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*
Ludwig Boltzmann Institute for Cell Biology and Immunobiology of the Skin, Department of Dermatology, University of Münster, Münster, Germany;
Ben May Institute for Cancer Research, University of Chicago, Chicago, IL 60637
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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; low levels of IL-2; and no
IL-4, resembling the cytokine pattern of T regulatory 1 cells. Ab
blocking of CTLA-4 resulted in inhibition of IL-10 release.
Accordingly, transfer of tolerance was not observed when recipients
were treated with an anti-IL-10 Ab. Hence we propose that T cells,
possibly of the T regulatory 1 type, transfer UV-mediated suppression
through the release of IL-10. Activation of CTLA-4 appears to be
important in this process. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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). Consequently, it has
been suggested that UV-induced tolerance is mediated by hapten-specific
T suppressor cells (reviewed in Ref. 7). Despite the clear
transfer experiments, this concept is controversial, mainly because the
cells transferring hapten-specific unresponsiveness are still poorly
characterized, and their mode of action is unclear in major parts
(7).
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In the present study we addressed whether CTLA-4 is involved in
UV-induced tolerance. Here, we show that T cells transferring
hapten-specific UV-mediated tolerance express CTLA-4 on their surface.
However, CTLA-4 not only appears to be a marker for T cells mediating
this effect, but also seems to be functionally relevant, since in vivo
injection of an Ab that blocks CTLA-4 resulted in the loss of tolerance
and transfer of suppression. Upon in vitro expansion,
CTLA-4+ T cells transferring suppression secrete
high levels of IL-10, TGF-ß, and IFN- and low levels of IL-2 but
no IL-4, resembling a T regulatory 1 (Tr1)-like cytokine pattern.
Transfer of tolerance was inhibited when recipients were treated with
an anti-IL-10 Ab. Thus, we propose that T cells, probably of the
Tr1 type, transfer UV-mediated suppression through the release of
IL-10. Activation of CTLA-4 appears to play an important role in this
process.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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C3H/HeN mice (8–10 wk old) were purchased from Harlan Winkelmann (Borchen, Germany). Animals were housed under specific pathogen-free conditions and treated according to institutional guidelines.
Abs and reagents
Hamster anti-murine Ab to CTLA-4 (clone UC10-4F10) was
produced as described previously (13). In vivo
neutralization of IL-10 was performed with a rat anti-IL-10 mAb
(clone JES5-2A5; BioSource, Ratingen, Germany). IL-10, IFN-, and
TGF-ß in the supernatant were determined by ELISA (R&D Systems,
Wiesbaden, Germany). The IL-2-dependent cell line CTLL-2 was used for
the detection of IL-2, while the IL-4-dependent cell line CT.4S was
used for detection of IL-4.
Contact hypersensitivity
Mice were sensitized by painting 25 µl of 2,4,-dinitrofluorobenzene (DNFB; Sigma, St. Louis, MO) solution (0.5% in acetone/olive oil, 4/1) on the shaved back on day 0 as previously described (14). On day 5, 20 µl of 0.3% DNFB was applied to the left ear; the vehicle acetone/olive oil was applied to the right ear. Ear swelling was quantitated with a spring-loaded micrometer (Mitutoyo, Kawasaki, Kanagawa, Japan) 24 h after challenge. CHS was determined as the amount of swelling of the hapten-challenged ear compared with the thickness of the vehicle-treated ear in sensitized animals and was expressed as centimeters x 10-3 (mean ± SD). The ear swelling response was measured in a blinded fashion. Mice that were ear-challenged without prior sensitization served as negative controls. Resensitization was performed as described above through shaved abdominal skin 14 days after the first challenge. The second challenge was performed on the right ear 5 days after the second sensitization. Each group consisted of at least seven mice. Each experiment was performed at least twice.
UV irradiation
The shaved back was exposed to UV radiation from a bank of four TL12 fluorescent lamps (Philips, Eindhoven, The Netherlands), which emit most of their energy within the UVB range (290–320 nm) with an emission peak at 313 nm. Mice were exposed to UV daily for 4 consecutive days (1000 J/m2/exposure). 24 h after the last UV exposure DNFB was applied carefully to the surface of the irradiated area as described above. As reported previously, the UV regimen applied does not cause generalized systemic immunosuppression, but induces hapten-specific tolerance (14, 15).
