJ). Murine rIFN- was purchased from PharMingen (San
Diego, CA). Monoclonal anti-mouse IL-12 Abs C17.8 (rat IgG2a),
C15.1 (rat IgG1), and C15.6 (rat IgG1) were previously described (30).
IFA and Mycobacterium tuberculosis H37 Ra were purchased
from Difco (Detroit, MI). A 1:1 mixture resulted in CFA with 5 mg/ml
M. tuberculosis. Bordetella pertussis toxin
was obtained from List Biological Laboratories, (Campbell, CA). Rat Ig
was purchased from Sigma.
Induction of EAE
Mice, 10 wk old, under anesthesia were immunized on day 0 in the hind footpads and at three sites on each side of the back with a total of 300 µl of 1:1 (v/v) mixture of MBP (2.67 mg/ml in PBS) and CFA containing 5 mg/ml M. tuberculosis H37Ra. On days 0 and 2, 400 ng B. pertussis toxin were given i.p.
Clinical scoring
Mice were weighed daily and observed for clinical signs of disease for more than 40 days postimmunization. A clinical scoring system with a scale of 0 to 5, with 0.5 points for intermediate signs, was used as follows: 0, normal; 1, flaccid tail, abnormal gait; 2, hind leg weakness or severe ataxia; 3, minimal hind leg movement; 4, hind leg and forelimb paralysis; 5, moribund due to EAE, with impaired breathing and little or no spontaneous movement. Mild disease had to be observed for 2 days or more and be confirmed by two independent, blinded observers to be considered positive. The score increment was defined as the maximal increase, during a relapse, in the clinical score from the prerelapse score.
Induction of relapses and treatment after recovery from first EAE episode
Mice that had recovered from the acute disease (day 18 or 19 postimmunization) were injected i.p. with a single dose of 50 µg SEB or 25 µg SEA, both in PBS, or with 100 ng murine rIL-12 in PBS with 1% mouse serum. On the day of the above treatment and on the subsequent 2 days, some of the mice received 1 mg/day of either anti-IL-12 mAb C.17.8 or control rat IgG.
The mice were observed daily for development of relapsing disease. Relapses occurred 1 to 3 days after SE administration. Relapses with onset occurring 3 to 5 days following the treatment were attributed to the intrinsically relapsing nature of EAE in these mice and coincided with relapses in mice that had been immunized on the same day but received no treatment following recovery from the initial episode. However, we cannot rule out the possibility that relapses occurring during this period may also be related to the effect of the SAG in the SAG-treated animals.
Measurement of cytokines in serum and splenocyte supernatants
Mice were given the above doses of SEA or SEB in 100 µl PBS via i.p. injection. Control mice were given 100 µl PBS. Blood was harvested in heparinized tubes by retro-orbital bleeding at 6 h and 24 h, centrifuged, sera removed and diluted at concentrations of 1:10 for IL-12 p40 and IL-12 p70 measurement.
For in vitro cytokine studies, spleens of mice were homogenized to
single-cell suspensions by passage through a stainless steel mesh. RBC
were removed by hypotonic lysis in NH4Cl-containing buffer.
IL-12 p40 and IL-12 p70 assays were performed in total spleen cell
populations stimulated either with medium alone (RPMI 1640 with
5% FBS with antibiotics) or with the same medium containing SEA or
SEB, 2.5 µg/ml. IL-12 p40 was assayed in supernatants of spleen cells
of mice using recombinant murine IL-12 as standard, following a
two-site RIA as described (30). Briefly, samples were placed in 96-well
plates (Dynatech Laboratories, Chantilly, VA) coated with 5
µg/ml of C17.15 anti-mouse IL-12 mAb and incubated overnight at
4°C. Plates were washed, and 125I-labeled C15.6 was
added. Bound radioactivity after 6 h incubation at 4°C was
measured in a microplate scintillation counter (Topcount, Packard,
Meriden, CT). Samples were assayed in triplicate. IL-12 p70 was
measured in a biologic assay based on IL-12-dependent induction of
IFN- in murine splenocytes, as described (30). The sensitivity of
RIA detecting IL-12 p40 is 30 pg/ml, and the sensitivity of biologic
assay detecting IL-12 p70 is 3 pg/ml. IFN- was assayed in
supernatants of spleen cells of mice using recombinant murine IFN-
as standard according to a two-site RIA as described (30).
