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Department of Biology and the University of California at San Diego Cancer Center University of California at San Diego, La Jolla, CA 92093; and Trudeau Institute, Saranac Lake, NY 12983
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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. These
results suggest there is a much more efficient response of CD4 memory T
cells to Ag re-exposure and that the expanded functional capacity of
memory cells will promote a rapid development of effector functions,
providing more rapid and effective immunity. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To address the activation requirements of memory T cells, we have developed an adoptive transfer system that allows recovery of a substantial number of resting, Ag-experienced, Ag-specific, TCR Tg T cells (9) with a known history of optimized stimulation with peptide Ag. The use of optimal doses of Ag and polarizing cytokines in vitro ensures that the memory cell population is derived from uniformly activated Ag-experienced cells. The host is Ag free and we can directly compare bona fide naive and resting memory CD4 T cells at the same frequency and with the same receptor so that qualitative differences between the two populations can be clearly delineated.
We have shown that when Th1- and Th2-polarized primary effector T cells are generated in vitro from naive CD4 T cells of pigeon cytochrome c (PCC)-specific TCR Tg mice (AND) and are transferred to adult thymectomized irradiated bone marrow reconstituted (ATXBM) recipients, the CD4+ T cells return to a resting state, persist for long periods of time (up to 1 year), and produce a cytokine profile similar to that of primary effectors (9). The persistence of this population, its resting memory phenotype, and the uniformly activated, Ag-experienced nature of the transferred population, as well as their enhanced functional capacity, identify these cells as canonical resting memory cells (2, 9).
Data from several earlier studies have argued that memory phenotype T cells, isolated based on cell surface markers, are less dependent on costimulation for activation compared with naive T cells (10, 11, 12, 13, 14), but the populations tested could have easily included cells that were activated or were responding to environmental Ags. Recent studies with TCR Tg CD8+ memory cells have presented evidence to suggest that these cells may be hyperresponsive to Ag compared with naive cells (15). However, the requirements for Ag triggering and costimulatory interactions for induction of proliferation and cytokine secretion by isolated Ag-specific CD4+ memory T cells are largely unknown. Using a high dose of peptide, we previously showed that CD4+ memory T cells could proliferate in response to a variety of APC and that stimulation with a highly cross-linking, high-affinity reagent, anti-CD3, could induce proliferation in the absence of APC (16). Similarly, resting memory cells were less dependent on costimulatory molecule interactions for cytokine secretion (3) when anti-CD3 was used as a source of a TCR signal. In contrast, recently generated effector T cells can proliferate and secrete many cytokines in the apparent absence of costimulation (17), although B7-1 (CD80) and ICAM-1 (CD54) costimulation are still required for optimal IL-2 secretion (16, 17, 18, 19).
Although it is well known that systemic Ab responses in primed animals are faster than primary responses, this could be due to increased frequency of Ag-specific T and B cells rather than a qualitative change in the kinetics of response. The kinetics of memory CD4 T cell response to Ag has not been carefully examined. A rapid response of memory CD4 T cells that produce high quantities of an array of effector cytokines could contribute to the speed of immune responses by immediately inducing B cell and macrophage function and thus promoting a much more rapid development of Ab and effector cells, leading to an increase in protection against pathogens.
In this study, we have measured the kinetics of T cell response and determined how the activation of CD4+ memory cells is influenced by Ag dose and by TCR affinity. We have directly compared resting memory cells to resting naive cells and effector cells. We find that memory CD4 T cells can be qualitatively distinguished from naive cells (which express the same TCR) by their faster production of cytokines, which leads to enhanced proliferation and cell division, as well as by the ability to respond to APC presenting lower densities of Ag. These results have important implications for understanding how the generation of memory CD4 T cells contribute to secondary responses and confer immune protection following natural or therapeutic immunization.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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H-2b/k and H-2k
V
11/Vß3 AND TCR Tg mice (Tg) were bred in the animal facilities at
the University of California, San Diego or at the Trudeau Institute and
were used at 2–6 mo of age. Tg males (H-2b), on
a C57BL/6 background (20), were bred to B10.BR females to
produce Tg H-2b/k offspring. Tg
H-2b/k mice were bred repeatedly (>12
generations) to B10.BR mice to obtain Tg H-2k
offspring. B10.BR mice were bred in facilities at the University of
California, San Diego or the Trudeau Institute. All transfers were done
in syngeneic mice.
Naive CD4+ T cell isolation
Spleen and lymph node cells from TCR Tg mice were isolated over
nylon wool columns, treated with a panel of depleting Abs and
complement, and purified over Percoll (Sigma, St. Louis, MO) gradients
to obtain small resting CD4+ T cells (16, 18). Spleen and lymph node cells were depleted with 3.155
(anti-CD8), CA4.2.12 and M5/114.15.2 (anti-class II), J11d
(anti-heat stable antigen, CD24), 33D1 (anti-CD11c), and M1/70
(anti-CD11b). Rat Abs were cross-linked with MAR18.5 (mouse
anti-rat 
-chain) and then incubated with guinea pig complement,
baby rabbit complement, and DNase I (Sigma). High-density resting
CD4+ T cells were isolated using discontinuous
Percoll gradient centrifugation (four layers, 40, 52, 63, and 80%).
Cells at the 63%/80% interface were collected and used for T cell
assays and for effector generation. Cells were routinely 90–99%
CD4+Vß3+.
Effector T cell generation
Th1 (IL-12 effector) and Th2 (IL-4 effector) cells were
generated from naive CD4+ TCR Tg cells as
described (9, 21). Briefly, purified
CD4+ T cells (3 x
105/ml) were stimulated with syngeneic T-depleted
spleen cells (1.5 x 106/ml), 10 µM PCC
(fragment 88-104) (PCCF), and 10 ng/ml murine IL-2 (from X63-IL-2 cell
line). Th1 and Th2 cells were generated by adding 2 ng/ml recombinant
murine IL-12 and 10 µg/ml anti-IL-4 (11B11) or 10 ng/ml IL-4
(from X63-IL-4 cell line) and 10 µg/ml anti-IFN- (XMG1.2),
respectively. Effector T cells were used 4–5 days after culture, and
were routinely 95–99%
CD4+Vß3+ cells. Previous
studies have established that few if any Tg+
memory phenotype cells develop in this particular TCR Tg mouse strain
(21, 22).
