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Laboratory of Experimental Immunology, Department of Pathophysiology, Faculty of Medicine, Catholic University of Leuven; and
Laboratory of Cell Growth, Differentiation, and Development, Flanders Interuniversity Institute for Biotechnology, Catholic University of Leuven, Belgium
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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production after TCR/CD3 triggering. We here investigated the capacity
of IL-12 to modify the expression on T cells of CD40 ligand (CD40L or
CD154), a molecule transiently expressed on activated T cells and known
to be of utmost importance for cognate interaction with B cells and for
activation of dendritic cells and macrophages. Our data demonstrate
that IL-12 up-regulates CD40L expression on anti-CD3-activated
human peripheral blood T cells. For optimal induction of CD40L, IL-12
synergizes with IL-2 as well as with other costimulatory interactions,
such as B7/CD28. The effect of IL-12 was observed at both the protein
and the mRNA level. T cells costimulated by IL-12 provided more
efficient help for IL-4-dependent B cell proliferation and for IgG
production than when activated in the absence of IL-12. This helper
activity was blocked by an mAb against CD40L, indicating that the
effect of IL-12 on B cells is mediated indirectly through CD40L. The
data thus suggest that the effects of IL-12 on cellular and humoral
immune responses are partly mediated through CD40L induction. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and is transiently expressed on activated
T cells (1, 2). Its receptor, CD40, is a 45- to 50-kDa glycoprotein,
member of the TNF receptor superfamily (1), and is expressed on B
cells, monocytes, dendritic cells (DC), and thymic epithelial cells
(3, 4, 5). The CD40L-CD40 interaction was first shown to be critical for
Th cell-dependent Ab responses (6, 7, 8, 9), as also evidenced by the failure
of isotype switching in humans and mice with a mutated CD40L (10, 11).
The CD40L-CD40 interaction induces production of proinflammatory
cytokines (TNF- and IL-1ß) as well as gelatinase production by
monocytes and macrophages (12, 13) and is required for macrophage
tumoricidal activity and microbicidal activity (14). Furthermore,
CD40L-CD40 interaction is important for up-regulation of APC functions,
including up-regulation of B7 expression and induction of IL-12
production (15, 16, 17, 18, 19). IL-12 is a heterodimer cytokine comprised of a
40-kDa (p40) and a 35-kDa (p35) subunit that are linked by a disulfide
bond. IL-12 is produced by macrophages, B cells, and DC and exerts
multiple effects on NK cells and T cells (20). As its main activity,
IL-12 promotes the differentiation of naive CD4+ T cells
into Th1 effector cells (21, 22, 23) and induces IFN- production by T
cells and NK cells in synergism with IL-2, mitogens, phorbol diester,
anti-CD3 mAb, or alloantigens (24). Most in vivo effects of IL-12
seem to be mediated through IFN-. However, antimicrobial activity of
IL-12 in experimental visceral leishmaniasis has also been demonstrated
in IFN- gene knockout mice (25). Moreover, IL-12 has been found to
influence IgG production, especially IgG1 and IgG2b (26, 27, 28, 29, 30, 31). These
data indicate that IL-12 has effects on macrophages and B cells that
are not mediated through IFN-. In view of the importance of the
CD40L-CD40 interaction for humoral immunity, and for antimicrobial
activity of macrophages, we considered CD40L expression as a potential
alternative target of IL-12 activity. We here report that IL-12 indeed
enhances functional CD40L expression on T cells. |
Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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All subjects donating blood for this study were healthy volunteers of both sexes, aged 20 to 50 yr. PBMC were isolated from heparinized venous blood on Ficoll-Hypaque density gradients. After washing, the cells were resuspended at a concentration of 5 x 106 cells/ml in complete culture medium consisting of RPMI 1640 (Boehringer Ingelheim, Heidelberg, Germany) supplemented with 2 mM L-glutamine, penicillin (100 U/ml), streptomycin (100 µg/ml), and 10% iron-supplemented bovine calf serum (HyClone, Logan, UT). Monocytes were removed by cold agglutination by rotating tubes for 30 min at 4°C. The agglutinated monocytes were sedimented out, and the lymphocytes were further purified using Lymphokwik-T (One Lambda, Inc., Los Angeles, CA) supplemented with complement-fixing anti-NK (anti-Leu 11b (anti-CD16), anti-Leu 7 (anti-CD57), and anti-NKH-1A (anti-CD56)) mAb as previously reported (32). The resulting T cell preparations contained >99% CD3+ and <1% CD16+ cells; CD14+ monocytes and HLA-DR+ cells were not detected. These cells could not be activated by PHA or rIL-2 alone (10 U/ml).