Histopathology
Animals under anesthesia were perfused through the heart with 10% phosphate-buffered formalin. Brains and spinal cords were fixed in formalin, dehydrated through graded alcohols, and embedded in paraffin. Five-micrometer sections of brain and spinal cord were cut serially and mounted on poly-L-lysine-coated glass slides. Five spinal cord sections and five brain sections obtained at similar levels from each mouse were stained. For assessment of inflammation, sections were stained with hematoxylin-eosin. For evaluation of demyelination, sections were stained with Luxol fast blue and counterstained with cresyl violet. The extent of inflammation and demyelination was scored on a scale of 0 to 3, based on the fraction of tissue section quadrants containing lesions out of 20, as previously described (31): 0, absent; 1, mild (1–7 quadrants); 2, moderate (8–13 quadrants); 3, severe (14–20 quadrants); and 0.5 points for intermediate degrees of histologic severity.
Statistical analysis
The two-tailed Student’s t test was used to assess
the significance of differences in clinical scores between groups.
Incidences of EAE relapses were compared using the 
2
test.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To determine whether SE induce IL-12 production by splenocytes
(most likely APCs) in vitro, we harvested spleen cells from naive
(PL/J x SJL/J)F1 mice and measured the production of
IL-12 p40 in cell culture supernatants 6 and 24 h after
stimulation with SE in vitro, with or without IFN- (100 U/ml)
pretreatment. Both SEA and SEB induced IL-12 p40 in (PL/J x
SJL/J)F1 splenocytes without IFN- pretreatment (data not
shown), confirming results of studies using murine peritoneal
macrophages (24). This induction was consistently higher when
splenocytes were pretreated with IFN- (100 U/ml) for 16 to 18 h
before stimulation. Figure 1
A
shows the results of a typical experiment, in which induction of IL-12
p40 by SEA and SEB is demonstrated in murine splenocytes after
pretreatment with IFN-. Without IFN- pretreatment, the
corresponding IL-12 p70 measured by biologic assay was either just
above the detection limit (
2 pg/ml) or absent. In contrast, IFN-
pretreatment resulted in consistently detectable amounts of IL-12 p70
after SE stimulation. Figure 1B shows an example of IL-12
p70 induction by SEA and SEB after IFN- pretreatment measured in the
same supernatants as in Figure 1A. Stimulation with IFN-
alone did not induce significant levels of IL-12 p40 or IL-12 p70 (data
not shown). The slight increase in IL-12 p40 after 24 h in culture
(as seen in Fig. 1A) is also noted with splenocytes that
were allowed to adhere for 24 h without IFN- or other stimuli;
this increase is never associated with detectable IL-12 p70.
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, we measured IFN- in supernatants of SE-stimulated spleen
cells. Large amounts of IFN-, up to 40 ng/ml, were detected after
both SEA and SEB stimulation, the peak of IFN- corresponding to that
of IL-12 p40 and IL-12 p70 at 24 h after stimulation (data not
shown). SE induce IL-12 in vivo
The in vitro and in vivo effects of SAG can be different,
particularly with respect to T cell activation vs anergy. In contrast,
SE are known to induce cytokines, including TNF, both in vivo and in
vitro (32). However, although neutralization of TNF alone significantly
delayed SEB-induced relapses, it did not completely prevent them (3).
