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T Cells to Nonpetide Microbial Antigens1
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*
Division of Dermatology and
Department of Microbiology and Immunology, UCLA School of Medicine, Los Angeles, CA 90095;
Molecular Biology Institute and Departments of
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Medicine and
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Biological Chemistry and
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Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA 90095; and
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Division of Rheumatology and Immunology, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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T cells have the ability to rapidly expand and produce
IFN- in response to nonpeptide Ags of microbial pathogens, in
particular a class of compounds known as the prenyl phosphates. We
investigated the ability of IL-15, a T cell growth factor, to modulate
prenyl phosphate-induced T cell proliferation and cytokine
production. IL-15 significantly enhanced the expansion of T
cells in the peripheral blood after stimulation in vitro with
isopentenyl pyrophosphate. Moreover, using T cell clones, we
determined that IL-15-induced T cell proliferation was dependent on the
IL-2Rß chain but not the IL-2R
chain. We therefore studied the
IL-15R chain expression in human T cells in the presence or
absence of nonpeptide Ags. We found IL-15R mRNA expression in
IL-15-stimulated and Ag-stimulated human T cells but not in
resting T cells. Although IL-15 itself had little effect on the
production of IFN-, IL-15 plus IL-12 acted synergistically to
augment IFN- production by T cells. Moreover, we showed that
this increase in IFN- could be explained by the dual activation of
STAT1 and STAT4 by IL-15 and IL-12, respectively. Taken together, these
results suggest that IL-15 may contribute to activation of human
T cells in the immune response to microbial pathogens. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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T cells
are known
to participate in the immune response to microbial pathogens, as
evidenced by their accumulation in infectious disease lesions
and their expansion in response to various microbial agents (1, 2, 3, 4). A
unique aspect of human T cells is their ability to recognize
structurally defined nonpeptide Ags (5, 6, 7). These T cell Ags
were originally defined by the study of T cell responses to
mycobacteria and include isopentenyl pyrophosphate
(IPP),3 a metabolite found in
prokaryotic and eukaryotic cells (6). The presence of IPP in all
microbial pathogens allows T cells to participate in a wide
range of infectious processes (8).
T cells are also under the control of the local cytokine
environment, in terms of the magnitude and nature of the responses.
IL-2 was shown to selectively stimulate the growth of resting human
T cells (9), and a recent study demonstrated that IL-2 and IL-12
can synergize to induce expansion of
CD3+CD56+ T cells with cytolytic
activity (10). We have previously reported that IL-12 enhances T
cell activation on stimulation by prenyl phosphate derivatives
(11).
IL-15 is a powerful T cell growth factor that is produced at the site
of disease during the course of mycobacterial infection (12). We
therefore wanted to ascertain whether IL-15 might influence the
T cell responses to nonpeptide Ag. In this report, we determined
that IL-15 significantly enhances the expansion of human T cells
stimulated with IPP and can sustain the proliferation of human T
cell clones. The data demonstrate that IL-15 activation of human
T cells requires the IL-2Rß chain and that Ag induced expression of
the IL-15R chain. Moreover, we show that IL-15 can synergize with
IL-12 to stimulate human T cell production of IFN- after
culture with nonpeptide Ag and that this effect correlates with the
activation of STAT proteins involved in IFN- signaling.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The prenyl pyrophosphate Ag, IPP, was identified as a
mycobacterial Ag that stimulates T cells (6). For these studies,
synthetic IPP was obtained from Sigma (St. Louis, MO).
Reagents
The culture medium was RPMI 1640 (Life Technologies
Laboratories, Grand Island, NY) supplemented with 20 mM HEPES (Life
Technologies), 2 mM glutamine (Sigma), 0.1 mM sodium pyruvate (Life
Technologies), 1x MEM nonessential amino acids, 0.5x MEM essential
amino acids, 8% FCS (HyClone Laboratories, Logan, UT), 4% human serum
(Sigma), and 5 x 10-2 mM 2-ME (Life
Technologies) and adjusted to pH 7.4 with 2 N NaOH. In some
experiments, cells were cultured in supplemented medium with 10%
heat-inactivated human serum (in the absence of FCS), which did not
affect the level of expansion or proliferative responses.
Purified rIL-15 (sp. act., 3.33 x 105 U/µg) was obtained from Immunex (Seattle, WA). rIL-2 (sp. act., 2 x 106 U/ml) was purchased from Endogen (Woburn, WA). rIL-12 was a generous gift from Hoffmann La Roche (sp. act., 1.2 x 108 U/ml).