Cell lines
The P815 cell line is an NK-resistant DBA/2 derived murine
mastocytoma cell line that expresses mouse FcRII and FcRIII. The
P815/CD80 cell line, transfected with human CD80 cDNA, was a gift from
L. L. Lanier (DNAX Research Institute of Molecular and Cellular
Biology, Palo Alto, CA) (33). The 3T6 mouse fibroblast cell line,
transfected with CD40L, was a gift from K. Thielemans (Free University
of Brussels, Brussels, Belgium). The P815 cells and the 3T6 cells were
cultured in complete culture medium supplemented with gentamicin (50
µg/ml), sodium pyruvate (1 mM/ml), nonessential amino acids (1/100),
50 µM 2-ME, and 10% FCS (Gibco, Paisley, Scotland). Geniticin (1
mg/ml) was added every 1 to 2 wk for selecting transfected cells. The
cells were given fresh medium every 2 or 3 days.
Isolation of tonsillar B and T lymphocytes
Fresh tonsils were obtained from children undergoing tonsillectomies. The tissue was dispersed by cutting with scalpel blades. Fragments were allowed to pass through a filter, and cell suspensions were collected. B cells were prepared by two cycles of rosetting with AET-treated SRBC and removal of E-rosetting cells on Ficoll-Hypaque density gradients. T cells were prepared by two cycles of Lymphokwik-T (One Lambda Inc., Canoga Park, CA). The resultant B cell preparations contained 95% CD20+ cells, and the tonsillar T cell preparations contained 97% CD3+ cells as determined by FACS analysis.
Cytokines and mAbs
Recombinant IL-12 was a gift from Genetics Institute (Cambridge,
MA). Recombinant IL-4 was obtained from Innogenetics (Gent, Belgium).
Anti-CD3 mAb UCHT-1 (IgG1) was a gift from Dr. P. Beverley, Imperial
Research Cancer Fund (London, U.K.). The clones producing anti-CD3
mAb OKT3 and anti-CD11b OKM1 were obtained from American Type
Culture Collection (Rockville, MD). Anti-CD28 mAb 9.3 was a gift from
C. June (Naval Medical Research Institute, Bethesda, MD). Anti-CD2 mAb
9.6 (IgG2a) was obtained from Oncogen (Seattle, WA), and mAb 9–1 was
purchased from XOMA Corp. (Berkeley, CA). mAb 9.6 blocks E rosette
formation and is directed against the CD58-binding epitope. The mAb 9-1
detects a CD2 neo-epitope on activated T cells. Humanized anti-Tac
mAb (directed at the p55 chain of the human lymphocyte IL-2R (CD25))
and humanized Mikß1 (a mAb to the p75 chain of the IL-2R (CD122))
were gifts from Dr. J. Hakimi (Hoffmann-La Roche, Nutley, NJ). A
neutralizing anti-IL-2 mAb (B-G5) was purchased from Innotest
(Besançon, France). Anti-IL-10R mAb (clone 37607.11) was
purchased from R&D Systems (Minneapolis, MN). A neutralizing
anti-IFN- mAb (D9D10) was a gift from Dr. M. de Ley (Department
of Biochemistry, Catholic University of Leuven, Leuven, Belgium).
Anti-CD40L mAb M90 (IgG1) (34) was a gift from W. Fanslow (Immunex
Corp., Seattle, CA). Anti-CD40L-FITC (clone 24-31) was obtained from
Ancell Corp. (Bayport, MN).