IL-12 is involved in EAE induction (20) and synergizes with TNF (33, 34). Therefore, we investigated whether in vivo SE administration
increases IL-12. We measured serum IL-12 p40 in mice 6 and 24 h
after the i.p. administration of 25 µg/mouse SEA or 50 µg/mouse
SEB. We demonstrated that this treatment induces increased levels of
p40 IL-12 in the sera of these mice (Fig. 2). The induction kinetics is similar to
that shown in murine endotoxic shock (30). We also measured the levels
of IL-12 p70 heterodimer in these sera and observed consistently
detectable levels only at the 6-h time point (data not shown).
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Previous studies have shown that anti-IL-12 Abs prevent acute
monophasic EAE, while IL-12 increases its severity (20). We examined
whether the neutralizing anti-IL-12 mAb C17.8 could inhibit or
prevent SEB- or SEA-induced EAE relapses. After recovering from the
initial acute EAE episode (day 18 or 19), mice received SEA 25
µg/mouse or SEB 50 µg/mouse i.p. On the day of SE treatment and on
the following 2 days, a group of mice received additional treatment
with anti-IL-12 mAb (1 mg/mouse i.p. per treatment), while the
control group received control rat IgG (same dose). As shown in Table I and Figure 3, the incidence and severity (measured
as mean increment in clinical score and mean maximal score) of
SAG-induced EAE relapses was significantly reduced
(p < 0.001 for both SEA and SEB) by treatment
with anti-IL-12 Ab, while treatment with control rat IgG was
ineffective.
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The above results confirm the ability of SE to induce clinical
relapses in (PL/J x SJL/J)F1 mice. In addition, this
strain of mice has a tendency toward spontaneous relapses, with
incidence varying between 20% (3) and 100% (6), depending in part on
the immunization protocol. Our unpublished results have shown a mean
incidence of spontaneous relapses of 75% (range: 50–100%), with
typical occurrence 7 to 10 days after recovery from the initial
paralysis. In this paper, we use the term "spontaneous relapses" to
denote relapses that occur in immunized mice that have received neither
SE nor IL-12 treatment after the recovery from their initial EAE
episode. We examined whether SE administration influences the
occurrence or severity of spontaneous relapses. We found that animals
treated with SE after recovery from the initial EAE event, in addition
to experiencing an immediate SE-induced relapse, had an increased
incidence and severity of later relapses (p <
0.0001) (Table II and Fig. 3
). Anti-IL-12
Ab treatment at the time of SE administration significantly decreased
the incidence and severity of relapses, while administration of the
control Ab rat IgG at the time of SE administration had no effect.
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, A and
B). In contrast, histopathology in SE +
anti-IL-12-treated mice revealed no inflammatory or demyelinating
changes (Fig. 4C), with the exception of minimal meningeal
infiltration in a single case out of three in SEB +
anti-IL-12-treated mice (Table III).
The differences between SE + control Ab and SE + anti-IL-12 were
statistically significant (p < 0.05).
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We postulated that anti-IL-12 treatment may suppress relapses
in mice not given SE treatment. We also wanted to determine whether
systemic administration of murine rIL-12 can mimic SE effects by
inducing EAE relapses and/or affecting the severity of relapses. After
recovery from the initial bout of EAE, five mice received
anti-IL-12 mAb C17.8 (1 mg/mouse/day i.p. for three consecutive
days) while four control mice received the same quantities of rat IgG.
None of the anti-IL-12-treated mice developed relapses, whereas
three of four (75%) control Ab-treated mice had relapses. The mean
severity of the relapse (±SD) in the rat IgG-treated group was 1.125
(±1.031); the mean increment was 1.125 (±0.25). The difference was
statistically significant (p = 0.04 compared
with the rat IgG-treated group) (Fig. 5).
