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The Wistar Institute, Philadelphia, PA 19104
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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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-chains ("allelic inclusion") in both TCR-transgenic
(Tg)5 and non-Tg
systems may similarly allow thymocytes expressing low levels of
autoreactive TCRs to evade thymic deletion (4, 17, 18, 19, 20, 21).
There is also evidence that thymocytes that are specific for self
peptides which are presented at low levels in the thymus (such as
tissue-specific Ags) can, in some cases, evade negative selection and
be exported to the periphery (8, 9, 22). Although these
and other studies (23, 24, 25) suggest that negative selection
can be sensitive to both the avidity of the autoreactive thymocyte for
its cognate self peptide and the amount of self peptide that is
presented in the thymus, how these parameters interact to determine the
efficiency of negative selection of autoreactive
CD4+ T cells in vivo is not well understood. In this report, we set out to examine how variation in the expression of an MHC class II-restricted self peptide can affect the degree to which autoreactive CD4+ T cells are negatively selected. We mated two separate lineages of Tg mice that express different amounts of the influenza virus hemagglutinin (HA) as a neo-self Ag (designated HA12 and HA104 mice) with TS1 mice, that express a Tg TCR with specificity for the major I-Ed-restricted T cell determinant from the HA (site 1 (S1)). We show that T cells expressing high levels of the clonotypic TCR are substantially deleted in both TS1 x HA12 and TS1 x HA104 mice. However, T cells that express low levels of the clonotypic TCR via allelic inclusion evaded deletion to different extents in TS1 x HA12 and TS1 x HA104 mice. We further show that T cells from both TS1 x HA12 and TS1 x HA104 mice can nevertheless use the clonotypic TCR to proliferate in response to S1 peptide in vitro, and in response to virus immunization in vivo. These findings demonstrate that the negative selection of autoreactive CD4+ T cells can be influenced by variations in self Ag expression, and that allelic inclusion can allow autoreactive CD4+ T cells with differing sensitivities for the self Ag to enter the peripheral T cell repertoire. Moreover, these processes provide a basis for the activation of autoreactive CD4+ T cells in vivo by viruses bearing homologues of self Ags ("molecular mimicry").
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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HA12 and HA104 mice contain DNA encoding either the N-terminal 237 amino acids or full-length polypeptide, respectively, of the influenza virus A/PR/8/34 (PR8) HA linked to the SV40 early region promoter/enhancer sequences as previously described (11, 26). TS1 mice express a transgene-encoded TCR specific for S1, the I-Ed-restricted determinant of PR8 HA (27). Mice referred to as TS1-negative (TS1neg) are TS1 and HA transgene-negative littermates derived from TS1 x HA matings and were used as controls. All lineages were backcrossed to BALB/c mice (Harlan Breeders, Indianapolis, IN) 5–14 generations before use in this study and were maintained in sterile microisolators at the Wistar Institute Animal Facility (Philadelphia, PA).
Flow cytometry
Thymocytes or pooled lymph node (LN) cells from inguinal,
brachial, axillary, and cervical LN as well as in vitro-cultured LN
cells were analyzed by three-color flow cytometry on a FACScan flow
cytometer (Becton Dickinson, San Jose, CA). Live cells from in vitro
cultures were washed and purified away from dead cells and other debris
using Lympholyte-M before Ab staining. The number of events collected
per sample was between 40,000 and 50,000, except for those described in
Fig. 4
, in which case, all events contained in 1/12th of the culture
volume were collected. The following mAbs were used for analysis:
6.5-biotin (27), anti-Vß8-biotin (F23.1, American
Type Culture Collection, Manassas, VA), anti-CD4-FITC,
anti-CD4-PE, and anti-CD8-PE (Life Technologies, Gaithersburg,
MD). Streptavidin-Red670 (Life Technologies) was used to detect
biotinylated reagents.
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Pooled LN cells (5 x 104) were cultured with 5 x 105 irradiated BALB/c splenocytes and graded doses of S1 peptide (SFERFEIFPK) synthesized and purified by the Wistar Institute peptide synthesis facility. Cells were cultured in 200 µl of supplemented IMDM as described (11) in 96-well flat-bottom tissue culture plates. When indicated, IL-2 from the transfectant cell line X-2 was added at a final concentration of 10 ng/ml (28). Cultures were pulsed with 0.5 mCi per well of [3H]thymidine 72 h after activation and were harvested 16 h later.
