| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Medicine, University of Cambridge, Cambridge, United Kingdom
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-herpesvirus human CMV
(HCMV)3 establishes
life-long infection with viral latency in cells of the myeloid lineage
and intermittent shedding of infectious virions from mucosal surfaces.
T cells play a crucial role in the control of HCMV; in HCMV-infected
individuals, impairment of T cell responses (e.g., in advanced HIV
infection or in allograft recipients who receive immunosuppressive
drugs) is frequently followed by uncontrolled HCMV reactivation that
leads to serious disease. HCMV provides an informative model of how
long-term human CD8+ T cell memory is maintained
in presence of persistent viral Ag. Strong virus-specific
CD8+ T cell responses develop during primary
infection and are maintained indefinitely. Healthy HCMV carriers have
large populations of circulating HCMV-specific
CD8+ T cells, many of which recognize peptides
derived from the virus structural protein pp65 (product of the
UL83 gene) (1) or the major
immediate-early (IE) proteins expressed in infected cells
(2). The CD8+ T cell response
against a defined HCMV peptide is typically dominated by relatively few
individual clones that are greatly expanded and maintained in PBMC for
long periods (3).
To understand the mechanisms by which T cell memory is generated and
maintained, there is much interest in using the cell surface phenotype
to distinguish between naive cells and Ag-experienced cells. For human
T cells, it was initially proposed that expression of the high m.w.
isoform of leukocyte common Ag, CD45RA, identified naive cells, whereas
the low m.w. isoform, CD45RO, identified Ag-experienced cells (4, 5). However, analysis of the phenotypic distribution of
Ag-specific CD8+ T cells in virus carriers using
either TCR clonotypic probing or class I MHC tetramers incorporating
HCMV or EBV peptides has clearly demonstrated that these Ag-specific
cells are distributed in both the CD45ROhigh and
CD45RAhigh populations (6, 7). In
long-term HCMV carriers, cells of an individual HCMV-specific
CD8+ T cell clone are present in both the
CD45RAhigh and CD45ROhigh
populations; the CD45RAhigh population
contributes 6- to 10-fold more than the
CD45ROhigh population to the total clone size in
PBMC (8). The pool of CD45RAhigh
CD8+ T cells thus contains a mixture of naive
cells and Ag-experienced cells. Hamman et al. (9) have
proposed that CD45RAhigh cells, which express the
TNFR family member CD27, represent naive cells, and that
CD45RAhighCD27- cells,
which have high levels of preformed perforin and shortened telomere
length, are a terminally differentiated effector population. More
recently, Sallusto et al. (10) described a subpopulation
of CD45RAhighCD8+ T cells
that express the chemokine receptor CCR7, which favors homing to lymph
nodes through interaction with secondary lymphoid chemokine expressed
on endothelial cells; these cells lack perforin, but upon stimulation
produce large amounts of IL-2, but not IFN-
. In contrast,
CD45RAhighCCR7- cells
express perforin and upon stimulation produce little IL-2
(10). The
CD45RAhighCD27- cells
characterized by Hamman et al. (9) appear to be a
subpopulation within the
CD45RAhighCCR7- cells.
Using MHC class I tetramers incorporating peptides of HIV or HCMV to identify Ag-specific CD8+ T cells, Champagne et al. (11) found that tetramer-positive cells were present in both the CD45RAhighCCR7+ and CD45RAhighCCR7- subpopulations of CD8+ T cells and suggested that CD45RAhighCCR7- cells might be terminally differentiated effector cells. Faint et al. (12) reported that CD45RAhighCD8+ T cells show a bimodal distribution of CD11a expression, and Ag-specific CD8+ T cells (identified by MHC class I tetramers incorporating peptides of HCMV or EBV) were found within the CD11ahigh subpopulation. They proposed that CD45RAhighCD11alow cells are naive cells, and that CD45RAhighCD11ahigh cells are a subset of Ag-experienced cells (12). Circulating melanoma specific CD8+ T cells have been described in patients with metastatic melanoma; MART-1-specific cells are predominantly CD45RO+, whereas tyrosinase-specific cells are predominantly CD45RA+ and express perforin, but appear to have impaired effector function in vivo (13, 14).
In this study, we found that expression of the costimulatory molecule CD28 distinguishes two populations within the CD45RAhigh CD8+ T cell pool, and we used peptide-MHC tetramers and TCR clonotypic analysis to determine the distribution of virus-specific clones between the CD28+CD45RAhigh and CD28-CD45RAhigh subpopulations. We used four-color flow cytometry to analyze the expression of chemokine receptors and adhesion and costimulation molecules on the CD28+CD45RAhigh, CD28-CD45RAhigh, CD28+CD45ROhigh, and CD28-CD45ROhigh subpopulations. To determine whether CD8+CD45RAhighCCR7- cells are terminally differentiated effector cells, we assessed the ability of purified CD8+CD45ROhigh and CD8+CD45RAhighCCR7- cells to respond to stimulation with specific viral peptide and observed strong proliferative and peptide-specific cytotoxic responses. Our results show that CD8+ T cell memory to HCMV is maintained by cells that show heterogeneity of activation state and costimulation molecule expression and are found within both the CD45ROhigh and CD28-CD45RAhigh T cell pools.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Seven healthy HCMV seropositive laboratory donors were studied, all of whom were also EBV seropositive. In addition, two further EBV seropositive laboratory donors were studied. One patient with primary HCMV infection was also studied, in whom the diagnosis was confirmed serologically by detection of HCMV-specific IgM and subsequent isotype switching to HCMV-specific IgG (Public Health Laboratory Service, Addenbrookes Hospital, Cambridge, U.K.).