Cell culture conditions and FACS analysis for CD40L expression
For stimulation with immobilized anti-CD3, wells were first
coated with OKT3 (final concentration, 5 µg/ml) in 300 µl of PBS
for 4 h at 37°C and then washed three times with PBS. Purified
peripheral blood T cells (5 x 105) were cultured
either on OKT3-coated plates or with anti-CD3 mAb UCHT-1 (1 µg)
bound to FcR on mitomycin C-treated P815 cells (1 x
106). All cultures were set up in a 1-ml volume in the
presence or the absence of rIL-12 (1 ng unless otherwise indicated) in
24-well culture plates. CD80 (transfected into P815 cells; 1 x
106/ml), soluble anti-CD28 mAb 9.3 (0.5 µg/ml), or a
pair of anti-CD2 mAbs (9-1 (2 µg/ml) and 9.6 (2 µg/ml)) were
included in the above cultures to provide a second signal. The culture
plates were incubated in a 37°C, humidified atmosphere of 5%
CO2. After 16, 40, and 64 h of incubation, the cell
pellets were stained with either anti-CD40L-FITC mAb or
isotype-matched negative control Ab for 30 min at 4°C. Following two
washes with PBS, the cells were fixed in 1% paraformaldehyde in saline
and analyzed on a FACSort flow cytometer (Becton Dickinson, Mountain
View, CA).
RNA isolation and reverse transcription-PCR
T cell cultures were harvested 4 or 16 h after the initial stimulation as described above. Approximately 5 x 106 stimulated T cells were pelleted and directly used for RNA isolation. Total RNA was isolated by the guanidium isothiocyanate method (35) and quantified spectrophotometrically. cDNA was prepared from 2.5 µg of total RNA using the SuperScript reverse transcriptase preamplification system (Life Technologies, Grand Island, NY) with oligo(dT) primer. The cDNA samples were then subjected to PCR analysis using the following primers: 5'-ACATACAACCAAACTTCTCCC-3' and 5'-AGATGTTGTTTTACTGCTGGC-3' for detection of CD40L, and 5'-GCTCACCATGGATGATGATATCGCC-3' and 5'-GGATGCCTCTCTTGCTCTGGGCCTC-3' for detectin of ß-actin as a cDNA quality control. Samples were amplified by Goldstar Taq polymerase (Eurogentec, Seraing, Belgium) by 24 cycles of denaturation at 94°C for 30 s, annealing at 60°C (CD40L) or at 56°C (ß-actin) for 30 s, and extension at 72°C for 1 min. PCR products were analyzed by electrophoresis on 1% agarose gels and visualized by ethidium bromide staining.
Analysis of Th cell activity for B cell proliferation and IgG production
Tonsillar B cells (1 x 105/well) and tonsillar T cells (irradiated, 3000 rad, 105/well) were cultured with soluble anti-CD3 mAb UCHT-1 (1 µg/ml) and mitomycin C-treated P815 mouse mastocytoma cells (1 x 106/ml), either parental or CD80 transfected, in the presence or the absence of rIL-12 (1 ng/ml) in 96-well flat-bottom microculture plates. Recombinant IL-4 (100 ng/ml) was added to all cell cultures. Anti-IL-2 (2 µg/ml) and anti-IL-2R mAbs (1 µg/ml for each) were also added to block the effects of endogenous IL-2 on CD40L expression and B cell proliferation. The final volume of each cell culture was 200 µl. After 5 days, cells were pulsed with 1 µCi of [3H]thymidine. Eight hours later, cells were harvested, and thymidine incorporation was measured using a beta counter.
Unseparated tonsillar mononuclear cells (containing B and T cells) (1 x 106/ml) were also cultured with soluble anti-CD3 mAb UCHT-1 (1 µg/ml) and mitomycin C-treated P815 mouse mastocytoma cells (1x106/ml), either parental or CD80 transfected, in the presence or the absence of rIL-12 (1 ng/ml) in 5-ml snap-cap Falcon tubes (Becton Dickinson, Lincoln Park, NJ) at 37°C in 5% CO2. The final volume of each cell culture was 1 ml. After 7 days, cells were spun down, and cell-free supernatant was harvested. The concentrations of human IgG were estimated by ELISA as previously described (9).