The protective effect of anti-IL-Abs was longer lasting than the
15 days of persistence of these Abs in the circulation. None of the
five animals followed 
50 days developed a relapse, in contrast to the
average of 60% of untreated mice that developed at least a third
attack.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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IL-12 is essential in the generation of Th1 responses and, therefore, plays a key role in the immune response to intracellular pathogens (19). Moreover, IL-12 is involved in the induction of T cell-mediated autoimmune diseases (35) including EAE (20, 21, 27). The role of IL-12 in the maintenance or recurrence of Th1 immune responses has also become a subject of recent investigations. The memory responses to certain infections appear to be IL-12-independent (36, 37). In the well-characterized model of murine leishmaniasis, we also recently demonstrated IL-12 independence of the Th1 response in the secondary infection (69). In contrast, the maintenance and chronicity of some, but not all, T cell-mediated autoimmunity appear to require IL-12. For example, the established chronic autoimmune reaction in experimental colitis is abrogated by neutralization of IL-12 (38). In contrast, however, administration of IL-12 during the established phase of autoimmune collagen-induced arthritis suppressed disease due to induction of IL-10 (39). Seder (40) has hypothesized that the differential IL-12 dependence of established Th1 responses in autoimmunity vs infectious diseases may reflect differences in the initial levels of endogenous IL-12 induction, with higher amounts of IL-12 produced during infection than during the response to an autoantigen. Because IL-12 also induces IL-10 (41, 42) in a potential autoregulatory loop, it is possible that the differential IL-12 dependence resides in the balance between IL-12 and IL-10. The role of IL-10 in EAE has been debated. A role in the recovery from EAE has been postulated based on the presence of IL-10 mRNA in the CNS of EAE animals in the recovery phase (43). With regard to the induction phase of EAE, the exogenous delivery of the cytokine in some studies was successful (44), while in other studies it was unsuccessful in preventing the disease (45). With regard to relapses, exogenous IL-10 could not prevent the SEB-induced relapses, while neutralization of the endogenous IL-10 worsened the relapses (46). This underscores the strength of cross-regulation in the endogenous cytokine network, which can determine the susceptibility, the course, and the cytokine dependence of autoimmunity. Recently, a unique IL-10/IL-12 immunoregulatory circuit controlling susceptibility to EAE has been demonstrated (47), and it is likely that perturbation of this loop (for example, as in our study) by microbial products powerfully changes the outcome and manifestations of EAE.
A clear possibility to consider in the case of relapsing autoimmunity is that IL-12 is important for the phenomenon of determinant (epitope) spreading. Evidence has accumulated indicating that propagation and reactivation of autoimmune diseases occur through the acquisition of autoreactivity to new self-determinants (48, 49, 50). Recently it has been shown that during the development of the determinant spreading cascade in murine relapsing EAE new sets of T cells are generated that exhibit a Th1 phenotype (50). Therefore, it is likely that the presence of IL-12 in the cytokine milieu during epitope spreading facilitates the development of these pathogenic neoautoreactive T cells.
Optimal Th1 responses require a synergy between IL-12 and the B7-CD28 interaction (51, 52). Blockade of B7 costimulation effectively prevented epitope spreading and clinical relapses in EAE (53, 54). Therefore, it is also important to characterize the role of IL-12, the other principal component required for optimal Th1 responses, in ongoing chronic or relapsing T cell-mediated autoimmunity. Here, we show that IL-12 neutralization can also prevent spontaneous relapses in EAE. In addition, we effectively prevented the occurrence of SE-induced relapses with an anti-IL-12 Ab. Although the assessment of the longevity of the protective effect of IL-12 neutralization was not the primary objective of this study, the fact that animals given anti-IL-12 Ab did not develop relapses for a long time following treatment while untreated animals did, provides further support to the hypothesis that once epitope spreading is prevented through blockade of costimulation and/or of IL-12, relapses are also prevented.
