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Department of Biology, University of Maryland, Baltimore, MD 21250 This work was supported by National Institutes of Health Grant 1R01CA52527 and U.S. Army Medical Research and Materiel Command Grant DAMD17–94-J-4323.
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Most of these studies have focussed on the direct activation of tumor-specific CD8+ T lymphocytes, either by providing appropriate costimulatory signals such as B7 (1, 2, 3, 4) or by providing cytokines normally produced by CD4+ T helper lymphocytes, such as IL-2 or IL-4 (5, 6). In contrast, we and others have reasoned that optimal tumor-specific CD8+ T cells and long term immune memory will only be generated if sufficient CD4+ Th cells are also stimulated (7, 8, 9, 10). As a result, we have targeted the activation of tumor-specific CD4+ T cells. We have hypothesized that class II-transfected tumor cells will present endogenously encoded peptides in the context of the transfected class II molecules and, therefore, directly present tumor peptides to CD4+ T helper lymphocytes. Reports from our laboratory as well as studies by others demonstrate that such genetically modified tumor cells are potent inducers of tumor-specific immunity in naive mice (7, 9, 11) as well as in tumor-bearing mice (12), demonstrating their potential as immunotherapeutic agents. Although these therapeutic results are consistent with the hypothesis that the genetically modified tumor cells directly present Ag to CD4+ T cells during the immunization process, there is no direct evidence demonstrating that the modified tumor cells directly present Ag to responding CD4+ T lymphocytes. Such a pathway would be unconventional, since CD4+ T cells are usually activated by the process of indirect Ag presentation or cross-priming, in which Ag is taken up and presented by host-derived professional APC (i.e., dendritic cells, macrophages, or B lymphocytes) rather than by the Ag-expressing cells themselves (13, 14). Since optimal exploitation of this immunotherapeutic approach will depend on a full understanding of the mechanism through which the genetically modified tumor cells activate T lymphocytes, the present studies were undertaken to identify the cell population(s) that serves as APC during the activation of tumor-specific CD4+ T cells following immunization with class II-transfected tumor cells.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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C57BL/6, A/J, and (C57BL/6 x A/J) ((B6 x
A/J)F1) mice were purchased from The Jackson Laboratory
(Bar Harbor, ME) or bred in the University of Maryland Baltimore County
animal facility. Bone marrow donors and recipients were female mice,
and chimeras were generated as previously described (15). Briefly,
recipient (B6 x A/J)F1 mice were maintained on
tetracycline water (0.2%) for 1 wk before and 5 wk after
reconstitution and were given gentamicin sulfate s.c. (500 µg) for 7
consecutive days beginning 1 day before irradiation/reconstitution.
Approximately 24 h before irradiation/reconstitution, recipients
were taken off food. Recipients were irradiated with 875 rad total body
irradiation using a 137Cs source (Kewaunee Scientific,
Statesville, NC) and reconstituted i.v. with one femur-equivalent of
donor bone marrow within 2 to 3 h of irradiation. Chimeras were
maintained in a pathogen-free environment for 6 wk before use. All
chimeras were tested by indirect immunofluorescence to ascertain bone
marrow genotype and assure chimeric status as follows. Concurrent with
the in vitro APC assays, spleens of chimeras were removed and stained
for MHC class I (H-2Kk for A/J (mAb 16-3-1) (16);
H-2KbDb for C57BL/6 (mAb 28-13-3) (17)) Ags.
Positively staining cells were gated relative to conjugate alone
controls, and positive cells were compared with wild-type A/J and
C57BL/6 splenocytes stained under identical conditions. The percentage
of the donor phenotype was calculated by comparing the percentage of
positive chimeric spleen cells vs that of wild-type cells. For example,
if 98 and 2% of
A/J
F12
chimeric splenocytes were stained with the 16-3.1 and 28-13-3 mAbs,
respectively, and 99 and 1% of A/J wild-type splenocytes were stained
with the 28-13-3 and 16-3.1 mAbs, respectively, then the
A/JF1 chimeras were considered 99% donor phenotype.