Adoptive transfer of immune response
Donor mice were treated as indicated, spleens and regional lymph nodes were removed thereafter, and single-cell suspensions were prepared. The cell number was adjusted (see individual experiments), and 200 µl was injected i.v. into each recipient mouse. Recipients were sensitized 24 h later by epicutaneous application of DNFB on the shaved abdomen. After 5 days, mice were challenged on the left ear, and ear swelling was evaluated 24 h later.
Depletion of subpopulations
For in vitro depletion of CTLA-4+ subpopulations, lymphocytes obtained from regional lymph nodes and spleens were incubated with magnetobeads (Dynabeads M-450 tosylactivated, Dynal, Oslo, Norway) that were coated with a purified hamster mAb directed against murine CTLA-4 (UC10-4F10-11) according to general protocols (Cell Separation and Protein Purification, Technical Handbook, Dynal). After incubation for 2 h at 4°C, magneto-separation was performed by placing the tubes into a magnet field (Dynal) for 4 min. The supernatant containing the CTLA-4- cells was removed. Cells were washed and adjusted to 5 x 108 cells/ml for i.v. injection. CTLA-4+ cells bound to the magnetobeads were detached by incubating cells overnight in cell culture medium at 37°C in a humidified atmosphere containing 5% CO2. Magnetobeads that had spontaneously detached from the cells after overnight incubation were removed with a magnet. Remaining (CTLA-4+) cells were harvested, washed, and adjusted for i.v. injection. The efficacy of separation was determined by flow cytometry (EPICS XL, Coulter, Miami, FL).
Cytokine induction in vitro
T lymphocytes were prepared from mice that were tolerized by
applying DNFB onto UV-irradiated skin and separated into
CTLA-4- and CTLA-4+
fractions by magnetobead separation. T cells (5 x
106/ml) were incubated with dendritic cells (DC;
1 x 106/ml) that were isolated from bone
marrow of syngeneic naive mice as described previously
(14). Coincubations were performed in the absence or the
presence of the water-soluble DNFB analogue 2,4-dinitrobenzenesulfonic
sodium salt (0.1 mM DNBS). Supernatants were tested for IL-2, IL-4,
IL-10, IFN-, and TGF-ß as described above.
Statistical analysis
Data were analyzed by Student’s t test, and differences were considered significant at p < 0.05.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To determine whether T lymphocytes transferring UV-mediated
suppression of CHS express CTLA-4, adoptive transfer experiments were
performed. C3H/HeN mice were sensitized by topical application of DNFB
onto UV-exposed skin. Since this procedure results in hapten-specific
tolerance (14), animals treated in this way are
subsequently referred to as UV tolerized. Ten days after hapten
application, spleen and regional lymph node cells were obtained for
i.v. injection into naive syngeneic mice (Fig. 1
). Before transfer,
cells were depleted from CTLA-4+ cells by
magnetobead separation. Unfractionated cells served as a control.
Depletion was efficient, as confirmed by FACS analysis (Fig. 2). Unfractionated cells contained a
CTLA-4+ and a CTLA-4-
subpopulation (Fig. 2A); the CTLA-4+
population was lost after CTLA-4 depletion (Fig. 2B). For
transfer of UV-induced immunosuppression, 1 x
108 cells of the unseparated or the
CTLA-4-depleted fraction were injected i.v. into naive mice. Recipients
were sensitized with DNFB 24 h after transfer, their ears were
challenged 5 days later, and ear swelling was measured 24 h
thereafter. As previously reported (16), the CHS response
in mice receiving unfractionated cells from UV-tolerized mice was
remarkably suppressed (Fig. 3A, group 3) compared with
that in mice that were just sensitized and challenged (Fig. 3A, group 1). In contrast, transfer of CTLA-4 depleted cells
did not inhibit subsequent sensitization (Fig. 3A, group 4).
Sham depletion control, i.e., incubation of lymphocytes with
magnetobeads not coated with the anti-CTLA-4 Ab, did not affect the
transfer of suppression (data not shown). Thus, T cells mediating
tolerance in UV-induced immunosuppression appear to express CTLA-4 on
their surface.