Statistical analysis
Statistical analysis was performed with the Wilcoxon test for paired samples. p < 0.05 was considered significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Different concentrations of rIL-12 were added to cultures of
purified T cells stimulated with immobilized anti-CD3 mAb OKT3, and
cells were then stained for CD40L expression. CD40L was not detected on
resting T cells or T cells incubated with rIL-12 alone (data not
shown). The expression of CD40L was weakly induced by anti-CD3
stimulation and significantly enhanced by rIL-12 (Table I
). Figure 1 shows that increasing doses of rIL-12
progressively enhanced the expression of CD40L on
anti-CD3-activated T cells. The optimal concentration of rIL-12 was
1 ng/ml. The highest CD40L expression on anti-CD3-activated T cells
in the presence of rIL-12 occurred after a 40-h cell culture, with a
decline of CD40L expression thereafter (Fig. 2).
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, addition of anti-CD28 mAb or anti-CD2 mAbs enhanced CD40L
expression, but rIL-12 still further augmented and prolonged the
expression of CD40L, again with maximal CD40L expression after 40
h of culture. IL-12 enhances CD40L expression on human T cells when costimulated with CD80
In previous studies we showed that the binding of CD28 on T cells
to its natural ligand CD80 on APC in the presence of anti-CD3 mAb
enhances and prolongs CD40L expression (9). We therefore tested whether
CD80 and IL-12 would synergize in inducing CD40L. To this end, we used
mouse mastocytoma P815 cells transfected with CD80 and coated with
anti-CD3 (via FcR binding) to stimulate T cells. As shown in
Figure 3 and Table II, up-regulation of CD40L induction by
CD80 was confirmed. IL-12 did not influence CD40L expression when T
cells were stimulated with anti-CD3 on P815 cells. When, however, T
cells were cultured with CD80-transfected P815 cells and anti-CD3
mAb, rIL-12 strongly enhanced CD40L expression, thus pointing to a
synergy between CD80 and IL-12 for induction of CD40L.
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Since IL-12 induces IFN- and IL-10 production by T cells (24, 36), we asked whether CD40L induction by IL-12 might be mediated
indirectly through these other cytokines. To this end, a blocking mAb
against the IL-10R or a neutralizing anti-IFN- mAb was added to
the cultures. Neither anti-IL-10R nor anti-IFN- mAb affected
the induction of CD40L expression by IL-12 (data not shown). Since
endogenous IL-2 plays an important role in the induction of CD40L on T
cells (37), we also evaluated whether IL-12 requires the presence of
IL-2 to enhance CD40L. T cells were stimulated with soluble
anti-CD3 mAb cross-linked by either parental P815 cell FcR or
CD80-transfected P815 cells. To parallel cultures, a neutralizing
anti-IL-2 mAb and two different anti-IL-2R (anti-Tac and
Mikß1) mAbs were added to block all IL-2 activity (38). As shown in
Figure 3, anti-IL-2 mAb and anti-IL-2R mAbs strongly, but not
completely, reduced CD40L expression on T cells cultured with either
anti-CD3 mAb plus CD80-transfected cells. Importantly, rIL-12 still
enhanced CD40L expression when IL-2 activity was blocked, indicating
that CD40L induction by rIL-12 is IL-2 independent. Together, the data
indicate that both IL-2-dependent and IL-2-independent signals (CD80
and IL-12) are involved in CD40L regulation.
Analysis of CD40L mRNA expression in purified human T cells costimulated by IL-12
Next, we studied the effect of IL-12 on the expression of CD40L
mRNA in activated T cells. T cells were incubated for 4 or 16 h
with mitomycin C-treated wild-type P815 cells or CD80-transfected P815
cells in the presence or the absence of rIL-12. Soluble anti-CD3
mAb was added as a primary signal. Total RNA was isolated, and reverse
transcription-PCR reactions using specific primers for CD40L and
ß-actin were performed. As shown in Figure 4, no CD40L mRNA was detected in T cells
cultured with P815 cells alone (lane 5) or in
P815 cells and anti-CD3 mAb in the presence (lane
7) or the absence (lanes 2 and6) of rIL-12 in either 4- or 16-h cell cultures. However,
CD80-transfected P815 cells induced early expression (at 4 h) of
CD40L mRNA (lane 3) in anti-CD3 activated
T cells. Interestingly, the addition of rIL-12 did not enhance CD40L
mRNA at 4 h of stimulation (lane 4), but
clearly enhanced CD40L mRNA expression at 16 h of stimulation
(lane 9). Thus, IL-12 seems to have a late
effect on CD40L mRNA.
