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Section of Immunobiology, Yale University School of Medicine, and Howard Hughes Medical Institute, New Haven, CT 06520
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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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Emerging evidence suggests that interaction with MHC molecules plays an active role in mediating the survival of naive as well as memory T cells. Recent studies have shown that neither CD4 nor CD8 T cells survive in an environment that is devoid of MHC expression (6, 7, 8, 9), and that the survival of CD4 T cells can be mediated by MHC class II expression on dendritic cells alone (7). Moreover, it has been shown for both CD4 and CD8 T cells that survival is specifically mediated by the MHC alleles upon which T cells are selected in the thymus, and that MHC alleles that are incapable of selecting a given T cell are also incapable of delivering peripheral survival signals to that T cell (9, 10). However, some T cell specificities can be selected by more than one MHC allele (11), and it remains unclear whether a T cell requires the same MHC molecule for survival in the periphery that mediates positive selection in the thymus or whether a T cell can be maintained in the periphery by a different selecting MHC molecule.
Although signals delivered by MHC molecules to T cells appear to be
necessary for peripheral survival, there is the possibility that
additional factors may contribute to this process as well. In vitro
studies have shown that cytokines can rescue T cells from apoptosis in
tissue culture. In one report, resting T cells were shown to undergo
apoptosis when taken from mice and placed into culture, but this death
could be prevented by the addition of IL-4 or IL-7, but not IL-2, IL-9,
IL-13, or IL-15 (12). Similarly, treatment with IL-4 or IL-7 was shown
to enhance the threshold for apoptosis induced by 
-irradiation in
human peripheral blood T cells (13). Clearly these cytokines can
mediate the survival of T cells in vitro; however, it has yet to be
determined whether physiological levels of IL-4 or IL-7 play a role in
mediating CD4 T cell survival in vivo.
In this report, we examine the longevity of naive CD4 T cells and identify two factors that are important to the maintenance of the naive CD4 T cell pool in vivo. We show a reduction in the total CD4 T cell pool following adult thymectomy, with a selective loss of naive CD4 T cells. However, this does not result in the loss of all peripheral naive CD4 T cells, in that a population of long-lived naive CD4 T cells survives long after thymectomy. To identify the factors that contribute to the maintenance of long-lived naive CD4 T cells, we transferred naive CD4 T cells into hosts varying in their expression of MHC class II. As in earlier reports, we find that the signals delivered through MHC class II are important for the survival of naive CD4 T cells. We extend these findings by showing that CD4 T cells that are capable of being selected in the thymus by two different MHC alleles will survive in the presence of either. However, survival is optimal in the presence of MHC class II molecules which are capable of presenting Ag in the periphery (restricting MHC allele), even in a case in which the T cells were selected in a thymus with a different MHC class II allele (selecting allele). These findings also suggest that the peripheral survival of naive CD4 T cells parallels thymic positive selection, in that MHC class II molecules which select more efficiently also mediate peripheral survival optimally. We also find that physiological levels of either IL-4 or IL-7 can serve to further enhance the longevity of naive CD4 T cells in vivo, suggesting that there are multiple mechanisms contributing to the maintenance of the naive CD4 T cell pool.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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AND TCR-
ß transgenic
(Tg)3 donor mice (TCR-specific for pigeon
cytochrome c presented by I-Eb or
I-Ek) were derived from a heterozygous mouse that was
generously provided by J. Kaye (Scripps Institute, La Jolla, CA) (14).
Subsequent generations of TCR Tg mice were maintained as heterozygotes
on B10.A(5R) and C57BL/6 backgrounds. The AND TCR Tg mice were also
crossed with IL-4-/- mice (15) (generously
provided by W. Müller, University of Köln, Köln,
Germany). These mice were back-crossed onto the B10.A(5R) background
(for at least seven generations) and bred to homozygosity for the IL-4
null mutation before breeding with the AND TCR Tg mice. C57BL/6 mice
were obtained from The Jackson Laboratory (Bar Harbor, ME). MHC class
II-/- recipient mice were obtained from Taconic
(Germantown, NY). CD4-/- mice (16) were maintained in
animal facilities at Yale University. The 107-1 I-E Tg mice (obtained
from R. Flavell, Yale University, New Haven, CT) (17), were derived on
B10 mice and back-crossed onto C57BL/6 (for at least seven
generations).
Thymectomy
Five- to six-week-old mice were anesthetized with a mixture of ketamine (Fort Dodge Laboratories, Fort Dodge, IA) and xylazine (Abbott Laboratories, North Chicago, IL) at 500 µg/25 g mouse for each anesthetic and kept under anesthesia using Metofane (Pitman-Moore, Mundelein, IL) just before surgery. A midline incision in the upper thoracic region exposed the sternum. A small incision of the sternum exposed the thymic lobes. The thymus was then removed by suction, and the wound was closed using surgical staples. Sham-thymectomized (STx) mice underwent the same procedure, with the exception that the thymus was left intact. Mice were kept warm with a heat lamp and observed after the surgery until they regained consciousness. Surgical staples were removed 1 wk later. Successful extraction of the thymus was verified upon sacrifice of the animals.
