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Institute for Experimental Immunology, University Hospital Zürich, Zürich, Switzerland
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Using 5 (and 6)-carboxyfluorescein diacetate, succinimidyl ester (CFSE)-labeled spleen cells from 318 TCR transgenic mice (14) specific for the lymphocytic choriomeningitis virus (LCMV) glycoprotein (GP), the present study aimed at analyzing the differentiation of naive CTL to effector and memory CTL in vitro and in vivo and to monitor the expression of selected activation and memory markers during differentiation as a function of cell division. The distinct differentiation stages were then correlated in vitro and in vivo with cytotoxic effector function and CTL phenotype.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Six- to 10-wk-old C57BL/6 mice and TCR transgenic 318 mice (14)
were bred at the Labortierkunde at University of Zürich
(Switzerland) and kept under specific pathogen-free conditions,
according to institutional guidelines. 318 mice express transgenic
V
2 and Vß8.1 TCR chains specific for the LCMV glycoprotein peptide
p33 presented on H-2Db on 50–60% of the
CD8+CTL. 318 mice have been bred onto the C57BL/6
background for at least six generations, and 318 spleen cells are not
rejected after transfer into sex-matched C57BL/6 recipients.
Virus
The LCMV WE strain was used in this study (15). Recombinant vaccinia virus expressing the LCMV GP (vacc GP (16)) was a gift from D. H. L. Bishop (Oxford, U.K.).
Cell lines
EL-4 thymoma cells (H-2b) were grown in Iscove’s modified Dulbecco’s medium (Life Technologies, Gaithersburg, MD) containing 5% FCS and supplemented with glutamine and streptomycin/penicillin.
CFSE labeling
CFSE was purchased from Molecular Probes (Eugene, OR). Erythrocytes were removed from spleen cell suspensions by water lysis. The cells were then washed with ice-cold PBS and resuspended at 5 x 106 cells/ml in ice-cold PBS. CFSE was kept as a 0.5 mM stock in DMSO and stored at -20°C in a desiccator box. Cells were labeled by diluting the 0.5 mM CFSE stock 1000-fold into the cell suspension (final concentration 0.5 µM) and incubating them for 10 min at 37°C. For high CFSE fluorescence intensities, cells were labeled at a final concentration of 5 µM by diluting a 5 mM stock 1000-fold. After labeling, FCS was added to 5% final concentration and the cells were immediately centrifuged and washed with ice-cold PBS. For i.v. injection into the tail vein, labeled cells were resuspended in BSS.
In vitro activation of transgenic T cells
A total of 3–5 x 106 spleen cells/well (24-well plate) or 107 spleen cells/well (6-well plate) from 318 TCR transgenic mice was labeled with CFSE and stimulated by adding 2 x 10-8 M of specific LCMV GP peptide p33 (KAVYNFATM) to the cultures. For technical reasons, the original position 41 cysteine in p33 was replaced by a methionine to prevent dimer formation. Cells were cultured in Iscove’s modified Dulbecco’s medium supplemented with 10% FCS, penicillin/streptomycin, glutamine, and 5 x 10-5 M 2-ME.
Adoptive transfer and in vivo activation of 318 CTL
318 spleen cells were labeled with CFSE, as described above. A
quantity amounting to 3–5 x 107 labeled 318 spleen
cells (318-CFSE) was resuspended in 400 µl of BSS and injected into
the tail vein of sex-matched C57BL/6 recipients (318-CFSE
B6). After
8–16 h, recipients were infected i.v. with the indicated doses of the
LCMV WE strain to activate LCMV GP p33-specific transgenic CTL.
Flow cytometry
Single cell suspensions were harvested from 318-CFSE CTL
cultures or prepared from lymph nodes and spleens of 318-CFSEB6
recipients and incubated with an anti-CD8 PE-coupled Ab
(PharMingen, San Diego, CA) to detect the CFSE-positive transgenic CTL.
To analyze cell surface expression levels of the various markers, the
cell suspensions were incubated with biotinylated mAbs against CD25,
CD44, CD69, CD62L, Fas, FasL, or V2 (all PharMingen), respectively,
followed by a streptavidin-Tricolor (Caltag, South San Francisco, CA)
incubation. For cell surface marker analyses, 5 x 105
to 9 x 105 live cells were acquired in a FACScan and
analyzed using CellQuest software (both Becton Dickinson, Mountain
View, CA).
In vitro cytotoxicity assay
After in vitro activation (24-well tissue culture plate) of 5 x 106 transgenic T cells/well in a volume of 1 ml (see above), standard cultures were counted where indicated or serially diluted (four steps, threefold dilutions) in MEM supplemented with 2% FCS in 96-well round-bottom plates. Specific cytotoxicity of the diluted cultures was then determined in a standard 51Cr release assay, as described (16). EL4 cells were coated with peptide p33 at a concentration of 10-6 M and were labeled in a total volume of 300 µl with 250 µCi 51Cr for 2 h at 37°C on a rocking platform. The labeled target cells were washed three times, and 104 cells were added to the effector cells in a final volume of 200 µl. After a 5- or 20-h incubation at 37°C, 60 µl of the supernatants was harvested and counted with a gamma counter.
In vivo cytotoxicity assay
To prepare target cells for in vivo evaluation of cytotoxic activity, erythrocytes from C57BL/6 spleen cell suspensions were lysed, washed, pulsed with 10-6 M p33 peptide for 90 min at 37°C, washed again, and labeled with a high CFSE fluorescence intensity, as described above. Uncoated control target cells were labeled with a low CFSE fluorescence intensity, as described above. For i.v. injection, 3 x 107 cells of each population were mixed in 500 µl BSS. Specific in vivo cytotoxicity was determined by collecting blood from the tail vein at the indicated time points, lysing erythrocytes using FACS lysing solution (Becton Dickinson), and detecting the differentially labeled fluorescent target cell populations by flow cytometry. The ratio r between the percentages of uncoated versus p33 coated (CFSElow/CFSEhigh) was calculated to obtain a numerical value of cytotoxicity.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CFSE-labeled 318 TCR transgenic T cells expressing a TCR specific
for the LCMV GP epitope p33 on H-2Db (318 transgenic mouse
line (14)) lose 50% of their fluorescence intensity after each cell
division upon stimulation with specific peptide. We have shown
previously that labeling of lymphocytes with CFSE does not interfere
with their biologic function and homing properties (17) and that
adoptively transferred cells can be readily detected in blood and
lymphoid organs by flow cytometry for several weeks (17, 18). To
monitor the differentiation of a naive CTL population into effector and
memory CTL, we followed the modulation of selected cell surface markers
associated with the effector and/or memory T cell phenotype as a
function of division cycle number. Spleen cells from 318 mice were
labeled with CFSE (318-CFSE) and activated in vitro with p33 (Fig. 1
) or with LCMV-infected macrophages
(data not shown). After 72 h in culture, the cells were harvested
and stained for CD8 and CD25, CD44, CD69, CD62L, Fas, FasL, or the
transgenic V2 TCR chain, respectively. In Fig. 1, the top
panel displays a two-dimensional CD8-PE versus CFSE (FITC)
fluorescence profile of cultures harvested 72 h after stimulation.
The contour plots reveal distinct, prominent peaks in the CD8-positive
transgenic CTL population, corresponding to single cell divisions.
These peaks are further displayed in the histogram below after gating
on the CD8-positive cells. After 48 h (not shown), we observed
four peaks, and 72 h after stimulation with p33, six to seven
distinct peaks were apparent. Peaks 0 and 1 are more readily identified
in the two-dimensional contour plots. Peak 0 represents CTL that have
not divided. One hundred percent of the CD8-positive cells were found
in the undivided peak when analyzed 24 h after stimulation (data
not shown). Thus, taking into account that the cells had not divided
within the first 24 h, we can calculate that the average
duplication time of an activated CTL is 8 h.