5-(and 6-)carboxyfluorescein diacetate succinimidyl ester (CFSE) labeling and adoptive transfer experiments
Pooled LN cells were labeled with CFSE (Molecular Probes, Eugene, OR) as previously described (29). Briefly, LN cells were washed in serum-free IMDM, incubated with 5 µM CFSE at 1 x 107 cells/ml, incubated with 50% serum, and washed with supplemented media. For in vitro culture, 1 x 106 CFSE-labeled cells were stimulated with 1 µM S1 peptide and 5 x 106 irradiated BALB/c splenocytes for 3 days before harvest, staining, and analysis by flow cytometry. For adoptive transfer, 1 x 107 CFSE-labeled cells were injected into the tail vein of BALB/c, HA12, or HA104 mice. At the time of the adoptive transfer, recipient mice were immunized s.c. at the tail base either with 2000 hemagglutinating units PR8 virus in CFA or with CFA alone. Four days after adoptive transfer, inguinal LN cells were harvested from the host mice, stained for CD4 and 6.5, and analyzed by flow cytometry.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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HA12 and HA104 mice contain sequences encoding either the N-terminal 237 amino acids (HA12 mice) or the complete coding sequence (HA104 mice) of the influenza virus PR8 HA linked to the SV40 early-region promoter-enhancer (11, 26). Both lineages express transgene mRNA in the thymus and in peripheral lymphoid tissues; however, higher levels of HA transgene mRNA were detected in HA104 mice than in HA12 mice (11, 26). We have previously shown that PR8-infected HA12 and HA104 mice generate reduced T cell proliferative responses (relative to BALB/c mice) to the major I-Ed-restricted T cell determinant from the HA (termed S1), consistent with induction of tolerance to S1 as a neo-self Ag in both lineages (11, 26).
To determine the mechanism by which S1-specific T cells are tolerized,
HA12 and HA104 mice were mated with Tg mice that express a S1-specific
TCR (designated TS1 mice), and the fate of developing S1-specific T
cells was determined by flow cytometry using the anti-clonotypic Ab
6.5 (27). As previously described (27),
30–40% of mature thymocytes and peripheral T cells in TS1 mice
(including CD8+ T cells) express high or
intermediate levels of the 6.5 TCR, reflecting incomplete allelic
exclusion of endogenous TCR -chain rearrangement (Fig. 1). By contrast, >98% of T cells
express the Tg Vß8.2 chain (27). Mature CD4
single-positive thymocytes and peripheral CD4+ LN
cells expressing high levels of the 6.5 TCR
(6.5high) were deleted in TS1 x HA12 and
TS1 x HA104 mice. However, the degree of deletion of T cells
expressing an intermediate amount of the 6.5 TCR
(6.5int) differed in the two lineages. TS1
x HA12 mice contained more CD4 single positive
6.5int thymocytes than TS1 x HA104 mice; a
similar pattern was apparent among peripheral
CD4+ LN cells (Fig. 1). Although both double Tg
mice contained substantially lower numbers of
6.5high T cells than were present in TS1 mice,
the number of CD4+ 6.5int
LN cells in TS1 x HA12 mice was reduced only 2.5-fold compared
with TS1 mice, whereas the number of CD4+
6.5int LN cells in TS1 x HA104 mice was
9-fold lower than in TS1 mice. Together, these data indicate that
S1-specific thymocytes undergo more substantial deletion in TS1 x
HA104 mice than in TS1 x HA12 mice, correlating with higher
levels of transgene mRNA.