Memory cell generation
Th1 and Th2 memory cells were generated as described previously (9) from transfer of Th1 and Th2 effectors, respectively. Briefly, 20 x 106 in vitro-generated effector T cells from AND mice and 3 x 106 (T-depleted) bone marrow cells (B10. BR) were transferred by injection into thymectomized, heavily irradiated B10.BR (syngeneic) hosts (9). One to 5 mo later, spleen and lymph nodes were removed and purified as described above for naive cells. Purified cells were routinely >90% CD4+ and 50–80% Vß3+. No thymic remnants or CD8+ T cells were found in reconstituted ATXBM recipients upon sacrifice. We usually recovered 2–5 x 106 CD4+Vß3+ T cells/mouse (7–21 wk posttransfer) after purification. In other studies, we have found that only the CD4 T cells expressing the Tg TCR respond to in vitro restimulation with PCCF peptide, as reculture produces memory effectors which are >95–98% Tg+ (G. Huston and S. L. Swain, unpublished data). All studies indicate that the memory cells in the adoptive host are resting, and we find that only 2% of the Tg+ cells incorporate 5-bromo-2'-deoxyuridine over a 5-day labeling period (H. Hu and S. L. Swain, unpublished data).
APC
The DCEK.ICAM fibroblast line (referred to here as
B7-1+ICAM-1+) which was
transfected with I-Ek, ICAM-1, and which
expresses B7.1 constitutively, was used as described
previously(17, 18). T-depleted spleen APC were prepared as
described elsewhere (21, 23) using 3.155 (anti-CD8),
RL172.4 (anti-CD4), HO13.4 (anti-Thy1.2), and F7D5K6
(anti-Thy1.2). For B cell preparations, 33D1 and M1/70 Abs were
used in addition to the above Abs and were cross-linked with MAR18.5.
The dense fraction of cells (from the 80/63 interface) was collected on
a Percoll gradient and then adhered to plastic at 37°C for 1 h.
Resulting cells were small and 
95% B220+. APC
populations were treated with mitomycin C (50–100 µg/ml; Sigma) for
45 min at 37°C before use.
Analysis of in vitro responses
Cells were cultured in RPMI 1640 (Irvine Scientific, Santa Ana, CA) supplemented with 200 µg/ml penicillin, 200 U/ml streptomycin, 4 mM glutamine, 5 x 10-5 M 2-ME, 10 mM HEPES, and 7.5% FCS (HyClone, Logan, UT). An equal number of CD4+Vß3+ T cells (naive, effector, or memory) (1–3 x 105/ml), determined by FACS analysis before plating, were stimulated in 0.2-ml volumes with mitomycin C-treated APC (0.3–1 x 105 fibroblast APC/ml) and various doses of PCCF (0.001–100 µM). In some experiments, APC were pulsed with peptide for 2 h before culture with T cells. Proliferation was measured at 48, 72, or 96 h of culture by incorporation of [3H]thymidine (1 µCi/well; ICN Pharmaceuticals, Irvine, CA) during the last 12–18 h. To follow cell division, T cells were labeled with 5- and 6-carboxyfluorescein diacetate succinimidyl ester (CFSE, C-1157; Molecular Probes, Eugene, OR) and analyzed after 1–3 days by flow cytometry. Briefly, T cells (5 x 107/ml) were labeled with 1 µM CFSE for 15 min at 37°C and then washed with cold PBS before use (24). T cells were counterstained with PE-labeled Vß3 (PharMingen, San Diego, CA) before flow cytometry analysis. CFSE histograms were gated on Vß3-positive cells. Studies using CFSE-labeled cells in vivo have shown an 80–90% loss of fluorescence after 1 day followed by stabilization and virtually no loss of fluorescence at later times (up to 8 wk) (25).
Cytokines and cytokine assays
Recombinant cytokines IL-2, IL-4, IFN-, and IL-5 were
obtained from culture supernatants of X63.Ag8–653 cells transfected
with murine cDNA for the respective cytokines (26).
Recombinant murine IL-12 was kindly provided by Dr. Stanley Wolf
(Genetics Institute, Cambridge, MA). The following anti-cytokine
Abs were purified from ascites or were prepared by Amicon (W. R.
Grace & Co., Beverly, MA) concentration of hybridoma supernatants:
11B11 (anti-IL-4), XMG1.2 and R46A2 (anti-IFN-), and TRFK4
and TRFK5 (anti-IL-5). IL-4, IFN-, and IL-5 were detected by
ELISA using 11B11, R46A2, and TRFK5, respectively, as coating Abs, and
biotinylated-rat anti-mouse IL-4 (BVD6) (PharMingen),
biotinylated-XMG1.2, and biotinylated-TRFK4, respectively, as second
step reagents. The data were quantitated from standard curves using
recombinant cytokines and were expressed in ng/ml. One nanogram of
IFN- equals 0.9 U of protein and 1 ng of IL-5 equals 0.8 U of
protein. Supernatants were collected at 24–28 h unless noted
otherwise. IL-2 was detected by bioassay as described previously
(6) by measuring proliferation of the NK cell line in the
presence of 11B11 (anti-IL-4). IL-2 was quantitated from a standard
curve using a stock that was referenced to recombinant murine IL-2
(PharMingen).
Flow cytometry
Anti-L-selectin (CD62L, clone Mel-14), anti-CD44 (clone IM7.8.1), anti-CD25 (clone 7D4), and anti-CD45RB (clone 23G2) were concentrated by Amicon ultrafiltration (Amicon, Beverly, MA) or ammonium sulfate and used at 10 µg/ml. PE-labeled anti-Vß3, FITC-, and cychrome-labeled anti-CD4 were purchased from PharMingen. FACS analysis was performed on a FACScan flow cytometer (Becton Dickinson, Mountain View, CA) with Cellquest software. Data were gated for viable CD4+Vß3+ cells.
Peptide analogues
Peptides of PCC were synthesized in the peptide facility at the University of California, San Diego and purified by HPLC. The peptides used had similar binding to I-Ek (27, 28) and had either a single amino acid substitution at residue 99 (K to A, K99A) or an insertion of 4 amino acids between residues 99 and 100 (QASA). The amino acid sequences were as follows: PCCF (88-104), KAERADLIAYLKQATAK; K99A, KAERADLIAYLAQATAK; and QASA, KAERADLIAYLKQASAQATAK.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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ll Tg TCR (specific for PPC peptide PCCF) can be reisolated
from the recipients of in vitro-generated Th1 or Th2 effectors. The
recovered cells have a memory phenotype and retain their Th1/Th2
polarization (9). Naive cells are originally stimulated
only with peptide Ag, and no Ag is introduced into the adoptive hosts.