Adoptive transfer
The preparation of CD4 T cells from TCR Tg mice was as
follows: Unless otherwise stated, mAbs used in cell
preparations were purified from supernatants of hybridomas maintained
in this laboratory using standard protein A or protein G affinity
chromatography. CD4 T cells were isolated from the spleens and lymph
nodes of donor animals by negative selection using mAbs against CD8
(clones 53-6.72 and 2.43) (American Type Culture Collection (ATCC),
Manassas, VA), MHC class II I-A (clone 212.A1) (18), and FcR
(clone 2.4-G2) (ATCC), followed by incubation with anti-mouse and
anti-rat Ig-coated magnetic beads (Collaborative Research, Bedford,
MA). Transfer was as follows: C57BL/6 and 107-1 recipients
underwent surgical thymectomy at 5–6 wk of age, and were allowed to
recover for 
2 wk before being used in experiments. On the day of
transfer, all recipient mice were sublethally irradiated (500 rad) and
reconstituted within 6 h with 1.5 x 107 CD4 T
cells obtained from AND TCR Tg mice on the C57BL/6 background.
Abs and flow cytometry
The following mAbs were used to stain cell surface molecules:
FITC-labeled anti-V11 TCR (clone RR8-1) (PharMingen, San Diego,
CA), biotin-labeled anti-CD45RB (clone 16A) (PharMingen),
phycoerythrin-labeled anti-L-selectin (clone Mel-14) (PharMingen),
and Quantum Red-labeled anti-CD4 (clone H129.19) (Sigma
BioSciences, St. Louis, MO). Bound biotin-labeled Abs were detected
with Texas Red avidin (Vector Laboratories, Burlingame, CA). RBCs were
eliminated from spleen suspensions by centrifugation over lymphocyte
separation medium (ICN Biomedicals, Aurora, OH) before
staining. Cells were surface-stained in Abs diluted in staining buffer
(PBS/5% FCS/0.01% sodium azide) containing 1 mg/ml mouse Ig for 30
min and subsequently washed twice in staining buffer. Biotinylated Abs
were subsequently detected with Texas Red avidin diluted in staining
buffer, for 10 min, then washed twice in staining buffer. Cells were
fixed in 1% paraformaldehyde before analysis. Four-color analysis was
performed on a FACStar system (Becton Dickinson, Mountain View, CA).
FACS data were analyzed using LYSYS software and CellQuest software
(Becton Dickinson).
Quantitation of cell numbers
Single-cell suspensions of spleen and a pool of mesenteric, inguinal, axilary, and brachial lymph nodes were prepared for each animal. To exclude RBCs from spleen suspensions and exclude trypan blue from lymph node cell suspensions, spleen and lymph node suspensions were counted to determine the total number of cells using Turk’s solution and 0.01% gentian violet (Sigma) in 3% acetic acid. The total number of donor CD4 T cells for each organ was calculated from the frequency of donor CD4 T cells determined by flow cytometric analysis and the total number of cells from each organ.
In vivo IL-7 depletion
Mice were depleted of endogenous levels of IL-7 using a modification of a protocol described previously (19). Anti-human/mouse IL-7 (mouse IgG2b) (Genzyme, Cambridge, MA) was injected i.p. in doses of 200 µg/0.2 ml on day 0 (day of thymectomy) and on days 2, 4, and 6 after thymectomy of AND TCR Tg or IL-4-/- AND TCR Tg mice. Mice were sacrificed and analyzed for cell numbers on day 7. Other IL-4-/- AND TCR Tg mice were injected i.p. with a control mouse IgG2b anti-trinitrophenyl Ab (clone 49.2) (PharMingen) in doses of 200 µg/0.2 ml on the same days.
ELISA assays
IL-4 levels were determined using ELISA kits (Endogen, Woburn,
MA). Assays were standardized with rIL-4 (Collaborative Research). IgE
levels were determined by a sandwich ELISA in which the capture Ab was
anti-mouse IgE (
-chain) (The Binding Site, Birmingham, U.K.) and
the detecting Ab was biotinylated monoclonal rat anti-mouse IgE
(Biosource International, Camarillo, CA). The IgE ELISA was
standardized with purified mouse anti-trinitrophenyl IgE (clone
IgE-3) (PharMingen). Biotinylated Abs were bound to horseradish
peroxidase-streptavidin (Zymed, South San Francisco, CA) in all
assays, and the substrate for horseradish peroxidase was the
trimethylbenzidine One-Step Substrate System (Dako,
Carpinteria, CA).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To study the longevity of naive CD4 T cells in vivo, AND TCR Tg
mice whose TCR is specific for cytochrome c (14) were
thymectomized at 5–6 wk of age; at various timepoints following
thymectomy, the survival of the naive CD4 T cell pool was determined.