The mechanisms of SAG-induced and spontaneous relapses may be
different. Activation of the residual SAG-responsive T cells with
specific Vß TCR (for example, Vß8 for SEB) (3) is postulated and
likely to be responsible for the SE-induced relapses. Epitope
spreading, as discussed above, is involved in spontaneous EAE relapses
(45). Our current findings implicate IL-12 in the mechanism of both
processes of T cell reactivation and corresponding clinical relapse in
EAE. With respect to the SE-induced relapses, we demonstrated that SE
induces IL-12 in vitro, consistent with previous results (24), and, to
our knowledge, documented for the first time induction of IL-12 by SAG
in vivo. Moreover, we showed that exogenous IL-12 mimicked SE action,
inducing rapid relapses, resembling effects recently shown in Lewis
rats (22). Because staphylococcal SAG also induce IFN- (55), it is
possible that IFN- production by T cells is stimulated by SE-induced
IL-12, and reciprocal stimulation of IFN- and IL-12 between T cells
and APC is initiated. Although both SE induced similar levels of IL-12
in vitro and in vivo, the severity of SEA-induced relapses was lower
than that of relapses induced by SEB. However, both SEA- and
SEB-induced relapses exhibited significant dependence of this IL-12
induction. The basis of these differences is currently not completely
elucidated. We used the same doses of SE that were shown in a previous
study (3) to induce relapses in (PL/J x SJL/J) mice.
Interestingly, in that study, SEA was also less efficient than SEB in
inducing relapses. It is possible that, despite similar IL-12
inducibility, the lower frequency of SEA-responsive T cells makes this
reciprocal stimulation between IL-12 and IFN- less efficient, which
may explain the lower severity of SEA-induced relapses.
Migration of T cells to the inflammatory compartment, in this case the CNS, may also be stimulated by SE via IL-12 in a manner similar to the demonstrated IL-12 mediation of skin-homing receptor induction by staphylococcal SAG (23). This can explain the absent or minimal inflammation or demyelination in the CNS of mice given SE + anti-IL-12 compared with the inflammatory infiltrates of mice given SE + control Ab observed in our study. IL-12 up-regulates the very late Ag (VLA)-4-dependent T-cell migration (56), a phenomenon known to be required for T cell entry into the brain parenchyma (57). We also demonstrated enhanced expression of VLA-4 on murine MBP-reactive T cells after exposure to IL-12 (C.S.C. and A.R., unpublished observations). Thus, the neutralization of IL-12 may have prevented the up-regulation of VLA-4 and the reentry of autoreactive T cells into the brain. In addition, IL-12 may provide a death-preventing signal to MBP reactive T cells, as shown for other Ag-specific T cells (58).
No or very few residual inflammatory cells were seen in the CNS of mice given SE and treated with anti-Il-12 Abs. Because the time elapsed after recovery from the initial attack was relatively short, one may have expected residual inflammatory infiltrates. Their absence could be interpreted as a stimulated efflux of inflammatory cells from the CNS of mice treated with anti-IL-12 Ab similar to that postulated in the case of EAE mice treated with altered peptide ligands in which relapses were also prevented (59). Another explanation, consistent with our observation that the first bout is relatively short and mild in these mice and with the fact that the clinical residual deficit after the first bout was also mild, is that the inflammation was almost completely resolved at the time of SE administration. In support of this explanation is the fact that histologic analysis of the CNS of mice with near-complete clinical recovery shortly after the first episode is usually normal or only minimally abnormal (C.S.C., A.R., and B.H., unpublished observations).
Because spontaneous relapses may occur through epitope spreading (49), our results suggest that IL-12 plays a role in this phenomenon. Because B7 blockade also prevents spontaneous relapses, this is additional evidence for the complementarity of these two costimulatory factors necessary for optimal Th1 responses in vivo and in vitro.
Previously, other cytokine-based immunologic manipulations have
affected either SAG-induced or spontaneous EAE relapses. Administration
of TGF-ß (46, 60, 61), IL-10 (46), or IFN-
(62) prevented
relapses, while anti-TGF-ß worsened them (63). Blockade of TNF
decreased the incidence and severity of relapses (3, 63) and
ameliorated EAE in a chronic/relapsing model (64). Interestingly, the
cytokines that can prevent relapses antagonize IL-12, while cytokines
implicated in relapse pathogenesis synergize with IL-12 (33, 65, 66).
Thus, disease-suppressing effects in relapsing EAE may be mediated
through IL-12 blockade, while relapses may involve IL-12 and
synergistic factors.