Moreover, there is good evidence that no environmental Ags stimulate
the Tg T cells (21, 22). These facts and the fact that the
recovered Tg+ cells are uniformly small, resting
cells which do not express activation Ags, but do express markers of Ag
experience such as CD44 (3, 9), identify them as resting
memory cells. We will refer to the T cells recovered from adoptive
hosts after 6 or more weeks as CD4 memory cells. Expression of CD4 and
Vß3 on the T cell subsets used in this study is shown in Fig. 1
(top panel).
Approximately 80% of the recovered memory CD4+
cells retained expression of the Vß3 and V11 TCR chains as shown
in Fig. 1 (bottom panels) with TCR expression on memory
cells similar or only slightly lower compared with those of naive T
cells (bottom panels). In four other experiments, expression
of the Tg TCR chains was equivalent or slightly lower on memory cells
vs naive cells (data not shown). In each of the experiments described,
the cell density has been readjusted before restimulation so that the
responses measured are from an equal number of
CD4+Vß3+ cells from each
group.
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Phenotype of T cells recovered from ATXBM recipients
Previously, we have shown that T cells with a memory phenotype can
be recovered from adoptively transferred ATXBM mice and that the cell
surface phenotype was stable over the 3–8 wk analyzed. As shown in
Fig. 2, the
CD4+Vß3+ T cells
recovered from ATXBM recipients were small (low forward light scatter
(FSC)) CD44high
IL-2R-(CD25). Recovered memory cells also
down-regulated expression of CD45RB; however, this marker was not
reliable in distinguishing memory from naive cells in this system. As
seen previously in a similar adoptive transfer model (31),
a subset of recovered T cells (approximately half) retained L-selectin
(CD62L) expression and may represent T cells that homed to lymph nodes.
Before transfer, effector T cells were nearly all
L-selectin+ (see Fig. 2). Compared with naive
cells, memory cells expressed higher levels of CD44 and higher levels
(2–3-fold) of both LFA-1 and ICAM-1 (Refs.32, 33, 34 , and
P. R. Rogers and S. L. Swain, unpublished data), but lower
levels of CD45RB and L-selectin compared with naive T cells. Memory
cells could also be distinguished from effectors by cell size and
expression of IL-2R. When memory cells are activated in vitro with
APC and Ag to become memory effector cells, they up-regulate expression
of CD45RB (100%+), IL-2R
(100%+), and L-selectin
(65%+) and retain high levels of CD44 (data not
shown).
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. Naive T cells secreted
predominantly IL-2, whereas memory T cells secreted IL-4, IL-5, and
IFN-, in addition to IL-2. However, in contrast to their Th1 and Th2
effector counterparts, memory T cells made 5–30 times less IL-4, IL-5,
and IFN-. Table I also shows that memory T cells retained their
original Th1 and Th2 polarization as shown previously in this model
(9). Polarization was even retained after 4 days of
activation in vitro (data not shown). We did not detect any significant
differences in the levels of cytokines secreted from memory T cells
recovered at 7 wk vs 21 wk after transfer (data not shown).
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Several studies have suggested that memory CD8 T cells are more
responsive to lower dose Ag than naive cells (13, 14, 15)
using proliferation as a readout. To confirm these observations in the
CD4 system, we directly compared naive and memory CD4 T cells for their
response to doses of native peptide (PCCF). Fig. 3 shows the proliferative response of
memory and naive T cells to
B7-1+ICAM-1+ APC presenting
various doses of peptide (PCCF) over a 2–4-day time course. Fig. 3a shows the response of naive and memory T cells to both
high-dose (2 µM) and low-dose (.002 µM) Ag at 48, 72, and 96
h. Both subsets showed a dose-dependent increase in DNA synthesis with
high-dose Ag over the 48–96-h time period. However, at low Ag dose
(0.002 µM), memory T cells responded significantly better than naive
T cells at 48 and 72 h, with responses ending in both populations
at 96 h. Both subsets showed a decrease in DNA synthesis at
96 h, which may be due to cytokine depletion and cessation of
proliferation. When analyzed over a wide range of doses, as shown in
Fig. 3b, both subsets responded in a dose-dependent manner
to increasing doses of Ag at 48 (left) and 72
(right) h but memory T cells responded better than naive T
cells at low doses of Ag (0.0002–0.02 µM). Thus, the memory
population is clearly able to respond better and with more rapid
kinetics when Ag is limiting.
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, CFSE-labeled T cells were cultured
with B7-1+ICAM-1+ APC and 1
µM PCCF peptide for up to 3 days. At each time point (days 1–3),
cells were counterstained with Vß3-PE and the number of cell
divisions was determined by flow cytometry. Fig. 4 shows histograms of
CFSE-labeled (Vß3-gated) cells on days 0–3. After 1 day, few or no
naive (Fig. 4, top) and memory (Fig. 4, bottom)
cells divided, although both populations showed diminished CFSE
staining due to decay of fluorescence (see Materials and
Methods) (25). Importantly, after 2 days, naive cells
underwent up to two divisions whereas memory cells underwent up to
three divisions. For naive T cells, on day 2, 35% of cells divided
twice, 32% divided once, and 23% of T cells showed no division
(overlapping with the profile at day 1). In contrast to naive T cells,
a large fraction of memory cells have undergone three divisions. For
memory T cells, 30% of cells divided three times, 31% twice, 15%
once, and 
17% showed no division. After 3 days, nearly all T cells
had divided at least once, but memory cells still showed more cell
divisions compared with naive T cells. Therefore, under these Ag dose
conditions, approximately equal numbers of naive and memory cells have
entered the dividing pool; however, memory cells appeared to be going
through more cell divisions or were dividing sooner vs naive T cells.
Under conditions of limiting Ag dose or costimulation, it remains
possible that more memory cells are initially recruited into the
dividing pool of cells in addition to showing more or sooner cell
divisions.