Because thymectomy prevents the addition of new naive cells to the
existing pool, and because the absence of specific Ag in the TCR Tg
mice prevents entrance of CD4 T cells into the effector and memory
pool, a fixed population of naive CD4 T cells is created. As seen in
Fig. 1
A, left panel, there is a
loss in the total number of CD4 T cells (total bars) when thymectomized
(ATx) animals are compared with STx littermates at 4 wk postthymectomy.
The reduction is seen primarily within the Tg+ CD4
T cell population (striped, top portion of bars), whereas the
Tg- population (bottom, solid portion of bars) is
unaffected. Because the TCR Tg+ CD4 T cells are primarily
of the naive phenotype as determined by L-selectin and CD45RB
expression (data not shown), this suggests that naive CD4 T cells are
preferentially lost during the 4 wk following adult thymectomy. To test
this, the same analysis was conducted to determine the survival of
naive CD4 T cells after thymectomy, using phenotypic markers of naive
and memory/effector CD T cells. It can be seen in Fig. 1A,
right panel, that there is a preferential loss of naive CD4
T cells (CD45RBhigh, L-selectinhigh), whereas
the effector/memory pool (the remaining CD4 T cells) remains intact. To
ensure that these results were not unique to this TCR Tg strain, the
same analysis was performed using a second TCR Tg strain whose TCR is
specific for a myelin basic protein peptide (20) and yielded similar
results (data not shown). In addition, non-Tg littermates showed the
same preferential loss of naive CD4 T cells after thymectomy (data not
shown).
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B). The results were
normalized between cohorts by expressing the number of naive CD4 T
cells in ATx mice as a percentage of the naive CD4 T cells found in
their STx littermates at each timepoint. As early as 1 wk
postthymectomy, the number of naive CD4 T cells in ATx mice is only
40% of the number in the STx littermates and continues to drop through
week 4 to 
17%. However, this does not result in the eventual loss
of all naive CD4 T cells. In fact, the percentage of naive CD4 T cells
in ATx mice does not change significantly after the first month,
demonstrating a long-lived population of naive CD4 T cells, as was
shown previously (1, 2, 3, 4). Taken together, these data suggest that there is a stable population of naive CD4 T cells that is maintained over time, despite the fact that a great number of naive CD4 T cells are lost.
MHC class II molecules that serve to present foreign peptides are more efficient at mediating survival of naive CD4 T cells than other selecting MHC class II molecules
Recent reports have placed great importance on the interactions of T cells with MHC molecules for T cell survival (6, 7, 8, 9, 10). For both CD4 (10) and CD8 (9) T cells, adoptive transfer studies have shown that MHC class II and MHC class I molecules, respectively, are required for the survival of naive T cells, and that the presence in the periphery of the selecting MHC molecule seen in the thymus is critical for survival. AND TCR Tg CD4 T cells recognize Ag in the context of MHC class II I-E (11, 14); however, these cells can also be selected on MHC class II I-Ab (11). We took advantage of this finding to ask whether the survival of Tg+ CD4 T cells in the periphery required the restricting class II I-E molecule or whether I-Ab could mediate survival as well, despite the fact that I-Ab is not capable of presenting the cytochrome c peptide to AND TCR Tg CD4 T cells (Ref. 11 ; S. Constant and K.B., unpublished observations).
To investigate this issue, we transferred Tg+ CD4 T cells
from I-Ab, I-E- C57BL/6 donor mice into
recipients that differed in MHC class II expression. The recipients
either 1) lacked MHC class II (class II-/-) (21); 2)
expressed the selecting MHC class II I-Ab but not I-E
(C57BL/6); or 3) expressed the selecting MHC class II I-Ab
as well as a restricting MHC class II I-E (107-1). The 107-1 recipient
is a C57BL/6 (I-Ab) mouse that carries an E
transgene; this transgene allows the expression of MHC class II
I-E, which is expressed, along with I-Ab, on all thymic
epithelial cells, B cells, macrophages, and dendritic cells (17) at
levels equivalent to wild-type MHC class II I-E-expressing mouse
strains (22). C57BL/6 (I-E-) TCR Tg CD4 T cell
donors were chosen to avoid transferring any contaminating donor
populations of MHC class II I-E+ APCs to the recipients.
Furthermore, Tg+ CD4 T cells derived from C57BL/6 mice are
not alloreactive to the MHC class II I-E on 107-1-derived APCs in vitro
(S. Constant and K.B., unpublished observations). The C57BL/6 and 107-1
recipients were thymectomized to eliminate homeostatic interference
from a continual input of new host T cells, but were otherwise
immunocompetent. All animals were irradiated, and each received
1.5 x 107 CD4 T cells from TCR Tg mice. Lymph nodes
and spleens were harvested at 6 wk after adoptive transfer, and the
survival of naive TCR Tg+ CD4 T cells was determined by
flow cytometry. Recovered CD4 T cells were considered naive
Tg+ CD4 T cells if they were V11+ and
bearing two phenotypic markers for naive CD4 T cells, CD45RB and
L-selectin. All of the naive CD4 T cells analyzed showed a resting,
nonactivated phenotype as determined by forward and side light scatter.