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To further confirm that T cells transferring suppression reside in
the CTLA-4+ fraction, spleen and regional lymph
node cells from UV-tolerized mice were obtained and subjected to CTLA-4
magnetobead separation as described above. This time, however,
CTLA-4+ cells were collected from the beads and
used for transfer. Successful positive selection was determined by FACS
analysis (Fig. 2C). Cells (5 x
105) injected i.v. significantly inhibited
sensitization of the recipients against DNFB (Fig. 3B, group
3). Note that when using unfractionated cells, 1 x
108 cells were necessary to transfer suppression
at comparable levels (Fig. 3A). The fact that a much lower
number of CTLA-4+ cells suffices to mediate
complete suppression indicates that the relevant cells reside in the
CTLA-4+ population. With decreasing the number of
CTLA-4+ cells, the inhibitory effect was
gradually reduced (data not shown).
Cytokine secretion pattern
The data obtained to date suggest that CTLA-4 can be used as a
marker for T cells transferring unresponsiveness in the model of
UV-induced tolerance. Thus, we tried to expand these T cells in vitro.
Lymph node cells and splenocytes were obtained from UV-tolerized mice
and separated into CTLA-4+ and
CTLA-4- cells. Cells were put into culture with
bone marrow-derived DC. Cells were cultured for 72 h in the
absence or the presence of the water-soluble DNFB analogue DNBS.
Supernatants were harvested and tested for the amounts of IL-2, IL-4,
IL-10, IFN-, and TGF-ß (Table I).
IL-4 was detectable in none of the samples. Incubation of
CTLA-4+ cells with DC and DNBS did not alter the
low constitutive IL-2 secretion, but remarkably enhanced the secretion
of IL-10, IFN-, and TGF-ß. Stimulation of the
CTLA-4- cell fraction with DC and DNBS caused a
similar increase in IFN- release, while IL-10 and TGF-ß were only
moderately induced. The cytokine secretion pattern observed in
CTLA-4+ cells (high release of IL-10, IFN-,
and TGF-ß; no release of IL-4; and moderate levels of IL-2) is
similar to that of the recently described Tr1 cells (17, 18). This cytokine secretion pattern was even more pronounced,
especially excessive IL-10 release, when cells were stimulated and
cultured for 11 days (Table II).
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Since CTLA-4 can serve as a marker for T cells that mediate
UV-induced tolerance, we next asked whether CTLA-4 is of functional
relevance for the development of tolerance to haptens applied through
UV-irradiated skin. To address this issue, mice were sensitized through
UV-exposed back skin and challenged on the left ear 5 days later. After
14 days, mice were resensitized through the nonirradiated shaved
abdominal skin and challenged on the right ear 5 days later. One group
of animals (Fig. 4, group 4) was injected
i.p. 3 h before resensitization with an Ab that blocks CTLA-4.
Mice that were initially sensitized through UV-exposed skin did not
show an ear swelling response after resensitization with the same
hapten through non-UV-exposed skin, indicating that hapten-specific
tolerance was induced (Fig. 4, group 3). In contrast, mice that
received a single dose of the blocking anti-CTLA-4 Ab before
resensitization (group 4) revealed a pronounced ear swelling response
comparable to that of positive control mice that were sensitized and
challenged but not UV irradiated (group 1).
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Next we studied whether transfer of suppression is inhibited when
CTLA-4 is functionally blocked in the recipient animals. Lymph node
cells from UV-tolerized mice were injected into recipient animals that
were immediately sensitized against DNFB. Three hours before adoptive
cell transfer and 24 h after sensitization, one group of animals
(Fig. 5, group 4) was injected i.p. with
an anti-CTLA-4 Ab (100 µg). The CHS response was measured 5 days
later. Compared with the positive control (group 1), injection of cells
from UV-irradiated and DNFB-treated mice (group 3) suppressed the
generation of CHS in the recipient animals (Fig. 5). The suppressive
activity on the CHS response by the adoptive cell transfer was
completely inhibited when the recipient mice were injected with
anti-CTLA-4 Ab (group 4). Application of an isotype control had no
effect (data not shown). Together, these findings and the data
presented in Fig. 4 indicate that CTLA-4 is of functional relevance in
mediating UV-induced tolerance and in transferring hapten-specific
suppression.