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We studied the functional relevance of IL-12-induced CD40L
expression by analyzing the effect of IL-12 on T cell-dependent B cell
proliferation and IgG production. This Th cell activity has been shown
to be CD40L dependent (7, 8). Tonsillar B cells were cultured with
rIL-4 and irradiated autologous T cells. B cell proliferation was
measured by [3H]thymidine incorporation. As shown in
Figure 5, no significant B cell
proliferation was found in the cultures where B cells were cocultured
with T cells stimulated with anti-CD3 mAb and P815 cells. However,
B cell proliferation was induced in the presence of CD80-costimulated T
cells, and this was further enhanced by rIL-12. When anti-CD40L mAb
was added, B cell proliferations were completely blocked. A control mAb
did not show any effect on B cell proliferation. In the experiments
shown in Figure 5, IL-2 activity was blocked with mAb to IL-2 and to
IL-2R - and ß-chains, because IL-2 also strongly influences CD40L
expression. However, similar data were obtained when IL-2 activity was
not blocked (data not shown). To exclude a direct effect of IL-12 on B
cells, B cells were cultured with 3T6 mouse fibroblasts transfected
with CD40L and exogenous rIL-4 in the presence or the absence of
rIL-12. Recombinant IL-12 did not have any effect on B cell
proliferation in this system (data not shown). Thus, the effect of
IL-12 on B cell proliferation most likely proceeds via modulation of
the interaction of CD40L on anti-CD3 activated T cells and of CD40
on B cells.
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, large amounts of IgG were produced
when T cells were stimulated with anti-CD3 mAb presented on
P815/CD80 cells. Interestingly, the addition of rIL-12 further enhanced
IgG production. Blocking experiments with anti-CD40L mAb resulted
in partial inhibition of IgG production by B cells. With relevance to
the effects of IL-12, anti-CD40L inhibited IgG production in the
presence of rIL-12 to a similar extent as in the absence of IL-12.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Requirements for optimal CD40L induction on T cells are incompletely understood. CD40L is not expressed on resting T cells. CD3-TCR triggering or ionomycin alone is sufficient to induce some CD40L expression (6, 39, 40). CD40L can be up-regulated by PMA (39, 40), and endogenous IL-2 production was found to be important for the expression of CD40L (37). Moreover, we have previously reported that ligation of B7 with CD28 strongly up-regulates and prolongs CD40L expression on anti-CD3-activated T cells (9). Roy et al. reported that Ag-induced expression of CD40L on TCR transgenic T cells was inhibited by Abs to class II MHC, CD4, and LFA-1, but not by CTLA-4 Ig, anti-B7-1, or anti-B7-2 (41). Ding et al. reported that induction of CD40L is only partially inhibited by CTLA-4 Ig, and that CD40L could be induced on CD4+ T cells from CD28-deficient mice (42). Thus, B7-independent costimulatory mechanisms are also involved in enhancing the expression of CD40L.
IL-12, as shown in this study, is such a helper signal that
up-regulates CD40L expression. Although IL-12 greatly induces IFN-
and IL-10 production (24, 36), it is unlikely that induction of CD40L
by IL-12 is an indirect effect of IFN- or IL-10, since a
neutralizing anti-IFN- mAb or anti-IL-10R mAb did not block
the effect of IL-12 on CD40L expression. Moreover, exogenous rIL-10
inhibited CD40L expression (our unpublished observations), and IFN-
has been shown by others to inhibit the expression of CD40L in mice
(40). The inhibition of IFN- on CD40L expression was not confirmed
in the human system (our unpublished observations). Although endogenous
IL-2 plays an important role in the induction of CD40L (37), it is not
likely that induction of CD40L by IL-12 is mediated through IL-2.
First, our data (43) as well as other reports (44) showed that IL-12
does not affect IL-2 production. Second, IL-12 still enhanced CD40L
expression in the presence of a neutralizing anti-IL-2 mAb and
anti-IL-2R mAbs that have previously been shown to block all IL-2
activity (38). On the other hand, it is clear from these experiments
that IL-12 synergizes with CD80 and IL-2 in inducing CD40L. Therefore,
optimal induction of CD40L occurs when IL-12, CD80, and IL-2 are all
present to signal the T cells.