Viral peptides
The following peptides of HCMV pp65 were used: NLVPMVATV (aa
495–503), restricted through HLA-A2; TPRVTGGGAM (aa 417–426),
restricted through HLA-B7; EFFWDANDIY (aa 511–525), restricted through
HLA-B44; and VFPTKDVAL (aa 187–195), restricted through HLA-B35 (all
supplied by Affiniti Research Products (Exeter, U.K.); >95% pure by
HPLC). Peptides of HCMV IE72 were: CRVLCCYVL (aa 309–317), restricted
through HLA-B7; and DELRRKMMYM (aa 198–207), restricted through HLA-B8
(2) (both gifts from Dr. F. Kern, Charitie, Humbolt
University, Berlin, Germany). Peptides of EBV EBNA3C were: EENLLDFVRF
(aa 281–290), restricted through HLA-B44.02; and PQPRAPIRPIPT (aa
880–891), restricted through HLA-B7 (supplied by Affiniti Research
Products). All peptides were dissolved in RPMI and used at a 40 µg/ml
final concentration (Table I
).
|
mAbs were specific for CD3, CD4, CD8, CD14, CD16, CD19, CD25,
CD27, CD28, CD45RO, CD45RA, CD56, CD57, CD62 ligand (CD62L), and HLA-DR
(TCS Biologicals, Burlingdale, CA); anti-TCR V3, -11, -13.1,
-14, and -17 (Immunotech); and anti-chemokine receptors CXCR4,
CCR5, CCR6, and CCR7 (BD Biosciences, Oxford, U.K.). Abs were
conjugated to FITC, PE, TriColor (TC), or allophycocyanin.
Because the anti-CCR7 was an unconjugated IgM, cells were stained
with anti-IgM biotin (BD PharMingen), washed, and then further
stained with streptavidin-Red 670 (Life Technologies, Paisley,
U.K.). Before immunostaining for four-color analysis,
CD8+ cells were enriched from fresh PBMC by
incubating PBMC with anti-CD8 MACS beads (Miltenyi Biotec, Auburn,
CA), followed by separation on a BS-positive selection column.
Because the anti-CD8 MACS beads did not occupy all the CD8 sites on
the cells, the enriched cells were restained with
anti-CD8-allophycocyanin (FL4) so that only high-expressing
CD8+ T cells were gated for subsequent analysis.
We also used an MHC class I peptide tetramer of HLA-B7 containing HCMV
pp65 peptide TPRVTGGGAM (gift from Dr. J. Lipolis, National Institutes
of Health Core Tetramer Facility, Atlanta, GA).
Purification of cell subpopulations
For clonotypic probing analysis, PBMC were stained with anti-CD8, anti-CD45RA, and anti-CD28 to sort the CD8+CD45RA- (CD45RO cells), CD8+CD28-CD45RAhigh, and CD8+CD28+CD45RAhigh T cell subpopulations using a FACSVantage cell sorter (BD Biosciences). To obtain the CD28-CD27+ and CD28-CD27- subpopulations of CD8+ T cells, PBMC were first depleted of CD16+ NK cells (by incubation with anti-CD16 IgM (Leu-11b; BD Biosciences) followed by complement) anddepleted of CD4+ cells with anti-CD4-conjugated MACS microbeads (Miltenyi Biotech). Cells were then stained with anti-CD28-FITC and anti-CD27-PE and sorted into CD28-CD27- and CD28-CD27+ subpopulations by a FACSVantage cell sorter. The purity of lymphocyte populations prepared by FACSVantage cell sorting or MACS microbeads was always >98%.
For functional studies, CD8+CD45ROhigh and CD8+CD45RAhigh cells were prepared from PBMC using negative cell sorting; PBMC were stained with FITC-conjugated anti-CD4, anti-CD19, anti-CD16, and anti-CD56 (to remove CD4+ T cells, B cells, and NK cells, respectively) and either anti-CD45RA or anti-CD45RO and sorted for nonstained cells using a FACS Vantage cell sorter, yielding CD8+CD45ROhigh and CD8+CD45RAhigh T cell populations, respectively. CD45RAhighCD28-CCR7-CD8+ T cells were also prepared by negative cell sorting, following staining with FITC-conjugated anti-CD4, anti-CD19, anti-CD16, anti-CD56, anti-CD45RO, anti-CD28, and anti-CCR7. Aliquots of the negative selected cells were restained with anti-CD8, anti-CD45RA, and anti-CD45RO to confirm their purity, which was >99% for CD45RAhigh cells and 98–99% for CD45ROhigh cells. For functional studies, CD28- cells were prepared from PBMC by negative selection using anti-CD28-FITC, followed by anti-FITC MACS microbeads (purity of lymphocyte populations, >98%).
For the functional studies, purified subpopulations of cells were stimulated in vitro with irradiated autologous peptide-pulsed PBMC in RPMI plus 10% FCS and 10% human AB serum plus 5 IU/ml human rIL-2 (provided by the Medical Research Council Centralized Facility for AIDS Reagents, National Institute of Biological Standards and Control) and cultured for 14 days, followed by assay of peptide-specific cytotoxicity as previously described (1, 3) and/or analysis by flow cytometry.
Generation of T cell clones and determination of TCR
-chain hypervariable sequence
T cell clones were generated from single-cell cultures by
limiting dilution analysis followed by recloning as previously
described (3). Total RNA was extracted from each clone,
and first-strand cDNA was derived from this before PCR using a panel of
36 TCR V family specific primers together with the corresponding C
region-specific primer (synthesized by Genosys, Cambridge, U.K.) as
previously described (3). The amplified PCR product from
the clonal V amplification was purified (Qiagen, Valencia,
CA) and sequenced by automated DNA sequencing (Department of
Biochemistry, University of Cambridge, Cambridge, U.K.).