Fig. 2A shows V11 expression of the naive
CD4 T cells (CD4+, CD45RBhigh,
L-selectinhigh) in the starting population of transferred
cells; only those V11high naive cells within the gate
were analyzed at 6 wk posttransfer. Most of the recovered naive CD4 T
cells maintain expression of the transgene. As shown in Fig. 2B, the C57BL/6 host (selecting MHC) sustains naive CD4 T
cells more efficiently than a class II-/- host. However,
the 107-1 host, which expresses I-E, the restricting MHC class II
molecule, mediates the survival of naive CD4 T cells two to three times
more efficiently than the host expressing only the selecting MHC class
II, despite the fact that the CD4 T cells transferred into both
recipients developed in the C57BL/6 (I-Ab, selecting)
background. These results confirm that MHC class II expression is
important for the survival of naive CD4 T cells. Moreover, there is a
preferential survival of naive CD4 T cells when placed in the
environment of restricting MHC molecules capable of presenting Ag,
regardless of the MHC class II allele upon which they were
selected.
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As illustrated in Fig. 2, naive CD4 T cells survived poorly in MHC
class II-deficient mice. Because MHC class II-deficient mice are nearly
devoid of peripheral CD4 T cells (21), it is possible that transferred
CD4 T cells engrafted differently in MHC class II-deficient recipients
compared with recipients that express MHC class II. To test whether
engraftment potential played a role, TCR Tg CD4 T cells were
transferred into CD4-deficient recipients (16). This recipient
expresses the selecting MHC class II I-Ab, but develops no
CD4 T cells, thus resembling the MHC class II-deficient phenotype. If
MHC class II was the only factor necessary for CD4 T cell survival, we
predicted that naive CD4 T cells would survive in these animals much as
they did in the C57BL/6 recipient. As illustrated in Fig. 3A, and much to our surprise, naive CD4 T
cells survived much more efficiently in C57BL/6 CD4-/-
recipients, showing a 13-fold augmentation over survival in C57BL/6 and
a 5-fold augmentation over survival in 107-1 mice. These data suggested
that there was an additional factor present in CD4-/-
mice that was greatly enhancing the survival of naive CD4 T cells.
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B shows that CD4-/- mice
have elevated IgE levels compared with C57BL/6 and 107-1 mice,
suggesting the presence of IL-4 in levels sufficient to induce class
switching to IgE. Interestingly, the MHC class II-/- mice
also exhibited elevated levels of IgE, yet were poor mediators of
survival of naive CD4 T cells. These results suggest that IL-4 or other
factors may play a role in enhancing the MHC class II-mediated survival
of naive CD4 T cells. The presence of IL-4 or IL-7 enhances the survival of naive CD4 T cells
If IL-4 or other cytokines are important to the survival of naive CD4 T cells in vivo, the absence of these cytokines would reduce the number of surviving naive CD4 T cells in the periphery. We wished to assess the roles of IL-4 and also of IL-7, because it was the only other cytokine found to mediate survival of CD4 T cells in vitro (12, 13). To do this, we thymectomized TCR Tg IL-4-/- mice (15) and compared the survival of naive CD4 T cells with thymectomized IL-4+/+ AND TCR Tg mice. Overall thymic cellularity as well as CD4/CD8 ratios and numbers of CD4 T cells in the periphery are comparable between these two strains of mice (data not shown); therefore, it is feasible to compare the two strains postthymectomy. It was not possible to use IL-7- or IL-7R-deficient mice in our thymectomy studies, because T cell development in these mice is severely impaired (25, 26, 27). Therefore, for IL-7 removal, we treated wild-type or IL-4-deficient ATx TCR Tg mice with anti-IL-7 Abs that had been shown previously to neutralize IL-7-induced tumor cell activities in mice (19). We analyzed survival at 1 wk postthymectomy, a time at which significant numbers of naive CD4 T cells are still present.
As shown in Fig. 4A, left panel,
depletion of either IL-4 or IL-7 alone had no effect on the number of
naive CD4 T cells found in ATx mice at 1 wk postthymectomy compared
with untreated, IL-4+/+ ATx mice. However,
IL-4-/- mice that also received anti-IL-7 Ab
treatment showed an approximate twofold reduction in the number of
naive CD4 T cells. A one-way ANOVA shows a significant effect arising
from differences between the anti-IL-7-treated
IL-4-/- mice and the other three groups
(p = 0.015). In a separate experiment (Fig. 4A, right panel), an injection of isotype-matched
control mouse IgG2b Abs had no effect on the naive CD4 T cell pool in
IL-4-/- mice when compared with untreated
IL-4-/- mice, whereas a lack of both IL-4 and IL-7 in the
periphery leads to a reduction in the number of naive CD4 T cells when
compared with both untreated IL-4-/- mice and isotype
control-treated mice (p = 0.032). It is
important to point out that these events are taking place in a
periphery that expresses the restricting MHC class II allele I-E,
suggesting that IL-4 and IL-7 serve to enhance the MHC class
II-mediated survival of naive CD4 T cells.