The signal transduction mechanism by which IL-12 induces CD40L requires
further investigation. It is also not clear yet whether IL-12 has an
effect on the transcription of the CD40L gene or on CD40L mRNA
stability in activated T cells. IL-12 is the only cytokine identified
to date that can induce phosphorylation of STAT4 (45, 46). In
STAT4-deficient mice, all IL-12 functions tested were disrupted,
including the induction of IFN-, mitogenesis, enhancement of NK
cytolytic function, and Th1 differentiation (47, 48). These results
demonstrate that STAT4 is essential for mediating responses to IL-12.
It will therefore be of major interest to study binding of
phosphorylated STAT4 to the promotor region of the CD40L gene.
Another interesting point in our experimental results is the synergy
between CD80 and IL-12 in inducing CD40L. Synergistic effects between
both helper signals have also been found for IFN- and IL-10
production (43, 49). IL-12R chains are expressed by activated T and NK
cells. Two IL-12R chains, termed ß1 and ß2, have been identified to
date. The IL-12R ß1 subunit is expressed in both Th1 and Th2 cells,
while the IL-12R ß2 subunit is selectively lacking in Th2 cells (50, 51). Recent reports showed that anti-CD28 mAb and IL-2 augment the
expression of IL-12R ß1 and induce high affinity IL-12 binding (which
correlates with ß2-chain expression) to anti-CD3-activated T
cells (52). Lack of high affinity IL-12 binding can explain why IL-12
had no effect on CD40L expression when T cells were stimulated with
P815 plus anti-CD3 mAb alone. When costimulated with CD80, the
strong effects of IL-12 on T cell CD40L expression most likely result
from induction of high affinity IL-12R expression.
To confirm that the effect of IL-12 on CD40L expression was
functionally relevant, we have studied cognate T cell interactions with
B cells. We choose not to perform studies with macrophages, because
IFN- induction by IL-12 would interfere strongly with the effect of
CD40L on these cells. Optimal activation of B cells by Th cells
requires direct contact between the two cell types through CD40 and
CD40L (1). When we cultured tonsillar T (irradiated) and B cells
together with anti-CD3 mAb and P815-CD80 cells, we found that
addition of IL-12 clearly enhanced B cell proliferation and IgG
production. An effect of IL-12 on B cells can be excluded because
resting and activated B cells do not express IL-12R (53). Moreover, in
control experiments in which we cultured B cells with 3T6 mouse
fibroblasts transfected with CD40L and exogenous rIL-4, IL-12 did not
have any effect on B cell proliferation (data not shown). Thus,
enhancement of B cell growth by IL-12 can be considered as proceeding
entirely through effects on Th cell function. Besides cognate
interactions, cytokines are also involved in T cell-dependent B cell
activation. IL-12 strongly enhances IFN- production by T cells, but
IFN- inhibits CD40L-induced B cell proliferation (54). IFN- is
thus probably not involved in enhanced B cell proliferation as observed
here. Moreover, we have added an excess of rIL-4 to the T-B cell
cultures for B cell proliferation to exclude indirect effects of IL-12
on T cell cytokine secretion. Finally, B cell proliferation was
completely blocked by an mAb against CD40L. Similar data were also
obtained for IgG production, which was enhanced by IL-12 and partially
blocked by anti-CD40L. Therefore, we suggest that IL-12 has a
helper effect on B cell function as a result of up-regulated CD40L
expression on T cells.
IL-12 favors Th1 development and enhances IFN- production and CTL
activity (20). Our findings now indicate that in vivo effects of IL-12
(26, 27, 28, 29, 30, 31) on humoral immunity might result from up-regulating CD40L
expression on T cells and their helper activity for B cell growth and
Ab production. This effect of IL-12 on CD40L expression might also
modulate inflammatory processes, because CD40-CD40L interaction results
in increased cytokine and gelatinase production by macrophages (12, 13, 17, 18, 19) and enhances antimicrobial defenses against intracellular
organisms (14). Antileishmanial effects of IL-12 have been observed in
IFN- knockout mice (25), and additional experiments should be
performed to study whether the IFN--independent effect is partly
mediated by CD40L. Although the biologic significance of our findings
for APC physiology requires further investigation in IFN- knockout
mice or IFN-R knockout mice, the induction of CD40L by IL-12 is
probably part of an important regulatory circuit between APC and T
cells. B7 and IL-12 both enhance CD40L expression on activated T cells
and their IFN- production in a synergistic way (49). CD40L and
IFN-, in turn, directly stimulate IL-12 production by macrophages
and DC (17, 18, 19), and they enhance the expression of costimulatory
molecules such as B7-1, B7-2, and intercellular adhesion molecule-1 on
the APC (5, 15, 16). Finally, a signal delivered to T cells via CD40L
triggering can up-regulate T cell activation and synergize with IL-12
to further induce IFN- production (55).