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To further explore memory cell response requirements, we examined
whether the ability of T cells to proliferate varies as the TCR
affinity for the peptide/MHC complex changes. We used peptide analogues
which have altered affinity for the TCR (25, 32). Native
peptide (PCCF) or PCCF analogues with higher (QASA) and lower (K99A)
abilities to stimulate T cells were added to Tg T cell subsets cultured
with a fixed number of APC
(B7-1+ICAM-1+). The peptide
analogues have similar affinity for MHC (I-Ek)
but have either a substitution in a TCR contact residue (K to A at
residue 99) or an insertion of four amino acids (QASA) between residues
99 and 100 (27, 28, 35). The K99A analogue triggers cells
less well and presumably binds the AND TCR with lower affinity,
whereas the QASA analogue triggers more efficiently and presumably
binds with higher affinity. The response of naive and memory cells to
doses of PCCF and peptide analogues presented by the costimulatory
fibroblast (B7-1+ICAM-1+)
is shown in Fig. 5 (top
panels) and by relatively costimulation-poor small B cells in the
bottom panels. In the top panel, memory cells
responded at lower doses of peptide and with higher maximum response
compared with naive T cells with each peptide tested, but response to
the "low affinity peptide" (K99A) was only seen at the very highest
dose. As expected, maximal responses to the high affinity peptide
(QASA) occurred at low dose, to the native PCCF at a slightly higher
dose, and to the weak affinity peptide only at the very highest dose.
Thus, memory cells show the same hierarchy in response to peptide
analogues or peptide affinity but show a greater proliferative response
vs naive cells. Memory cells are very sensitive to affinity, but are
triggered either at low doses of high affinity (QASA) or high doses of
low-affinity peptide (K99A).
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(bottom
panels). In this experiment, the APC were prepulsed with peptide
to ensure exclusive presentation by the purified small B cells. Whereas
naive T cells responded poorly to peptide (even the high-affinity
analogue QASA), memory cells responded very well. These data are in
agreement with and extend our previous studies (16) which
showed that memory cells could respond to resting B cells presenting a
single high dose of peptide or to CD3 cross-linking in the absence of
costimulation. In addition to Th2 memory cells (Figs. 3 and 5), Th1
memory cells also showed enhanced responses with low doses of peptide.
As seen in Fig. 6, Th1 memory cells
incorporated more thymidine vs naive T cells in response to both
B7-1+ICAM-1+ fibroblast
(Fig. 6, left) and B cell APC (Fig. 6, right). In
addition to increased responses at low doses of peptide (0.01–1 µM),
maximal thymidine incorporation was seen at a 10-fold lower dose of
peptide in memory cells (0.1 µM vs 1 µM for fibroblast APC and 1
µM vs 10 µM for B cell APC).
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Although naive and memory cells secrete cytokines in response to
high doses of Ag, we wanted to determine whether memory cells were more
like naive cells or effectors in response to varying doses of Ag
presented on highly costimulatory APC. We assessed the effect of
peptide dose in cultures of CD4 subsets stimulated with highly
costimulatory APC
(B7-1+ICAM-1+). In Fig. 7, results are presented normalized for
maximum cytokine production achieved by each population. Since the
quantities of IFN- (from Th1 subsets) and IL-4 (from Th2 subsets)
produced by naive CD4 T cells are negligible, these cytokines are not
shown for naive cells. For the same reasons, since the production of
Th1 cytokines by Th2 cells and vice versa was negligible they are not
shown. All CD4 T cell subsets showed an Ag dose-dependent increase in
cytokine secretion. Naive CD4 cells required 1 µM PCCF for optimum
IL-2 production, whereas effectors secreted near optimum levels at 0.1
µM peptide. Memory cells were more like naive cells than effectors in
the dose of Ag required for half maximal IL-2 secretion. Memory and
naive cells required 0.06 µM peptide for half maximal IL-2
secretion, and memory cell secretion of IL-4 occurred at a similar
level of Ag (Fig. 7, top, and bottom,
respectively). Thus, memory and naive CD4 T cells seem to have similar
Ag dose requirements for cytokine accumulation. The dose of Ag required
for half maximal IFN- secretion was somewhat higher (Fig. 7, middle). In contrast, effector cells only required 0.01
µM peptide for half maximal IL-2 production. In addition, effectors
required 5–15-fold less Ag than memory cells for half maximal
secretion of IL-4 and IFN-. Therefore, at low Ag doses
(10-3–10-2 µM), only
effector cells can secrete detectable levels of cytokines.
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To determine whether resting memory cells can actually respond
faster than naive cells, and thus behave more like effector cells, we
compared the kinetics of cytokine secretion and accumulation in
cultures of memory CD4 T cells to that of naive and effector cells,
each activated with highly costimulatory APC presenting a high dose of
Ag (10 µM). Representative results from one of several experiments,
this one using Th2-polarized effectors and memory cells, are shown in
Fig. 8. Naive T cells secreted IL-2 that
was only barely detectable after 4 h with maximal accumulation of
IL-2 in supernatants at 24–48 h. No IL-4 was detected in culture
supernatants, even up to 60 h (Fig. 8 and data not shown). Th2
memory cells secreted similar amounts of IL-2 (as shown in Table I),
but supernatant accumulations reached peak levels more rapidly compared
with naive T cells, with significant amounts of IL-2 already detected
by 4 h and peak amounts found at 12 h. In addition to IL-2,
Th2 memory cells secreted substantial amounts of IL-4 (and IL-5; data
not shown) which were initially detectable by 2 h. IL-4
accumulation was maximal at 24 h whereas IL-5 accumulation (data
not shown) was maximal at 48 h. Compared with memory cells,
effector T cells made much higher amounts of IL-2, IL-4 (Fig. 8), and
IL-5 (Table I) but with similar or only slightly faster kinetics (Fig. 8). Memory cells were also similar to effector cells in the kinetics of
cytokine mRNA induction with maximal transcripts seen at 1–2 h after
stimulation (X. Zhang et al., manuscript in preparation). Therefore, it
appears that memory T cells produced cytokines at a rapid pace more
like effector than naive cells. IL-2 and IL-4 are know to be autocrine
growth factors for T cells, and the early production of cytokines by
memory cells may lead to faster or enhanced proliferation of memory vs
naive T cells.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, Fig. 8, and our unpublished data). In addition, memory
cells are able to proliferate in response to APC at lower Ag dose and
to peptides, which results in lower affinity interactions. Taken
together, these properties suggest that a key component of the enhanced
protection against reinfection, which accompanies specific
immunization, is the ability of memory CD4 T cells to "jump start"
the secondary immune response by quickly providing an array of highly
effective cytokines to B cells and other APC, such as macrophages,
before these cells are themselves highly activated (i.e., without the
requirement for APC with high levels of costimulation) and before
available Ag has risen to high levels. This is in marked contrast to
the behavior of naive CD4 T cells in the primary response, which
require recognition of high densities of Ag on professional APC such as
dendritic cells (36, 37), and which are found to interact
with B cells only after several days. These changes can be expected to
be of particular importance in memory responses to infectious agents,
because the response potentially could be triggered early in infection
and protective responses mounted before the infectious agent replicated
extensively.