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, bottom panel of
histograms). CD25, CD69, CD44, Fas, and FasL expression levels were
increased by a factor of 5–10 even on CTL that had not divided. CD62L
and transgenic TCR (V2) expression levels were unaltered on
undivided cells. CD25 and CD44 levels remained elevated during further
divisions, while CD69, Fas, and FasL levels declined and reached
expression levels comparable with naive cells within six cell
divisions. In 72-h cultures, CD62L was not down-regulated below the
levels of naive CTL within the first six divisions, which would be
characteristic of LCMV effector CTL generated in vivo (19). However, in
48-h cultures, CD62L was down-modulated on dividing cells (see below).
TCR levels decreased with increasing numbers of cell divisions. Tracing CTL differentiation in vivo
To follow cell division and CTL activation in vivo, we adoptively
transferred 3–5 x 107 318-CFSE spleen cells into
nonirradiated recipients and subsequently activated the transfused CTL
by i.v. infection of the recipients with LCMV. In the experiments
depicted in Fig. 2, recipients were left
untreated or were infected with 105 or 103 PFU
of LCMV, respectively. Three days later, the
CD8+CFSE+ transgenic CTL in spleen and
mesenteric lymph nodes were analyzed for cell division by flow
cytometry. CFSE-labeled CD8+CTL were readily detected in
spleen and lymph nodes. Three days after injection of 103
PFU of LCMV, the transferred CTL had divided one to six times in the
spleen. In the mesenteric lymph nodes, few CTL had divided. Injection
of 105 PFU of LCMV resulted in a more homogenous
stimulation and proliferation in the spleen than after injection with a
low dose (compare spleen: middle and bottom
panels, Fig. 2): The majority of CTL had divided six or seven
times in the spleen after high dose infection, whereas the whole
spectrum of CTL that had divided zero to six times was found in spleens
after low dose infection. In the lymph nodes, CTL had divided one to
six or seven times after high dose infection, but hardly any dividing
cells were found in the lymph nodes of mice receiving a low virus dose.
When comparing splenic CTL with mesenteric CTL at a given dose, we
found that the majority of the CTL in the spleen had been activated
before mesenteric CTL, which is manifested by a more synchronous
proliferation of splenic CTL at a high LCMV dose (compare middle
panels spleen versus lymph node) and the absence of large numbers
of dividing CTL in the lymph nodes at low virus doses (compare
bottom panels spleen versus lymph node), respectively. Thus,
after systemic infection, the bulk of CTL was first activated in the
spleen, and stimulation was more synchronous in the spleen after
infection with high doses of LCMV. Similar as in vitro and given that
CTL require approximately 24 h before starting to proliferate, we
can calculate ((72 - 24 h) ÷ 6) that also in vivo the
average duplication time of an activated CTL after viral infection is
8 h.
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. Fig. 3 shows that
CD8+CFSE+CTL had divided up to five times in
the mesenteric lymph nodes (upper two panels), and that CD8
was slightly up-regulated on these proliferating CTL. Expression levels
of the various markers were then compared with the endogenous CD8 T
cells and with naive 318 CTL from controls. In contrast to what was
found in vitro (for comparison, see Table I), CD25 was strongly up-regulated only
after the fourth cell division. As in cultured CTL, CD69 was
immediately up-regulated even on cells that had not yet divided. CD62L
was gradually down-modulated with increasing numbers of cell divisions.
Compared with in vitro stimulation, CD44 expression increased only
after the first cell division in vivo. In vivo, Fas was minimally
up-regulated on activated cells. The TCR was down-regulated in a
similar fashion in vivo as in vitro. Similar results were obtained with
splenic CTL (data not shown).
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For enhanced resolution of TCR modulation (the resolution of detection
of TCR expression using V2-PE Ab is superior over V2-biotin
streptavidin-Tricolor staining), we separately stained CFSE-labeled
lymph node cells for CD8 or transgenic V2, respectively. We found
that the TCR was further down-regulated after each cell division on a
significant proportion, but not all CTL, resulting in populations of
CTL expressing a wide range of TCR levels after each division
(reflected by a smear in Fig. 4). After
four to five cell divisions, a significant number of CTL that had
normal TCR levels were visible (Fig. 4, compare black arrows), and at
the same time a significant number of CTL that expressed low TCR levels
were detected (Fig. 4, compare white arrows). Thus, it appears that the
TCR was expressed over a broad range, with some of the CTL further
decreasing their TCR levels after each cell division.
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To investigate at which stage differentiating CTL acquired
cytotoxic effector function, their potential to lyse target cells was
evaluated as a function of cell division. Toward this end, 318-CFSE
spleen cells were stimulated in vitro with p33 and assayed after
different time points for cell division and cytotoxic effector
function. Fig. 5A shows that
CTL that had been stimulated for 16 h and had not divided (0 div)
did not lyse peptide-coated target cells. In contrast, cultures that
had divided once after 30 h (0–1 div) displayed significant
specific cytotoxicity. Similarly, CTL that had divided up to four times
after 48 h (0–4 div) were cytotoxic in a 5-h 51Cr
release assay (Fig. 5B). Thus, activated CTL gained effector
function within the first cell division and continued to express
cytotoxic effector function while proliferating.
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B (right histogram) shows
that 318-CFSE CTL that were stimulated with p33 and were cultured for 7
days had divided 6–10 times. When testing the CTL for effector
function, these long-term cultures, unlike effector cultures that had
divided 0–4 times, did not display any significant immediate
cytotoxicity in a 5-h 51Cr release assay (Fig. 5B, bottom graph). However, when incubating the
CTL for 20 h, they developed maximal cytolysis. Thus, CTL, having
divided 6–10 times, displayed delayed effector function. A phenotypic
analysis of the differentiating 318 CTL revealed that CTL with
immediate effector function were CD44high and had
down-regulated CD62L, whereas CTL with delayed effector function
reexpressed CD62L and displayed a
CD44highCD62L+ memory phenotype. (Fig. 5C). Taken together, LCMV-specific CTL differentiated from
naive CD44lowCD62L+ to
CD44highCD62L+ memory CTL via an intermediate
CD44highCD62L- effector stage within 6–10
cell divisions. The intermediate effector stage displayed immediate
cytotoxic activity, whereas memory CTL required restimulation to
develop cytotoxic activity. Acquisition of effector function in vivo
To examine the dynamics of effector function during the
differentiation of naive CTL to memory CTL in vivo, the rejection of
p33-presenting target cells was monitored: Since LCMV was already
administered to activate naive CTL, a challenge infection with virus
early after priming could not be used to assay for cytotoxic activity
in a viral plaque assay. To circumvent this problem, we developed an in
vivo cytotoxicity assay: Normal syngeneic spleen cells serving as
target cells were pulsed with the p33 and were labeled with a high CFSE
(CFSEhigh) intensity. To control for the elimination of
target cells by noncontact-dependent or unspecific lymphokine-mediated
mechanism, unpulsed spleen cells were labeled with a low CFSE
fluorescence (CFSElow) intensity. CSFEhigh and
CFSElow target cells were mixed at a ratio of 1:1 and
transferred into the different types of recipients, and the dynamics of
CTL effector function were measured by monitoring the rejection of the
CSFEhigh target cells by flow cytometry 4, 11, and 20
h after transfer (Fig. 6A).
Effector mice were prepared by adoptively transferring 3 x
107 318 spleen cells into C57BL/6 recipients (318B6) and
infecting the recipients with 1000 PFU of LCMV 3 days before transfer
of the target cell mixture. Memory mice were generated by infecting
318B6 recipients with LCMV 60 days before target cell injection.
Untreated 318 transgenic mice (instead of normal mice) served as naive
controls to compensate for elevated LCMV CTL precursor frequencies.