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Jan L. Ceuppens, Laboratory of Experimental Immunology, U.Z. Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium. E-mail address:
3 Abbreviations used in this paper: CD40L, CD40 ligand; DC, dendritic cells.
Received for publication June 16, 1997. Accepted for publication October 17, 1997.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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production and type 1 cytokine responses. Immunity 4:471.[Medline]
production. Eur. J. Immunol. 26:1621.[Medline]
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M. Martin, R. E. Schifferle, N. Cuesta, S. N. Vogel, J. Katz, and S. M. Michalek Role of the Phosphatidylinositol 3 Kinase-Akt Pathway in the Regulation of IL-10 and IL-12 by Porphyromonas gingivalis Lipopolysaccharide J. Immunol., July 15, 2003; 171(2): 717 - 725. [Abstract] [Full Text] [PDF]
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P. A. Kosinski, J. Laughlin, K. Singh, and L. R. Covey A Complex Containing Polypyrimidine Tract-Binding Protein Is Involved in Regulating the Stability of CD40 Ligand (CD154) mRNA J. Immunol., January 15, 2003; 170(2): 979 - 988. [Abstract] [Full Text] [PDF]
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 B. O. Lee, L. Haynes, S. M. Eaton, S. L. Swain, and T. D. Randall The Biological Outcome of CD40 Signaling Is Dependent on the Duration of CD40 Ligand Expression: Reciprocal Regulation by Interleukin (IL)-4 and IL-12 J. Exp. Med., September 2, 2002; 196(5): 693 - 704. [Abstract] [Full Text] [PDF]
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 M. Martin, D. J. Metzger, S. M. Michalek, T. D. Connell, and M. W. Russell Distinct Cytokine Regulation by Cholera Toxin and Type II Heat-Labile Toxins Involves Differential Regulation of CD40 Ligand on CD4+ T Cells Infect. Immun., July 1, 2001; 69(7): 4486 - 4492. [Abstract] [Full Text] [PDF]
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G. Pirtskhalaishvili, G. V. Shurin, A. Gambotto, C. Esche, M. Wahl, Z. R. Yurkovetsky, P. D. Robbins, and M. R. Shurin Transduction of Dendritic Cells with Bcl-xL Increases Their Resistance to Prostate Cancer-Induced Apoptosis and Antitumor Effect in Mice J. Immunol., August 15, 2000; 165(4): 1956 - 1964. [Abstract] [Full Text] [PDF]
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N. C. Matthews, M. Wadhwa, C. Bird, F. E. Borras, and C. V. Navarrete Sustained Expression of CD154 (CD40L) and Proinflammatory Cytokine Production by Alloantigen-Stimulated Umbilical Cord Blood T Cells J. Immunol., June 15, 2000; 164(12): 6206 - 6212. [Abstract] [Full Text] [PDF]
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S. Skov, M. Bonyhadi, N. Odum, and J. A. Ledbetter IL-2 and IL-15 Regulate CD154 Expression on Activated CD4 T Cells J. Immunol., April 1, 2000; 164(7): 3500 - 3505. [Abstract] [Full Text] [PDF]
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A. C. Grammer, R. D. McFarland, J. Heaney, B. F. Darnell, and P. E. Lipsky Expression, Regulation, and Function of B Cell-Expressed CD154 in Germinal Centers J. Immunol., October 15, 1999; 163(8): 4150 - 4159. [Abstract] [Full Text] [PDF]
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M. D. Sharma, M. Leite de Moraes, F. Zavala, C. Pontoux, and M. Papiernik Induction and Inhibition of CD40-CD40 Ligand Interactions: A New Strategy Underlying Host-Virus Relationships J. Immunol., November 15, 1998; 161(10): 5357 - 5365. [Abstract] [Full Text] [PDF]
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