We have previously shown that naive CD4 T cells from TCR Tg mice can be
activated in vitro, transferred to recipient mice (ATXBM), and
recovered up to 1 year later. Recovered T cells in this and earlier
studies display a memory phenotype (9), proliferate, and
secrete cytokines in response to specific peptide presented by APC. We
and others have shown that memory cells (recovered from adoptively
transferred hosts) are resting cells in the G0
state of the cell cycle. The definition of these cells as memory T
cells is based on several major criteria which include Ag-experience
(assured by the protocol for generating the cells), phenotype (shown in
Fig. 2), and function. When naive Tg cells are cultured in vitro with
Ag and costimulatory APC, no resting cells are found after 4 days and
the recovered cells are uniformly transgene positive (Fig. 1, effector)
and have all undergone multiple rounds of division (D. Jelley-Gibbs
et al., unpublished data). Thus, the Tg cells derived from this
effector population after transfer to adoptive hosts are by definition
Ag experienced. Moreover, we know that the cells have all been exposed
to optimal levels of Ag in the presence of high levels of
costimulation. This is critical because memory phenotype cells isolated
from normal mice, not purposely stimulated with Ag, that have been used
in many previous studies have an unknown history.
Memory T cells, as defined operationally by their ability to give
strong response to previously injected Ag, have been previously
characterized as small resting cells that are
CD44high L-selectinlow
CD45RBlow (or CD45RO+ in
human) (33) and high for expression of many integrin and
adhesion molecules (34, 38). LFA-1 and Ly6C, in addition
to CD44 and CD25, have been useful in discriminating memory cells in a
CD8 adoptive transfer model (34). In our adoptive transfer
model, the CD4 cells recovered after 7–21 wk were small resting
IL-2R-CD44highLFA-1high
(Ref. 9 , Fig. 2, and our unpublished data). The phenoytpe
of T cells recovered from our model is very similar to that of cells
that have been activated in vivo in response to Ag (24, 39, 40). Using an adoptive transfer model with normal mouse
recipients, Gudmundsdottir et al. (24) showed that
administration of Ag induced Tg T cell to up-regulate CD44 and
down-regulate both CD62L and CD45RB. Moreover, recent studies show that
memory cells which develop in intact, ATXBM, and class II-deficient
recipients are similar in phenotype and function (help and cytokine
secretion) (2, 9, 30). These cells are not distinguishable
from cells generated in vivo in response to Ag plus adjuvant
(6). Most important, the recovered cells displayed memory
function in that they responded to specific restimulation with Ag by
proliferating, by secreting effector cytokines similar to memory cells
generated in vivo in response to Ag or pathogens in non-Tg models
(6, 41), and by providing effective help to B cells in
situ (9). Thus, we are confident that the cell population
we analyzed in these studies corresponds to long-lived resting memory
that is traditionally generated in non-Tg models by stimulation with Ag
presented in adjuvant. One potential drawback of these earlier
experiments was the possibility that Ag persisted and that activated
Ag-specific cells were also part of the population. That is not a
concern in the current studies because the adoptive hosts have never
received Ag and the original naive CD4 T cells were primed only with
peptide.
Our studies focus on how the properties of memory cells can determine
their behavior and give us insights into how the secondary response is
regulated. The kinetics of cytokine production and Ag-specific
proliferation have not previously been described for purified
populations of Ag-specific CD4 memory cells, although memory cells
generated in vivo have been shown to produce similar quantities of IL-2
as naive cells (6). Our results demonstrate that resting
memory cells respond to Ag with faster kinetics of cytokine RNA
accumulation (X. Zhang et al., manuscript in preparation) and protein
secretion than naive T cells. The kinetics of proliferation (Fig. 3)
and cytokine accumulation (Fig. 8) from memory cells was faster than
that of naive cells and was more similar to that of effector cells.
This rapid response is also seen in vivo, when Ag is given to recipient
mice reconstituted with Tg T cells (X. Zhang et al., manuscript in
preparation). Memory Th2 cells produced significant amounts of IL-2 and
IL-4 (and IFN- from Th1 memory cells; data not shown) by 4 h,
whereas naive cells required 12 h to accumulate equivalent amounts
of IL-2. This rapid cytokine production is seen despite the fact that
the phenotypic profile of memory cells indicated that they are
homogeneously small resting cells expressing negligible levels of
activation makers such as CD25 and despite the fact that much lower
levels of cytokines are produced by memory cells compared with
effectors (Table I). The rapid pace of cytokine production will allow
memory cells to provide regulatory functions within a few hours of
re-encountering Ag when they may be able to directly target the
cytokines to the APC, so that the low levels of cytokine produced may
be sufficient or even optimum for biological activity. In support of
this data, recent results from Rocha and colleagues (42)
suggest that memory CD8 cells secrete IFN- more rapidly than naive
cells. A possible explanation for the rapid production of cytokines is
suggested by studies which showed that differentiation of T cells is
accompanied by demethylation of the cytokine promoter regions
(43, 44). Heritable changes like demethylation, if they
occur in cytokine promoters in general, could be responsible for the
induction of rapid cytokine synthesis without a lag period such as we
observe in memory CD4 T cells.
One of the most dramatic and likely most important differences that
distinguishes naive from memory CD4 T cells is the ability of the
latter to secrete IL-4, IL-5, and IFN- upon restimulation (Table I,
Figs. 7 and 8, and Ref. 3). Our in vitro results are in
agreement with in vivo studies which show that upon initial
restimulation, resting CD4 memory T cells from normal animals make IL-2
in titers roughly equivalent to naive CD4 cells and also produce
detectable quantities of IL-4 and IFN- (2, 45, 46). As
shown in Table I, memory T cells can produce multiple cytokines upon
restimulation. These "effector" cytokines can directly mediate
effector function such as B cell help (47), Ig secretion,
macrophage activation, and Th1/Th2 polarization. Thus, the potential
impact of the interaction of a memory CD4 T cell with an APC is great
because the APC will be rapidly exposed to a range of cytokines that
can drive its activation or differentiation.