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To examine whether peripheral LN cells that evade deletion by the
neo-self S1 peptide in TS1 x HA12 and TS1 x HA104 mice
could be activated by the S1 peptide, LN cells were incubated with 1
µM S1 peptide and analyzed by flow cytometry 3 days later (Fig. 2). Activation of T cells was assessed by
increases in forward and side light scattering properties (Fig. 2A). The majority of S1 peptide-stimulated LN cells from
TS1neg mice were small and resting, but increased in size in response
to anti-CD3 stimulation. When LN cells from the different
Tg+ lineages were incubated with S1 peptide,
similar increases in size and granularity were observed, although the
number of cells undergoing activation progressively decreased in
TS1 x HA12 and TS1 x HA104 mice relative to those from TS1
mice. Two points were apparent when the levels of Vß8 and the 6.5 TCR
were compared between resting and activated cells. First, the activated
cells all expressed equivalent levels of Vß8 (Fig. 2B),
and therefore had similar TCR densities; however, cells from TS1
x HA12 and TS1 x HA104 mice had lower levels of the 6.5 TCR
compared with TS1 T cells (Fig. 2C). Second, activated cells
from TS1, TS1 x HA12, and TS1 x HA104 mice included cells
expressing higher levels of the 6.5 TCR than were present as background
staining on cells from TS1neg mice (Fig. 2C). This
segregation of 6.5 staining with activation indicates that the T cells
that evade negative selection because they express low levels of the
6.5 TCR nevertheless use the 6.5 TCR to respond to S1 peptide in
vitro.
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Peripheral T cells from TS1, TS1 x HA12, TS1 x HA104,
and TS1neg mice were analyzed for their ability to proliferate in
response to S1 peptide in vitro by two approaches. First, LN cells from
the various lineages were incubated with graded doses of S1 peptide,
and, after 3 days, their proliferation was assessed by
[3H]thymidine uptake (Fig. 3A). LN cells from TS1 x
HA12 mice required roughly 30-fold higher concentrations of S1 peptide
to achieve the half-maximal proliferation observed for LN cells from
TS1 mice. LN cells from TS1 x HA104 mice were less sensitive than
TS1 x HA12 LN cells, but nonetheless displayed proliferative
responses that exceeded those of LN cells from TS1neg mice.
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B). In response to stimulation with 1 µM S1 peptide
and in the absence of exogenous IL-2, LN cells from TS1 and TS1 x
HA12 mice underwent equivalent proliferation per
6.5+ T cell, and addition of exogenous IL-2 led
to 
3-fold increases in the amount of proliferation from both
cultures. In contrast, stimulation with a 10-fold lower concentration
of S1 peptide (0.1 µM) resulted in substantially less proliferation
per 6.5+ T cell in LN cells from TS1 x HA12
than from TS1 mice. The reduced proliferation per
6.5+ T cell exhibited by LN cells from TS1
x HA12 mice in response to lower concentrations of S1 peptide
correlates with their lower levels of the 6.5 TCR, and reflects the
reduced avidity of these T cells for the S1 peptide. The T cells from
TS1 x HA104 mice appeared to have even lower avidities for the S1
peptide: LN cells from TS1 x HA104 mice stimulated with 1 µM S1
peptide were 6-fold less proliferative than TS1 or TS1 x HA12
LN cells on a per 6.5+ T cell basis when
incubated in the absence of IL-2, and little or no proliferation was
exhibited in response to 0.1 µM S1 peptide. Moreover, the S1-specific
T cells from TS1 x HA104 mice appeared to be more dependent on
exogenous IL-2 than either TS1 or TS1 x HA12 T cells for their
proliferation when incubated with 1 µM S1 peptide, because the
addition of IL-2 caused a much greater increase (10-fold) in the
amount of proliferation than was the case for either TS1 or TS1 x
HA12 T cells. Thus, when adjusted for differences in the frequency of
6.5+ T cells, the LN cells from TS1 x HA12
mice appeared less sensitive and proliferated relatively poorly in
response to low doses of S1 peptide, but were as responsive as TS1 T
cells when incubated with high doses of S1 peptide. The S1-specific T
cells from TS1 x HA104 mice, in contrast, proliferated relatively
poorly in response to either peptide dose, even when adjusted for their
low precursor frequency, and were more sensitive to the addition of
exogenous IL-2.