Fig. 6A shows that naive 318 mice required overnight
activation before developing any significant CTL activity, which is
evidenced by a reduction of the p33-coated CFSEhigh
indicator cells. In contrast, early differentiating CTL in effector
mice immediately eliminated p33 CFSEhigh target cells
within 4 h. Memory mice showed significant cytotoxicity at 4 and
11 h, and completely eliminated p33-coated target cells by 20
h. This contrasted with the in vitro generated memory CTL that required
reactivation and suggested that in vivo the memory population was more
rapidly reactivated and/or contained effector CTL. To resolve this
question, the LCMV-specific 318 CTL populations in naive, effector, and
memory mice were analyzed for the expression of CD62L. Fig. 6B shows that in naive 318 mice, 90% of the transgenic CTL
were CD62L+ (and CD44low, not shown). In
effector mice, more than 90% of the LCMV-specific transgenic CTL were
CD62L- (and CD44high, not shown).
Interestingly, in memory mice, 40–50% of the transgenic CTL were
CD62L- (and CD44high, not shown), a phenotype
typical for LCMV effector CTL.
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B6 memory mice and found that 50% of the 318 CTL in the
spleen were CD62L negative, while only 20% of the lymph node 318 CTL
were CD62L- (Fig. 7). Both
populations were CD44high (not shown). When spleen and
lymph node cells from these mice were tested for immediate effector
function in a 6-h cytotoxicity assay, we observed that in contrast to
lymph node CTL, splenic CTL significantly lysed p33-coated target cells
(Fig. 7). After prolonged incubation for 19 h, lymph node CTL had
also gained effector function, yet it was not possible to analyze
whether this cytotoxicity was mediated by the residual 19%
CD62L-CTL population. Taken together, after LCMV infection
in vivo, CTL differentiated into a
CD44highCD62L- activation stage exerting rapid
effector function. In memory mice, a
CD44highCD62L- population with rapid effector
function coexisted with a CD44highCD62L+
population exerting delayed effector function. Thus, based on the
expression of CD44 and CD62L, two types of phenotypically and
functionally distinct memory CTL were found in LCMV memory mice.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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As previously described for in vitro polyclonally activated B cells (24), we were able to monitor the modulation of selected T cell surface molecules on differentiating CTL in dependence of the division cycle number. The analysis of in vitro and in vivo stimulated CTL revealed that the investigated surface markers were strongly modulated within the first six cell divisions.
CD25
The activation of CTL in vitro is strictly dependent on IL-2 (25). Consistent with this, we found that in vitro CD25 was up-regulated before the first cell division. In vivo, however, CD25 up-regulation was observed only after the third to fourth cell division, confirming recent studies showing that in IL-2-deficient mice, CTL proliferated in response to superantigen (26) and antigenic peptide (27). Thus, it appears that in vivo other cytokines or, as shown with CD4 T cells, costimulation through B7.2 (28) may substitute for IL-2.
CD69, Fas, and FasL
As expected, the early activation marker CD69 was rapidly up-regulated and returned to naive levels within six cell divisions. Interestingly, Fas and FasL also followed an expression pattern similar to that of an early activation marker. This suggests that activated T cells may only be susceptible to Fas-induced apoptosis at an early differentiation stage. Experiments conducted to test for this showed that the addition of anti-Fas Ab to CTL cultures (10 µg/ml) marginally inhibited proliferation (by a factor of 2) when added within the first 48 h (data not shown). Thus, although recent reports have suggested that expression of FasL may generate immune privileged sites by Fas-mediated elimination of autoimmune T cells (29, 30), our in vitro data imply that only a minority of Fas-expressing early effector cells are susceptible to Fas-FasL-induced apoptosis and that late effector CTL may be refractory to Fas-mediated apoptosis. Consistent with this, it was found that the expression of Bcl-xL in activated T cells can protect them from Fas-mediated apoptosis (31).
CD44 and CD62L
CD44 is required for extravasation of activated T cells into inflammatory sites by interacting with the ligand hyaluronate (32). Since CD44 was immediately up-regulated within the first cell division, this suggests that activated T cells immediately gain the potential to change their extravasation properties. On the other hand, the lymph node homing receptor CD62L was substantially decreased only after the fourth cell division in vivo, suggesting that early during differentiation T lymphocytes maintain the capacity to remain in or home back into lymph nodes. Based on our in vitro data, naive T cells started to proliferate after an initial activation lag time of 24 h, and thereafter duplicated every 8 h. Thus, we could calculate that approximately 56 h after encountering specific Ag, activated T cells may lose the potential to home to lymph nodes. From this, one could conclude that early during an immune response, activated T cells are retained in the secondary lymphoid organ, perhaps to eliminate draining Ag and/or to provide helper function for the establishment of a B cell response. T cells that have left the lymph node despite expressing the lymph node homing receptor CD62L, as well as late effector cells that have down-regulated CD62L may be recruited to inflammatory sites by CD44-mediated extravasation.
Even though CD62L is well known as a lymph node homing receptor (33), it was striking to see how accurately the migration patterns of activated CTL could be deduced from the CD62L expression patterns, e.g., we showed that CD62L- effector and memory CTL were predominately found in the spleen and were reduced in the lymph nodes. Similarly, experiments in which CTL were primed with a high dose of LCMV down-regulated CD62L on undivided cells within 18 h (not shown) and would mean that, after a strong stimulus, extravasation should be accelerated. Consistent with this, a recent study reported that Vß8+ T cells appeared in the inflammatory site 16 h after priming with the strong stimulus staphylococcal enterotoxin B (32). Thus, it appears that deducing the homing properties of CTL from the expression of CD44 and CD62L matches well with in vivo observations.
T cell receptor
Recent studies have shown that the TCR is down-regulated upon encountering Ag (34, 35). Our data show that a similar phenomenon is observed after stimulation of CTL with peptide in vitro or during viral infection in vivo. Down-modulation was not a consequence of cell division since nondividing CTL activated by a high Ag dose down-regulated the TCR (not shown). Thus, our data show that TCR modulation is observed during the course of a natural viral infection; however, the biologic role of TCR down-regulation is unclear. Since many intermediate mediators may be shared by different signaling pathways (36), excessive triggering of one signaling cascade may result in nonspecific induction of alternate genes. Thus, one can speculate that, generally, down-regulation of surface molecules coupled to downstream regulatory pathways may serve to desensitize the responding cell toward the original signal and prevent unspecific activation of additional genes. Experiments performed in our adoptive transfer system and showing that a high virus dose capable of immediately delivering a strong stimulatory signal resulted in nonspecific cytotoxic effector function, support this view (not shown).
Our data reveal that within a given cell division cycle, TCR down-regulation was not homogenous: A proportion of the CTL expressed normal, while other CTL had reduced TCR levels. With increasing numbers of cell divisions, the degree of TCR down-modulation increased, resulting in an overall stepwise TCR down-regulation. After four to five divisions, we found significant numbers of CTL expressing normal and cells expressing greater than 10-fold reduced TCR levels. It is possible that TCRhighCTL emerged from TCRlow cells that have reexpressed the TCR because they have not reencountered Ag, while TCRlowCTL are the result of continuous reexposure to viral Ag. Another possibility is that a proportion of the CTL was activated, but divided without any significant TCR modulation, as could be seen in experiments recently published by Iezzi et al. (37). It is also not clear whether the TCRhigh or TCRlow CTL populations represent separate CTL lineages, either one of which may differentiate into memory CTL. Studies to investigate the fate of these two distinct populations are underway.
Cytotoxic effector function
It is an open question after how many cell divisions CTL acquire effector function and whether effector function correlates with the expression of a distinct (set of) surface markers. For CTL, one of the primary effector functions is cytotoxic activity. Our results show that undivided CTL that had been stimulated for 16 h in vitro failed to develop any cytotoxic activity, whereas cells that had divided once within 30 h specifically lysed target cells. Similarly, differentiating, proliferating CTL developed cytotoxic activity in vitro and in vivo during a phase in which the investigated surface markers were strongly modulated. Since in this assay system cytotoxicity is mediated by perforin (38), our data suggest that sufficient perforin may have to accumulate in cytotoxic granules within 30 h to promote cytotoxic function. Consistent with this, cultures that were treated with mitomycin C to inhibit proliferation (data not shown) still developed cytotoxic activity, supporting the notion that the acquisition of effector function does not seem to require a certain number of cell divisions, but may rather parallel perforin synthesis. In this context, it should be noted, however, that depending on the T cell lineage and the effector function investigated, the apparent acquisition of an effector stage may vary significantly.