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IL-10 has been implicated to be involved in mediating UV-induced
tolerance (reviewed in Ref. 19). Since 1) transfer of
tolerance is critically dependent on CTLA-4+ T
cells, which, as demonstrated in Table I, upon in vitro stimulation
secrete high levels of IL-10; and 2) CTLA-4 blockade inhibits
UV-induced tolerance in vivo (Fig. 4), we studied whether blockade of
CTLA-4 suppresses IL-10 secretion. Therefore, the neutralizing
anti-CTLA-4 Ab was added to CTLA-4+
lymphocytes from UV-tolerized mice that were propagated in the presence
of DC and DNBS for 11 days. The CTLA-4 Ab only marginally affected the
secretion of IL-2 and IFN-, but significantly reduced enhanced IL-10
release (Table II).
Neutralization of IL-10 inhibits transfer of tolerance
The data obtained to date suggest that 1) CTLA-4 signaling is
crucial for mediation and transfer of tolerance; and 2) blockade of
CTLA-4 impairs regulatory T cells in their ability to release IL-10.
These observations imply that transfer of tolerance is critically
dependent on IL-10. Hence, we determined whether neutralization of
IL-10 in the recipients is associated with a loss of hapten-specific
unresponsiveness. Lymph node cells from UV-tolerized mice were injected
into recipient animals that were immediately sensitized against DNFB.
Three hours before adoptive cell transfer and 24 h after
sensitization, one group of animals was injected i.p. with an
anti-IL-10 Ab (250 µg for each injection). CHS response was
measured 5 days later. Compared with the positive control (Fig. 6, group 1), injection of cells from
UV-irradiated and DNFB-treated mice suppressed generation of CHS in the
recipient animals (Fig. 6, group 3). The suppressive activity on the
CHS response by the adoptive cell transfer was reversed when the
recipient mice were injected with anti-IL-10 Ab (group 4), while
injection of an isotype control had no effect (data not shown). These
findings indicate that the transfer of UV-induced tolerance is
critically dependent on IL-10.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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). Since both impairment of CHS and induction of
hapten-specific tolerance are caused by the identical procedure, it was
postulated for quite a long time that the same mechanisms are involved
and that induction of tolerance is the direct consequence of the
inhibition of CHS induction. However, there is accumulating evidence
that the molecular basis of UV-induced tolerance is different from the
mechanism responsible for UV-impaired induction of CHS
(20). Whereas a key event in the suppression of CHS by UV
irradiation appears to be the depletion of Langerhans cells from the
epidermis (4, 21), the mechanisms that cause tolerance
still remain unclear in major parts (reviewed in Refs. 7
and 22). Nevertheless, unresponsiveness can be adoptively
transferred by injecting T cells from UV-tolerized mice into naive
animals (6). These recipients cannot be sensitized against
the specific hapten, whereas their sensitizing response to another
unrelated hapten is not affected. The cells transferring suppression
have been poorly characterized, but certainly belong to the T cell
group (6, 16, 23). Here we show that they express CTLA-4
on their surface, since depletion of CTLA-4+
cells resulted in complete loss of transfer of suppression. Likewise,
when lymph node cells and splenocytes were enriched for
CTLA-4+ cells, a significantly lower number of
cells sufficed to transfer suppression. Glass et al. proposed that T
suppressor cells are universally induced during sensitization
(24). Vice versa, one could hypothesize that primed
effector cells are induced during tolerization. Provided these putative
cells would be CTLA-4-, depletion of these cells
during CTLA-4 enrichment could also contribute to enhanced suppression
following transfer. Whether this is the case is currently under
investigation.
CTLA-4, however, cannot be regarded as a specific marker for the cells
transferring suppression, since it is likely that only a minority of
cells transferred is responsible for mediating hapten-specific
unresponsiveness in the recipient. Nevertheless, CTLA-4 can serve as a
marker to enrich these T cells for in vitro propagation. When lymph
node cells from UV-tolerized mice were coincubated with DC, differences
in the cytokine secretion pattern between CTLA-4+
and CTLA-4- became obvious.