Quantitation of TCR clonotypes in phenotypically defined subpopulations
Complementary 15–20 mer oligonucleotide probes based on the TCR
-chain hypervariable region of immunodominant peptide-specific CTL
clones were designed. Such probes are highly specific for individual
CTL clonotypes (8). mRNA was extracted from purified
subpopulations of cells, reverse transcribed into cDNA, and amplified
in duplicate using TCR V-specific PCR primers as described
previously. A positive control sample from the original defined CTL
clone and a negative control sample from the pooled PBMC of four HCMV-
and HIV-seronegative donors were amplified simultaneously in duplicate
using the same primers. Each PCR product was separated on an agarose
gel and blotted onto a Zeta-probe nylon filter (Bio-Rad, Hercules,
CA). After washing and prehybridization, the filter was
incubated overnight with a -32P end-labeled
clonotypic probe in hybridization buffer. After washing, the amount of
probe that had bound to each sample on the filter was quantitated using
an Instant Imager (Beckman Coulter, Palo Alto, CA). The filter was
stripped by soaking in 0.4 M NaOH, washed, and then rehybridized with a
TCR -chain constant region probe that detects all TCR sequences. In
each subpopulation studied we calculated the relative abundance of the
clonotype sequence as a proportion of all TCR sequences of the same
V family: relative abundance of clonotype sequence = 100
x ((cpm clonotypic probe/cpm TCR constant probe for the T cell
population of interest)/(cpm clonotypic probe/cpm TCR constant probe
for the positive control clone))
In each purified subpopulation of cells, the clone size was calculated
by multiplying the proportion of CD8+ cells that
had the corresponding V segment (determined by flow cytometry) by
the relative abundance of the clonotype sequence.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To determine the expression of CD28 within
CD8+CD45RAhigh cells, PBMC
from six HCMV-seropositive donors and two EBV-seropositive donors were
stained with anti-CD8-allophycocyanin, anti-CD45RO-FITC,
anti-CD45RA-TC, and anti-CD28-PE and analyzed by four-color
flow cytometry. After gating on CD8+ T cells, the
relationship between the expression of CD45RA and CD28 for a single
HCMV carrier is illustrated in Fig. 1A, in which four populations
can be identified: 1) a circumscribed population that is
CD28+CD45RAhigh (and
CD45RBlow and CD45ROlow;
data not shown), 2) a population that is
CD28+CD45RAlow/-CD45ROhigh, 3) a
small population that is
CD28-CD45RA-CD45ROhigh, and 4) a
population that is
CD28-CD45RAhighCD45ROlow. The
relative proportions of CD8+ cells in each
subpopulation varied little from subject to subject. To identify
HCMV-specific cells, PBMC were also stained with
anti-CD8-allophycocyanin, anti-CD45RA-FITC, anti-CD28-TC,
and HLA-B7-HCMVpp65 peptide tetramer-PE. Fig. 1B shows
the expression of CD28 and CD45RA after gating on tetramer-staining
CD8+ T cells. Tetramer-staining cells were
predominantly CD28- and were almost entirely
absent from the
CD28+CD45RAhigh
population.
|
-chain, and designed a clonotypic oligonucleotide probe for each
immunodominant peptide-specific clonotype. Using quantitative clonotype
probing, we determined the distribution of cells of each virus-specific
clone within purified
CD28-CD45RAhigh or
CD28+CD45RAhigh
subpopulations prepared from PBMC by cell sorting (Fig. 2). We calculated the number of cells of
the clone in PBMC by multiplying the relative proportion of clonotype
sequence within all TCR sequences of the same V family by the
proportion of CD8+ cells that express the same
V segment determined by flow cytometry. As we had previously found,
individual CTL clones that recognized HCMV peptides could be very large
(Table II). Clones specific for either
HCMV pp65 or IE72 were very abundant in the
CD28-CD45RAhigh
subpopulation, but were almost entirely absent from the
CD28+CD45RAhigh
subpopulation (clonotype detection range, 0–3%; close to the limit of
detection of the assay within the purity achieved by cell sorting). For
comparison with another persistent herpesvirus, we also derived EBV
peptide-specific CD8+ CTL clones, designed
clonotypic probes, and used these to determine the distribution of
EBV-specific clones within the same purified T cell subpopulations. An
HLA-B4402-restricted EBNA3C-specific clone from one subject was also
very abundant in the CD45ROhigh and the
CD28-CD45RAhigh
subpopulations, but not in the
CD28+CD45RAhigh
subpopulation (Table II). HLA-B7-restricted EBNA3C-specific clones from
three other subjects were almost entirely distributed within
CD45ROhigh cells (data not shown).
|
|
Using four-color flow cytometry, we studied the expression of
CD28, CD27, and CD45RA on peripheral blood CD8+ T
cells (Fig. 3). In six healthy HCMV
carriers, the proportion of CD8+ T cells that
were CD28+CD27+ ranged from
37 to 66%, the proportion that were
CD28+CD27- ranged from 1
to 3%, the proportion that were
CD28-CD27+ ranged from 9
to 26%, and the proportion that were
CD28-CD27- ranged from 24
to 38%. Thus, the vast majority of
CD28+CD8+ cells were also
CD27+; the
CD28+CD27- population was
always small. Among CD27+ cells, the level of
expression of CD27 on CD28+ cells was generally
higher than that on CD28- cells. We analyzed the
expression of CD45RA, CCR7, and CD62L after gating on either
CD8+CD28+ or
CD8+CD28- cells. The
CD8+CD28-CD27+
cells were predominantly CD45RAhigh, were
almost all CCR7-, and were 25–65%
CD62L+ (data not shown). The
CD8+CD28-CD27-
cells were also predominantly CD45RAhigh (Fig. 3), were almost all CCR7-, and were 10–55%
CD62L+ (data not shown).
|
family (Fig. 4). For
most clones, cells of the clone were distributed in both the
CD28-CD27- and
CD28-CD27+ subpopulations,
and in general, the clone size in 106 cells of
each subpopulation was greater in the
CD28-CD27+ subpopulation
than in the CD28-CD27-
subpopulation (Table III). In healthy
HCMV carrier 017, an individual HCMV-specific clone 17A was almost
entirely partitioned in the
CD28-CD27- subpopulation,
in which it comprised 38–48% of V17+
sequences; in the
CD28-CD27+ population,
this clonotype was consistently very low, close to the limit of
detection of the assay (determined by the binding of the clonotypic
probe to the negative control sample; Fig. 4B). When
purified CD28- PBMC from this donor were
stimulated in vitro with irradiated autologous peptide-pulsed PBMC and
cultured for 14 days in the presence of exogenous IL-2, there was a
strong proliferative response of
V17+CD8+ T cells that
remained CD28- and CD27-
(Fig. 5).
|
|
|
Recirculation of T cells among blood, secondary lymphoid
tissue, and peripheral tissues is an essential part of anti-viral
immune surveillance. The complex trafficking of lymphocytes is partly
regulated by specific chemokines that bind to chemokine receptors
expressed on T cells, and memory and naive T cells would be expected to
express distinctive patterns of chemokine receptors. We used four-color
flow cytometry to analyze the chemokine receptor expression on
CD8+CD28+CD45RAhigh,
CD8+CD28+CD45ROhigh,
CD8+CD28-CD45ROhigh,
and
CD8+CD28-CD45RAhigh
T cells in PBMC derived from six donors, four of whom were both
HCMV-seropositive and EBV-seropositive, using Abs against CCR5, CCR6,
CCR7, and CXCR4 shown for a representative donor (Fig. 6). For each of the four T cell
subpopulations, the results were generally consistent between
individual donors and between the HCMV-seropositive and
HCMV-seronegative donors (Table IV).