The absence of CD62L has been linked to the effector stage (19, 23, 39, 40, 41). In our assays, CD62L was not down-regulated in vitro when the cultures were analyzed after 72 h. However, these cultures usually also displayed reduced cytotoxic effector function. In contrast, CD62L was consistently down-modulated in cultures tested 48 h after stimulation or after repetitive administration of p33 (not shown) or on CTL activated in vivo. Thus, effector function correlated with low CD62L levels, but also seemed to require persisting Ag. After a single administration of p33, our culture conditions simulate a situation in which the stimulating peptide is rapidly degraded or turned over since it is known that the average t1/2 of peptides in serum-complemented medium is 10–100 min (42). The observation that CD62L was not (anymore) reduced 3 days after stimulation in vitro may be explained by the possibility that peptide was degraded too rapidly to result in sustained CD62L down-regulation.
CTL memory
The nature of T cell memory is debated about. Two opposing but not mutually exclusive views have emerged, one postulating that long-lived memory T cells persist in the absence of Ag (8, 9, 10), the other suggesting that protective T cell memory against peripheral infections depends on persisting Ag (6, 7, 11, 12). Long-lived memory T cells may confer protection against a systemic infection because this allows early restimulation and development of effector function. On the other hand, antivirally protective T cells may rather represent continuously activated, Ag-dependent effector T cells that can promote immediate effector function, migrate through solid tissue, interfere with replication and spreading of a sequestered pathogen, and thus promote protection to a peripheral infection. Thus, in order for long-lived memory T cells to intervene with a local peripheral infection, they may require a period of restimulation before they can exert effector function. This lag period may give a rapidly replicating pathogen enough time to replicate locally and cause direct tissue damage in the case of cytopathic viruses or to infect a sufficient number of target cells, rendering them susceptible to immunopathologic destruction in the case of noncytopathic viruses. In such a situation, long-lived memory T cells would not appear to be antivirally protective to a peripheral challenge (11, 12, 43).
During the acute phase, 100% of the LCMV-specific effector CTL expressed a CD44highCD62L- phenotype. CTL from 6–9-day-old cultures acquired a previously described CD44highCD62L+ memory stage (22) after 6–10 divisions and, in contrast to acute phase effector CTL, required prolonged incubation periods to develop cytotoxic activity. In LCMV memory mice, we and others (19) detected a CD44highCD62L- and a CD44highCD62L+ transgenic LCMV-specific CTL population after 30 to 60 days. Such mixed CTL populations were capable of rapidly eliminating Ag in vivo (our data) and in vitro (19). Together with the observation that acute phase effector CTL are CD62L- in vivo, we may conclude that the CD62L- effector memory CTL population accounts for rapid effector function found in LCMV memory mice. Conversely, the CD62L+ memory CTL representing the major population in the lymph nodes did not display rapid effector function. A similar correlation has been proposed for human CD4 T cells, in which CD45Rlow T cells represent Ag-primed memory T cells with rapid response kinetics and CD45Rhigh memory T cells are long lived and quiescent (44). Reviewing of several studies suggests that the CD62L-negative effector memory phenotype correlates with persisting Ag, whereas the CD62L+ memory stage appears when Ag is lost: Pihlgren et al. showed that peptide injection without adjuvant resulted in a transient down-regulation of CD62L on day 3, followed by the appearance of CD44highCD62L+ memory CTL after 6 wk (22). At this late time point, one can expect that the soluble priming peptide has been cleared from the host. On the other hand, Rogers et al. analyzed OVA-specific CD62L-negative memory T cells 36 days after s.c. immunization of OVA peptide in CFA (41). Similarly, Bradley et al. (39, 40) showed that memory T cells were confined to a CD62L- population in mice primed with keyhole limpet hemocyanin precipitated on alum or emulsified in CFA or IFA. Thus, in general, under conditions in which Ag can persist on an alum depot, in an emulsified form, or in adjuvant-induced granulomas (45), at least a fraction of memory T cells acquired a CD62L-negative phenotype, while CD44highCD62L+ memory CTL developed when Ag had been cleared. CD62L may therefore represent an activation marker that is down-regulated on effector T cells only in the presence of sufficient Ag. The effector memory CTL population in LCMV memory mice may be driven by persisting Ag, which is consistent with the findings that LCMV or retrotranscribed genomic components thereof can be recovered long after the infection has been cleared (46, 47, 48). Yet, while it seems clear that persisting Ag can maintain effector memory CTL, it is not resolved whether the presence of effector memory CTL always correlates with persisting Ag. It is also possible that the detection of elevated frequencies of effector memory CTL over prolonged time periods correlates with the initial clonal burst size (9). Collectively, our interpretation of the data is that the CD44highCD62L- memory CTL population represents effector memory CTL capable of immediately eliminating specific Ag, whereas CD44highCD62L+CTL may represent memory cells that require restimulation for cytotoxic effector function.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Stephan Oehen, Institute for Experimental Immunology, University Hospital Zürich, Schmelzbergstr. 12, 8091 Zürich, Switzerland. E-mail address:
3 Abbreviations used in this paper: CD62L, CD62 ligand; BSS, balanced salt solution; CFSE, 5 (and 6)-carboxyfluorescein diacetate, succinimidyl ester; FasL, Fas ligand; GP, glycoprotein; LCMV, lymphocytic choriomeningitis virus; PE, phycoerythrin; PFU, plaque-forming unit.