Cells, transfectants, and hybridomas
The SaI sarcoma and its transfectants were cultured as
previously described (7). SaI sarcoma cells transfected with syngeneic
MHC class II A
k and Aßk genes
(SaI/Ak cells) have been previously described (7). SaI
cells expressing I-Ab class II molecules
(SaI/Ab cells) were generated by transfecting SaI cells
with the Ab and Aßb cDNAs
contained in the pKCR3 plasmid (18) plus the pSV2.neo plasmid using the
transfection procedure previously described (7). SaI,
SaI/Ak, or SaI/Ab cells expressing an
endoplasmic reticulum-retained hen egg lysozyme gene (HEL; SaI/HEL,
SaI/Ak/HEL, SaI/Ab/HEL cells) were generated as
previously described by transfection with the BCMG-HEL plasmid
containing the hygromycinR gene (19). Transfectants
expressing MHC class II genes or HEL were maintained in medium
supplemented with 400 µg/ml G418 or 400 µg/ml hygromycin,
respectively. Double transfectants were maintained on both drugs. 3A9
is an I-Ak-restricted HEL46–61-specific T cell
hybridoma (20) and was maintained as previously described (19); JK1290
is an I-Ab-restricted HEL specific hybridoma (21) and was
maintained in Iscove’s modified Dulbecco’s medium supplemented with
10% Fetalclone I (Hyclone, Logan, UT), 1% penicillin, 1%
streptomycin, and 1% gentamicin.
Tumor challenges
For tumorigenicity studies, mice were inoculated i.p. with live tumor cells, observed daily for survival, and killed when they became moribund. The inoculation dose was chosen based on previous titration studies (7). For immunization studies, chimeric mice were inoculated i.p. with 5 x 105 to 106 live tumor cells and killed 6 or 7 days later. For tumor challenge studies, mice were inoculated i.p. with the indicated number of tumor cells and examined three times per week for tumor growth. Ascites tumors usually became palpable within 10 to 14 days of inoculation and grew progressively. Based on our previous experience with the SaI tumor, if mice do not develop palpable tumor within 2 mo of challenge, they will remain tumor free during their lifetime (7). Tumor incidence is the number of mice with progressively growing tumors divided by the total number of mice challenged. Tumor-bearing mice were killed according to University of Maryland Baltimore County institutional animal care and use committee guidelines when they became moribund. The mean survival time is the time between inoculation and sacrifice.
In vitro Ag presentation assays
Splenocytes from immunized mice were prepared from mechanically
dissociated spleens, and B lymphocytes were removed by panning as
previously described (22). Resulting T cells (5 x
106 cells/well) were cocultured in flat-bottom 96-well
plates with fresh naive A/J or C57BL/6 splenocytes in a final volume of
250 µl/well containing 1 mg/ml lysozyme. Responder to stimulator
ratios were 10:1 and/or 50:1. Supernatants were harvested after 24
h and assayed for IL-2 content using ELISA kits as described by the
manufacturer (Endogen, Boston, MA). Samples were run in triplicate, and
the mean ± SD determined for each sample. In most cases, SDs were
5% of test values. Background values (IL-2 release in the absence of
HEL) were subtracted from experimental values (IL-2 release in the
presence of HEL) to obtain specific IL-2 release. Values were converted
to picograms per milliliter using a standard curve incorporated into
the IL-2 assay. In some experiments splenocytes were depleted of
CD4+ or CD8+ T lymphocytes in vitro (22) or in
vivo (12) before use in an APC assay. APC assays using splenocytes from
chimeric mice plus T cell hybridomas 3A9 and JK1290 were performed as
previously described (19).