Abs against STAT3, STAT4, and STAT5 were purchased from Santa Cruz Biotechnology (Santa Cruz, CA). Anti-STAT1 Ab was used as previously described (13).
PBMC isolation and T cell expansion
Peripheral blood was obtained from healthy donors at the UCLA
Medical Center. PBMC were isolated from heparinized blood by density
gradient centrifugation on Ficoll-Paque (Pharmacia LKB Biotechnology,
Piscataway, NJ) and cultured in 24-well plates at 106
cell/ml with RPMI 1640 supplemented as described below. To induce the
activation of T cells, PBMC were incubated with IPP at 30 µM
or with medium alone, in the presence or absence of IL-12 and/or IL-15
or IL-2. Cells cultured with IPP for 4 days were harvested, and the
percentage of T cells was determined by flow cytometry. Cells
were labeled with biotinylated Ab to TCR- (anti-TCR-1 mAb
(14)) followed by streptavidin-PerCP (Becton Dickinson, San Jose, CA),
and analyzed by flow cytometry on a FACScan flow cytometer (Becton
Dickinson). Responding cells were evidenced by their blastoid
appearance. Lymphocytes were gated based on their forward scatter (FSC)
and side scatter (SSC) profile for each experiment. The percentage of
T cells from freshly isolated PBMC at time zero was also
determined.
T cell clones
The IPP-reactive T cell clones used in this study have been
described (15, 16). T cell clones were maintained by periodic
restimulation with PHA as previously described (17). T cell
proliferation assays were performed with T cell clones in the absence
of APC as described (7) to determine the effect of rIL-2, rIL-15, and
rIL-12 on IPP-induced T cell responses. In brief, resting
T cell clones were used 2 to 16 wk following restimulation. During this
resting time, T cells were maintained by the twice weekly
addition of IL-2 (40 IU/ml). The cells were deprived of IL-2 for 3 to 5
days before the experiments were performed. After 2 to 16 wk,
irradiated APC had died and the cells were 98 to 99% T cells as
determined by ungated one-color flow cytometry with the
anti-TCR1 mAb, as described (7). T cells were plated in
triplicate in round-bottom 96-well plates at 1 x
105 cells per well. When indicated, IPP was added (3
µM), and cells were cultured for 72 h at 37°C in a
CO2 incubator. Cells were pulsed with [3H]TdR
(0.5 mCi/well) and harvested 6 to 8 h later, and
[3H]TdR incorporation was measured in a liquid
scintillation counter. Titration experiments using proliferation assays
were performed to determine, for each recombinant cytokine, a
suboptimal dose stimulating weak or no proliferation by itself. The
following concentration of cytokines were subsequently used: rIL-15 (10
ng/ml); rIL-2 (10 ng/ml); rIL-12 (100 U/ml). Cultures were performed in
triplicate.
IL-2R blocking experiments
T cells were cultured with rIL-15 in the presence of
anti-IL-2R Ab (M-A251, PharMingen, San Diego, CA),
anti-IL-2Rß (Mik-ß2, PharMingen) Ab, or isotype control mouse
IgG for 72 h and then assayed for [3H]TdR
incorporation during the final 6 h of incubation.
IL-15R mRNA detection
Cells from T cell clones were cultured in the presence or
absence of nonpeptide Ag as described above. After 12 h of
incubation, cells were solubilized in 4 M guanidinium isothiocyanate
(18). RNA was isolated by phenol-chloroform extraction and ethanol
precipitation. DNA was removed using RNase-free DNase (10 U, Promega,
Madison, WI). cDNA was synthesized using Superscript reverse
transcriptase (Life Technologies Life Science) and oligo(dT) priming.
cDNA samples were amplified with IL-15R-specific PCR primers and
with Taq polymerase (Perkin-Elmer, Norwalk, CT) for 35
cycles of denaturation at 94°C for 30 s and annealing-extension
at 65°C for 45 s. PCR products were electrophoresed on 1.5%
agarose gels, transferred to filters, probed with a
32P-labeled IL-15R oligo internal to the PCR primers,
and visualized by autoradiography. Cell populations were normalized
according to the CD3 RNA by PCR. Oligonucleotide sequences for
CD3 PCR and probe have been published previously (18). The sequences
of oligonucleotide primer pairs used for PCR amplification of
IL-15-R were: 5'-TGCGTGTTGAACAAGGCCACGAAT-3' and
5'-TCTGTGGTTCCTGTGGAAGGTGAT-3'. The sequence of oligonucleotide probe
used to confirm the PCR product was:
5'-ACAACACAGCGGCCACAACAGCAGCTAT-3'. PBMC stimulated with PHA (5
µg/ml, Sigma) for 16 h were used as a positive control for cDNA
synthesis and PCR.