CTLA-4+ cells upon stimulation with DC and the
specific hapten released high amounts of IL-10, TGF-ß, and IFN-
and low levels of IL-2, but no IL-4. In contrast, identically treated
CTLA-4- cells behaved similarly in terms of
IFN-, IL-2, and IL-4, while the pronounced induction of IL-10 and
TGF-ß secretion was not observed. Hence the cytokine pattern of our
CTLA-4+ cells resembles that of Tr1 cells
described recently by Groux et al. (17, 18). Tr1 cells are
induced by chronic activation of lymphocytes in the presence of IL-10;
are CD4+ and 
ß+; and
produce IL-10, IFN-, and TGF-ß with little or no IL-2 and IL-4.
Induction of IL-10 secretion in our CTLA-4+ cells
was only observed when DC and the specific hapten were added.
Coincubation with DC in the presence of TNBS, the water-soluble
analogue of the unrelated hapten TNCB, did not induce IL-10 production
(data not shown), implying that IL-10 secretion by
CTLA-4+ cells is hapten specific. In addition, we
can exclude that the preparation of CTLA-4+ cell
by itself could promote Ag-nonspecific triggering causing IL-10
release, since transfer of CTLA-4+ T cells
obtained from DNFB-tolerized donors into naive mice did not suppress
sensitization of the recipients against the unrelated hapten oxazolone
(data not shown).
There is convincing evidence that IL-10 plays an important role in
mediating the immunosuppressive effects of UV radiation
(25, 26, 27). Several studies suggested that Th2 cells mediate
the suppressive effects of UV radiation by down-regulating Th1
functions through their production of IL-10 (reviewed in Ref.
19 and 28). Our cells, however, do not appear
to belong to the Th2 type due to the absence of IL-4 production and
their significant IFN- production. Shreedar et al. were the first to
clone T cells with suppressive activity from UV-exposed mice that were
sensitized with FITC (23). Cells cloned were
CD4+, CD8-,
TCR-ß+, MHC restricted, and specific for
FITC. They produced IL-10, but not IL-4 or IFN-, whereas cells from
unirradiated animals produced high amounts of IFN- and little IL-4
and IL-10. T cells from UV-exposed mice blocked APC functions and IL-12
production. Even more importantly, injection of cloned T cells into
untreated recipients suppressed the induction of CHS against FITC. The
phenotype of these cells resembled that of Tr1 cells to some extent,
but, in contrast to Tr1 cells, failed to secrete IFN-. Hence,
Shreedar et al. tentatively designated these cells Tr2 cells
(23). The differences between our observations and those
of Shreedar may be due to differences in the experimental approaches.
Shreedar analyzed cloned cells, whereas we cultured our cells for 2 wk
at the longest. While Shreedar used FITC as a hapten, we performed our
studies with DNFB. There are indications that the outcome and the type
of immune reaction may depend on the type of hapten
(29).
CTLA-4 not only appears to be a marker for the T cells transferring
UV-mediated suppression but also seems to be functionally relevant.
Injection of an Ab that blocks CTLA-4 (13) into
UV-tolerized mice enabled sensitization against the respective hapten.
These data indicate for the first time that blockade of CTLA-4 can
break UV-induced tolerance. In vivo blockade of CTLA-4 slightly
enhanced sensitization (Fig. 4). However, this potentiation was never
so pronounced that this effect could be responsible for the restoration
of the CHS response in tolerized animals. Tang et al. recently showed
that treatment of mice with a soluble form of CTLA-4 (CTLA-4Ig) during
primary sensitization induced long lasting unresponsiveness against
DNFB (29). CTLA-4Ig binds to B7 (CD80/86) with 20-fold
higher avidity than CD28 and thus inhibits the interaction of CD28 with
its B7 counterparts (30). Blockade of costimulation
through the B7-CD28 pathway by CTLA-4Ig has been shown to inhibit a
variety of in vivo immune responses, in some instances leading to
Ag-specific tolerance as demonstrated by Tang et al. (29).