|
|
In healthy virus carriers, CD8+CD28-CD45RAhighCCR7- cells are not terminally differentiated
We have previously shown that both the CD45ROhigh and CD45RAhighCD8+ T cell populations can respond to defined HCMV peptides by proliferation and differentiation into peptide-specific cytotoxic effector T cells that are CD45ROhighCD45RAlow (8). On the basis of short term culture it has recently been suggested that CD8+CD45RA+CCR7- cells might be terminally differentiated effector cells (11). To test this hypothesis, we purified CD8+CD28-CD45RAhighCCR7- cells by negative selection to avoid ligation of cell surface CD8 or CD45RA, and as a positive control we also purified CD8+CD45ROhigh cells. Each purified population of cells was stimulated in vitro with irradiated autologous peptide-pulsed PBMC and cultured for 14 days in the presence of exogenous IL-2, followed by assay of peptide-specific cytotoxicity and analysis of surface expression of CD28, CD45RA, CD45RO, CCR5, CCR6, and CCR7 by flow cytometry.
As expected, following stimulation with peptide the
CD8+CD45ROhigh cells
proliferated, generating a large population of tetramer-positive
effector cells that up-regulated CD45RO and showed strong
peptide-specific cytotoxicity. These effector cells showed varying
levels of CD28 expression, but were CCR5high,
CCR6-, and CCR7- (Fig. 7). Following stimulation with peptide,
purified
CD8+CD28-CD45RAhighCCR7-
cells also proliferated and differentiated into peptide-specific
cytotoxic effector cells. These effector cells down-regulated CD45RA,
up-regulated CD45RO, and remained CD28-; they
were also CCR5high, CCR6-,
and CCR7-.
|
During acute primary HCMV infection in a single subject we
detected activated pp65 peptide-specific cytotoxic
CD8+ T cells in unstimulated PBMC; at a standard
E:T cell ratio, the magnitude of peptide-specific cytotoxicity was
greatest at the peak of symptoms (3 wk after the onset of symptoms) and
diminished to low levels by 8 wk after the onset of symptoms
(8). We analyzed the expression of CD28 and CD45RO on
tetramer-positive CD8+ T cells in cryopreserved
cells obtained from the same subject during and after acute primary
HCMV infection. At the peak of symptoms (3 wk after the onset of
symptoms) 80% of the tetramer-positive CD8+
cells were CD28-CD45RO+
and CCR7- (Fig. 8). During convalescence there was a
progressive expansion of the
CD28-CD45RAhighCCR7-
tetramer-positive population, which may reflect apoptotic death of some
highly activated
CD28-CD45RO+ cells and/or
redistribution of
CD28-CD45RAhigh cells from
inflamed tissues to the circulation after resolution of acute
disseminated HCMV infection. These findings are in agreement with our
previous observation in this subject that cells of an immunodominant
pp65-specific CD8+ clone were initially abundant
in CD45RO+ cells, but became progressively
enriched in CD45RA+ cells during convalescence,
consistent with clonal reversion from CD45RO+ to
CD45RA+ with time (8).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The current study adds to the evidence that the cells of a single
expanded Ag-experienced CD8+ T cell clone are
very heterogeneous in phenotype in vivo, reflecting many states of
activation/differentiation (3, 8). Naive cells are
CD28+CD45RAhighCCR7+CD62L+CD27+
and CD11alow. Following activation by Ag, all
daughter cells permanently up-regulate CD11a (proposed in Ref.
12) and up-regulate CD45RO, at least initially. Some
daughter cells remain
CD28+CD45RO+CCR7+;
these cells have been termed central memory cells (10).
CD45RO+CCR7- cells have
been termed effector memory cells (10). Our results show
that these cells are, in fact, made up of two subpopulations of
daughter cells, namely
CD28+CD45RO+CCR7-
and
CD28-CD45RO+CCR7-,
that also differ in the expression of CD57. The precise relationship
among these three different populations of
CD45RO+ cells requires further study; it is
unclear whether CD28-CD45RO+ cells can
arise directly from activated naive cells or via intermediate
CD28+CD45RO+ cells.
CD28-CD45RO+CCR7-
cells predominate in peripheral blood during acute primary HCMV
infection and revert to
CD28-CD45RA+CCR7-
cells in convalescence; on
CD28-CD45RA+ cells, the
pattern of surface expression of a wide range of chemokine receptors
and adhesion molecules closely resembles that on
CD28-CD45RO+ cells. The
factors that lead to the transition from
CD28-CD45RO+ to
CD28-CD45RA+ are not yet
understood. Our results show that when
CD28-CD45RA+CCR7-
cells are activated by peptide Ag in vitro, they proliferate, remain
CD28-, and up-regulate CD45RO and CCR5. The
circulating
CD28-CD45RO+CCR7-
population, some of which express CCR5, is relatively rich in HCMV
tetramer-positive cells (Fig. 1
) and may include cells that have
recently been activated by exposure to HCMV Ag in vivo.
The generation of phenotypic diversity within the clonal progeny of a single virus-specific cell may be an instructive process as a result of differences in the activation state of APC to which the naive cell and later daughter cells are exposed (15, 16) and differences in the cytokine milieu during their activation and differentiation (17). An alternative possibility is that activation of a single CD8+ T cell might give rise to daughter cells of different phenotypes by a stochastic process. In either case, the diversity of phenotypes may be modified by subsequent selection of those daughter cells whose activation state and/or homing pathway are best suited to control the virus at a given site. In the case of a persistent virus that infects cells in different tissues, we speculate that those viral Ags expressed in nonlymphoid tissues such as the intestine or respiratory tract may evoke specific CD8+ T cells that have a different phenotype and pathway of recirculation compared with other viral Ags expressed in lymphoid tissues. Whereas CD8+ T cell clones specific for the HCMV structural protein pp65 are abundant in CD28-CD45RAhigh cells, it is interesting that in the same donor the phenotype of expanded CD8+ T cell clones specific for EBV EBNA3C expressed in latently infected B cells was dominated by CD45RO+ cells and included very few CD28-CD45RAhigh cells.
