| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
*
Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel; and
Department of Surgery "A," Assaf Harofeh Medical Center, Tel-Aviv University, Zerifin, Israel
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
How these two mechanisms of lymphocytotoxicity contribute to tumor immunosurveillance is not well understood, and this problem has been complicated by recent evidence that some CD95L-expressing tumors may become immune privileged (9, 10). Moreover, CD95 expression and function in malignancy is unclear, as is its role in tumor immunity, although Bradley et al. (11) have recently shown that CD95 makes tumor cells more immunogenic as well as susceptible to CTLs. However, the role of CTL or NK cells that express perforin in tumor immunity is better understood. Indeed, Kagi et al. (12) reported that perforin-deficient (PO)3 mice were considerably more susceptible than perforin-expressing mice for the growth of one million fibrosarcoma MC57G cells, suggesting a central role for perforin-based lymphocytotoxicity in tumor immune surveillance. The MHC nonexpressing tumor cell, RMA-S, derived from the T cell lymphoma RBL-5, was used to show that perforin was also involved in controlling tumor growth mediated by NK cells (12, 13). In addition, Kagi and coworkers showed that perforin plays a crucial role in viral and chemical carcinogenesis, as well as with both naive and primed mice responding to a series of syngeneic tumor cell lines of different histological origin, including the lymphoma EL4, MBL-2 melamona B16, and fibrosarcoma MC57G. These findings were consistent with the failure to find a significant role for the death receptor CD95 in tumor immunosurveillance (13). In contrast, Mori et al. (14) showed that the CD95-based pathway of lymphocyte action was tumor cell dependent. Therefore, we decided to examine the role of perforin and CD95 in immunity against a series of tumors, concentrating on two sublines (D122 and 39.5) of the metastatic Lewis lung carcinoma 3LL of C57BL/6 mice.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Two- to 4-mo-old C57BL/6 (B/6) (H-2b), PO (H-2b), DBA/2 (H-2d), and BALB/c (H-2d) mice were supplied by the Animal Breeding Center of this Institute. The PO mice were previously described (15). D122, a highly metastatic and low immunogenic subclone of the Lewis lung carcinoma (3LL) and its H-2Kb transfectant, 39.5, a highly immunogenic and nonmetastatic form of the tumor, were previously described (16). The 3LL tumors were cultured in D122 medium (DMEM with 10% heat-inactivated FCS, 2 mM glutamine, 100 U/ml penicillin, 100 µg/ml streptomycin, 1 mM sodium pyruvate, and 1% nonessential amino acids). Single-cell suspensions were obtained by trypsinization followed by two washes. The B/6 (H-2b) T cell leukemia EL4, DBA/2 (H2d) mastocytoma P815, and A/J leukemia YAC-1 were maintained in ascitic form in syngeneic mice or maintained for short periods in RHFM medium (RPMI 1640 containing 10% heat-inactivated FCS, 10 mM HEPES, 2 mM glutamine, 100 U/ml penicillin, 100 µg/ml streptomycin, and 5 x 10-5 M 2-ME). Several lines of leukemia L1210 of DBA/2 were used: L1210wt (wild type), L1210–3, selected for low CD95 expression; LF+ transfected with mouse CD95 overexpression construct (17), kindly provided by Dr. Pierre Golstein; and LF-, which expresses low levels of the CD95 Ag as a result of transfection with a CD95 antisense construct (18), kindly provided by Dr. William Clark. Transfected LF+ and LF- cells were resistant to G418, as expected. Cells were maintained in CD95 medium (RPMI 1640 containing 5% heat-inactivated FCS, 1 mM sodium pyruvate, 10 mM HEPES, 100 U/ml penicillin, 100 µg/ml streptomycin, and 5 x 10-5 M 2-ME). RMA-S is a clone of the Rauscher virus-induced lymphoma RBL-5, selected for low MHC (H-2b) expression (19). Cultures were maintained in a RMA-S medium (RPMI with 10% heat-inactivated FCS and 1% combined antibiotics).