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B, and confirmed by one-way ANOVA, there is no effect of
anti-IL-7 treatment and/or IL-4 deficiency on the memory/effector
CD4 T cell pool. Taken together, these data indicate that the presence of physiological levels of either IL-4 or IL-7 is sufficient to enhance the survival of naive CD4 T cells in the presence of MHC class II molecules. Depletion of one can be compensated by the other, but removal of both leads to partial loss of naive CD4 T cells.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Thymectomy of TCR Tg mice showed that many naive CD4 T cells are lost following adult thymectomy; however, a stable population of long-lived naive CD4 T cells is established within the first 4 wk after thymectomy. These data are supported by previous studies in ATx TCR Tg mice in which the naive CD4 T cells remaining after thymectomy were shown to be in interphase, indicating long-lived CD4 T cells (3, 28). However, in pulse-chase 5-bromodeoxyuridine labeling studies, the loss of naive CD4 T cells that was evident early in our thymectomy studies was not observed. This can be explained by the fact that their analysis of the cells began at 4 wk postthymectomy, by which time a stable population has been achieved. Our data also reconcile the conflicts between the 5-bromodeoxyuridine labeling studies, which concluded that CD4 T cells are long-lived (1, 2, 3, 4), and other studies, which suggested without quantitative determinations that naive CD4 T cells were short-lived (5).
In exploring factors that contribute to the longevity of naive CD4 T
cells, we have confirmed that the presence of MHC class II molecules is
important to the maintenance of the naive CD4 T cell pool. In previous
studies, it was shown that TCR Tg CD4 T cells will disappear following
adoptive transfer into recipients lacking the MHC haplotype, which
supports positive selection of these T cells (10). In our studies of
transfer into MHC class II-/- hosts, we did not observe a
complete disappearance of the TCR Tg naive CD4 T cells, although the
analysis was conducted within the same time frame. There are several
possible explanations for this discrepancy. The first and simplest
explanation is that we transferred a much larger number of CD4 T cells
into our recipients that perhaps would have subsequently disappeared
completely. The second is that our recipients, although devoid of MHC
class II molecules and thus CD4 T cells, were otherwise
immunocompetent. This may provide a more supportive environment for
persistence compared with the immunodeficient hosts used in the
previous study. As was shown in Fig. 3B, the MHC class
II-/- recipients showed high levels of serum IgE,
indicating the presence of IL-4, which may have served to promote
survival to a small degree in an immunocompetent host, even in the
absence of MHC class II. A third possibility is that naive CD4 T cells
may disappear more rapidly in the presence of a nonselecting MHC
molecule compared with a lack of MHC altogether; however, for CD8 T
cells this has not been shown to be the case (9).
With regard to the presence of IgE in the CD4-/- and MHC
class II-/- mice, we believe that the class switch was
driven by the presence of IL-4. However, CD4-/- mice have
been shown to be defective in Th2 responses, and thus in IL-4
production (29, 30, 31). It is possible that there are other sources of
IL-4 production in these mice that arise from responses that do not
require TCR/CD4/MHC class II interactions. One possible source is
T cells. A recent report shows that T cell clones as well
as primary T cells are capable of IL-4 production (32).
Alternatively, NK1 T cells, a specialized subset of ß T cells that
recognize the conserved MHC class I-like CD1 molecule, are capable of
releasing IL-4 within minutes of activation (reviewed in 33). In
mice that overexpress NK1 T cells, there is increased production of
IL-4 and IgE (34). It is possible that in mice which lack CD4 T cells
and are thus somewhat immunocompromised, there is a dysregulation of
these other cell types driven by the need to respond to environmental
Ags, resulting in augmented IL-4 production. Also of note in the
CD4-/- recipients is the recovery of a greater number of
naive CD4 T cells than was originally transferred into these hosts.
Such slight expansions in similar systems has been shown previously
(35). Given the results in Fig. 4, it is possible that this larger
recovery may be due to the excess of IL-4 shown to be present in the
CD4-/- recipients. There may also be an excess of IL-7 in
these mice which is unknown at this time. Additional experiments will
address these issues directly.