Our finding of the same clonotype in both
CD28-CD27+ and
CD28-CD27- subpopulations
confirms that these subsets represent different activation states of
the same lineage (18). Loss of CD27 expression on
CD8+ T cells is associated with increased
expression of perforin and granzyme B and cytotoxic activity in the
absence of prior restimulation in vitro. It has been suggested that
these CD27- cells might be
terminally differentiated and possibly incapable of further cell
division (18). Our results (Fig. 5) show that following
stimulation with specific peptide, the
CD28-CD27- population
contains cells that are capable of sustained proliferation in vitro;
the ability of CD28-CD27-
cells to proliferate in vitro may depend on the specific experimental
conditions used, in particular the provision of autologous APC and
exogenous IL-2 (19). It has previously been suggested that
the CD27+CD45RAhigh population of
human CD8+ T cells may represent naive cells
(9). However, we found that expanded pp65-specific clones
were abundant in both
CD27+CD28- and
CD27-CD28- cells. Thus,
for human CD8+ T cells the phenotype
CD27+CD45RAhigh should not
be used to identify naive cells;
CD27+CD45RAhigh cells do contain naive cells,
but also contain a significant subpopulation of
CD28-CD27+ Ag-experienced
expanded clones. In general, among CD8+ T cells
that express CD27, those cells that are CD28+
express a higher level of CD27 compared with
CD28- cells (Fig. 3). Our results are consistent
with those of Kern et al. (20), who demonstrated that the
CD27int population contained many more
HCMV-specific cells than the CD27high population.
In the paper that proposed that CD27+CD45RAhigh
cells might represent naive CD8+ T cells, the
CD27+CD45RAhigh population did, in
fact, contain a significant population of CD27int
cells that stained positively for intracellular perforin and granzyme B
(Fig. 6 of Ref. 9), which probably correspond to the
Ag-experienced CD27+CD28- clones we
describe.
Our results disagree with the recent suggestion that
CD45RAhighCCR7- cells
might be terminally differentiated effector cells (11).
Champagne et al. (11) reported that
CD45RA+CCR7- cells failed to
proliferate in response to stimulation with a combination of
anti-CD3 and anti-CD28; this is not surprising, because as we
have shown almost all CD45RA+CCR7-
cells lack the expression of CD28. In contrast, when we stimulated
purified
CD28-CD45RA+CCR7-
cells with fresh autologous peptide-pulsed APC, we observed
strong proliferative responses accompanied by up-regulation of CD45RO.
This difference in functional response is probably due to experimental
conditions. We used fresh
CD28-CD45RA+CCR7-
cells and studied the response over 14 days because of the kinetics of
proliferation of CD28- cells in response to
peptide stimulation (Fig. 5), whereas in equivalent experiments
Champagne et al. (11) used cryopreserved cells and studied
the response for the first 96 h only.
The adhesion molecule and chemokine receptor expression by
CD28+CD45RAhigh cells is that
expected of naive CD8+ T cells, namely, high
expression of CD62L, CCR7, and CXCR4, which favor recirculation through
lymph nodes via interaction with high endothelial addressins,
secondary lymphoid chemokine or macrophage inflammatory
protein-3 (MIP-3), and stromal cell-derived factor-1,
respectively. CD28+CD45RO+
cells have a complex pattern of homing molecule expression; some
express one or more receptors that favor recirculation through lymph
nodes (CD62L with or without CCR7), while others constitutively express
CCR5 and/or CCR6, which would favor recruitment into inflamed tissues
where MIP-1
, MIP-1, and RANTES or MIP-3 are expressed. Almost
all CD28-CD45RAhigh cells
lack CCR7, most express little or no CXCR4, and a minority express
CD62L, which suggests that recirculation through uninflamed lymph nodes
may be less efficient; almost all
CD28-CD45RAhigh cells lack
constitutive expression of CCR5 and CCR6. Faint et al.
(12) reported a greater proportion of HCMV
tetramer-positive CD45RAhigh cells in cells
derived from liver compared with cells from lymph node, consistent with
preferential recirculation of
CD28-CD45RAhigh cells
through nonlymphoid tissues. The up-regulation of CCR5 on
CD28-CD45RAhigh cells
following activation in vitro suggests that these cells may express
additional homing receptors when they migrate into tissues in which
viral Ag is expressed during HCMV reactivation from latency.
It remains an important challenge to relate the phenotype of a CD8+ T cell to its functional role in vivo. From many years there has been a binary functional classification of Ag-experienced T cells as either effector cells or memory cells (21). In this classification effector cells are generated early in the immune response and then decline rapidly, show immediate ex vivo cytotoxicity, and upon transfer into recipients can control acute infection, but not chronic infection, whereas memory cells are generated later in the immune response, do not show immediate ex vivo cytotoxicity, and upon transfer into recipients fail to control acute infection, but do control chronic infection, because they proliferate in response to Ag and differentiate into effector cells. An important limitation of this classification is that the effector activity of a given cell is an all-or-none property, whereas subsequent experimental data from purified populations of Ag-specific T cells assayed directly ex vivo indicate that the cytotoxic activity of an Ag-specific T cell in vivo is, in fact, a quantitative variable. Following the primary immune response, the magnitude of cytotoxic activity per cell varies between Ag-specific T cells purified from different tissues at a given time point (22), and in the spleen cytotoxic activity per cell tends to decrease (by up to 8-fold) with time after Ag exposure (23). Similarly, compared with that seen during primary HCMV infection (8), the magnitude of virus-specific cytotoxicity per cell shown by tetramer-positive CD8+ T cells purified from PBMC of healthy carriers of HCMV was modest (7). In unstimulated CD8+ T cells in PBMC of healthy adults, staining of intracellular perforin also shows a continuous spectrum, with highest levels in CD27-CD45RA+ cells (9) or CD11ahighCD45RA+ cells (12). Thus in long term memory, Ag-experienced daughter cells of a single clone exhibit a spectrum of states of activation/differentiation that include quantitative (rather than qualitative) differences in levels of cytotoxicity. Because the mutually exclusive categories of effector cell and memory cell are no longer adequate to describe the complexity of Ag-experienced cells, the term effector memory cell has been introduced to describe effector cells found in long term memory, which may differ from the effector cells in acute virus infection in their susceptibility to apoptosis and capacity for proliferation. The term effector memory cells was originally applied to CD45RO+CCR7- cells (10), but this nomenclature may lead to confusion, because CD45RO+CCR7- cells are made up of both CD28+ and CD28- cells, and effector-phenotype cells are also abundant in CD27-CD45RA+ cells (9) or CD11ahighCD45RA+ cells (12). Rather than descriptive terms, we favor a more precise classification based directly on the expression of sets of surface molecules that reflect the diversity of cellular differentiation.