Indirect immunofluorescence and flow cytometry
Tumor cells, transfectants, and splenocytes were monitored for cell surface Ag expression by indirect immunofluorescence as previously described (7) and analyzed on an Epics XL flow cytometer (Coulter, Hialeah, FL). The following mAbs were used: I-Ak (10-3-6 or 10-2-16) (23), I-Ab (34-5-3S) (17), Kk (16-3-1) (16), Dd (34-5-8) (24), and lysozyme (HyHEL 7 and 10) (25). Cells monitored for intracellular lysozyme were fixed with paraformaldehyde and stained with a mixture of the HyHEL 7 and 10 mAbs (25) as previously described (19). Isotype controls were performed for surface and cytoplasmically stained cells, and staining was essentially identical with that in fluorescent conjugate alone controls.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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k and Aßk
genes (SaI/Ak tumor cells), induced potent CD4+
T cell-dependent, tumor-specific immunity in syngeneic A/J and
semisyngeneic (C57BL/6 x A/J)F1 mice. In vitro
experiments using HEL-specific, I-Ak-restricted T cell
hybridomas showed that SaI/Ak tumor cells transfected with
a gene encoding an endoplasmic reticulum-retained HEL
(SaI/Ak/HEL tumor cells) present endogenously synthesized
HEL peptide to CD4+ T cells (19). The genetically modified
tumor cells, therefore, are capable of presenting tumor-encoded Ag
directly to T cells. To determine whether during the immunization
process the tumor cells themselves are APC for endogenously encoded
tumor Ags (direct Ag presentation) or if host-derived cells are the APC
(indirect Ag presentation or cross-priming), we used the following
genetic approach. (C57BL/6 x A/J)F1 mice are lethally
irradiated and reconstituted with either C57BL/6
(H-2KbAbDb)
or A/J
(H-2KkAkDd)
bone marrow so that the resulting chimeric mice (B6F1 or
A/JF1, respectively) have host-derived APC of either the
C57BL/6 or the A/J genotype, respectively. The chimeras are
subsequently challenged with either SaI/Ak/HEL or
SaI/Ab/HEL tumor cells, respectively, and the MHC
restriction pattern of the response is determined. If the tumor cells
are the exclusive APC for the tumor-encoded Ag (HEL), then the response
will be restricted to the MHC class II genotype of the tumor cells.
However, if host-derived cells are the exclusive APC for tumor-encoded
HEL, then the T cell response will be restricted to the genotype of the
reconstituting bone marrow in the chimeras. If both tumor cells and
host cells are APC for tumor-encoded Ags, then the response will be
restricted to both the tumor and bone marrow genotypes. SaI sarcoma cells transfected with MHC class II and/or HEL genes express these gene products at the cell surface or intracellularly
SaI/Ak and SaI/Ak/HEL cells were
available from previous experiments (7, 19). SaI/Ab and
SaI/Ab/HEL cells were generated by gene transfection as
described in Materials and Methods. The resulting
transfectants were stained for cell surface expression of MHC class II
molecules (live cells) or for intracellular expression of lysozyme
(paraformaldehyde-fixed and saponin-permeabilized cells). As shown in
Figure 1
, cells transfected with the MHC
class II I-Ak and I-Ab genes expressed
comparable levels of these molecules, as measured by staining with the
10-2-16 and 34-5-3S mAbs, respectively (Fig. 1, i and
j, and e and f for SaI/Ak
and SaI/Ab cells, respectively). Similarly, cells
transfected with the HEL construct expressed comparable levels of
intracellular lysozyme as measured by staining with the mixture of
HyHEL 7 and HyHEL 10 mAbs (Fig. 1, n, p, and
r for SaI/HEL, SaI/Ak/HEL, and
SaI/Ab/HEL cells, respectively.), while untransfected cells
were negative for lysozyme (Fig. 1, m, o, and
q). HEL transfectants were also stained for cell
surface HEL expression and were negative (data not shown). Supernatants
of the transfectants were assayed by ELISA for HEL secretion and showed
low levels of soluble HEL (1–5 ng/ml/6.7 x 105
cells/24 h). The transfectants were also stained for MHC class I
H-2Kk, H-2Dd, and H-2Ld Ag
expression, and these levels were approximately equivalent among all
transfectants and parental SaI cells (data not shown).