In our studies, the cytokine production of memory cells increased with
Ag dose, and memory and naive cells had equivalent requirements for
peptide concentration to induce each cytokine as did naive cells for
IL-2 induction (Fig. 7). These requirements were higher than those of
the corresponding effector population, which produced detectable and
maximal cytokines at a lower dose (generally at least a 10-fold lower
dose). Thus, in this respect, memory CD4 T cells seem to retain the Ag
dose restriction of naive cells for TCR triggering for cytokine
production.
Although the kinetics of memory cell and naive cell proliferation with
high doses of Ag presented by a costimulatory APC is similar, memory
CD4 T cells can be triggered to begin proliferation at lower doses of
Ag than naive CD4 T cells (Fig. 3), and their responses at the low
doses are greater than those of naive CD4 T cells. The difference
between naive and memory CD4 T cells with respect to Ag dose is also
seen when peptide analogues are used to stimulate the two subsets (Fig. 5). For both the analogue giving higher affinity (QASA) and that giving
lower affinity (K99A) interaction, memory cells gave detectable
responses at lower doses compared with naive CD4 T cells and at low
doses they incorporate more radiolabel, suggesting a higher rate of
proliferation. Our results are in agreement with previous studies which
suggested that memory or primed CD8 cells proliferate in vitro to lower
peptide doses (15) and display more rapid effector
function (48) compared with naive T cells.
How much of these differences in response to low doses of peptide are
due to cytokine availability and how much to possible differences in
efficiency of TCR triggering is unknown. This enhanced proliferative
capacity is not likely due only to the amount of autocrine IL-2
secreted (which is quite similar, see Table I), or increased levels of
transgene (TCR) expression (Fig. 1), but may be influenced by the more
rapid kinetics of cytokine secretion (Fig. 8) and lower costimulatory
requirements. It is also possible that in memory cells there is altered
tyrosine phosphorylation and/or different coupling of the TCR to
downstream signaling cascades (49). Our results are in
agreement with studies both in vivo (13, 50) and in vitro
(15) which show that CD8 memory cells give a more vigorous
and sustained response than naive cells. However, in contrast to one
report (15), the increased response of memory cells we
observe does not require addition of exogenous IL-2. The ability of
weak agonist peptide such as K99A or low doses of PCCF (or QASA) to
activate memory but not naive cells also suggests that memory cells are
triggered more easily, or are able to form more stable cell-cell
contact, or are able to sustain signaling long enough to activate
downstream messengers. This lower threshold of activation may allow
memory cells to divide occasionally in the presence of low levels of
cognate or perhaps cross-reacting Ag. Such potential responses to
cross-reacting Ag may be critical in inducing fast responses to viruses
which often vary their major Ags to evade the immune system.
The ability of memory T cells to respond to Ag with faster kinetics often has been attributed to their increased precursor frequency in vivo (5, 7, 51, 52) and to selection for higher affinity (53). However, we suggest that the more rapid kinetics of cytokine secretion and proliferation is intrinsic to the memory phenotype and that coupled with the ability to secrete increased amounts of effector cytokines, the ability to respond to B cells, and the ability to respond to lower doses of Ag enable memory CD4 T cells to respond sooner and with greater effectiveness. This in turn would drive a faster response of B cells and other targets of T cell help. We thus postulate that these qualitative differences change the characteristics of the overall response such that infectious organisms are dispatched rapidly, accomplishing host protection.
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Footnotes |
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2 Current address: La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121.
3 Current address: Rhone-Poulenc Rorer, Centre de Recherche de Vitry-Alfortville, 13, quai Jules Guesde B.P. 14, 94403 Vitry sur Seine, France.
4 Address correspondence and reprint requests to Dr. Susan L. Swain at her current address: Trudeau Institute, P.O. Box 59, 100 Algonquin Avenue, Saranac Lake, NY 12983. E-mail address:
5 Abbreviations used in this paper: Tg, transgenic; PCC, pigeon cytochrome c; AND, PCC-specific TCR Tg mouse; ATXBM, adult thymectomized irradiated bone marrow reconstituted; PCCF, PCC (fragment 88-104); CFSE, 5- and 6-carboxyfluorescein diacetate succinimidyl ester.