As a second approach to examine their capacity to undergo S1-specific
proliferation, LN cells from the different lineages were labeled with
the fluorescent dye CFSE, stimulated with 1 µM S1 peptide, and 3 days
later, analyzed by flow cytometry (Fig. 4). Because CFSE-labeled cells decrease
in staining intensity by one-half with each cycle of cell division
(29), the extent of cell division in response to S1
peptide could be assessed. Neither TS1 CD4+ T
cells incubated in the absence of S1 peptide nor TS1neg
CD4+ T cells incubated with S1 peptide underwent
significant cell division during the culture period. By contrast, the
majority of the CD4+ T cells from TS1 mice
underwent division in response to S1 peptide, with the most prominent
peaks corresponding to four and five cell divisions. Moreover, most of
the CD4+ T cells that divided expressed high or
intermediate levels of the 6.5 TCR, although a population of T cells
expressing low levels of the 6.5 TCR also underwent division in
response to S1 peptide. Significantly, although fewer
CD4+ T cells from TS1 x HA12 mice divided
in response to S1 peptide compared with TS1 mice, the number of divided
cells was substantial and generated a CFSE profile displaying prominent
peaks representing cells that had undergone five to six divisions. The
CD4+ T cells from TS1 x HA104 mice, in
contrast, underwent less division in response to 1 µM S1 peptide than
did those from TS1 x HA12 mice, and did not yield clearly defined
peaks. Comparison of CFSE intensity with 6.5 staining also revealed
that the cells from TS1 x HA12 and TS1 x HA104 mice that
underwent division in each case expressed lower levels of the 6.5 TCR,
reflecting deletion of 6.5high T cells in these
lineages.
Together, these data indicate that the 6.5+ LN cells that persist in TS1 x HA12 and TS1 x HA104 mice can proliferate in response to S1 peptide in vitro, although to differing extents. The 6.5+ T cells from TS1 x HA12 and TS1 mice proliferated similarly on a per cell basis in response to high doses of S1 peptide (1 µM), and activated T cells underwent similar numbers of divisions. However, in response to a lower dose of S1 peptide (0.1 µM), the S1-specific T cells from TS1 x HA12 mice were less proliferative on a per cell basis, reflecting their lower avidities for the S1 peptide. The LN cells from TS1 x HA104 mice were less responsive on a per-cell basis and were more dependent on exogenous IL-2 in their responsiveness to 1 µM S1 peptide, suggesting that lower avidities and/or anergy induction limit their ability to proliferate in response to S1.
Activation of autoreactive S1-specific T cells by PR8 virus in vivo
Because autoreactive T cells from TS1 x HA12 and TS1 x
HA104 mice could be activated in vitro in response to S1 peptide, it
was of interest to determine whether these T cells were susceptible to
activation upon encountering the S1 peptide when presented by a virus
particle in vivo. To examine this, LN cells from TS1, TS1 x HA12,
and TS1 x HA104 mice were labeled with CFSE and injected into
mice with the same HA transgene status but that did not contain the TS1
transgene (i.e., TS1 LN cells into BALB/c mice, TS1 x HA12 LN
cells into HA12 mice, and TS1 x HA104 LN cells into HA104 mice).
The recipient mice were then immunized either with PR8 virus in CFA or
with CFA alone. Although this protocol is not expected to give rise to
significant virus replication, it allowed us to compare T cell division
that might be induced in response to virus-derived S1 peptide with
division that could occur in response to nonspecific inflammatory
signals (provided here by the use of CFA). Four days after adoptive
transfer and virus immunization, draining LN cells from the mice were
harvested and analyzed by flow cytometry (Fig. 5A). Transferred
CD4+ T cells from TS1, TS1 x HA12, and
TS1 x HA104 mice all underwent division in response to
immunization with PR8 virus in CFA, as indicated by a progressive loss
of CFSE intensity. Significantly, although fewer precursors were
activated in LN cells from both TS1 x HA12 and TS1 x HA104
mice than from TS1 mice, autoreactive LN cells in each case underwent
multiple rounds of division in response to virus immunization. By
contrast, in mice immunized with CFA alone, the few cells found in the
low intensity CFSE peak did not exceed in number those detected in
control mice that either received CFSE-labeled cells without
immunization, or that were immunized but did not receive labeled cells
(Fig. 5B). Moreover, the CD4+ T cells
from TS1, TS1 x HA12, and TS1 x HA104 mice that underwent
division expressed levels of 6.5 that paralleled those expressed by in
vitro-activated T cells (i.e., high levels of 6.5 on TS1 T cells, and
progressively lower levels on TS1 x HA12 and TS1 x HA104
cells) (Figs. 2 and 5C). Accordingly, peripheral
autoreactive CD4+ T cells from TS1 x HA12
and TS1 x HA104 mice can be activated and undergo proliferation
in vivo in response to a virus that contains the S1 peptide. That
division was observed in response to PR8 virus in CFA, but not to CFA