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Numerous in vitro studies have demonstrated that both
I-Ak and I-Ab MHC class II molecules
present HEL-derived peptides to CD4+ T cells (21, 26, 27, 28).
To ascertain that HEL peptides are presented by both class II alleles
when the alleles are expressed by SaI sarcoma cells, semisyngeneic
(C57BL/6 x A/J)F1 mice were challenged i.p. with
parental SaI, SaI/Ak, SaI/Ab, SaI/HEL,
SaI/Ak/HEL, and SaI/Ab/HEL tumor cells and
followed for tumor incidence. As shown in Table I, wild-type SaI and SaI/HEL tumor cells
were lethal in 
94% of F1 mice, indicating that HEL
expression alone does not cause tumor rejection. SaI/Ak and
SaI/Ab cells were significantly less lethal than SaI cells;
however, they still caused tumors in a significant number of
F1 mice (50 and 40% lethal, respectively). In contrast,
SaI/Ak/HEL and SaI/Ab/HEL tumor cells were
rejected by 100% of F1 mice, suggesting that HEL peptides
are presented by the I-Ak and I-Ab MHC class II
molecules of the tumor cells and function as nominal Ag for T cell
recognition.
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If the genetically modified tumor cells are the exclusive APC for
tumor Ags, then AF1 bone marrow chimeras immunized
with B tumor cells will have HEL-specific T cells restricted to the
tumor (B) MHC genotype. In contrast, if host-derived cells are the APC,
then the chimeras will have HEL-specific T cells restricted to the
genotype of the host (A) regardless of the genotype of the tumor. To
test these alternatives, A/J F1 and B6F1
chimeras were generated and challenged i.p. with SaI/Ab/HEL
or SaI/Ak/HEL tumor cells, respectively. Seven days after
tumor cell immunization, spleens were removed and depleted of B cells
and adherent cells by panning, and the remaining T cells were incubated
in vitro with lysozyme plus fresh A/J or C57BL/6 splenocytes as APC.
Supernatants were harvested 24 h later and tested for IL-2
content. Since the goal of these experiments is to characterize the
earliest Ag-specific response, T cells were tested 1 wk
postimmunization. Likewise, T cells were assayed for IL-2 secretion
without an in vitro or in vivo boost to the Ag (HEL), so that the
primary or initial response would be measured.
A/JF1 and B6F1 bone marrow chimeras were
generated as described in Materials and Methods. The
efficiency of chimera formation was determined using indirect
immunofluorescence to measure the percentage of donor genotype cells in
the recipients’ spleens. Table II lists
the chimeras used in subsequent experiments and shows the MHC class I
genotype (H-2Kk for A/J vs
H-2Db for C57BL/6) of splenocytes from the chimeras
as measured by immunofluorescence. As shown, all the chimeras used in
the following experiments were 97.9%, and most chimeras were
99.5%, of the donor genotype. Chimeras were also tested functionally
for hemopoietic reconstitution. Splenocytes of representative chimeras
were used as APC for intact HEL to I-Ak- and
I-Ab-restricted HEL-specific hybridomas, 3A9 and JK1290,
respectively. A/JF1 and A/J splenocytes presented HEL to
3A9 hybridoma cells, but not to JK1290 hybridoma cells. In contrast,
B6F1 and C57BL/6 splenocytes presented Ag to JK1290
cells, but not to 3A9 hybridoma cells (data not shown). APC of the bone
marrow chimeras, therefore, are phenotypically and functionally the
donor genotype.
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shows the results of three
representative, independent experiments assessing IL-2 production by
total T cells from tumor-immunized, chimeric mice. In two experiments
(Expt. 1 and 2) A/JF1 chimeras were immunized with
SaI/Ab/HEL tumor cells, while in one experiment (Expt. 4),
B6F1 chimeras were immunized with SaI/Ak/HEL
tumor cells. In all three experiments HEL-specific T cells restricted
to both the tumor and the host genotype were present. IL-2 release by
immune T cells cocultured in vitro with lysozyme plus irrelevant
genotype APC (SWR, H-2q) was at background levels
(data not shown). Therefore, at 1 wk postimmunization with genetically
modified tumor cells, both tumor cells and host bone marrow-derived
cells were APC for tumor- encoded Ags.