In contrast to CTLA-4Ig, the anti-CTLA-4 Ab that we used for the in
vivo studies does not interfere with B7-CD28 interaction, but only
inhibits CTLA-4 signaling. Since in vivo blockade of CTLA-4 results in
the loss of tolerance (Fig. 4) and the loss of suppressive transfer
(Fig. 5), functional CTLA-4 signaling in T cells appears to be crucial
in mediating UV-induced tolerance. Taking into account that transfer of
suppression is critically dependent on T cells expressing CTLA-4, the
in vivo blocking data indicate that activation of CTLA-4 on these cells
is critically involved in the mediation and transfer of tolerance.
The underlying mechanism by which CTLA-4 signaling mediates tolerance remains to be determined. Since upon in vitro stimulation with hapten-coupled DC, CTLA-4+ cells released high amounts of IL-10, one mechanism by which the anti-CTLA-4 Ab could break tolerance is by inhibiting the release of IL-10 that has been suggested to be crucial in tolerance induction (31, 32). Accordingly, the blocking Ab reduced in vitro IL-10 release significantly, when added to CTLA-4+ cells stimulated with DC in the presence of the specific hapten. Thus, we postulate that ligation of CTLA-4 results in enhanced release of IL-10, which ultimately mediates UV-induced immunosuppression. In this context it is important to mention that induction of release of immunosuppressive cytokines upon ligation of CTLA-4 has been previously observed; engagement of CTLA-4 by cross-linking Ab induces TGF-ß (33), which is a potent inhibitor of T cell-mediated immune responses both in vitro and in vivo (34, 35, 36, 37, 38). Accordingly, stimulation of CTLA-4+ cells obtained from UV-tolerized mice with hapten-coupled DC induced the release of TGF-ß. Whether this is due to CTLA-4 ligation in our system cannot be answered, since we have not yet performed Ab blocking studies in vitro.
Since blockade of CTLA-4 in our experiments was able to break tolerance in vivo, on the one hand, and to inhibit IL-10 secretion in vitro, on the other hand, we surmised that the T cells obtained from UV-tolerized mice exert their regulatory activity in the recipient animals by release of IL-10. In this case, the inhibitory activity of the adoptive transfer should be suppressed when IL-10 is neutralized in the recipients. Indeed, animals receiving T cells from DNFB-tolerized donors could be normally sensitized against DNFB when they were injected with an anti-IL-10 Ab. Injection of the same amounts of anti-IL-10 Ab into naive mice before sensitization caused a slight, but not significant, enhancement of the subsequent ear swelling response (data not shown). Hence, it is unlikely that the restoration of the ear swelling response by the anti-IL-10 Ab in mice receiving T suppressor cells is just due to a potentiation of CHS reactivity. Consequently, these findings indicate that transfer of UV-mediated tolerance is critically dependent on IL-10. Although we cannot exclude other possibilities with absolute certainty, e.g., that the anti-CTLA-4 Ab could operate through cell killing or redirecting cell traffic or homing, we suspect that triggering of IL-10 release is the most likely mechanism. Hence, induction of immunosuppressive cytokines, especially of IL-10, following ligation of CTLA-4 may represent a mechanism by which the CTLA-4 molecule functions as a negative regulator of T cell responses.
On the first glance, inhibition of transfer of suppression by in vivo blockade of IL-10 may appear to be in contrast to previous observations made by Rivas and Ullrich (25). In this study inhibition of CHS in the recipient animals after adoptive transfer was not affected by injecting anti-IL-10 Ab. The most likely explanation for these differences is that Rivas and Ullrich studied systemic UV-induced immunosuppression, while we used the local model. There is ample evidence that although both systemic and local immunosuppressions inhibit the induction of CHS and induce hapten-specific tolerance, their effects are mediated by different mechanisms (39, 40).
Since TGF-ß release was also induced by CTLA-4+ T cells upon stimulation with DC, the question arises of whether TGF-ß is also involved in mediating transfer of UV-induced suppression. In contrast to the clear-cut data when blocking IL-10 in vivo, injection of a neutralizing anti-TGF-ß Ab did not inhibit transfer of suppression (data not shown). However, since neither detailed dose-response studies nor injections with different kinetics were performed, it cannot be excluded with absolute certainty that TGF-ß may be involved as well.