Preparing and culturing CTL and NK cells
Alloreactive peritoneal exudate CTLs (PELs) were generated, prepared, and purified as previously described (20). Briefly, mice were injected i.p. with tumor cells (25 x 106/mouse). Eight to 11 days after a primary alloimmunization, or 4 to 5 days after a secondary injection (given 6–12 wk after priming), the mice were killed and their peritoneal cavities rinsed with PBS supplemented with 5% heat-inactivated newborn calf serum (PBS-NCS). The resulting crude peritoneal cells were incubated on nylon wool columns for 60 min at 37°C to deplete adherent cells such as B cells and macrophages. Nonadherent cells were eluted by rinsing the columns with cold PBS-NCS. The eluted cells (PEL) contained >95% T cells, 80–90% of which were CD8+, about half of which formed specific conjugates (21). Syngeneic CTLs were prepared by injecting mice i.p. three times at 7-day intervals (25–160 x 106 for EL4; 2–4 x 106 for 39.5 or B16) with irradiated (10,000 rad) tumor cells. Four to 5 days after the last immunization, PELs were prepared as above. The NK cells used were from freshly isolated spleen cells of naive mice. Splenocytes were suspended in ACK to remove RBC and washed in PBS.
Lymphocytotoxicity
Target cells were labeled with Na251CrO4 (1 h at 37°C) and washed twice with PBS-NCS before use. Lytic assays were conducted in U-shaped 96-well microtiter plates with 3–10 x 104 labeled target cells per well and effector cells at the indicated ratios. The plates were centrifuged at room temperature to promote conjugate formation, incubated for 2–5 h at 37°C, and then recentrifuged to terminate the assay. A 100-µl supernatant from each well was harvested, and its radioactivity was determined using a gamma counter. The percentage lysis was calculated as previously described.
Tumor growth in naive and immunized mice
For immunization, PO and B/6 mice were inoculated s.c. or i.p. with 2 or 4 x 106 irradiated (10,000 rad) D122, Kb39.5, or 120 x 106 EL4 tumor cells. D122, 39.5, EL4, or RMA-S tumor cells (in 100 µl) were injected into the right flank of naive or immunized mice. Tumor size was measured by calipers every second or third day at the greatest right-angle diameters. Life span was recorded up to 70 days after inoculation or until the tumor’s largest diameter reached 2.5 cm.
Cell staining and flow cytometry
Cells (0.25 x 106) were washed in staining medium (0.5–1% BSA in PBS plus 0.02% azide), pelleted, suspended in 30 µl (0.25 µg) hamster anti-mouse CD95 Ab (Jo2; PharMingen, San Diego, CA), and incubated on ice for 30 min with occasional shaking. After the cells were washed and pelleted, they were suspended in 30 µl of FITC-goat anti-hamster F(ab')2 Ab (1:100 dilution) (Jackson ImmunoResearch, West Grove, PA) and incubated as above. To analyze surface Fas expression on the 5 [and 6]-carboxyfluorescein diacetate succinimidyl ester (CFSE; Molecular Probes, Eugene, OR)-labeled cells (see below), Jo2 Ab was added as above, followed by biotinylated goat anti-hamster (30 µl, 1:250 dilution, incubation on ice and washed as above) and PE-streptavidin (30 µl, 1:150 dilution, 30 min on ice). After a final wash, the cells were resuspended in PBS plus 0.02% azide and analyzed by FACS.
For staining tumor cells with CFSE (22, 23), cells were washed twice and resuspended at 5–10 x 107/ml in PBS. CFSE was added to make a final concentration of 5 µM, and the suspension was incubated for 10 min at 37°C. After having been washed twice in PBS, cells were resuspended in PBS to the desired concentration and naive animals were injected i.p. Injected cells were analyzed by FACS.