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, one experiment using A/JF1 chimeric
mice immunized with SaI/Ab/HEL tumor cells (Expt. 3) and a
second experiment using B6F1 chimeric mice immunized
with SaI/Ak/HEL tumor cells (Expt. 5). As shown in Table II, mice depleted for CD4+ or CD8+ T cells had
1.2 or 0.6% of these cells, respectively, demonstrating functional
depletion of these populations. As shown in Table III, in both the
depletion experiments most of the IL-2 activity was produced by
CD4+ T cells, since depletion of CD4+ T cells
reduced IL-2 activity to negligible levels. Consistent with the results
of Expt. 1, 2, and 4, in Expt. 3, both tumor genotype and host genotype
APC stimulated HEL-specific IL-2 release, indicating that both tumor
cells and host-derived cells are APC for tumor-encoded Ag (HEL). In
contrast, in Expt. 5, only host genotype
(H-2b) cells stimulated IL-2 secretion,
suggesting that in these mice only host-derived cells are the APC for
tumor-encoded Ags.
The five experiments shown in Table III are representative of 25
similar experiments performed using chimeric or (C57BL/6 x
A/J)F1 mice. Results similar to those of Expt. 5, in which
only host genotype APC stimulated IL-2 secretion, were noted in only
two of these experiments, while the remaining experiments all showed
either host and tumor genotype presentation, or tumor genotype
presentation alone. It was occasionally observed that tumor-encoded Ags
were exclusively presented by host-derived cells; however, such
presentation was a relatively rare event. Similar experiments using
class II- SaI/HEL tumor cells showed no direct Ag
presentation (data not shown), indicating that direct Ag presentation
by tumor cells to CD4+ T cells requires MHC class II
expression by the tumor. Therefore, as measured at 1 wk
postimmunization, CD4+ T cells specific for tumor-encoded
Ags were activated via Ag presentation by both tumor and host-derived
cells, indicating that both direct and indirect (cross-priming)
pathways are used.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Our data indicate that both tumor cells and host-derived cells are APC for tumor-encoded HEL. These experiments were designed to test Ag presentation of an intracellular, surrogate tumor Ag; however, ELISA assays of SaI/Ak/HEL supernatants show low levels of secreted HEL. Since the SaI/Ak/HEL transfectants are "leaky" for HEL, one cannot determine whether intracellular tumor Ag presentation is normally indirect via host-derived APC, or if cross-priming occurs because soluble HEL is available. If leakiness is the reason for the observed cross-priming, then the relative roles of direct vs indirect presentation for bonafide tumor Ags will be dependent on the cellular locale and behavior of tumor Ag.
Cross-priming or indirect Ag presentation is the usual route for activation of CD4+ T cells. In this process, tumor Ag (in this case, lysozyme) is released from tumor cells, trafficks via the lymphatic and/or circulatory system to the closest regional lymph node(s), and is internalized by professional APC within the lymph node. Alternatively, Ag may be internalized in the periphery by professional APC and brought to the regional lymph node by the APC. In either case, internalized Ag is processed by the APC and presented as peptide in the context of MHC class II molecules on the surface of the APC (32). Since only a small percentage of CD4+ T cells has the appropriate receptor for a given Ag, localization of Ag to the regional lymph node allows exposure to the maximal number of CD4+ T cells. Trafficking of Ag to the regional lymph node during a conventional immune response, therefore, optimizes contact of Ag with the appropriate T cells.
If tumor cells are the APC, Ag presentation could occur either at the tumor site or in the regional lymph node. Presentation at the tumor site is unlikely, since unless a very large number of CD4+ T cells traffick to the site, it is improbable that T cells with an appropriate TCR will be exposed to Ag. Trafficking of the transfectants to the regional nodes is more likely. Tumors are known to metastasize via the lymphatic circulation, and a recent study using genetically modified, nonmetastatic tumor cells demonstrated tumor cells in draining nodes (33). The class II-transfected tumor cells, therefore, may migrate to the draining lymph nodes; however, the precise logistics of the Ag presentation process remain unclear.