Received for publication March 23, 1998. Accepted for publication July 14, 1998.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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N. Brewig, A. Kissenpfennig, B. Malissen, A. Veit, T. Bickert, B. Fleischer, S. Mostbock, and U. Ritter Priming of CD8+ and CD4+ T Cells in Experimental Leishmaniasis Is Initiated by Different Dendritic Cell Subtypes J. Immunol., January 15, 2009; 182(2): 774 - 783. [Abstract] [Full Text] [PDF]
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 V. V. Ganusov and R. J. De Boer Estimating In Vivo Death Rates of Targets due to CD8 T-Cell-Mediated Killing J. Virol., December 1, 2008; 82(23): 11749 - 11757. [Abstract] [Full Text] [PDF]
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S. Sad, R. Dudani, K. Gurnani, M. Russell, H. van Faassen, B. Finlay, and L. Krishnan Pathogen Proliferation Governs the Magnitude but Compromises the Function of CD8 T Cells J. Immunol., May 1, 2008; 180(9): 5853 - 5861. [Abstract] [Full Text] [PDF]
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A. J. Currie, R. G. van der Most, S. A. Broomfield, A. C. Prosser, M. G. Tovey, and B. W. S. Robinson Targeting the Effector Site with IFN-{alpha}{beta}-Inducing TLR Ligands Reactivates Tumor-Resident CD8 T Cell Responses to Eradicate Established Solid Tumors J. Immunol., February 1, 2008; 180(3): 1535 - 1544. [Abstract] [Full Text] [PDF]
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H. Richards, M. P. Longhi, K. Wright, A. Gallimore, and A. Ager CD62L (L-Selectin) Down-Regulation Does Not Affect Memory T Cell Distribution but Failure to Shed Compromises Anti-Viral Immunity J. Immunol., January 1, 2008; 180(1): 198 - 206. [Abstract] [Full Text] [PDF]
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K. E. Matthews, J. S. Qin, J. Yang, I. F. Hermans, M. J. Palmowski, V. Cerundolo, and F. Ronchese Increasing the Survival of Dendritic Cells In Vivo Does Not Replace the Requirement for CD4+ T Cell Help during Primary CD8+ T Cell Responses J. Immunol., November 1, 2007; 179(9): 5738 - 5747. [Abstract] [Full Text] [PDF]
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 I. Jarchum, J. C. Baker, T. Yamada, T. Takaki, M. P. Marron, D. V. Serreze, and T. P. DiLorenzo In Vivo Cytotoxicity of Insulin-Specific CD8+ T-Cells in HLA-A*0201 Transgenic NOD Mice Diabetes, October 1, 2007; 56(10): 2551 - 2560. [Abstract] [Full Text] [PDF]
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P. H. Horne, M. A. Koester, K. Jayashankar, K. E. Lunsford, H. L. Dziema, and G. L. Bumgardner Disparate Primary and Secondary Allospecific CD8+ T Cell Cytolytic Effector Function in the Presence or Absence of Host CD4+ T Cells J. Immunol., July 1, 2007; 179(1): 80 - 88. [Abstract] [Full Text] [PDF]
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 R.-H. Xu, M. Fang, A. Klein-Szanto, and L. J. Sigal Memory CD8+ T cells are gatekeepers of the lymph node draining the site of viral infection PNAS, June 26, 2007; 104(26): 10992 - 10997. [Abstract] [Full Text] [PDF]
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 J. E. Knickelbein, S. Divito, and R. L. Hendricks Modulation of CD8+ CTL Effector Function by Fibroblasts Derived from the Immunoprivileged Cornea Invest. Ophthalmol. Vis. Sci., May 1, 2007; 48(5): 2194 - 2202. [Abstract] [Full Text] [PDF]
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 C. Chiu, A. G. Heaps, V. Cerundolo, A. J. McMichael, C. R. Bangham, and M. F. C. Callan Early acquisition of cytolytic function and transcriptional changes in a primary CD8+ T-cell response in vivo Blood, February 1, 2007; 109(3): 1086 - 1094. [Abstract] [Full Text] [PDF]
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M. Fang and L. J. Sigal Direct CD28 Costimulation Is Required for CD8+ T Cell-Mediated Resistance to an Acute Viral Disease in a Natural Host J. Immunol., December 1, 2006; 177(11): 8027 - 8036. [Abstract] [Full Text] [PDF]
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T. A. Stoklasek, K. S. Schluns, and L. Lefrancois Combined IL-15/IL-15R{alpha} Immunotherapy Maximizes IL-15 Activity In Vivo J. Immunol., November 1, 2006; 177(9): 6072 - 6080. [Abstract] [Full Text] [PDF]
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S.-W. Lee, Y. Park, A. Song, H. Cheroutre, B. S. Kwon, and M. Croft Functional Dichotomy between OX40 and 4-1BB in Modulating Effector CD8 T Cell Responses J. Immunol., October 1, 2006; 177(7): 4464 - 4472. [Abstract] [Full Text] [PDF]
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S. Laffont, J. D. Coudert, L. Garidou, L. Delpy, A. Wiedemann, C. Demur, C. Coureau, and J.-C. Guery CD8+ T-cell-mediated killing of donor dendritic cells prevents alloreactive T helper type-2 responses in vivo Blood, October 1, 2006; 108(7): 2257 - 2264. [Abstract] [Full Text] [PDF]
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R. A. Luu, K. Gurnani, R. Dudani, R. Kammara, H. van Faassen, J.-C. Sirard, L. Krishnan, and S. Sad Delayed Expansion and Contraction of CD8+ T Cell Response during Infection with Virulent Salmonella typhimurium J. Immunol., August 1, 2006; 177(3): 1516 - 1525. [Abstract] [Full Text] [PDF]
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Y. Meng, H. Harlin, J. P. O'Keefe, and T. F. Gajewski Induction of Cytotoxic Granules in Human Memory CD8+ T Cell Subsets Requires Cell Cycle Progression J. Immunol., August 1, 2006; 177(3): 1981 - 1987. [Abstract] [Full Text] [PDF]
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D. Masopust, S.-J. Ha, V. Vezys, and R. Ahmed Stimulation History Dictates Memory CD8 T Cell Phenotype: Implications for Prime-Boost Vaccination J. Immunol., July 15, 2006; 177(2): 831 - 839. [Abstract] [Full Text] [PDF]
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 F. Nishimura, J. E. Dusak, J. Eguchi, X. Zhu, A. Gambotto, W. J. Storkus, and H. Okada Adoptive Transfer of Type 1 CTL Mediates Effective Anti-Central Nervous System Tumor Response: Critical Roles of IFN-Inducible Protein-10. Cancer Res., April 15, 2006; 66(8): 4478 - 4487. [Abstract] [Full Text] [PDF]
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A. L. Every, D. R. Kramer, S. I. Mannering, A. M. Lew, and L. C. Harrison Intranasal Vaccination with Proinsulin DNA Induces Regulatory CD4+ T Cells That Prevent Experimental Autoimmune Diabetes. J. Immunol., April 15, 2006; 176(8): 4608 - 4615. [Abstract] [Full Text] [PDF]
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J. Yang, S. P. Huck, R. S. McHugh, I. F. Hermans, and F. Ronchese Perforin-dependent elimination of dendritic cells regulates the expansion of antigen-specific CD8+ T cells in vivo PNAS, January 3, 2006; 103(1): 147 - 152. [Abstract] [Full Text] [PDF]
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 A. R. Haas, J. Sun, A. Vachani, A. F. Wallace, M. Silverberg, V. Kapoor, and S. M. Albelda Cycloxygenase-2 Inhibition Augments the Efficacy of a Cancer Vaccine Clin. Cancer Res., January 1, 2006; 12(1): 214 - 222. [Abstract] [Full Text] [PDF]
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K. E. Lunsford, M. A. Koester, A. M. Eiring, P. H. Horne, D. Gao, and G. L. Bumgardner Targeting LFA-1 and CD154 Suppresses the In Vivo Activation and Development of Cytolytic (CD4-Independent) CD8+ T Cells J. Immunol., December 15, 2005; 175(12): 7855 - 7866. [Abstract] [Full Text] [PDF]
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J. K. Ahn, H. Chung, D.-s. Lee, Y. S. Yu, and H. G. Yu CD8brightCD56+ T Cells Are Cytotoxic Effectors in Patients with Active Behcet's Uveitis J. Immunol., November 1, 2005; 175(9): 6133 - 6142. [Abstract] [Full Text] [PDF]