There is also heterogeneity among the activated effector T
cells generated in acute virus infection. Many acutely activated
cytotoxic cells (in blood, spleen, or infected peripheral tissues) fail
to proliferate in vitro and die rapidly by apoptosis (24).
However, a subpopulation of Ag-specific cytotoxic cells can survive in
vitro and give rise to long term memory in vivo (25).
Cytotoxic effector cells generated by strong antigenic stimulation in
vitro can also give rise to progeny that are capable of sustained
proliferation in vivo (26). It will be of particular
interest to identify the phenotype(s) of the subpopulation of effector
cells in acute virus infection in vivo that is destined not to die, but
to give rise to long term memory. Based on the results presented in
this paper, our current model of human CD8+ T
cell differentiation is illustrated in Fig. 9.
|
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Mark Wills, Department of Medicine, University of Cambridge, Clinical School Hills Road, Cambridge, U.K. CB2 2QQ. E-mail address: mrw1004{at}cam.ac.uk
3 Abbreviations used in this paper: HCMV, human CMV; CD62L, CD62 ligand; IE, immediate-early; MIP-3, macrophage inflammatory protein-3; TC, TriColor.
Received for publication December 17, 2001. Accepted for publication March 19, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  E. M. Iancu, P. Corthesy, P. Baumgaertner, E. Devevre, V. Voelter, P. Romero, D. E. Speiser, and N. Rufer Clonotype Selection and Composition of Human CD8 T Cells Specific for Persistent Herpes Viruses Varies with Differentiation but Is Stable Over Time J. Immunol., July 1, 2009; 183(1): 319 - 331. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Kondo and M. Takiguchi Human memory CCR4+CD8+ T cell subset has the ability to produce multiple cytokines Int. Immunol., May 1, 2009; 21(5): 523 - 532. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. A. Burgers, C. Riou, M. Mlotshwa, P. Maenetje, D. de Assis Rosa, J. Brenchley, K. Mlisana, D. C. Douek, R. Koup, M. Roederer, et al. Association of HIV-Specific and Total CD8+ T Memory Phenotypes in Subtype C HIV-1 Infection with Viral Set Point J. Immunol., April 15, 2009; 182(8): 4751 - 4761. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Jagannathan, C. M. Osborne, C. Royce, M. M. Manion, J. C. Tilton, L. Li, S. Fischer, C. W. Hallahan, J. A. Metcalf, M. McLaughlin, et al. Comparisons of CD8+ T Cells Specific for Human Immunodeficiency Virus, Hepatitis C Virus, and Cytomegalovirus Reveal Differences in Frequency, Immunodominance, Phenotype, and Interleukin-2 Responsiveness J. Virol., March 15, 2009; 83(6): 2728 - 2742. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 O. C. Goodyear, G. Pratt, A. McLarnon, M. Cook, K. Piper, and P. Moss Differential pattern of CD4+ and CD8+ T-cell immunity to MAGE-A1/A2/A3 in patients with monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma Blood, October 15, 2008; 112(8): 3362 - 3372. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. Pipeling, E. E. West, C. M. Osborne, A. B. Whitlock, L. K. Dropulic, M. H. Willett, M. Forman, A. Valsamakis, J. B. Orens, D. R. Moller, et al. Differential CMV-Specific CD8+ Effector T Cell Responses in the Lung Allograft Predominate over the Blood during Human Primary Infection J. Immunol., July 1, 2008; 181(1): 546 - 556. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. C. P. Waller, N. McKinney, R. Hicks, A. J. Carmichael, J. G. P. Sissons, and M. R. Wills Differential costimulation through CD137 (4 1BB) restores proliferation of human virus-specific "effector memory" (CD28 CD45RAHI) CD8+ T cells Blood, December 15, 2007; 110(13): 4360 - 4366. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Rezvani, A. S. M. Yong, B. N. Savani, S. Mielke, K. Keyvanfar, E. Gostick, D. A. Price, D. C. Douek, and A. J. Barrett Graft-versus-leukemia effects associated with detectable Wilms tumor-1 specific T lymphocytes after allogeneic stem-cell transplantation for acute lymphoblastic leukemia Blood, September 15, 2007; 110(6): 1924 - 1932. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Egli, S. Binggeli, S. Bodaghi, A. Dumoulin, G. A. Funk, N. Khanna, D. Leuenberger, R. Gosert, and H. H. Hirsch Cytomegalovirus and polyomavirus BK posttransplant Nephrol. Dial. Transplant., September 1, 2007; 22(suppl_8): viii72 - viii82. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. J. Plunkett, O. Franzese, H. M. Finney, J. M. Fletcher, L. L. Belaramani, M. Salmon, I. Dokal, D. Webster, A. D. G. Lawson, and A. N. Akbar The Loss of Telomerase Activity in Highly Differentiated CD8+CD28-CD27- T Cells Is Associated with Decreased Akt (Ser473) Phosphorylation J. Immunol., June 15, 2007; 178(12): 7710 - 7719. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Precopio, M. R. Betts, J. Parrino, D. A. Price, E. Gostick, D. R. Ambrozak, T. E. Asher, D. C. Douek, A. Harari, G. Pantaleo, et al. Immunization with vaccinia virus induces polyfunctional and phenotypically distinctive CD8+ T cell responses J. Exp. Med., June 11, 2007; 204(6): 1405 - 1416. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. J. C. Miles, M. van der Sande, D. Jeffries, S. Kaye, J. Ismaili, O. Ojuola, M. Sanneh, E. S. Touray, P. Waight, S. Rowland-Jones, et al. Cytomegalovirus Infection in Gambian Infants Leads to Profound CD8 T-Cell Differentiation J. Virol., June 1, 2007; 81(11): 5766 - 5776. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Romero, A. Zippelius, I. Kurth, M. J. Pittet, C. Touvrey, E. M. Iancu, P. Corthesy, E. Devevre, D. E. Speiser, and N. Rufer Four Functionally Distinct Populations of Human Effector-Memory CD8+ T Lymphocytes J. Immunol., April 1, 2007; 178(7): 4112 - 4119. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Khan, D. Best, R. Bruton, L. Nayak, A. B. Rickinson, and P. A. H. Moss T Cell Recognition Patterns of Immunodominant Cytomegalovirus Antigens in Primary and Persistent Infection J. Immunol., April 1, 2007; 178(7): 4455 - 4465. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. M. M. van Leeuwen, J. J. Koning, E. B. M. Remmerswaal, D. van Baarle, R. A. W. van Lier, and I. J. M. ten Berge Differential Usage of Cellular Niches by Cytomegalovirus versus EBV- and Influenza Virus-Specific CD8+ T Cells J. Immunol., October 15, 2006; 177(8): 4998 - 5005. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Sinclair and P. Sissons Latency and reactivation of human cytomegalovirus J. Gen. Virol., July 1, 2006; 87(7): 1763 - 1779. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Sauce, M. Larsen, S. J. Curnow, A. M. Leese, P. A. H. Moss, A. D. Hislop, M. Salmon, and A. B. Rickinson EBV-associated mononucleosis leads to long-term global deficit in T-cell responsiveness to IL-15 Blood, July 1, 2006; 108(1): 11 - 18. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Riou, A. R Dumont, B. Yassine-Diab, E. K Haddad, and R.-P. Sekaly IL-4 influences the differentiation and the susceptibility to activation-induced cell death of human naive CD8+ T cells Int. Immunol., June 1, 2006; 18(6): 827 - 835. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. R. Hadrup, J. Strindhall, T. Kollgaard, T. Seremet, B. Johansson, G. Pawelec, P. thor Straten, and A. Wikby Longitudinal Studies of Clonally Expanded CD8 T Cells Reveal a Repertoire Shrinkage Predicting Mortality and an Increased Number of Dysfunctional Cytomegalovirus-Specific T Cells in the Very Elderly J. Immunol., February 15, 2006; 176(4): 2645 - 2653. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Baeten, S. Louis, C. Braud, C. Braudeau, C. Ballet, F. Moizant, A. Pallier, M. Giral, S. Brouard, and J.-P. Soulillou Phenotypically and Functionally Distinct CD8+ Lymphocyte Populations in Long-Term Drug-Free Tolerance and Chronic Rejection in Human Kidney Graft Recipients J. Am. Soc. Nephrol., January 1, 2006; 17(1): 294 - 304. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. Wills, O. Ashiru, M. B. Reeves, G. Okecha, J. Trowsdale, P. Tomasec, G. W. G. Wilkinson, J. Sinclair, and J. G. P. Sissons Human Cytomegalovirus Encodes an MHC Class I-Like Molecule (UL142) That Functions to Inhibit NK Cell Lysis J. Immunol., December 1, 2005; 175(11): 7457 - 7465. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. M. M. van Leeuwen, G. J. de Bree, E. B. M. Remmerswaal, S.-L. Yong, K. Tesselaar, I. J. M. t. Berge, and R. A. W. van Lier IL-7 receptor {alpha} chain expression distinguishes functional subsets of virus-specific human CD8+ T cells Blood, September 15, 2005; 106(6): 2091 - 2098. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. W. Sylwester, B. L. Mitchell, J. B. Edgar, C. Taormina, C. Pelte, F. Ruchti, P. R. Sleath, K. H. Grabstein, N. A. Hosken, F. Kern, et al. Broadly targeted human cytomegalovirus-specific CD4+ and CD8+ T cells dominate the memory compartments of exposed subjects J. Exp. Med., September 6, 2005; 202(5): 673 - 685. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Wikby, F. Ferguson, R. Forsey, J. Thompson, J. Strindhall, S. Lofgren, B.-O. Nilsson, J. Ernerudh, G. Pawelec, and B. Johansson An Immune Risk Phenotype, Cognitive Impairment, and Survival in Very Late Life: Impact of Allostatic Load in Swedish Octogenarian and Nonagenarian Humans J. Gerontol. A Biol. Sci. Med. Sci., May 1, 2005; 60(5): 556 - 565. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Almanzar, S. Schwaiger, B. Jenewein, M. Keller, D. Herndler-Brandstetter, R. Wurzner, D. Schonitzer, and B. Grubeck-Loebenstein Long-Term Cytomegalovirus Infection Leads to Significant Changes in the Composition of the CD8+ T-Cell Repertoire, Which May Be the Basis for an Imbalance in the Cytokine Production Profile in Elderly Persons J. Virol., March 15, 2005; 79(6): 3675 - 3683. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Anfossi, J.-M. Doisne, M.-A. Peyrat, S. Ugolini, O. Bonnaud, D. Bossy, V. Pitard, P. Merville, J.-F. Moreau, J.-F. Delfraissy, et al. Coordinated Expression of Ig-Like Inhibitory MHC Class I Receptors and Acquisition of Cytotoxic Function in Human CD8+ T Cells J. Immunol., December 15, 2004; 173(12): 7223 - 7229. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. F. Ochsenbein, S. R. Riddell, M. Brown, L. Corey, G. M. Baerlocher, P. M. Lansdorp, and P. D. Greenberg CD27 Expression Promotes Long-Term Survival of Functional Effector-Memory CD8+ Cytotoxic T Lymphocytes in HIV-infected Patients J. Exp. Med., December 6, 2004; 200(11): 1407 - 1417. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. M. Aandahl, M. F. Quigley, W. J. Moretto, M. Moll, V. D. Gonzalez, A. Sonnerborg, S. Lindback, F. M. Hecht, S. G. Deeks, M. G. Rosenberg, et al. Expansion of CD7low and CD7negative CD8 T-cell effector subsets in HIV-1 infection: correlation with antigenic load and reversion by antiretroviral treatment Blood, December 1, 2004; 104(12): 3672 - 3678. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. A. Kolber Impact of Immune Plasticity on Development of Cellular Memory Responses to Human Immunodeficiency Virus Type 1 Clin. Vaccine Immunol., November 1, 2004; 11(6): 1002 - 1007. [Full Text] [PDF]
|
|
|
|
|
|
M. P. Weekes, M. R. Wills, J. G. P. Sissons, and A. J. Carmichael Long-Term Stable Expanded Human CD4+ T Cell Clones Specific for Human Cytomegalovirus Are Distributed in Both CD45RAhigh and CD45ROhigh Populations J. Immunol., November 1, 2004; 173(9): 5843 - 5851. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Boissonnas, C. Combadiere, E. Lavergne, M. Maho, C. Blanc, P. Debre, and B. Combadiere Antigen Distribution Drives Programmed Antitumor CD8 Cell Migration and Determines Its Efficiency J. Immunol., July 1, 2004; 173(1): 222 - 229. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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]