Although the activation of CD4+ T cells by genetically modified tumor cells has not been previously studied, other investigators have examined the activation of CD8+ T cells during immunization with transfected tumor cells. Three studies have examined Ag presentation by cytokine modified tumor cells (granulocyte-macrophage CSF, IL-4, IL-7, or IL-3) and have found that cytokine expression facilitates cross-priming (34, 35) or that tumor-specific CD8+ T cells are exclusively activated by host-derived APC (36). Two of these studies also investigated whether B7-transfected tumor cells directly or indirectly presented Ag to tumor-specific CD8+ T cells. In one study, Ag presentation was exclusively via cross-priming (37), while in the other report, Ag presentation was directly via the B7-transfected tumor cells (34). Most of these results, therefore, were unexpected, since cytokine and B7-transfected tumor cells were presumed to induce tumor-specific immunity by direct presentation of tumor Ags to T cells (1, 3, 5).
There are several potential explanations for the observed differences between previously reported studies and the results of the present report. 1) The present report addresses Ag presentation to CD4+ T cells, while earlier studies examined presentation to CD8+ T cells. The varying results could be due to differences in Ag presentation to CD4+ vs CD8+ T cells. 2) In this report, Ag presentation during the primary response (7 days postpriming) was studied, while earlier reports examined later time points (35) and/or secondary responses (34, 36, 37). Since tumor cells remain intact in vivo for only a limited time, direct Ag presentation may occur during the early stage of the immunization process while tumor cells remain intact, and indirect Ag presentation may dominate during later stages when tumor debris is available. 3) In two of these studies (36, 37), the transfected tumor cells were irradiated, and secretion of the surrogate tumor Ag was not assessed. If soluble Ag was available, cross-priming would be the expected result. 4) One of these studies (35) was not designed to measure direct Ag presentation, so even if direct presentation by genetically modified tumor cells occurred, it would not have been detected.
In contrast, studies by Kündig and colleagues (38) demonstrated that fibroblasts transfected with a viral Ag, if injected into a lymph node, directly present Ag to CD8+ T cells, thereby stimulating potent viral-specific CD8+ CTL. The logistics of CD8+ T cell activation by genetically modified therapeutic cells are, therefore, unclear, with data supporting both direct and indirect pathways.
The finding that genetically modified tumor cells directly activate CD4+ T cells has clear implications for the design of immunizing and immunotherapeutic agents. If cell-based immunogens are to be considered as vaccines and/or immunotherapeutic agents, then the cells should be engineered to optimally present Ag to CD4+ T cells. If Ag presentation activity correlates with immunization potential, measurements of in vitro Ag presentation activity may be prognostic of therapeutic efficacy. Depending on the desired type of Th cell (Th1 vs Th2), immunizing cells could be tailored to facilitate activation of a particular subpopulation, perhaps via coexpression or simultaneous bolus administration of cytokines favoring differentiation of one or the other helper population (i.e., IL-12, IL-10, etc.).
Although concern has been voiced about using tumor cell-based immunogens in a clinical setting, a significant number of phase I or II clinical trials using tumor cell material have been completed or are in progress (http://cancernet.nci.nih.gov). Since these trials have not identified any significant safety issues and in some cases have shown modest therapeutic responses (despite overwhelming tumor load), the clinical use of tumor cell-based immunogens is feasible. All the trials using cell-based strategies have been exclusively aimed at enhancing CD8+ T cell responses. The data presented in this report combined with published therapeutic studies (12) strongly argue that an optimal cell-based vaccine should also target the activation of CD4+ T lymphocytes.