Based on the present data we propose the following scenario for UV-induced tolerance. A subtype of CTLA-4+ T cells is induced after tolerization by application of haptens through UV-exposed skin. Upon resensitization, these CTLA-4+ T cells may meet the APC carrying the specific hapten in the regional lymph nodes. Triggering of CTLA-4 by B7 molecules expressed on the APC induces the release of IL-10, which subsequently inhibits resensitization, thereby rendering the respective animal tolerant to this hapten. The same process may occur when CTLA-4+ T cells from UV-tolerized animals are adoptively transferred into naive recipients. Since the CTLA-4+ T cells become only activated when the specific hapten is presented, this may explain the hapten specificity of UV-mediated tolerance. However, once IL-10 is released in an Ag-specific manner, its immunosuppressive effects should be general (bystander suppression) (18). Whether this is the case in vivo is currently under investigation. How IL-10 might inhibit resensitization also remains to be determined. It recently was shown that induction of apoptosis via the Fas/FasL system is crucial for the induction of UV-induced tolerance (41, 42). Hence, we are currently investigating whether IL-10 affects apoptotic pathways in DC or T cells.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Thomas Schwarz, Department of Dermatology, University of Munster, Von Esmarchstrasse 56, D-48149 Munster, Germany.
3 Abbreviations used in this paper: CHS, contact hypersensitivity; DC, dendritic cell; DNFB, 2,4-dinitrofluorobenzene; DNBS, 2,4-dinitrobenzenesulfonic sodium salt; Tr, regulatory T cells.
Received for publication February 18, 2000. Accepted for publication May 30, 2000.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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in the immune suppression induced by ultraviolet radiation. J. Leukocyte Biol. 56:769.
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J. P. McGlade, S. Gorman, J. C. Lenzo, J. W. Tan, T. Watanabe, J. J. Finlay-Jones, W. R. Thomas, and P. H. Hart Effect of Both Ultraviolet B Irradiation and Histamine Receptor Function on Allergic Responses to an Inhaled Antigen J. Immunol., March 1, 2007; 178(5): 2794 - 2802. [Abstract] [Full Text] [PDF]
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A. Schwarz, A. Maeda, and T. Schwarz Alteration of the Migratory Behavior of UV-Induced Regulatory T Cells by Tissue-Specific Dendritic Cells J. Immunol., January 15, 2007; 178(2): 877 - 886. [Abstract] [Full Text] [PDF]
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Y. Matsumura, S. N. Byrne, D. X. Nghiem, Y. Miyahara, and S. E. Ullrich A Role for Inflammatory Mediators in the Induction of Immunoregulatory B Cells J. Immunol., October 1, 2006; 177(7): 4810 - 4817. [Abstract] [Full Text] [PDF]
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 M. Gunzer, H. Riemann, Y. Basoglu, A. Hillmer, C. Weishaupt, S. Balkow, B. Benninghoff, B. Ernst, M. Steinert, T. Scholzen, et al. Systemic administration of a TLR7 ligand leads to transient immune incompetence due to peripheral-blood leukocyte depletion Blood, October 1, 2005; 106(7): 2424 - 2432. [Abstract] [Full Text] [PDF]
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S. Gorman, J. W.-Y. Tan, J. A. Thomas, S. L. Townley, P. A. Stumbles, J. J. Finlay-Jones, and P. H. Hart Primary Defect in UVB-Induced Systemic Immunomodulation Does Not Relate to Immature or Functionally Impaired APCs in Regional Lymph Nodes J. Immunol., June 1, 2005; 174(11): 6677 - 6685. [Abstract] [Full Text] [PDF]
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A. Maeda, A. Schwarz, K. Kernebeck, N. Gross, Y. Aragane, D. Peritt, and T. Schwarz Intravenous Infusion of Syngeneic Apoptotic Cells by Photopheresis Induces Antigen-Specific Regulatory T Cells J. Immunol., May 15, 2005; 174(10): 5968 - 5976. [Abstract] [Full Text] [PDF]