Triggering and reactivation of autoimmunity by infectious products are documented in both spontaneous and experimental disease. Spontaneous EAE in MBP-specific transgenic mice occurred only in animals kept in a normal, pathogen-containing environment and not in animals kept in a specific pathogen-free facility (67). The effects of SAG on EAE exacerbations have been attributed either to restricted TCR-dependent mechanisms (3) or to nonspecific mechanisms, which include cytokine release (4). The present study supports the latter hypothesis that SAG also employ nonspecific mechanisms in reactivating EAE. The role of cytokines in the infection-induced reactivation of autoimmunity has been investigated, particularly with respect to TNF (3, 46, 68). Segal et al. (27) recently implicated IL-12 in the pathogenesis of this phenomenon as well. Our results extend these observations and bring them into the context of bacterial T cell SAG.
In conclusion, we show the ability of SE to induce IL-12 and demonstrate the involvement of IL-12 in SE-induced and spontaneous relapses of EAE. These findings may help to elucidate immunopathogenic mechanisms of relapsing autoimmunity and may provide clues to the immunopathology of MS. Neutralization of IL-12 may prove an effective therapy for autoimmune demyelination.
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Acknowledgments |
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Footnotes |
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2 Current address: Departments of Neurology and Research, Laboratory of Neurobiology, University Hospital Basel, Basel, Switzerland.
3 Address correspondence and reprint requests to Dr. Abdolmohamad Rostami, Department of Neurology, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA 19104-4283. E-mail:
4 Abbreviations used in this paper: EAE, experimental autoimmune encephalomyelitis; MS, multiple sclerosis; CNS, central nervous system; MBP, myelin basic protein; SAG, superantigen; SE, staphyloccocal enterotoxin; SEB, staphyloccocal enterotoxin B; SEA, staphyloccocal enterotoxin A.
Received for publication March 12, 1998. Accepted for publication July 1, 1998.
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 S. Marusic, M. W. Leach, J. W. Pelker, M. L. Azoitei, N. Uozumi, J. Cui, M. W.H. Shen, C. M. DeClercq, J. S. Miyashiro, B. A. Carito, et al. Cytosolic phospholipase A2{alpha}-deficient mice are resistant to experimental autoimmune encephalomyelitis J. Exp. Med., September 19, 2005; 202(6): 841 - 851. [Abstract] [Full Text] [PDF]
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 H. Kimura, S.-C. Tzou, R. Rocchi, M. Kimura, K. Suzuki, A. F. Parlow, N. R. Rose, and P. Caturegli Interleukin (IL)-12-Driven Primary Hypothyroidism: the Contrasting Roles of Two Th1 Cytokines (IL-12 and Interferon-{gamma}) Endocrinology, August 1, 2005; 146(8): 3642 - 3651. [Abstract] [Full Text] [PDF]
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A. Elhofy, J. Wang, M. Tani, B. T. Fife, K. J. Kennedy, J. Bennett, D. Huang, R. M. Ransohoff, and W. J. Karpus Transgenic expression of CCL2 in the central nervous system prevents experimental autoimmune encephalomyelitis J. Leukoc. Biol., February 1, 2005; 77(2): 229 - 237. [Abstract] [Full Text] [PDF]
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 M. Matsui, O. Moriya, M. L. Belladonna, S. Kamiya, F. A. Lemonnier, T. Yoshimoto, and T. Akatsuka Adjuvant Activities of Novel Cytokines, Interleukin-23 (IL-23) and IL-27, for Induction of Hepatitis C Virus-Specific Cytotoxic T Lymphocytes in HLA-A*0201 Transgenic Mice J. Virol., September 1, 2004; 78(17): 9093 - 9104. [Abstract] [Full Text] [PDF]