Intracellular analysis of cytokine production by T cells
Intracellular cytokine staining was used to determine the
cytokine production by T cells at the single cell level and was
performed as previously described (11). To induce the intracellular
accumulation of newly synthesized proteins, monensin (Calbiochem, La
Jolla, CA)(2 µM) was added for 2 h to the cells in culture with
the nonpeptide Ags. Cells were then harvested and stained for surface
expression of TCR. After being washed with PBS-2% FCS, the
cells were fixed with 4% paraformaldehyde in PBS for 30 min at room
temperature. Cells were washed with PBS-2% FCS and permeabilized with
0.5% (w/v) saponin (Sigma) in PBS for 30 min at room temperature.
FITC-conjugated anti-IFN- (used at the manufacturer’s
recommended concentrations, PharMingen) was added to the permeabilized
cells and allowed to bind for 30 min. Cells were then washed with
PBS-0.5% saponin and finally with PBS-2% FCS to allow membrane
closure. Samples were analyzed on a FACScan flow cytometer, and data
were analyzed using LYSIS software. Negative control samples were
incubated with irrelevant, isotype-matched Abs in parallel with all
experimental samples. To demonstrate Ab specificity, recombinant
cytokine blocking experiments were performed by preincubation of a 100-
to 1000-fold molar excess of recombinant cytokine with the
anti-cytokine Ab for 1 h before the addition of the sample.
This procedure resulted in >95% inhibition of the cytokine
detection.
Preparation of cell extracts
Whole-cell extracts were prepared from cells that were or were not exposed to cytokines (IL-12, 100 U/ml; IL-15, 100 ng/ml) for 45 min as described (13). Briefly, cells were washed with cold PBS and lysed in a buffer containing 50 nM Tris (pH 8.0), 300 mM NaCl, 0.5% Nonidet P-40, 10% glycerol, 1 mM EDTA, 1 mM DTT, 0.1 mM sodium vanadate, 1 mM phenylmethylsulfonyl fluoride, 0.5 µg of leupeptin per ml, and 3 µg of aprotinin per ml.
Gel mobility shift analysis
Gel mobility shift analysis was performed as previously described (19), using a 32P-end-labeled double-stranded oligodeoxynucleotide, high affinity serum-inducible element (hSIE), 5'-GTCGACATTTCCCGTAAATCGTCGA-3' (20). Briefly, whole-cell extracts were incubated with labeled probe in binding buffer for 20 min at room temperature before electrophoresis on 5% polyacrylamide gels and autoradiography. When used, Abs were incubated with cell extracts for 15 min at room temperature before addition of probe.
Statistical analysis
Nonparametric statistical analysis by the signed rank test for
paired samples was used for comparison of T cells after culture.
Values of p < 0.05 were considered significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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T cell proliferation
Initially, we sought to determine whether IL-15 could
enhance the expansion of human T cells stimulated with
nonpeptide Ag. We investigated the role of IL-15, alone or in
combination with IL-12, on human T cell expansion after
stimulation with the nonpeptide Ag IPP. PBMC from healthy donors were
cultured with IL-12, IL-15, or IL-12 + IL-15 in the presence or
absence of IPP. After 4 days of culture, the percentage of T
cells was determined by flow cytometry. The results of these
experiments indicated that IL-15 significantly increased the number of
T cells after stimulation with IPP (Fig. 1
B). These
IL-15-induced expansions were independent of V1 or V2 expression
or of high or low T cell starting populations, as has been
described for IL-2-induced T cell expansions (9). In contrast,
IL-12 had little effect on the expansion of T cells in response
to IPP (Fig. 1C). When IL-15 and IL-12 were
simultaneously added to PBMC and cultured with IPP, the increase in the
expansion of T cells was similar to the effect induced by IL-15
alone (Fig. 1D).