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K. Loser, A. Scherer, M. B. W. Krummen, G. Varga, T. Higuchi, T. Schwarz, A. H. Sharpe, S. Grabbe, J. A. Bluestone, and S. Beissert An Important Role of CD80/CD86-CTLA-4 Signaling during Photocarcinogenesis in Mice J. Immunol., May 1, 2005; 174(9): 5298 - 5305. [Abstract] [Full Text] [PDF]
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V. M. Jovasevic, L. Gorelik, J. A. Bluestone, and M. B. Mokyr Importance of IL-10 for CTLA-4-Mediated Inhibition of Tumor-Eradicating Immunity J. Immunol., February 1, 2004; 172(3): 1449 - 1454. [Abstract] [Full Text] [PDF]
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A. Schwarz, A. Maeda, M. K. Wild, K. Kernebeck, N. Gross, Y. Aragane, S. Beissert, D. Vestweber, and T. Schwarz Ultraviolet Radiation-Induced Regulatory T Cells Not Only Inhibit the Induction but Can Suppress the Effector Phase of Contact Hypersensitivity J. Immunol., January 15, 2004; 172(2): 1036 - 1043. [Abstract] [Full Text] [PDF]
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A. Cavani, F. Nasorri, C. Ottaviani, S. Sebastiani, O. De Pita, and G. Girolomoni Human CD25+ Regulatory T Cells Maintain Immune Tolerance to Nickel in Healthy, Nonallergic Individuals J. Immunol., December 1, 2003; 171(11): 5760 - 5768. [Abstract] [Full Text] [PDF]
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F. Maszyna, H. Hoff, D. Kunkel, A. Radbruch, and M. C. Brunner-Weinzierl Diversity of Clonal T Cell Proliferation Is Mediated by Differential Expression of CD152 (CTLA-4) on the Cell Surface of Activated Individual T Lymphocytes J. Immunol., October 1, 2003; 171(7): 3459 - 3466. [Abstract] [Full Text] [PDF]
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Y. Aragane, A. Maeda, A. Schwarz, T. Tezuka, K. Ariizumi, and T. Schwarz Involvement of Dectin-2 in Ultraviolet Radiation-Induced Tolerance J. Immunol., October 1, 2003; 171(7): 3801 - 3807. [Abstract] [Full Text] [PDF]
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K. Komura, M. Hasegawa, Y. Hamaguchi, E. Saito, Y. Kaburagi, K. Yanaba, S. Kawara, K. Takehara, M. Seki, D. A. Steeber, et al. Ultraviolet Light Exposure Suppresses Contact Hypersensitivity by Abrogating Endothelial Intercellular Adhesion Molecule-1 Up-Regulation at the Elicitation Site J. Immunol., September 15, 2003; 171(6): 2855 - 2862. [Abstract] [Full Text] [PDF]
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S. Artik, K. Haarhuis, X. Wu, J. Begerow, and E. Gleichmann Tolerance to Nickel: Oral Nickel Administration Induces a High Frequency of Anergic T Cells with Persistent Suppressor Activity J. Immunol., December 15, 2001; 167(12): 6794 - 6803. [Abstract] [Full Text] [PDF]
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 Y. Belkaid, K. F. Hoffmann, S. Mendez, S. Kamhawi, M. C. Udey, T. A. Wynn, and D. L. Sacks The Role of Interleukin (IL)-10 in the Persistence of Leishmania major in the Skin after Healing and the Therapeutic Potential of Anti-IL-10 Receptor Antibody for Sterile Cure J. Exp. Med., November 19, 2001; 194(10): 1497 - 1506. [Abstract] [Full Text] [PDF]
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 M. D. Griffin, W. Lutz, V. A. Phan, L. A. Bachman, D. J. McKean, and R. Kumar Dendritic cell modulation by 1alpha ,25 dihydroxyvitamin D3 and its analogs: A vitamin D receptor-dependent pathway that promotes a persistent state of immaturity in vitro and in vivo PNAS, May 18, 2001; (2001) 121172198. [Abstract] [Full Text]
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M. D. Griffin, W. Lutz, V. A. Phan, L. A. Bachman, D. J. McKean, and R. Kumar Dendritic cell modulation by 1alpha ,25 dihydroxyvitamin D3 and its analogs: A vitamin D receptor-dependent pathway that promotes a persistent state of immaturity in vitro and in vivo PNAS, June 5, 2001; 98(12): 6800 - 6805. [Abstract] [Full Text] [PDF]
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