Received for publication June 4, 1999. Accepted for publication December 15, 1999.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
production. J. Immunol. 140:1401.[Abstract]
. J. Exp. Med. 174:547. (IFN-) and interleukin 3 (IL-3) genes in newly activated primary CD8+ T lymphocytes: regional IFN- promoter demethylation and mRNA expression are heritable in CD44hi CD8+ T cells. J. Exp. Med. 188:103.This article has been cited by other articles:
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|
|
|
|
 |
|
 B. Schnyder and W. J. Pichler Mechanisms of Drug-Induced Allergy Mayo Clin. Proc., March 1, 2009; 84(3): 268 - 272. [Abstract] [Full Text] [PDF]
|
|
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|
 |
|
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|
|
|
|
 |
|
 O. Dienz, S. M. Eaton, J. P. Bond, W. Neveu, D. Moquin, R. Noubade, E. M. Briso, C. Charland, W. J. Leonard, G. Ciliberto, et al. The induction of antibody production by IL-6 is indirectly mediated by IL-21 produced by CD4+ T cells J. Exp. Med., January 16, 2009; 206(1): 69 - 78. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
 |
|
 D. Zhou, B. D. Medoff, L. Chen, L. Li, X.-f. Zhang, M. Praskova, M. Liu, A. Landry, R. S. Blumberg, V. A. Boussiotis, et al. The Nore1B/Mst1 complex restrains antigen receptor-induced proliferation of naive T cells PNAS, December 23, 2008; 105(51): 20321 - 20326. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
 |
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
 |
|
 J. N. Agrewala, D. M. Brown, N. M. Lepak, D. Duso, G. Huston, and S. L. Swain Unique Ability of Activated CD4+ T Cells but Not Rested Effectors to Migrate to Non-lymphoid Sites in the Absence of Inflammation J. Biol. Chem., March 2, 2007; 282(9): 6106 - 6115. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
 |
|
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|
|
|
|
 |
|
 A. Boesteanu, A. L. Rankin, and A. J. Caton Impact of effector cell differentiation on CD4+ T cells that evade negative selection by a self-peptide Int. Immunol., July 1, 2006; 18(7): 1017 - 1027. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
G. Raimondi, W. J. Shufesky, D. Tokita, A. E. Morelli, and A. W. Thomson Regulated Compartmentalization of Programmed Cell Death-1 Discriminates CD4+CD25+ Resting Regulatory T Cells from Activated T Cells. J. Immunol., March 1, 2006; 176(5): 2808 - 2816. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
 |
|
 F. S. Dhabhar and K. Viswanathan Short-term stress experienced at time of immunization induces a long-lasting increase in immunologic memory Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2005; 289(3): R738 - R744. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
L. Krymskaya, W.-H. Lee, L. Zhong, and C.-P. Liu Polarized Development of Memory Cell-Like IFN-{gamma}-Producing Cells in the Absence of TCR {zeta}-Chain J. Immunol., February 1, 2005; 174(3): 1188 - 1195. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. C. Becker, S. M. Coley, E. J. Wherry, and R. Ahmed Bone Marrow Is a Preferred Site for Homeostatic Proliferation of Memory CD8 T Cells J. Immunol., February 1, 2005; 174(3): 1269 - 1273. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Junt, E. Scandella, R. Forster, P. Krebs, S. Krautwald, M. Lipp, H. Hengartner, and B. Ludewig Impact of CCR7 on Priming and Distribution of Antiviral Effector and Memory CTL J. Immunol., December 1, 2004; 173(11): 6684 - 6693. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Yamashita, R. Shinnakasu, Y. Nigo, M. Kimura, A. Hasegawa, M. Taniguchi, and T. Nakayama Interleukin (IL)-4-independent Maintenance of Histone Modification of the IL-4 Gene Loci in Memory Th2 Cells J. Biol. Chem., September 17, 2004; 279(38): 39454 - 39464. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Zand, B. J. Briggs, A. Bose, and T. Vo Discrete Event Modeling of CD4+ Memory T Cell Generation J. Immunol., September 15, 2004; 173(6): 3763 - 3772. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Andris, S. Denanglaire, F. de Mattia, J. Urbain, and O. Leo Naive T Cells Are Resistant to Anergy Induction by Anti-CD3 Antibodies J. Immunol., September 1, 2004; 173(5): 3201 - 3208. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. S. Chin, C. H.T. Miller, L. Graham, M. Parviz, S. Zacur, B. Patel, A. Duong, and H. D. Bear Bryostatin 1/ionomycin (B/I) ex vivo stimulation preferentially activates L-selectinlow tumor-sensitized lymphocytes Int. Immunol., September 1, 2004; 16(9): 1283 - 1294. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. P. Pappu and P. A. Shrikant Alteration of Cell Surface Sialylation Regulates Antigen-Induced Naive CD8+ T Cell Responses J. Immunol., July 1, 2004; 173(1): 275 - 284. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. K. Sojka, D. Bruniquel, R. H. Schwartz, and N. J. Singh IL-2 Secretion by CD4+ T Cells In Vivo Is Rapid, Transient, and Influenced by TCR-Specific Competition J. Immunol., May 15, 2004; 172(10): 6136 - 6143. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Haynes, S. M. Eaton, E. M. Burns, M. Rincon, and S. L. Swain Inflammatory Cytokines Overcome Age-Related Defects in CD4 T Cell Responses In Vivo J. Immunol., May 1, 2004; 172(9): 5194 - 5199. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L.-X. Wang, J. Kjaergaard, P. A. Cohen, S. Shu, and G. E. Plautz Memory T Cells Originate from Adoptively Transferred Effectors and Reconstituting Host Cells after Sequential Lymphodepletion and Adoptive Immunotherapy J. Immunol., March 15, 2004; 172(6): 3462 - 3468. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. A. Aronica, S. McCarthy, S. Swaidani, D. Mitchell, M. Goral, J. R. Sheller, and M. Boothby Recall Helper T Cell Response: T Helper 1 Cell-resistant Allergic Susceptibility without Biasing Uncommitted CD4 T Cells Am. J. Respir. Crit. Care Med., March 1, 2004; 169(5): 587 - 595. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.-A. Younes, B. Yassine-Diab, A. R. Dumont, M.-R. Boulassel, Z. Grossman, J.-P. Routy, and R.-P. Sekaly HIV-1 Viremia Prevents the Establishment of Interleukin 2-producing HIV-specific Memory CD4+ T Cells Endowed with Proliferative Capacity J. Exp. Med., December 15, 2003; 198(12): 1909 - 1922. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Bellier, V. Thomas-Vaslin, M.-F. Saron, and D. Klatzmann Turning immunological memory into amnesia by depletion of dividing T cells PNAS, December 9, 2003; 100(25): 15017 - 15022. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. G. Lakkis and M. H. Sayegh Memory T Cells: A Hurdle to Immunologic Tolerance J. Am. Soc. Nephrol., September 1, 2003; 14(9): 2402 - 2410. [Full Text] [PDF]
|
|
|
|
|
|