To extend earlier findings regarding MHC and the onward survival of naive T cells, we find that there is a preference in the periphery for an MHC class II molecule that is capable of presenting the foreign Ag to the TCR in question, regardless of which MHC class II molecule mediated positive selection in the thymus. It could be argued that the recipients that expressed both MHC class II I-A and I-E molecules have a more dense expression of MHC class II on the cell surface than the recipients that only expressed the selecting I-A molecule; hence, the former would mediate the survival of naive CD4 T cells more efficiently due to quantity of signal rather than quality. However, using an Ab that recognizes both MHC class II I-A and I-E, we find that this is not the case, and that total MHC class II density on the cell surface is equivalent between these two strains of mice (data not shown). In addition, although it is known that TCR Tg T cells from AND mice cannot respond to cytochrome c peptide in conjunction with I-Ab, it is unknown whether they can respond to other foreign peptides presented by I-Ab, which could potentially skew our results or our interpretations. However, we feel that this possibility is highly unlikely. If AND TCR Tg T cells could respond to I-Ab plus foreign peptides, we would find more Tg+ CD4 T cells in an adoptive I-Ab host, from proliferation in response to environmental Ags, than in I-Ek hosts, but this is not the case. In addition, AND TCR Tg mice themselves on the I-Ab background would contain a significant number of Tg+ cells bearing the memory phenotype if response to foreign peptides were possible, but this is also not the case. We would argue that the I-E MHC class II molecule mediates survival better than I-A because it makes a more productive interaction with the AND TCR than the I-A MHC class II molecule. In the thymus, although MHC class II I-A can positively select the AND TCR, I-E mediates positive selection a good deal more efficiently (11). Therefore, our findings indicate that survival in the periphery closely parallels positive selection in the thymus. This possibility has been introduced elsewhere (36), along with an analysis of the role for self-peptide/self-MHC complexes in this process.
It appears that MHC class II molecules are not the only players that support the peripheral survival of naive CD4 T cells. Our data support a role for the cytokines IL-4 and IL-7 in the survival of naive CD4 T cells in vivo. Although it was clear in in vitro studies that excess amounts of IL-4 or IL-7 could prevent apoptosis in T cells, it was unclear whether physiological levels of IL-4 or IL-7 were required for the optimal survival of CD4 T cells in vivo. For naive CD4 T cells, it appears that these two cytokines play a role in maintaining the naive CD4 T cell pool in vivo, whereas the memory/effector pool remains intact in their absence. However, it is possible that a loss occurs in this population as well, but is subsequently replaced by expansion of the remaining memory CD4 T cells, as it is well documented that memory T cells have a great capacity for peripheral expansion compared with naive T cells (35, 37, 38, 39, 40).
Although IL-4 and IL-7 enhance the survival of naive CD4 T cells in vivo, our data suggest that the presence of MHC class II has a greater impact on this process, and that these cytokines serve to augment the MHC class II-mediated survival of naive CD4 T cells. We make this argument based on the fact that MHC class II-deficient recipients and MHC class II+ CD4-deficient recipients both have elevated levels of IgE, indicating the presence of IL-4. When the survival of naive CD4 T cells in such mice is compared with C57BL/6 and 107-1 recipients, the MHC class II-deficient recipients are the poorest mediators of survival of naive CD4 T cells; the MHC class II+ CD4 deficient recipients are the most efficient mediators.
Taken together, these data indicate that the CD4 T cells emerging from the thymus have the potential for long life, provided they make productive interactions with MHC class II molecules, with some interactions being more productive than others. This process appears to parallel positive selection in the thymus. In addition, the cytokines IL-4, IL-7, and perhaps other as yet unknown factors can augment the MHC class II-mediated survival of naive CD4 T cells.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Kim Bottomly, Section of Immunobiology, Yale University School of Medicine, and Howard Hughes Medical Institute, 310 Cedar Street, New Haven, CT 06520-8011.
3 Abbreviations used in this paper: Tg, transgenic; STx, sham-thymectomized; ATx, adult-thymectomized.
Received for publication September 1, 1998. Accepted for publication December 30, 1998.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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/ß T cells in secondary lymphoid organs. J. Exp. Med. 177:891.. J. Immunol. 136:949.[Abstract]
cell clones can be defined phenotypically and functionally as Th1/Th2 cells and illustrate the association of CD4 with Th2 differentiation. J. Immunol. 160:1965.This article has been cited by other articles:
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L. E. Makaroff, D. W. Hendricks, R. E. Niec, and P. J. Fink Postthymic maturation influences the CD8 T cell response to antigen PNAS, March 24, 2009; 106(12): 4799 - 4804. [Abstract] [Full Text] [PDF]
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 S. Kohler and A. Thiel Life after the thymus: CD31+ and CD31- human naive CD4+ T-cell subsets Blood, January 22, 2009; 113(4): 769 - 774. [Abstract] [Full Text] [PDF]
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 T. N. Jorgensen, A. McKee, M. Wang, E. Kushnir, J. White, Y. Refaeli, J. W. Kappler, and P. Marrack Bim and Bcl-2 Mutually Affect the Expression of the Other in T Cells J. Immunol., September 15, 2007; 179(6): 3417 - 3424. [Abstract] [Full Text] [PDF]
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 N. J. Hill, A. B. Stotland, and N. E. Sarvetnick Distinct regulation of autoreactive CD4 T cell expansion by interleukin-4 under conditions of lymphopenia J. Leukoc. Biol., March 1, 2007; 81(3): 757 - 765. [Abstract] [Full Text] [PDF]
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J. D. French, C. L. Roark, W. K. Born, and R. L. O'Brien {gamma}{delta} T cell homeostasis is established in competition with {alpha}{beta} T cells and NK cells PNAS, October 11, 2005; 102(41): 14741 - 14746. [Abstract] [Full Text] [PDF]
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A. M. Marleau and N. Sarvetnick T cell homeostasis in tolerance and immunity J. Leukoc. Biol., September 1, 2005; 78(3): 575 - 584. [Abstract] [Full Text] [PDF]
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L. Pace, C. Pioli, and G. Doria IL-4 Modulation of CD4+CD25+ T Regulatory Cell-Mediated Suppression J. Immunol., June 15, 2005; 174(12): 7645 - 7653. [Abstract] [Full Text] [PDF]
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C. J. Cooper, G. L. Turk, M. Sun, A. G. Farr, and P. J. Fink Cutting Edge: TCR Revision Occurs in Germinal Centers J. Immunol., December 1, 2004; 173(11): 6532 - 6536. [Abstract] [Full Text] [PDF]
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C. J. Van De Wiele, J. H. Marino, B. W. Murray, S. S. Vo, M. E. Whetsell, and T. K. Teague Thymocytes between the {beta}-Selection and Positive Selection Checkpoints Are Nonresponsive to IL-7 as Assessed by STAT-5 Phosphorylation J. Immunol., April 1, 2004; 172(7): 4235 - 4244. [Abstract] [Full Text] [PDF]
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J.-F. Poulin, M. Sylvestre, P. Champagne, M.-L. Dion, N. Kettaf, A. Dumont, M. Lainesse, P. Fontaine, D.-C. Roy, C. Perreault, et al. Evidence for adequate thymic function but impaired naive T-cell survival following allogeneic hematopoietic stem cell transplantation in the absence of chronic graft-versus-host disease Blood, December 15, 2003; 102(13): 4600 - 4607. [Abstract] [Full Text] [PDF]
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M. A. Burchill, C. A. Goetz, M. Prlic, J. J. O'Neil, I. R. Harmon, S. J. Bensinger, L. A. Turka, P. Brennan, S. C. Jameson, and M. A. Farrar Distinct Effects of STAT5 Activation on CD4+ and CD8+ T Cell Homeostasis: Development of CD4+CD25+ Regulatory T Cells versus CD8+ Memory T Cells J. Immunol., December 1, 2003; 171(11): 5853 - 5864. [Abstract] [Full Text] [PDF]
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 I. Grandjean, L. Duban, E. A. Bonney, E. Corcuff, J. P. Di Santo, P. Matzinger, and O. Lantz Are Major Histocompatibility Complex Molecules Involved in the Survival of Naive CD4+ T Cells? J. Exp. Med., October 6, 2003; 198(7): 1089 - 1102. [Abstract] [Full Text] [PDF]
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S. Ilangumaran, S. Ramanathan, J. La Rose, P. Poussier, and R. Rottapel Suppressor of Cytokine Signaling 1 Regulates IL-15 Receptor Signaling in CD8+CD44high Memory T Lymphocytes J. Immunol., September 1, 2003; 171(5): 2435 - 2445. [Abstract] [Full Text] [PDF]
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S. Jaleco, L. Swainson, V. Dardalhon, M. Burjanadze, S. Kinet, and N. Taylor Homeostasis of Naive and Memory CD4+ T Cells: IL-2 and IL-7 Differentially Regulate the Balance Between Proliferation and Fas-Mediated Apoptosis J. Immunol., July 1, 2003; 171(1): 61 - 68. [Abstract] [Full Text] [PDF]
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C. J. Cooper, M. T. Orr, C. J. McMahan, and P. J. Fink T Cell Receptor Revision Does Not Solely Target Recent Thymic Emigrants J. Immunol., July 1, 2003; 171(1): 226 - 233. [Abstract] [Full Text] [PDF]
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T. Dao, J. M. Blander, and D. B. Sant'Angelo Recognition of a Specific Self-Peptide: Self-MHC Class II Complex Is Critical for Positive Selection of Thymocytes Expressing the D10 TCR J. Immunol., January 1, 2003; 170(1): 48 - 54. [Abstract] [Full Text] [PDF]
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J. T. Tan, B. Ernst, W. C. Kieper, E. LeRoy, J. Sprent, and C. D. Surh Interleukin (IL)-15 and IL-7 Jointly Regulate Homeostatic Proliferation of Memory Phenotype CD8+ Cells but Are Not Required for Memory Phenotype CD4+ Cells J. Exp. Med., June 17, 2002; 195(12): 1523 - 1532. [Abstract] [Full Text] [PDF]