alone, indicates that the high concentration of S1 peptide generated
from PR8 virus, rather than nonspecific inflammatory signals, led to
activation of the autoreactive T cells.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Although HA12 and HA104 mice both use the SV40 early region
promoter/enhancer to drive transgene expression, differences in
transgene integration led to higher levels of transgene mRNA expression
in HA104 than HA12 mice (26). S1-specific T cells were
able to evade negative selection in TS1 x HA12 and TS1 x
HA104 mice because they expressed intermediate and low levels of the Tg
TCR -chain via coexpression of endogenous TCR -chains. The
ability of T cells to express more than one TCR -chain ("allelic
inclusion") is not particular to these T cells because 30% of
normal human and murine ß T cells express two -chains
(20, 21). The variable coexpression of endogenous TCR
-chains most likely reduced the sensitivity of
6.5+ thymocytes for the S1 peptide to varying
degrees, and the greater amount of S1 (and/or expression on more cell
types) in HA104 vs HA12 mice caused thymocytes with progressively lower
densities of the 6.5 TCR to be deleted. Thus, differences in the
expression of the S1 peptide affected the extent to which
6.5int T cells were negatively selected in
TS1 x HA12 and TS1 x HA104 mice. This finding is similar to
other studies examining negative selection of
CD4+ T cells specific for neo-self Ags, in which
differences in the pattern of transgene expression were found to affect
the degree of deletion of autoreactive thymocytes (4, 30).
It is likely that variations in the expression of bona fide self
peptides can similarly influence the efficiency with which autoreactive
CD4+ T cells are negatively selected during
thymic development.
Despite substantial deletion of T cells expressing high levels of the
6.5 TCR in both TS1 x HA12 and TS1 x HA104 mice,
6.5int and 6.5low T cells
that evaded deletion could nevertheless be activated if they were
provided with high concentrations of S1 peptide in vitro. The ability
of 6.5int and 6.5low T
cells to respond to the S1 peptide is noteworthy in light of a previous
study in which autoreactive CD4+ T cells
expressing dual TCRs were found to react with their cognate self
peptide (in this case C5) only after stimulation via their
nonautoreactive TCR -chains (19). In the studies here,
T cells from TS1 x HA12 and TS1 x HA104 mice appeared to
have been activated via the 6.5 TCR in response to S1 peptide
stimulation, as evidenced by the segregation of 6.5 staining into the
blasting population of T cells following stimulation (Fig. 2). Thus,
although low levels of the 6.5 TCR allowed T cells to evade negative
selection by the S1 peptide during their development by reducing their
sensitivity for the S1 peptide, these T cells could nevertheless use
the 6.5 TCR to respond to high concentrations of the S1 peptide in
vitro and in vivo.
Although both TS1 x HA12 and TS1 x HA104 mice contained peripheral CD4+ T cells that could be activated by the S1 peptide, these peripheral T cells differed in their proliferative capacity following activation. When adjusted for the relative frequency of 6.5+ T cells, LN cells from TS1 x HA12 mice proliferated as well as TS1 LN cells in response to 1 µM S1 peptide in the presence or absence of exogenous IL-2. Likewise, CFSE analysis conducted in the absence of exogenous IL-2 indicated that S1-specific T cells from TS1 and TS1 x HA12 mice underwent equivalent rounds of division in response to this dose of S1 peptide. At a lower dose of S1 peptide (0.1 µM), LN cells from TS1 x HA12 mice were less responsive on a per 6.5+ cell basis than were TS1 LN cells, reflecting the low levels of the 6.5 TCR and reduced avidities that allowed these cells to evade negative selection during thymic development. The LN cells from TS1 x HA104 mice, in contrast, appeared less proliferative on a per 6.5+ cell basis at both 1 µM and 0.1 µM S1 peptide, and were more dependent on the addition of exogenous IL-2 for proliferation. This greater requirement for exogenous IL-2 could reflect the induction of anergy among S1-responsive T cells (5). Using a different lineage of HA Tg mice (designated HA28), we recently showed that HA as a self Ag can induce TS1 cells to become anergic/suppressor cells (6). However, in TS1 x HA28 mice, anergy induction was associated with little thymic clonal deletion, and with a characteristic cell surface phenotype (CD25hi/CD45RBint) that was expressed by 6.5high cells, but not by 6.5int or 6.5low cells (6). Because 6.5high T cells are substantially deleted in TS1 x HA104 mice, it is unlikely that a similar mechanism explains the dependency of these T cells on exogenous IL-2. However, it remains possible that S1-specific T cells are anergized by a distinct mechanism in TS1 x HA104 mice; indeed, anergy induction has previously been proposed for TS1 T cells that evaded deletion in mice that express the HA on hematopoietic cells and in which 6.5high T cells are substantially deleted (31).