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 C. Weir, C. C. A. Bernard, and B. T. Backstrom IL-5-deficient mice are susceptible to experimental autoimmune encephalomyelitis Int. Immunol., November 1, 2003; 15(11): 1283 - 1289. [Abstract] [Full Text] [PDF]
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C. Deng, C. Radu, A. Diab, M. F. Tsen, R. Hussain, J. S. Cowdery, M. K. Racke, and J. A. Thomas IL-1 Receptor-Associated Kinase 1 Regulates Susceptibility to Organ-Specific Autoimmunity J. Immunol., March 15, 2003; 170(6): 2833 - 2842. [Abstract] [Full Text] [PDF]
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B. Gran, G.-X. Zhang, S. Yu, J. Li, X.-H. Chen, E. S. Ventura, M. Kamoun, and A. Rostami IL-12p35-Deficient Mice Are Susceptible to Experimental Autoimmune Encephalomyelitis: Evidence for Redundancy in the IL-12 System in the Induction of Central Nervous System Autoimmune Demyelination J. Immunol., December 15, 2002; 169(12): 7104 - 7110. [Abstract] [Full Text] [PDF]
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 G-X Zhang, M Kishi, H Xu, and A Rostami Mature bone marrow-derived dendritic cells polarize Th2 response and suppress experimental autoimmune encephalomyelitis Multiple Sclerosis, December 1, 2002; 8(6): 463 - 468. [Abstract] [PDF]
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H. P. M. Brok, M. van Meurs, E. Blezer, A. Schantz, D. Peritt, G. Treacy, J. D. Laman, J. Bauer, and B. A. 't Hart Prevention of Experimental Autoimmune Encephalomyelitis in Common Marmosets Using an Anti-IL-12p40 Monoclonal Antibody J. Immunol., December 1, 2002; 169(11): 6554 - 6563. [Abstract] [Full Text] [PDF]
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 G. Matarese, V. Sanna, R. I. Lechler, N. Sarvetnick, S. Fontana, S. Zappacosta, and A. La Cava Leptin Accelerates Autoimmune Diabetes in Female NOD Mice Diabetes, May 1, 2002; 51(5): 1356 - 1361. [Abstract] [Full Text] [PDF]
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G.-X. Zhang, H. Xu, M. Kishi, D. Calida, and A. Rostami The Role of IL-12 in the Induction of Intravenous Tolerance in Experimental Autoimmune Encephalomyelitis J. Immunol., March 1, 2002; 168(5): 2501 - 2507. [Abstract] [Full Text] [PDF]
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S. Lassmann, C. Kincaid, V. C. Asensio, and I. L. Campbell Induction of Type 1 Immune Pathology in the Brain Following Immunization Without Central Nervous System Autoantigen in Transgenic Mice With Astrocyte-Targeted Expression of IL-12 J. Immunol., November 1, 2001; 167(9): 5485 - 5493. [Abstract] [Full Text] [PDF]
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K. Chen, Y. Wei, G. C. Sharp, and H. Braley-Mullen Induction of Experimental Autoimmune Thyroiditis in IL-12-/- Mice J. Immunol., August 1, 2001; 167(3): 1720 - 1727. [Abstract] [Full Text] [PDF]
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K. Hong, E. L. Berg, and R. O. Ehrhardt Persistence of Pathogenic CD4+ Th1-Like Cells In Vivo in the Absence of IL-12 but in the Presence of Autoantigen J. Immunol., April 1, 2001; 166(7): 4765 - 4772. [Abstract] [Full Text] [PDF]
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B. M. Segal, J. T. Chang, and E. M. Shevach CpG Oligonucleotides Are Potent Adjuvants for the Activation of Autoreactive Encephalitogenic T Cells In Vivo J. Immunol., June 1, 2000; 164(11): 5683 - 5688. [Abstract] [Full Text] [PDF]
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J. T. Chang, E. M. Shevach, and B. M. Segal Regulation of Interleukin (IL)-12 Receptor {beta}2 Subunit Expression by Endogenous IL-12: A Critical Step in the Differentiation of Pathogenic Autoreactive T Cells J. Exp. Med., March 15, 1999; 189(6): 969 - 978. [Abstract] [Full Text] [PDF]
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