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R. Barouch-Bentov, E. E. Lemmens, J. Hu, E. M. Janssen, N. M. Droin, J. Song, S. P. Schoenberger, and A. Altman Protein Kinase C-{theta} Is an Early Survival Factor Required for Differentiation of Effector CD8+ T Cells J. Immunol., October 15, 2005; 175(8): 5126 - 5134. [Abstract] [Full Text] [PDF]
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R. Thimme, V. Appay, M. Koschella, E. Panther, E. Roth, A. D. Hislop, A. B. Rickinson, S. L. Rowland-Jones, H. E. Blum, and H. Pircher Increased Expression of the NK Cell Receptor KLRG1 by Virus-Specific CD8 T Cells during Persistent Antigen Stimulation J. Virol., September 15, 2005; 79(18): 12112 - 12116. [Abstract] [Full Text] [PDF]
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N. Parameswaran, R. Suresh, V. Bal, S. Rath, and A. George Lack of ICAM-1 on APCs during T Cell Priming Leads to Poor Generation of Central Memory Cells J. Immunol., August 15, 2005; 175(4): 2201 - 2211. [Abstract] [Full Text] [PDF]
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H. van Faassen, M. Saldanha, D. Gilbertson, R. Dudani, L. Krishnan, and S. Sad Reducing the Stimulation of CD8+ T Cells during Infection with Intracellular Bacteria Promotes Differentiation Primarily into a Central (CD62LhighCD44high) Subset J. Immunol., May 1, 2005; 174(9): 5341 - 5350. [Abstract] [Full Text] [PDF]
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S. Chea, C. J. Dale, R. De Rose, I. A. Ramshaw, and S. J. Kent Enhanced Cellular Immunity in Macaques following a Novel Peptide Immunotherapy J. Virol., March 15, 2005; 79(6): 3748 - 3757. [Abstract] [Full Text] [PDF]
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 C. Bouneaud, Z. Garcia, P. Kourilsky, and C. Pannetier Lineage relationships, homeostasis, and recall capacities of central- and effector-memory CD8 T cells in vivo J. Exp. Med., February 22, 2005; 201(4): 579 - 590. [Abstract] [Full Text] [PDF]
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C. Ruedl, K. Schwarz, A. Jegerlehner, T. Storni, V. Manolova, and M. F. Bachmann Virus-Like Particles as Carriers for T-Cell Epitopes: Limited Inhibition of T-Cell Priming by Carrier-Specific Antibodies J. Virol., January 15, 2005; 79(2): 717 - 724. [Abstract] [Full Text] [PDF]
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S. J. Prasad, K. J. Farrand, S. A. Matthews, J. H. Chang, R. S. McHugh, and F. Ronchese Dendritic Cells Loaded with Stressed Tumor Cells Elicit Long-Lasting Protective Tumor Immunity in Mice Depleted of CD4+CD25+ Regulatory T Cells J. Immunol., January 1, 2005; 174(1): 90 - 98. [Abstract] [Full Text] [PDF]
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G. Kassiotis and B. Stockinger Anatomical Heterogeneity of Memory CD4+ T Cells Due to Reversible Adaptation to the Microenvironment J. Immunol., December 15, 2004; 173(12): 7292 - 7298. [Abstract] [Full Text] [PDF]
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A. B. Kamath, J. Woodworth, X. Xiong, C. Taylor, Y. Weng, and S. M. Behar Cytolytic CD8+ T Cells Recognizing CFP10 Are Recruited to the Lung after Mycobacterium tuberculosis Infection J. Exp. Med., December 6, 2004; 200(11): 1479 - 1489. [Abstract] [Full Text] [PDF]
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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]
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P. A. Stumbles, R. Himbeck, J. A. Frelinger, E. J. Collins, R. A. Lake, and B. W. S. Robinson Cutting Edge: Tumor-Specific CTL Are Constitutively Cross-Armed in Draining Lymph Nodes and Transiently Disseminate to Mediate Tumor Regression following Systemic CD40 Activation J. Immunol., November 15, 2004; 173(10): 5923 - 5928. [Abstract] [Full Text] [PDF]
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S. Roychowdhury, K. F. May Jr., K. S. Tzou, T. Lin, D. Bhatt, A. G. Freud, M. Guimond, A. K. Ferketich, Y. Liu, and M. A. Caligiuri Failed Adoptive Immunotherapy with Tumor-Specific T Cells: Reversal with Low-Dose Interleukin 15 but not Low-Dose Interleukin 2 Cancer Res., November 1, 2004; 64(21): 8062 - 8067. [Abstract] [Full Text] [PDF]
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M. A. Cannarile, N. Decanis, J. P. M. van Meerwijk, and T. Brocker The Role of Dendritic Cells in Selection of Classical and Nonclassical CD8+ T Cells In Vivo J. Immunol., October 15, 2004; 173(8): 4799 - 4805. [Abstract] [Full Text] [PDF]
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L. Quemeneur, L. Beloeil, M.-C. Michallet, G. Angelov, M. Tomkowiak, J.-P. Revillard, and J. Marvel Restriction of De Novo Nucleotide Biosynthesis Interferes with Clonal Expansion and Differentiation into Effector and Memory CD8 T Cells J. Immunol., October 15, 2004; 173(8): 4945 - 4952. [Abstract] [Full Text] [PDF]
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A. E. Foster, M. Marangolo, M. M. Sartor, S. I. Alexander, M. Hu, K. F. Bradstock, and D. J. Gottlieb Human CD62L- memory T cells are less responsive to alloantigen stimulation than CD62L+ naive T cells: potential for adoptive immunotherapy and allodepletion Blood, October 15, 2004; 104(8): 2403 - 2409. [Abstract] [Full Text] [PDF]
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J. Lustgarten, A. L. Dominguez, and M. Thoman Aged Mice Develop Protective Antitumor Immune Responses with Appropriate Costimulation J. Immunol., October 1, 2004; 173(7): 4510 - 4515. [Abstract] [Full Text] [PDF]
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C. D. Peacock and R. M. Welsh Origin and Fate of Lymphocytic Choriomeningitis Virus-Specific CD8+ T Cells Coexpressing the Inhibitory NK Cell Receptor Ly49G2 J. Immunol., July 1, 2004; 173(1): 478 - 484. [Abstract] [Full Text] [PDF]
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E. J. Wherry and R. Ahmed Memory CD8 T-Cell Differentiation during Viral Infection J. Virol., June 1, 2004; 78(11): 5535 - 5545. [Full Text] [PDF]
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M. A. Lyman, S. Aung, J. A. Biggs, and L. A. Sherman A Spontaneously Arising Pancreatic Tumor Does Not Promote the Differentiation of Naive CD8+ T Lymphocytes into Effector CTL J. Immunol., June 1, 2004; 172(11): 6558 - 6567. [Abstract] [Full Text] [PDF]
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H. van Faassen, R. Dudani, L. Krishnan, and S. Sad Prolonged Antigen Presentation, APC-, and CD8+ T Cell Turnover during Mycobacterial Infection: Comparison with Listeria monocytogenes J. Immunol., March 15, 2004; 172(6): 3491 - 3500. [Abstract] [Full Text] [PDF]
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U. Karrer, M. Wagner, S. Sierro, A. Oxenius, H. Hengel, T. Dumrese, S. Freigang, U. H. Koszinowski, R. E. Phillips, and P. Klenerman Expansion of Protective CD8+ T-Cell Responses Driven by Recombinant Cytomegaloviruses J. Virol., March 1, 2004; 78(5): 2255 - 2264. [Abstract] [Full Text] [PDF]
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J. Duraiswamy, M. Bharadwaj, J. Tellam, G. Connolly, L. Cooper, D. Moss, S. Thomson, P. Yotnda, and R. Khanna Induction of Therapeutic T-Cell Responses to Subdominant Tumor-associated Viral Oncogene after Immunization with Replication-incompetent Polyepitope Adenovirus Vaccine Cancer Res., February 15, 2004; 64(4): 1483 - 1489. [Abstract] [Full Text] [PDF]
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K. S. Schluns, K. D. Klonowski, and L. Lefrancois Transregulation of memory CD8 T-cell proliferation by IL-15R{alpha}+ bone marrow-derived cells Blood, February 1, 2004; 103(3): 988 - 994. [Abstract] [Full Text] [PDF]
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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]