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Acknowledgments |
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Footnotes |
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2 Abbreviations used in this paper: A/JF1, lethally irradiated (C57BL/6 x A/J)F1 mouse reconstituted with A/J bone marrow; SaI/Ak, SaI tumor cells transfected with Ak and Aßk genes; SaI/Ab, SaI tumor cells transfected with Ab and Aßb genes; HEL, hen egg lysozyme; SaI/HEL, SaI tumor cells transfected with the hen egg lysozyme gene; B6F1, lethally irradiated (C57BL/6 x A/J)F1 mouse reconstituted with C57BL/6 bone marrow; F1, (C57BL/6 x A/J)F1 mouse.
3 B. Pulaski and S. Ostrand-Rosenberg. Reduction of established spontaneous mammary carcinoma metastases following immunotherapy with MHC class II and B7.1 cell-based tumor vaccines. Submitted for publication.
Received for publication May 20, 1997. Accepted for publication October 1, 1997.
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A. Muntasell, M. Carrascal, L. Serradell, P. v. Veelen, F. Verreck, F. Koning, G. Raposo, J. Abian, and D. Jaraquemada HLA-DR4 Molecules in Neuroendocrine Epithelial Cells Associate to a Heterogeneous Repertoire of Cytoplasmic and Surface Self Peptides J. Immunol., November 1, 2002; 169(9): 5052 - 5060. [Abstract] [Full Text] [PDF]
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M. Yasukawa, H. Ohminami, K. Kojima, T. Hato, A. Hasegawa, T. Takahashi, H. Hirai, and S. Fujita HLA class II-restricted antigen presentation of endogenous bcr-abl fusion protein by chronic myelogenous leukemia-derived dendritic cells to CD4+ T lymphocytes Blood, September 1, 2001; 98(5): 1498 - 1505. [Abstract] [Full Text] [PDF]
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L. Qi and S. Ostrand-Rosenberg H2-O Inhibits Presentation of Bacterial Superantigens, but Not Endogenous Self Antigens J. Immunol., August 1, 2001; 167(3): 1371 - 1378. [Abstract] [Full Text] [PDF]
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Y. Guilloux, X.-f. Bai, X. Liu, P. Zheng, and Y. Liu Optimal Induction of Effector but not Memory Antitumor Cytotoxic T Lymphocytes Involves Direct Antigen Presentation by the Tumor Cells Cancer Res., February 1, 2001; 61(3): 1107 - 1112. [Abstract] [Full Text]
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L. Qi, J.-M. Rojas, and S. Ostrand-Rosenberg Tumor Cells Present MHC Class II-Restricted Nuclear and Mitochondrial Antigens and Are the Predominant Antigen Presenting Cells In Vivo J. Immunol., November 15, 2000; 165(10): 5451 - 5461. [Abstract] [Full Text] [PDF]
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E. V. Fedoseyeva, F. Boisgerault, N. G. Anosova, W. S. Wollish, P. Arlotta, P. E. Jensen, S. J. Ono, and G. Benichou CD4+ T Cell Responses to Self- and Mutated p53 Determinants During Tumorigenesis in Mice J. Immunol., June 1, 2000; 164(11): 5641 - 5651. [Abstract] [Full Text] [PDF]
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B. A. Pulaski, D. S. Terman, S. Khan, E. Muller, and S. Ostrand-Rosenberg Cooperativity of Staphylococcal aureus Enterotoxin B Superantigen, Major Histocompatibility Complex Class II, and CD80 for Immunotherapy of Advanced Spontaneous Metastases in a Clinically Relevant Postoperative Mouse Breast Cancer Model Cancer Res., May 1, 2000; 60(10): 2710 - 2715. [Abstract] [Full Text]
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R. M. Tempero, M. L. VanLith, K. Morikane, G. J. Rowse, S. J. Gendler, and M. A. Hollingsworth CD4+ Lymphocytes Provide MUC1-Specific Tumor Immunity In Vivo That Is Undetectable In Vitro and Is Absent in MUC1 Transgenic Mice J. Immunol., November 15, 1998; 161(10): 5500 - 5506. [Abstract] [Full Text] [PDF]
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