M. Iwata, Y. Eshima, and H. Kagechika Retinoic acids exert direct effects on T cells to suppress Th1 development and enhance Th2 development via retinoic acid receptors Int. Immunol., August 1, 2003; 15(8): 1017 - 1025. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Kimachi, K. Sugie, and H. M. Grey Effector T cells have a lower ligand affinity threshold for activation than naive T cells Int. Immunol., July 1, 2003; 15(7): 885 - 892. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Mortarini, A. Piris, A. Maurichi, A. Molla, I. Bersani, A. Bono, C. Bartoli, M. Santinami, C. Lombardo, F. Ravagnani, et al. Lack of Terminally Differentiated Tumor-specific CD8+ T Cells at Tumor Site in Spite of Antitumor Immunity to Self-Antigens in Human Metastatic Melanoma Cancer Res., May 15, 2003; 63(10): 2535 - 2545. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Blander, D. B. Sant'Angelo, D. Metz, S.-W. Kim, R. A. Flavell, K. Bottomly, and C. A. Janeway Jr. A Pool of Central Memory-Like CD4 T Cells Contains Effector Memory Precursors J. Immunol., March 15, 2003; 170(6): 2940 - 2948. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. N. J. Bullock, D. W. Mullins, and V. H. Engelhard Antigen Density Presented By Dendritic Cells In Vivo Differentially Affects the Number and Avidity of Primary, Memory, and Recall CD8+ T Cells J. Immunol., February 15, 2003; 170(4): 1822 - 1829. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Fadel, D. A. Ozaki, and M. Sarzotti Enhanced Type 1 Immunity After Secondary Viral Challenge in Mice Primed as Neonates J. Immunol., September 15, 2002; 169(6): 3293 - 3300. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L.-X. Wang, B.-G. Chen, and G. E. Plautz Adoptive Immunotherapy of Advanced Tumors with CD62 L-Selectinlow Tumor-Sensitized T Lymphocytes Following Ex Vivo Hyperexpansion J. Immunol., September 15, 2002; 169(6): 3314 - 3320. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Klugewitz, F. Blumenthal-Barby, A. Schrage, P. A. Knolle, A. Hamann, and I. N. Crispe Immunomodulatory Effects of the Liver: Deletion of Activated CD4+ Effector Cells and Suppression of IFN-{gamma}-Producing Cells After Intravenous Protein Immunization J. Immunol., September 1, 2002; 169(5): 2407 - 2413. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Zwaveling, S. C. F. Mota, J. Nouta, M. Johnson, G. B. Lipford, R. Offringa, S. H. van der Burg, and C. J. M. Melief Established Human Papillomavirus Type 16-Expressing Tumors Are Effectively Eradicated Following Vaccination with Long Peptides J. Immunol., July 1, 2002; 169(1): 350 - 358. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. M. Borghans and R. J. De Boer Memorizing innate instructions requires a sufficiently specific adaptive immune system Int. Immunol., May 1, 2002; 14(5): 525 - 532. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Arpin, G. Angelov, T. Walzer, M. Tomkowiak, and J. Marvel Hyperproliferative Response of a Monoclonal Memory CD8 T Cell Population Is Characterized by an Increased Frequency of Clonogenic Precursors J. Immunol., March 1, 2002; 168(5): 2147 - 2153. [Abstract] [Full Text] [PDF]
|
|
|
|
|
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J. Harbertson, E. Biederman, K. E. Bennett, R. M. Kondrack, and L. M. Bradley Withdrawal of Stimulation May Initiate the Transition of Effector to Memory CD4 Cells J. Immunol., February 1, 2002; 168(3): 1095 - 1102. [Abstract] [Full Text] [PDF]
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M. A. C. de Lafaille, S. Muriglan, M.-J. Sunshine, Y. Lei, N. Kutchukhidze, G. C. Furtado, A. K. Wensky, D. Olivares-Villagomez, and J. J. Lafaille Hyper Immunoglobulin E Response in Mice with Monoclonal Populations of B and T Lymphocytes"" J. Exp. Med., November 5, 2001; 194(9): 1349 - 1360. [Abstract] [Full Text] [PDF]
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O. F. Bathe, N. Dalyot-Herman, and T. R. Malek IL-2 During In Vitro Priming Promotes Subsequent Engraftment and Successful Adoptive Tumor Immunotherapy by Persistent Memory Phenotypic CD8+ T Cells J. Immunol., October 15, 2001; 167(8): 4511 - 4517. [Abstract] [Full Text] [PDF]
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H. Gudmundsdottir and L. A. Turka A Closer Look at Homeostatic Proliferation of CD4+ T Cells: Costimulatory Requirements and Role in Memory Formation J. Immunol., October 1, 2001; 167(7): 3699 - 3707. [Abstract] [Full Text] [PDF]
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O. Adolfsson, B. T. Huber, and S. N. Meydani Vitamin E-Enhanced IL-2 Production in Old Mice: Naive But Not Memory T Cells Show Increased Cell Division Cycling and IL-2-Producing Capacity J. Immunol., October 1, 2001; 167(7): 3809 - 3817. [Abstract] [Full Text] [PDF]
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S.-i. Fujii, K. Shimizu, T. Shimizu, and M. T. Lotze Interleukin-10 promotes the maintenance of antitumor CD8+ T-cell effector function in situ Blood, October 1, 2001; 98(7): 2143 - 2151. [Abstract] [Full Text] [PDF]
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S. Mirshahidi, C.-T. Huang, and S. Sadegh-Nasseri Anergy in Peripheral Memory Cd4+ T Cells Induced by Low Avidity Engagement of T Cell Receptor J. Exp. Med., September 17, 2001; 194(6): 719 - 732. [Abstract] [Full Text] [PDF]
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O. Bruna-Romero, G. Gonzalez-Aseguinolaza, J. C. R. Hafalla, M. Tsuji, and R. S. Nussenzweig Complete, long-lasting protection against malaria of mice primed and boosted with two distinct viral vectors expressing the same plasmodial antigen PNAS, September 5, 2001; (2001) 191380898. [Abstract] [Full Text] [PDF]
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 R. N. Germain The Art of the Probable: System Control in the Adaptive Immune System Science, July 13, 2001; 293(5528): 240 - 245. [Abstract] [Full Text]
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L.-M. Stott, R. N. Barker, and S. J. Urbaniak Identification of alloreactive T-cell epitopes on the Rhesus D protein Blood, December 15, 2000; 96(13): 4011 - 4019. [Abstract] [Full Text] [PDF]
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J. Strong, Q. Wang, and N. Killeen Impaired survival of T helper cells in the absence of CD4 PNAS, February 27, 2001; 98(5): 2566 - 2571. [Abstract] [Full Text] [PDF]
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T. J. Sullivan, J. J. Letterio, A. van Elsas, M. Mamura, J. van Amelsfort, S. Sharpe, B. Metzler, C. A. Chambers, and J. P. Allison Lack of a role for transforming growth factor-beta in cytotoxic T lymphocyte antigen-4-mediated inhibition of T cell activation PNAS, February 27, 2001; 98(5): 2587 - 2592. [Abstract] [Full Text] [PDF]
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O. Bruna-Romero, G. Gonzalez-Aseguinolaza, J. C. R. Hafalla, M. Tsuji, and R. S. Nussenzweig Complete, long-lasting protection against malaria of mice primed and boosted with two distinct viral vectors expressing the same plasmodial antigen PNAS, September 25, 2001; 98(20): 11491 - 11496. [Abstract] [Full Text] [PDF]
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