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C. Jackaman, C. S. Bundell, B. F. Kinnear, A. M. Smith, P. Filion, D. van Hagen, B. W. S. Robinson, and D. J. Nelson IL-2 Intratumoral Immunotherapy Enhances CD8+ T Cells That Mediate Destruction of Tumor Cells and Tumor-Associated Vasculature: A Novel Mechanism for IL-2 J. Immunol., November 15, 2003; 171(10): 5051 - 5063. [Abstract] [Full Text] [PDF]
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Y. Chapdelaine, D. K. Smith, J. A. Pedras-Vasconcelos, L. Krishnan, and S. Sad Increased CD8+ T Cell Memory to Concurrent Infection at the Expense of Increased Erosion of Pre-existing Memory: The Paradoxical Role of IL-15 J. Immunol., November 15, 2003; 171(10): 5454 - 5460. [Abstract] [Full Text] [PDF]
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L. Lefrancois, A. Marzo, and K. Williams Sustained Response Initiation Is Required for T Cell Clonal Expansion But Not for Effector or Memory Development In Vivo J. Immunol., September 15, 2003; 171(6): 2832 - 2839. [Abstract] [Full Text] [PDF]
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P. Stamou, J. de Jersey, D. Carmignac, C. Mamalaki, D. Kioussis, and B. Stockinger Chronic Exposure to Low Levels of Antigen in the Periphery Causes Reversible Functional Impairment Correlating with Changes in CD5 Levels in Monoclonal CD8 T Cells J. Immunol., August 1, 2003; 171(3): 1278 - 1284. [Abstract] [Full Text] [PDF]
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T. Storni, C. Ruedl, W. A. Renner, and M. F. Bachmann Innate Immunity Together with Duration of Antigen Persistence Regulate Effector T Cell Induction J. Immunol., July 15, 2003; 171(2): 795 - 801. [Abstract] [Full Text] [PDF]
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 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]
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A. Camporeale, A. Boni, G. Iezzi, E. Degl'Innocenti, M. Grioni, A. Mondino, and M. Bellone Critical Impact of the Kinetics of Dendritic Cells Activation on the in Vivo Induction of Tumor-specific T Lymphocytes Cancer Res., July 1, 2003; 63(13): 3688 - 3694. [Abstract] [Full Text] [PDF]
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A. M. Byers, C. C. Kemball, J. M. Moser, and A. E. Lukacher Cutting Edge: Rapid In Vivo CTL Activity by Polyoma Virus-Specific Effector and Memory CD8+ T Cells J. Immunol., July 1, 2003; 171(1): 17 - 21. [Abstract] [Full Text] [PDF]
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J. M. Curtsinger, D. C. Lins, and M. F. Mescher Signal 3 Determines Tolerance versus Full Activation of Naive CD8 T Cells: Dissociating Proliferation and Development of Effector Function J. Exp. Med., May 5, 2003; 197(9): 1141 - 1151. [Abstract] [Full Text] [PDF]
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J. Duraiswamy, M. Sherritt, S. Thomson, J. Tellam, L. Cooper, G. Connolly, M. Bharadwaj, and R. Khanna Therapeutic LMP1 polyepitope vaccine for EBV-associated Hodgkin disease and nasopharyngeal carcinoma Blood, April 15, 2003; 101(8): 3150 - 3156. [Abstract] [Full Text] [PDF]
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V. Douin-Echinard, J.-M. Peron, V. Lauwers-Cances, G. Favre, and B. Couderc Involvement of CD70 and CD80 intracytoplasmic domains in the co-stimulatory signal required to provide an antitumor immune response Int. Immunol., March 1, 2003; 15(3): 359 - 372. [Abstract] [Full Text] [PDF]
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E. V. Ravkov, C. M. Myrick, and J. D. Altman Immediate Early Effector Functions of Virus-Specific CD8+CCR7+ Memory Cells in Humans Defined by HLA and CC Chemokine Ligand 19 Tetramers J. Immunol., March 1, 2003; 170(5): 2461 - 2468. [Abstract] [Full Text] [PDF]
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U. Karrer, S. Sierro, M. Wagner, A. Oxenius, H. Hengel, U. H. Koszinowski, R. E. Phillips, and P. Klenerman Memory Inflation: Continuous Accumulation of Antiviral CD8+ T Cells Over Time J. Immunol., February 15, 2003; 170(4): 2022 - 2029. [Abstract] [Full Text] [PDF]
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C. E. Hirst, M. S. Buzza, C. H. Bird, H. S. Warren, P. U. Cameron, M. Zhang, P. G. Ashton-Rickardt, and P. I. Bird The Intracellular Granzyme B Inhibitor, Proteinase Inhibitor 9, Is Up-Regulated During Accessory Cell Maturation and Effector Cell Degranulation, and Its Overexpression Enhances CTL Potency J. Immunol., January 15, 2003; 170(2): 805 - 815. [Abstract] [Full Text] [PDF]
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R. L. Hengel, V. Thaker, M. V. Pavlick, J. A. Metcalf, G. Dennis Jr., J. Yang, R. A. Lempicki, I. Sereti, and H. C. Lane Cutting Edge: L-Selectin (CD62L) Expression Distinguishes Small Resting Memory CD4+ T Cells That Preferentially Respond to Recall Antigen J. Immunol., January 1, 2003; 170(1): 28 - 32. [Abstract] [Full Text] [PDF]
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 B. P. Olivieri, V. Cotta-de-Almeida, and T. Araujo-Jorge Benznidazole Treatment following Acute Trypanosoma cruzi Infection Triggers CD8+ T-Cell Expansion and Promotes Resistance to Reinfection Antimicrob. Agents Chemother., December 1, 2002; 46(12): 3790 - 3796. [Abstract] [Full Text] [PDF]
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L. A. E. Harmala, E. G. Ingulli, J. M. Curtsinger, M. M. Lucido, C. S. Schmidt, B. J. Weigel, B. R. Blazar, M. F. Mescher, and C. A. Pennell The Adjuvant Effects of Mycobacterium tuberculosis Heat Shock Protein 70 Result from the Rapid and Prolonged Activation of Antigen-Specific CD8+ T Cells In Vivo J. Immunol., November 15, 2002; 169(10): 5622 - 5629. [Abstract] [Full Text] [PDF]
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J. Hernandez, S. Aung, K. Marquardt, and L. A. Sherman Uncoupling of Proliferative Potential and Gain of Effector Function by CD8+ T Cells Responding to Self-Antigens J. Exp. Med., August 5, 2002; 196(3): 323 - 333. [Abstract] [Full Text] [PDF]
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K. Haglund, I. Leiner, K. Kerksiek, L. Buonocore, E. Pamer, and J. K. Rose Robust Recall and Long-Term Memory T-Cell Responses Induced by Prime-Boost Regimens with Heterologous Live Viral Vectors Expressing Human Immunodeficiency Virus Type 1 Gag and Env Proteins J. Virol., June 27, 2002; 76(15): 7506 - 7517. [Abstract] [Full Text] [PDF]
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S. P. Li, Z. Cai, W. Shi, A. Brunmark, M. Jackson, and P.-J. Linton Early Antigen-Specific Response by Naive CD8 T Cells Is Not Altered with Aging J. Immunol., June 15, 2002; 168(12): 6120 - 6127. [Abstract] [Full Text] [PDF]
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S. N. Mueller, C. M. Jones, C. M. Smith, W. R. Heath, and F. R. Carbone Rapid Cytotoxic T Lymphocyte Activation Occurs in the Draining Lymph Nodes After Cutaneous Herpes Simplex Virus Infection as a Result of Early Antigen Presentation and Not the Presence of Virus J. Exp. Med., March 4, 2002; 195(5): 651 - 656. [Abstract] [Full Text] [PDF]
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R. M. Coles, S. N. Mueller, W. R. Heath, F. R. Carbone, and A. G. Brooks Progression of Armed CTL from Draining Lymph Node to Spleen Shortly After Localized Infection with Herpes Simplex Virus 1 J. Immunol., January 15, 2002; 168(2): 834 - 838. [Abstract] [Full Text] [PDF]
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M. J. Estcourt, A. J. Ramsay, A. Brooks, S. A. Thomson, C. J. Medveckzy, and I. A. Ramshaw Prime-boost immunization generates a high frequency, high-avidity CD8+ cytotoxic T lymphocyte population Int. Immunol., January 1, 2002; 14(1): 31 - 37. [Abstract] [Full Text] [PDF]