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E. Kelly, A. Won, Y. Refaeli, and L. V. Parijs IL-2 and Related Cytokines Can Promote T Cell Survival by Activating AKT J. Immunol., January 15, 2002; 168(2): 597 - 603. [Abstract] [Full Text] [PDF]
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J. C. Rathmell, E. A. Farkash, W. Gao, and C. B. Thompson IL-7 Enhances the Survival and Maintains the Size of Naive T Cells J. Immunol., December 15, 2001; 167(12): 6869 - 6876. [Abstract] [Full Text] [PDF]
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J. Geginat, F. Sallusto, and A. Lanzavecchia Cytokine-driven Proliferation and Differentiation of Human Naive, Central Memory, and Effector Memory CD4+ T Cells J. Exp. Med., December 10, 2001; 194(12): 1711 - 1720. [Abstract] [Full Text] [PDF]
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Q. Wang, J. Strong, and N. Killeen Homeostatic Competition Among T Cells Revealed by Conditional Inactivation of the Mouse Cd4 Gene J. Exp. Med., December 10, 2001; 194(12): 1721 - 1730. [Abstract] [Full Text] [PDF]
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O. Alpdogan, C. Schmaltz, S. J. Muriglan, B. J. Kappel, M.-A. Perales, J. A. Rotolo, J. A. Halm, B. E. Rich, and M. R. M. van den Brink Administration of interleukin-7 after allogeneic bone marrow transplantation improves immune reconstitution without aggravating graft-versus-host disease Blood, October 1, 2001; 98(7): 2256 - 2265. [Abstract] [Full Text] [PDF]
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V. Dardalhon, S. Jaleco, S. Kinet, B. Herpers, M. Steinberg, C. Ferrand, D. Froger, C. Leveau, P. Tiberghien, P. Charneau, et al. IL-7 differentially regulates cell cycle progression and HIV-1-based vector infection in neonatal and adult CD4+ T cells PNAS, July 19, 2001; (2001) 161272698. [Abstract] [Full Text] [PDF]
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J. T. Tan, E. Dudl, E. LeRoy, R. Murray, J. Sprent, K. I. Weinberg, and C. D. Surh IL-7 is critical for homeostatic proliferation and survival of naive T cells PNAS, July 5, 2001; (2001) 161126098. [Abstract] [Full Text] [PDF]
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W. C. Kieper, M. Prlic, C. S. Schmidt, M. F. Mescher, and S. C. Jameson IL-12 Enhances CD8 T Cell Homeostatic Expansion J. Immunol., May 1, 2001; 166(9): 5515 - 5521. [Abstract] [Full Text] [PDF]
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S. Gozalo-Sanmillan, J. M. McNally, M. Y. Lin, C. A. Chambers, and L. J. Berg Cutting Edge: Two Distinct Mechanisms Lead to Impaired T Cell Homeostasis in Janus Kinase 3- and CTLA-4-Deficient Mice J. Immunol., January 15, 2001; 166(2): 727 - 730. [Abstract] [Full Text] [PDF]
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C. Viret, X. He, and C. A. Janeway Jr. On the Self-Referential Nature of Naive MHC Class II-Restricted T Cells J. Immunol., December 1, 2000; 165(11): 6183 - 6192. [Abstract] [Full Text] [PDF]
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C. Ferreira, T. Barthlott, S. Garcia, R. Zamoyska, and B. Stockinger Differential Survival of Naive CD4 and CD8 T Cells J. Immunol., October 1, 2000; 165(7): 3689 - 3694. [Abstract] [Full Text] [PDF]
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S. R. M. Clarke and A. Y. Rudensky Survival and Homeostatic Proliferation of Naive Peripheral CD4+ T Cells in the Absence of Self Peptide:MHC Complexes J. Immunol., September 1, 2000; 165(5): 2458 - 2464. [Abstract] [Full Text] [PDF]
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P. Muranski, B. Chmielowski, and L. Ignatowicz Mature CD4+ T Cells Perceive a Positively Selecting Class II MHC/Peptide Complex in the Periphery J. Immunol., March 15, 2000; 164(6): 3087 - 3094. [Abstract] [Full Text] [PDF]
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 K. Murali-Krishna, L. L. Lau, S. Sambhara, F. Lemonnier, J. Altman, and R. Ahmed Persistence of Memory CD8 T Cells in MHC Class I-Deficient Mice Science, November 12, 1999; 286(5443): 1377 - 1381. [Abstract] [Full Text]
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T. K. Teague, D. Hildeman, R. M. Kedl, T. Mitchell, W. Rees, B. C. Schaefer, J. Bender, J. Kappler, and P. Marrack Activation changes the spectrum but not the diversity of genes expressed by T cells PNAS, October 26, 1999; 96(22): 12691 - 12696. [Abstract] [Full Text] [PDF]
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J. T. Tan, E. Dudl, E. LeRoy, R. Murray, J. Sprent, K. I. Weinberg, and C. D. Surh IL-7 is critical for homeostatic proliferation and survival of naive T cells PNAS, July 17, 2001; 98(15): 8732 - 8737. [Abstract] [Full Text] [PDF]
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V. Dardalhon, S. Jaleco, S. Kinet, B. Herpers, M. Steinberg, C. Ferrand, D. Froger, C. Leveau, P. Tiberghien, P. Charneau, et al. IL-7 differentially regulates cell cycle progression and HIV-1-based vector infection in neonatal and adult CD4+ T cells PNAS, July 31, 2001; 98(16): 9277 - 9282. [Abstract] [Full Text] [PDF]
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