An alternative explanation for the poor proliferative responses of T
cells from TS1 x HA104 mice is that a combination of the
decreased avidity of the TCR for the S1 peptide and the reduced
frequency of responsive T cells leads to a greater requirement for
exogenous IL-2 (32). Indeed, consistent with this previous
study, the LN cells from TS1 x HA12 mice were more responsive to
exogenous IL-2 when stimulated with 0.1 µM S1 peptide than when they
were stimulated with 1 µM S1 peptide (see Fig. 3B). It is
possible, then, that a combination of reduced avidity and lower
precursor frequency explains the IL-2 dependency of LN cells from
TS1 x HA104 mice when stimulated with S1 peptide in vitro.
However, significantly, T cells from both TS1 x HA12 and TS1
x HA104 mice underwent division in response to PR8 virus in vivo. The
ability of the LN cells from TS1 x HA104 mice to proliferate in
vivo in response to virus immunization is particularly noteworthy in
light of their dependency on the addition of exogenous IL-2 for
proliferation in vitro. Therefore, neither the decreased levels of the
6.5 TCR that allowed these cells to evade deletion, nor peripheral
regulatory mechanisms (such as anergy induction or suppression),
prevented these autoreactive T cells from being activated by the S1
peptide when presented in the context of a viral Ag.
The in vivo activation of S1-specific T cells from TS1 x HA12 and
TS1 x HA104 mice by PR8 virus demonstrates that a viral Ag can
activate CD4+ T cells that evade negative
selection by a self peptide via allelic inclusion ("molecular
mimicry"). Inasmuch as the S1-specific T cells from TS1 x HA12
mice were more proliferative than their TS1 x HA104 counterparts,
they would appear to pose the greater threat for mediating autoimmune
damage to the host’s tissues. However, in this regard it is noteworthy
that the activated S1-specific T cells from TS1 x HA104 mice can
contain a higher proportion of effector cells that secrete high levels
of IFN-
, and thus may mediate more potent cell-mediated
anti-self responses (33). Because it is likely that variations in
the amount and/or pattern of expression of bona fide self peptides can
similarly affect the proliferative and/or differentiative capacity of
autoreactive T cells that evade thymic deletion, it will be important
to determine how these differences influence their capacity to mediate
autoimmune disease.
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Acknowledgments |
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Footnotes |
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2 Current address: Division of Biochemistry and Pharmacology, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Grounds, Aberdeen, MD 21010.
3 Current address: Department of Pediatrics, St. Louis Children’s Hospital, St. Louis, MO 63110.
4 Address correspondence and reprint requests to Dr. Andrew J. Caton, The Wistar Institute, Room 262, 3601 Spruce Street, Philadelphia, PA 19104.
5 Abbreviations used in this paper: Tg, transgenic; HA, hemagglutinin; S1, site 1; CFSE, 5-(and 6-)carboxyfluorescein diacetate succinimidyl ester; LN, lymph node; PR8, A/PR/8/34; TS1neg, TS1-negative.