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W. Weninger, M. A. Crowley, N. Manjunath, and U. H. von Andrian Migratory Properties of Naive, Effector, and Memory CD8+ T Cells J. Exp. Med., October 1, 2001; 194(7): 953 - 966. [Abstract] [Full Text] [PDF]
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K. Sato, Y. Torimoto, Y. Tamura, M. Shindo, H. Shinzaki, K. Hirai, and Y. Kohgo Immunotherapy using heat-shock protein preparations of leukemia cells after syngeneic bone marrow transplantation in mice Blood, September 15, 2001; 98(6): 1852 - 1857. [Abstract] [Full Text] [PDF]
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J. Hernandez, S. Aung, W. L. Redmond, and L. A. Sherman Phenotypic and Functional Analysis of CD8+ T Cells Undergoing Peripheral Deletion in Response to Cross-Presentation of Self-Antigen J. Exp. Med., September 10, 2001; 194(6): 707 - 718. [Abstract] [Full Text] [PDF]
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J. P. Medema, D. H. Schuurhuis, D. Rea, J. van Tongeren, J. de Jong, S. A. Bres, S. Laban, R. E.M. Toes, M. Toebes, T. N.M. Schumacher, et al. Expression of the Serpin Serine Protease Inhibitor 6 Protects Dendritic Cells from Cytotoxic T Lymphocyte-induced Apoptosis: Differential Modulation by T Helper Type 1 and Type 2 Cells J. Exp. Med., September 4, 2001; 194(5): 657 - 668. [Abstract] [Full Text] [PDF]
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 Y. Kudo, C A R Boyd, I L Sargent, and C W G Redman Tryptophan degradation by human placental indoleamine 2,3-dioxygenase regulates lymphocyte proliferation J. Physiol., August 15, 2001; 535(1): 207 - 215. [Abstract] [Full Text] [PDF]
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J. K. Sandberg, N. M. Fast, and D. F. Nixon Functional Heterogeneity of Cytokines and Cytolytic Effector Molecules in Human CD8+ T Lymphocytes J. Immunol., July 1, 2001; 167(1): 181 - 187. [Abstract] [Full Text] [PDF]
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J. M. Faint, N. E. Annels, S. J. Curnow, P. Shields, D. Pilling, A. D. Hislop, L. Wu, A. N. Akbar, C. D. Buckley, P. A. H. Moss, et al. Memory T Cells Constitute a Subset of the Human CD8+CD45RA+ Pool with Distinct Phenotypic and Migratory Characteristics J. Immunol., July 1, 2001; 167(1): 212 - 220. [Abstract] [Full Text] [PDF]
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N. Auphan-Anezin and A.-M. Schmitt-Verhulst Differential Survival of Transferred CD8 T Cells and Host Reconstitution Depending on TCR Avidity for Host-Expressed Alloantigen J. Immunol., June 15, 2001; 166(12): 7200 - 7207. [Abstract] [Full Text] [PDF]
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D. J. Nelson, S. Mukherjee, C. Bundell, S. Fisher, D. van Hagen, and B. Robinson Tumor Progression Despite Efficient Tumor Antigen Cross-Presentation and Effective "Arming" of Tumor Antigen-Specific CTL J. Immunol., May 1, 2001; 166(9): 5557 - 5566. [Abstract] [Full Text] [PDF]
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R. J. Hogan, E. J. Usherwood, W. Zhong, A. D. Roberts, R. W. Dutton, A. G. Harmsen, and D. L. Woodland Activated Antigen-Specific CD8+ T Cells Persist in the Lungs Following Recovery from Respiratory Virus Infections J. Immunol., February 1, 2001; 166(3): 1813 - 1822. [Abstract] [Full Text] [PDF]
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M. Ahmadzadeh, S. F. Hussain, and D. L. Farber Heterogeneity of the Memory CD4 T Cell Response: Persisting Effectors and Resting Memory T Cells J. Immunol., January 15, 2001; 166(2): 926 - 935. [Abstract] [Full Text] [PDF]
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K. Izeradjene, J.-P. Revillard, and L. Genestier Inhibition of thymidine synthesis by folate analogues induces a Fas-Fas ligand-independent deletion of superantigen-reactive peripheral T cells Int. Immunol., January 1, 2001; 13(1): 85 - 93. [Abstract] [Full Text] [PDF]
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H. Yamada, G. Matsuzaki, Y. Iwamoto, and K. Nomoto Unusual cytotoxic activities of thymus-independent, self-antigen-specific CD8+ T cells Int. Immunol., December 1, 2000; 12(12): 1677 - 1683. [Abstract] [Full Text] [PDF]
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A. L. Marzo, B. F. Kinnear, R. A. Lake, J. J. Frelinger, E. J. Collins, B. W. S. Robinson, and B. Scott Tumor-Specific CD4+ T Cells Have a Major ""Post-Licensing"" Role in CTL Mediated Anti-Tumor Immunity J. Immunol., December 1, 2000; 165(11): 6047 - 6055. [Abstract] [Full Text] [PDF]
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D. Nelson, C. Bundell, and B. Robinson In Vivo Cross-Presentation of a Soluble Protein Antigen: Kinetics, Distribution, and Generation of Effector CTL Recognizing Dominant and Subdominant Epitopes J. Immunol., December 1, 2000; 165(11): 6123 - 6132. [Abstract] [Full Text] [PDF]
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I. Apostolou, A. Cumano, G. Gachelin, and P. Kourilsky Evidence for Two Subgroups of CD4-CD8- NKT Cells with Distinct TCR{alpha}{beta} Repertoires and Differential Distribution in Lymphoid Tissues J. Immunol., September 1, 2000; 165(5): 2481 - 2490. [Abstract] [Full Text] [PDF]
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B. K. Cho, V. P. Rao, Q. Ge, H. N. Eisen, and J. Chen Homeostasis-stimulated Proliferation Drives Naive T Cells to Differentiate Directly into Memory T Cells J. Exp. Med., August 21, 2000; 192(4): 549 - 556. [Abstract] [Full Text] [PDF]
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K. Murali-Krishna and R. Ahmed Cutting Edge: Naive T Cells Masquerading as Memory Cells J. Immunol., August 15, 2000; 165(4): 1733 - 1737. [Abstract] [Full Text] [PDF]
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H. Andersen, D. Dempsey, R. Chervenak, and S. R. Jennings Expression of Intracellular IFN-{gamma} in HSV-1-Specific CD8+ T Cells Identifies Distinct Responding Subpopulations During the Primary Response to Infection J. Immunol., August 15, 2000; 165(4): 2101 - 2107. [Abstract] [Full Text] [PDF]
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P. Bousso, F. Lemaitre, J. Bilsborough, and P. Kourilsky Facing Two T Cell Epitopes: A Degree of Randomness in the Primary Response Is Lost Upon Secondary Immunization J. Immunol., July 15, 2000; 165(2): 760 - 767. [Abstract] [Full Text] [PDF]
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S. Gasser, P. Corthesy, F. Beerman, H. R. MacDonald, and M. Nabholz Constitutive Expression of a Chimeric Receptor That Delivers IL-2/IL-15 Signals Allows Antigen-Independent Proliferation of CD8+CD44high But Not Other T Cells J. Immunol., June 1, 2000; 164(11): 5659 - 5667. [Abstract] [Full Text] [PDF]
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T. J. Dengler and J. S. Pober Human Vascular Endothelial Cells Stimulate Memory But Not Naive CD8+ T Cells to Differentiate into CTL Retaining an Early Activation Phenotype J. Immunol., May 15, 2000; 164(10): 5146 - 5155. [Abstract] [Full Text] [PDF]
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D. Wodarz, R. M. May, and M. A. Nowak The role of antigen-independent persistence of memory cytotoxic T lymphocytes Int. Immunol., April 1, 2000; 12(4): 467 - 477. [Abstract] [Full Text] [PDF]
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I. F. Hermans, D. S. Ritchie, J. Yang, J. M. Roberts, and F. Ronchese CD8+ T Cell-Dependent Elimination of Dendritic Cells In Vivo Limits the Induction of Antitumor Immunity J. Immunol., March 15, 2000; 164(6): 3095 - 3101. [Abstract] [Full Text] [PDF]
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