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T
cell proliferation using highly purified T cells. For these
experiments, four human T cell clones were used. T cell
clones cultured in the presence of IL-15 proliferated in a
dose-dependent manner (Fig. 2). In
contrast, three of four T cell clones cultured in the presence
of IL-12 proliferated weakly (data not shown and Fig. 3, media control). Moreover, we found
that IL-15 was a more potent inducer of T cell proliferation
than IL-2 (Fig. 2).
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T cells stimulated with nonpeptide Ag was investigated using the
T cell clones. IL-15 alone or in combination with IL-12
increased the proliferation of T cells stimulated with IPP (Fig. 3
), similar to the results observed with healthy donors (Fig. 1).
IL-15R interaction in the in vitro human T cell response to
IL-15
The effects of IL-15 are mediated through the IL-15R
composed of the IL-15, IL-2ß, and IL-2 chains (21, 22). To
determine whether IL-15 potentiates T cell responses through
this IL-15R, we used neutralizing Ab to specific subunits of the IL-2
receptor. T cell clones were cultured with IL-15 in the presence
of anti-IL-2R mAb or anti-IL-2Rß mAb. Anti-IL-2Rß mAb
inhibited the IL-15-induced proliferation of the T cells as
compared with an isotype-matched control (Fig. 4). The proliferation of the T
cells when the cells were cultured with IL-15 was not affected by the
presence of anti-IL-2R mAb. Because IL-15R complex consists of
IL-2Rß and IL-2R chains and the unique IL-15R chain, these
results indirectly suggested that human T cells express
IL-15R chain (21). To directly determine whether the IL-15R was
expressed by T cells, cells from a T clone were culture
with medium, with IL-15, with nonpeptide Ag, or with the Ag plus IL-15
for 12 h, and IL-15R mRNA was measured by PCR. The results
showed that IL-15 induced the IL-15R chain and that IL-15R mRNA
was detectable only in stimulated T cells (Fig. 5).
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T cell cytokine response to
nonpeptide Ag
To test the effect of IL-15 alone or in combination with
IL-12 on the cytokine profile produced by T cells stimulated
with prenyl pyrophosphate Ag, we measured cytokine production at the
single cell level. PBMC from healthy donors were cultured with IL-12,
IL-15, or IL-12 + IL-15 in the presence or absence of IPP for 4
days, and the number of IFN-+ T cells was
determined by flow cytometry. Culture of PBMC with IL-15 or IL-12
alone, in either the presence or the absence of Ag, did not have a
significant effect on the percentage of IFN-+ T
cells (Fig. 6).
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production by T cells was observed (Fig. 7A, p < 0.01,
signed rank test). As shown in a representative donor of 12, PBMC
cultured in the presence of IL-15 + IL-12 did not induce
detectable +-IFN-+ T cells, whereas
PBMC stimulated with IPP and cultured with IL-15 + IL-12 induced
16.5% of the T cells to produce IFN- (Fig. 7B). In the same group of healthy donors, we found
that IL-2 + IL-12 also were synergistic in inducing IFN-
production (Fig. 8), in accordance with
previous results (11). We also investigated IL-4 production by T
cells in culture with IL-15, IL-12, or both cytokines, in the presence
or absence of IPP. In contrast to IFN- production, the addition of
IL-15 and IL-12 did not augment IL-4 production, which remained at
<5% of T cells, whether the experiments were performed in the
absence or presence of Ag (data not shown). These results show that
IL-15 can synergize with IL-12 to preferentially stimulate human
T cells to produce the type 1 cytokine, IFN-.
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+ T cells
after stimulation of T cell clones with IPP, in the presence of
IL-15, IL-12, or IL-15 + IL-12. A higher IFN- response was
observed when IL-15 and IL-12 were added together in the presence of Ag
(Fig. 9). Two of the clones, HF.2 and
DG.SF13, had a low number of IFN-+ cells when stimulated
in the presence of IL-15 or IL-12. However, in the presence of both
cytokines, a much higher percentage of HF.2 and DG.SF13 cells produced
IFN- when stimulated with IPP (Fig. 9). IL-15 and IL-12 had an
additive effect on the number of IFN--producing cells for the 12G12
and DG.SFP6 clones (Fig. 9). These results indicate that IL-15 together
with IL-12 are potent inducers of IFN- in T cell clones
stimulated with a nonpeptide Ag.