|
|
|
|
|
|
L. E. Gamadia, E. M. M. van Leeuwen, E. B. M. Remmerswaal, S.-L. Yong, S. Surachno, P. M. E. Wertheim-van Dillen, I. J. M. ten Berge, and R. A. W. van Lier The Size and Phenotype of Virus-Specific T Cell Populations Is Determined by Repetitive Antigenic Stimulation and Environmental Cytokines J. Immunol., May 15, 2004; 172(10): 6107 - 6114. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Kondo, Y. Akatsuka, K. Kuzushima, K. Tsujimura, S. Asakura, K. Tajima, Y. Kagami, Y. Kodera, M. Tanimoto, Y. Morishima, et al. Identification of novel CTL epitopes of CMV-pp65 presented by a variety of HLA alleles Blood, January 15, 2004; 103(2): 630 - 638. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. M. Finney, A. N. Akbar, and A. D. G. Lawson Activation of Resting Human Primary T Cells with Chimeric Receptors: Costimulation from CD28, Inducible Costimulator, CD134, and CD137 in Series with Signals from the TCR{zeta} Chain J. Immunol., January 1, 2004; 172(1): 104 - 113. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. V. D. Soares, F. J. Plunkett, C. S. Verbeke, J. E. Cook, J. M. Faint, L. L. Belaramani, J. M. Fletcher, N. Hammerschmitt, M. Rustin, W. Bergler, et al. Integration of apoptosis and telomere erosion in virus-specific CD8+ T cells from blood and tonsils during primary infection Blood, January 1, 2004; 103(1): 162 - 167. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Brandes, K. Willimann, A. B. Lang, K.-H. Nam, C. Jin, M. B. Brenner, C. T. Morita, and B. Moser Flexible migration program regulates {gamma}{delta} T-cell involvement in humoral immunity Blood, November 15, 2003; 102(10): 3693 - 3701. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. K. Gandhi, M. R. Wills, G. Okecha, E. K. Day, R. Hicks, R. E. Marcus, J. G. P. Sissons, and A. J. Carmichael Late diversification in the clonal composition of human cytomegalovirus-specific CD8+ T cells following allogeneic hemopoietic stem cell transplantation Blood, November 1, 2003; 102(9): 3427 - 3438. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Rezvani, M. Grube, J. M. Brenchley, G. Sconocchia, H. Fujiwara, D. A. Price, E. Gostick, K. Yamada, J. Melenhorst, R. Childs, et al. Functional leukemia-associated antigen-specific memory CD8+ T cells exist in healthy individuals and in patients with chronic myelogenous leukemia before and after stem cell transplantation Blood, October 15, 2003; 102(8): 2892 - 2900. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Rufer, A. Zippelius, P. Batard, M. J. Pittet, I. Kurth, P. Corthesy, J.-C. Cerottini, S. Leyvraz, E. Roosnek, M. Nabholz, et al. Ex vivo characterization of human CD8+ T subsets with distinct replicative history and partial effector functions Blood, September 1, 2003; 102(5): 1779 - 1787. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Anichini, A. Scarito, A. Molla, G. Parmiani, and R. Mortarini Differentiation of CD8+ T Cells from Tumor-Invaded and Tumor-Free Lymph Nodes of Melanoma Patients: Role of Common {gamma}-Chain Cytokines J. Immunol., August 15, 2003; 171(4): 2134 - 2141. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Sauce, N. Rufer, P. Mercier, M. Bodinier, J.-P. Remy-Martin, A. Duperrier, C. Ferrand, P. Herve, P. Romero, F. Lang, et al. Retrovirus-mediated gene transfer in polyclonal T cells results in lower apoptosis and enhanced ex vivo cell expansion of CMV-reactive CD8 T cells as compared with EBV-reactive CD8 T cells Blood, August 15, 2003; 102(4): 1241 - 1248. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P.-M. Roger, J. Durant, M. Ticchioni, P. Halfon, J.-P. Breittmayer, C. Brignone, S. Chaillou, B. Dunais, P. Dellamonica, A. Bernard, et al. Apoptosis and proliferation kinetics of T cells in patients having experienced antiretroviral treatment interruptions J. Antimicrob. Chemother., August 1, 2003; 52(2): 269 - 275. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Strauss, I. Knape, I. Melzner, and K.-M. Debatin Constitutive Caspase Activation and Impaired Death-Inducing Signaling Complex Formation in CD95-Resistant, Long-Term Activated, Antigen-Specific T Cells J. Immunol., August 1, 2003; 171(3): 1172 - 1182. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. L. Shacklett, C. A. Cox, J. K. Sandberg, N. H. Stollman, M. A. Jacobson, and D. F. Nixon Trafficking of Human Immunodeficiency Virus Type 1-Specific CD8+ T Cells to Gut-Associated Lymphoid Tissue during Chronic Infection J. Virol., May 15, 2003; 77(10): 5621 - 5631. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. M. Aandahl, J. K. Sandberg, K. P. Beckerman, K. Tasken, W. J. Moretto, and D. F. Nixon CD7 Is a Differentiation Marker That Identifies Multiple CD8 T Cell Effector Subsets J. Immunol., March 1, 2003; 170(5): 2349 - 2355. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Schwaiger, A. M. Wolf, P. Robatscher, B. Jenewein, and B. Grubeck-Loebenstein IL-4-Producing CD8+ T Cells with a CD62L++(bright) Phenotype Accumulate in a Subgroup of Older Adults and Are Associated with the Maintenance of Intact Humoral Immunity in Old Age J. Immunol., January 1, 2003; 170(1): 613 - 619. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. M. van Leeuwen, L. E. Gamadia, P. A. Baars, E. B. Remmerswaal, I. J. ten Berge, and R. A. van Lier Proliferation Requirements of Cytomegalovirus-Specific, Effector-Type Human CD8+ T Cells J. Immunol., November 15, 2002; 169(10): 5838 - 5843. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