Received for publication April 20, 2000. Accepted for publication August 1, 2000.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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chains on the surface of T cells in T cell receptor transgenic mice. J. Exp. Med. 178:1807. genes poses an autoimmune hazard due to low-level expression of autospecific receptors. Immunity 8:563.[Medline]
-chains on the surface of normal murine T cells. Eur. J. Immunol. 25:1617.[Medline]
-chains: dual receptor T cells. Science 262:422.This article has been cited by other articles:
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  J. Larkin III, A. L. Rankin, C. C. Picca, M. P. Riley, S. A. Jenks, A. J. Sant, and A. J. Caton CD4+CD25+ Regulatory T Cell Repertoire Formation Shaped by Differential Presentation of Peptides from a Self-Antigen J. Immunol., February 15, 2008; 180(4): 2149 - 2157. [Abstract] [Full Text] [PDF]
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A. L. Rankin, A. J. Reed, S. Oh, C. Cozzo Picca, H. M. Guay, J. Larkin III, L. Panarey, M. K. Aitken, B. Koeberlein, P. E. Lipsky, et al. CD4+ T Cells Recognizing a Single Self-Peptide Expressed by APCs Induce Spontaneous Autoimmune Arthritis J. Immunol., January 15, 2008; 180(2): 833 - 841. [Abstract] [Full Text] [PDF]
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 A. Boesteanu, A. L. Rankin, and A. J. Caton Impact of effector cell differentiation on CD4+ T cells that evade negative selection by a self-peptide Int. Immunol., July 1, 2006; 18(7): 1017 - 1027. [Abstract] [Full Text] [PDF]
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F. F. Shih, J. Racz, and P. M. Allen Differential MHC Class II Presentation of a Pathogenic Autoantigen during Health and Disease J. Immunol., March 15, 2006; 176(6): 3438 - 3448. [Abstract] [Full Text] [PDF]
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P. Sinha, H. H. Chi, H. R. Kim, B. E. Clausen, B. Pederson, E. E. Sercarz, I. Forster, and K. D. Moudgil Mouse Lysozyme-M Knockout Mice Reveal How the Self-Determinant Hierarchy Shapes the T Cell Repertoire against This Circulating Self Antigen in Wild-Type Mice J. Immunol., August 1, 2004; 173(3): 1763 - 1771. [Abstract] [Full Text] [PDF]
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M. A. Lerman, J. Larkin III, C. Cozzo, M. S. Jordan, and A. J. Caton CD4+ CD25+ Regulatory T Cell Repertoire Formation in Response to Varying Expression of a neo-Self-Antigen J. Immunol., July 1, 2004; 173(1): 236 - 244. [Abstract] [Full Text] [PDF]
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 F. F. Shih, L. Mandik-Nayak, B. T. Wipke, and P. M. Allen Massive Thymic Deletion Results in Systemic Autoimmunity through Elimination of CD4+ CD25+ T Regulatory Cells J. Exp. Med., February 2, 2004; 199(3): 323 - 335. [Abstract] [Full Text] [PDF]
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J. Trani, D. J. Moore, B. P. Jarrett, J. W. Markmann, M. K. Lee, A. Singer, M.-M. Lian, B. Tran, A. J. Caton, and J. F. Markmann CD25+ Immunoregulatory CD4 T Cells Mediate Acquired Central Transplantation Tolerance J. Immunol., January 1, 2003; 170(1): 279 - 286. [Abstract] [Full Text] [PDF]
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A. J. Reed, M. P. Riley, and A. J. Caton Virus-Induced Maturation and Activation of Autoreactive Memory B Cells J. Exp. Med., December 18, 2000; 192(12): 1763 - 1774. [Abstract] [Full Text] [PDF]
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
), TS1 x HA12 (
),
TS1 x HA104 (
), and TS1neg (•) mice were harvested and
incubated in vitro with serial 3-fold dilutions of S1 peptide plus
irradiated APC. [3H]Thymidine was added for the final
16 h of a 96-h culture before harvest and measurement of
[3H]thymidine incorporation. Each data point is the mean
of triplicate wells; error bars indicate ± 1 SD. Data are
representative of at least six experiments. B,
S1-specific proliferation per 6.5+ cell with or without
exogenous IL-2. LN cells from TS1, TS1 x HA12, TS1 x HA104,
and TS1neg mice were harvested and either stained with 6.5 for analysis
by flow cytometry, or incubated in vitro with either 0.1 or 1 µM S1
peptide plus irradiated APC with or without 10 ng/ml exogenous IL-2.
[3H]Thymidine was added for the final 16 h of a
96-h culture before harvest and measurement of
[3H]thymidine incorporation. The amount of
[3H]thymidine incorporation was then divided by the
number of 6.5+ LN cells for that mouse. Each data point is
the mean of triplicate wells; error bars indicate ± 1 SD. Data
are representative of at least three experiments.