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T
cells
IL-15 and IL-12 are cytokines that deliver intracellular
signals through JAK-STAT proteins, a family of signal transduction
molecules that have critical signaling roles for IFN- (23).
Specifically, binding sites for STATs 1, 4, 5, and 6 in the first
intron of the human IFN- gene were detected (23). We wanted to
determine whether the observed synergistic effect of IL-15 and IL-12 on
IFN- production by-IPP stimulated T cells could be explained
at the molecular level, on the basis of STAT activation. To examine the
particular STAT proteins activated by IL-15 in IPP-stimulated T
cells, we performed gel shift assays using a radiolabeled hSIE
oligonucleotide probe, which binds several STAT proteins and complexes.
The results indicate that IL-15 induced a distinct hSIE-binding complex
as compared with media alone (Fig. 10A). To determine
the identity of this hSIE-binding complex induced by IL-15, specific
Abs against STAT1, STAT3, STAT4, and STAT5 were used. We observed that
anti-STAT1 Ab supershifted the hSIE-binding complex induced by
IL-15 (Fig. 10A), indicating that the complex induced
by this cytokine contained STAT1. The anti-STAT3, -4, and -5 Abs
had no effect on the binding complex (Fig. 10A).
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T cells with IL-12
alone or in combination with IL-15 (Fig. 10B). IL-12
alone induced a distinct hSIE-binding complex as compared with the
IL-15 lane. Furthermore, as expected, anti-STAT4 Ab blocked the
formation of the complex induced by IL-12 (Fig. 10B).
These observations were in agreement with the tyrosine phosphorylation
of STAT4 observed in response to IL-12 (24). As a control,
anti-STAT5 Ab showed no effect (Fig. 10B). We
observed that when IL-15 and IL-12 were added together to T
cells, both IL-15-induced and IL-12-induced hSIE-binding complexes
appeared. Anti-STAT1 treatment supershifted the component of the
complex induced by IL-15. In comparison, anti-STAT3 Ab had no
effect (Fig. 10B). These data indicated that STAT1
and STAT4 are components of the DNA-binding complexes induced by IL-15
and IL-12, respectively. Furthermore, the data suggest that the
synergistic action of IL-15 and IL-12 on IFN- release is due to the
simultaneous activation of STAT1 and STAT4 proteins. |
Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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T cells react with nonpeptide Ag released by
extracellular and intracellular bacteria, it has been proposed that
these lymphocytes may be easily activated when infectious agents enter
the body (25). Because this recognition is facilitated by an
extracellular presentation pathway (7), it was therefore suggested that
the recognition of these phosphorylated metabolites could be one
strategy used by the immune system to signal the presence of live
microorganisms to the host (25). In the present study, we investigated
the role of IL-15 in the T cell response to nonpeptide Ag. By
examining T cell proliferation and intracellular cytokine expression,
we determined that IL-15 significantly augments the response of human
T cells to nonpeptide Ag and can synergize with IL-12 to
stimulate IFN- production from these cells.
IL-15 and IL-2 are two T cell growth factors that share many features;
however, further recent studies revealed dramatic differences between
these two cytokines in their cellular sites of synthesis and
in the control of their synthesis and secretion (26, 27). In contrast
to IL-2, IL-15 appears to be more abundantly expressed in a widely
variety of tissues, including placenta, skeletal muscle, kidney, and
activated monocytes/macrophages (28). In the present work, we showed
that IL-15, a cytokine involved in the immune response to mycobacterial
infection (12), augments T cell responses to isoprenoid Ag and
could also sustain the proliferation of human T cell clones even
in the absence of Ag and to a greater degree than IL-2. These data are
consistent with other studies, indicating that IL-15 augments T
cell activation in response to infectious agents such as salmonellosis
and malaria (29, 30). Thus, the production of IL-15 by cells of the
innate immune response such as macrophages, and the higher
susceptibility of human T cells to IL-15, might be important in
the early stages of the immune response to infection when
IL-2-secreting cells are not yet recruited. Furthermore, since there is
a high degree of redundancy in the function of cytokines, it has been
speculated that IL-15 could act as a compensatory mechanism to IL-2 in
situations in which IL-2 is diminished (31).
The redundancy of cytokines can be partially explained by the sharing
of common receptor subunits among members of the receptor family, as in
the case of IL-15 and IL-2 (27). The immunologic activities of these
two cytokines partially overlap because IL-2R and IL-15R use the same
ß- and -chains (21, 28, 32). However, there are also distinct
activities due to use of specific -chains. By studying the mechanism
of IL-15 action on human T cells, we demonstrated that IL-15
used the ß-chain, common to both IL-2R and IL-15R, in accord with
previous studies (21) but did not use the IL-2R chain. Although it
was recently reported that IPP triggered the expression of the IL-2R
chain on T cells (33), our results using highly purified
T cells indicated that IL-15 did not use the IL-2R chain. Moreover,
we showed for the first time the expression of IL-15R chain in
activated human T cells. These data indicate that the difference
in the T cell-proliferative response to IL-2 and IL-15 could be
due to the expression of high affinity IL-15R on activated T
cells. Coexpression of IL-15R with IL-2Rß is required to
significantly enhance affinity for IL-15, and the expression of
IL-15R chains requires cellular activation (22).
Previous studies of TCR-ß-bearing cells showed that the T
cell cytokine pattern is influenced by cytokines produced by innate
immune responses (34, 35). We have recently shown that the rapid
response of T cells after stimulation with prenyl pyrophosphate
Ags is characterized by the selective induction of IFN- with no
induction of IL-4 and that IL-12 in combination with IL-2 augmented the
IFN- response (11). In the present report, we studied the ability of
IL-15, alone or in combination with IL-12, to influence human T
cell response to nonpeptide Ag to determine the role of IL-15 in the
priming for IFN-. Our data with nonpeptide Ag-stimulated PBMC
demonstrate that IL-15 did not increase the IFN- response of
T cells to IPP. Moreover, no effect of IL-12 alone was observed on the
IFN- production by Ag-stimulated PBMC. However, IL-15 can synergize
with IL-12 to induce IFN- production by T cells stimulated
with nonpeptide Ag. The synergistic action of IL-15 and IL-12 in
inducing IFN- production was equivalent to the combined activity of
IL-2 plus IL-12 (11). Furthermore, using highly purified T cell
populations that recognize prenyl pyrophosphate Ag in the absence of
other accessory cells (7), we were able to determine that IL-15
potentiates IL-12 activity on IFN- production by
nonpeptide-stimulated T cells. Similar results were recently
reported for NK cells, showing that IL-12 and IL-15 are synergistic in
their ability to increase proliferation, cytotoxicity, and IFN-
production from these cells (36). An additive effect of IL-12 and IL-15
on mouse CD4+ T cells has also been described
(37).
We wanted to determine the molecular mechanism responsible for the
synergistic effect of IL-15 and IL-12 on IFN- production by T
cells. Previously, it has been shown that IL-15 induced DNA-binding
activity of STAT3 and STAT5 in T and NK cells (38). We found for the
first time that IL-15 induced STAT1 phosphorylation, and in this way
our data provide evidence that IL-15 can induce other STAT proteins
involved in IFN- production depending on the cell type. We also
confirmed that IL-12 induced the nuclear DNA-binding complex that
contained STAT4 and that the combination of IL-15 and IL-12
simultaneously activated STAT1 and STAT4. It has been recently
demonstrated that IL-12 induced strong tyrosine phosphorylation of
STAT4 and variable weak phosphorylation of STAT3 and that it activates
STAT1 in NK cells (39). Therefore, differential activation of both
separate and overlapping STAT proteins by IL-15 and IL-12 may provide a
molecular basis for the similarities and differences in the actions of
these cytokines on T cells. Since these STAT proteins have been
shown to induce IFN- promoter activity (23), the synergistic action
of IL-15 and IL-12 on IFN- production by Ag-stimulated T
cells probably is regulated by the simultaneous induction of multiple
STAT proteins.
Our results demonstrate that IL-15 is involved in the activation of
human T cells in response to prenyl pyrophosphate Ags. Moreover,
we showed that IL-15 can synergize with IL-12 to stimulate human
T cell production of IFN- and that this effect could be explained at
the molecular level by the activation of STAT1 and STAT4 proteins by
IL-15 and IL-12. Therefore, we speculate that IL-15 contributes to
cell-mediated immunity against infection by stimulation of Ag-activated
T cells that produce the type 1 cytokine pattern.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Robert L. Modlin, Division of Dermatology, 52-121 CHS, UCLA School of Medicine, 10833 Le Conte Ave., Los Angeles, CA 90095. E-mail address:
3 Abbreviations used in this paper: IPP, isopentenyl pyrophosphate; FSC, forward scatter; SSC, side scatter; hSIE, high affinity serum-inducible element.
Received for publication September 30, 1997. Accepted for publication January 7, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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/ß and requires a DNA element to which a tyrosine-phosphorylated 91-kDa protein binds. Proc. Natl. Acad. Sci. USA 90:6806.-chains on human peripheral blood mononuclear cells and effect of immunosuppressive drugs on receptor expression. J. Immunol. 157:2813.[Abstract]
. J. Immunol. 157:126.[Abstract]
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A. B. Kamath, L. Wang, H. Das, L. Li, V. N. Reinhold, and J. F. Bukowski Antigens in tea-beverage prime human Vgamma 2Vdelta 2 T cells in vitro and in vivo for memory and nonmemory antibacterial cytokine responses PNAS, May 13, 2003; 100(10): 6009 - 6014. [Abstract] [Full Text] [PDF]
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 D. Zhou, X. Lai, Y. Shen, P. Sehgal, L. Shen, M. Simon, L. Qiu, D. Huang, G. Z. Du, Q. Wang, et al. Inhibition of Adaptive V{gamma}2V{delta}2+ T-Cell Responses during Active Mycobacterial Coinfection of Simian Immunodeficiency Virus SIVmac-Infected Monkeys J. Virol., March 1, 2003; 77(5): 2998 - 3006. [Abstract] [Full Text] [PDF]
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 I. Van Rhijn, L. H. Van den Berg, C. W. Ang, J. Admiraal, and T. Logtenberg Expansion of human {gamma}{delta} T cells after in vitro stimulation with Campylobacter jejuni Int. Immunol., March 1, 2003; 15(3): 373 - 382. [Abstract] [Full Text] [PDF]
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J. Dunne, S. Lynch, C. O'Farrelly, S. Todryk, J. E. Hegarty, C. Feighery, and D. G. Doherty Selective Expansion and Partial Activation of Human NK Cells and NK Receptor-Positive T Cells by IL-2 and IL-15 J. Immunol., September 15, 2001; 167(6): 3129 - 3138. [Abstract] [Full Text] [PDF]
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B. Cipriani, G. Borsellino, H. Knowles, D. Tramonti, F. Cavaliere, G. Bernardi, L. Battistini, and C. F. Brosnan Curcumin Inhibits Activation of V{gamma}9V{delta}2 T Cells by Phosphoantigens and Induces Apoptosis Involving Apoptosis-Inducing Factor and Large Scale DNA Fragmentation J. Immunol., September 15, 2001; 167(6): 3454 - 3462. [Abstract] [Full Text] [PDF]
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R. Ishimitsu, H. Nishimura, T. Yajima, T. Watase, H. Kawauchi, and Y. Yoshikai Overexpression of IL-15 In Vivo Enhances Tc1 Response, Which Inhibits Allergic Inflammation in a Murine Model of Asthma J. Immunol., February 1, 2001; 166(3): 1991 - 2001. [Abstract] [Full Text] [PDF]
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 M. Umemura, K. Hirose, W. Wajjwalku, H. Nishimura, T. Matsuguchi, Y. Gotoh, M. Takahashi, M. Makino, and Y. Yoshikai Impaired IL-15 production associated with susceptibility of murine AIDS to mycobacterial infection J. Leukoc. Biol., January 1, 2001; 69(1): 138 - 148. [Abstract] [Full Text]
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 T. A. Fehniger and M. A. Caligiuri Interleukin 15: biology and relevance to human disease Blood, January 1, 2001; 97(1): 14 - 32. [Full Text] [PDF]
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V. E. Garcia, K. Uyemura, P. A. Sieling, M. T. Ochoa, C. T. Morita, H. Okamura, M. Kurimoto, T. H. Rea, and R. L. Modlin IL-18 Promotes Type 1 Cytokine Production from NK Cells and T Cells in Human Intracellular Infection J. Immunol., May 15, 1999; 162(10): 6114 - 6121. [Abstract] [Full Text] [PDF]
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L. P. Perera, C. K. Goldman, and T. A. Waldmann IL-15 Induces the Expression of Chemokines and Their Receptors in T Lymphocytes J. Immunol., March 1, 1999; 162(5): 2606 - 2612. [Abstract] [Full Text] [PDF]
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