RT-PCR for Fas
Total RNA was isolated from 1 x 106 cells, accurately counted, and lysed in 200 µl TriReagent (Molecular Research Center, Cincinnati, OH). Chloroform (50 µl) was added at room temperature, and the mixture was vortexed and incubated for 15 min on ice. After centrifuging in the cold at the maximal Eppendorf speed for 15 min, we mixed 120 µl of the upper layer containing total RNA with 120 µl of isopropanol, and the mixture was vortexed, incubated on ice for 30 min, and centrifuged as before. The pellet was then suspended in 1 ml cold 75% ethanol and vortexed and centrifuged as previously described. After removing the ethanol, we dissolved the air-dried pellet in 11 µl diethyl pyrocarbonate (DEPC) H2O. The Life Technologies method was used for cDNA preparation as follows. The total RNA was incubated at 65°C for 5 min and, after fast chilling, 9 µl of the following mixture was added: 4 µl of 5 x 1st standard buffer, 1 µl of 10 mM dNTPs, 2 µl of 100 mM DTT, 0.5 µl of 1 mg/ml oligo(dT), 0.5 µl RNasin, and 1 µl Moloney murine leukemia virus reverse transcriptase. After incubating the mixture at 37°C for 1.5 h, 180 µl DEPC H2O was added.
cDNAs were analyzed by RT-PCR for Fas expression and compared with GAPDH expression. Each 20-µl portion of the reaction mixture contained 3 µl cDNA, 8.7 µl DEPC H2O, 2 µl of 10x buffer, 3.2 µl of 1.25 nM dNTPs, 1.5 µl downstream primer (5'-346ATG CAC ACT CTG CGA TGAAG365-3'), 1.5 µl upstream primer (5'-670TTG GTA TGG TTT CAC GAC TG689-3'); both primers (derived from mouse cDNA) were from 10 µM and 0.1 µl Taq DNA polymerase (for GAPDH, the same mixture was used with the corresponding primers at 10 µM). Each sample was mixed, briefly centrifuged, overlaid with 30 µl mineral oil, and placed in the thermocycler (Programmable Thermal Controller, MJ Research, Cambridge, MA) set as follows: 35 cycles of 1 min denaturation at 94°C, 1 min annealing at 55°C, 1 min elongation at 72°C, and a final elongation of 5 min at 72°C. The size of the RT-PCR product was 344 bp. The samples were then resolved on a 1% agarose gel containing ethidium bromide (in TBE running buffer, 100 V, 50 min) and observed by UV light. That band intensity reflected the amount of RNA analyzed was established by showing linearity of band intensity as a function of the amount of RNA subjected to RT-PCR.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To determine how perforin and the CD95L/CD95 pathways contribute
to tumor immunity, we tested the growth of the EL4, D122, and 39.5
tumor cell lines, all of B/6 origin, in both B/6 and perforin-deficient
PO mice (both H-2b). The results (Table I
) show that while both the B/6 and PO
mice were susceptible to the progressively growing D122 and EL4, the PO
mice exhibited greater innate resistance to the 39.5 line, which had
been derived from the H-2Kb-transfected D122 line
(16). We next tested tumor growth in PO and B/6 mice that
had been vaccinated with x-irradiated tumor cells. PO mice vaccinated
against either 39.5, D122, or EL4 were more resistant to 39.5 or D122
tumor cells. Vaccinated with EL4, both strains were resistant to the
homologous tumor, but B/6 mice were resistant to neither D122 nor 39.5
(Table I). Hence PO mice showed superior acquired immunity against the
otherwise three progressor tumors studied.
|
Resistance to the growth of at least some tumors, observed in both
naive and vaccinated animals, could be mediated by NK cells or by CTL
or both. Confirming a previous report (13), we found that
spleen cells procured from PO mice exhibited only minimal NK-like
activity, compared with perforin-expressing mice (Table II). Hence, the adaptive resistance of PO
mice to tumor growth (Table I
) was probably not due to NK cell
activity. In support of this conclusion, we found (data not shown) that
mutant, MHC class I-nonexpressing RMA-S tumor cells grew faster in PO
mice than in perforin-expressing mice, as was previously reported
(24). CTLs appeared more likely to mediate the tumor
immunoprotective activity seen in PO mice, because CTLs had been
observed in both PO and C57BL/6 mice immunized against the syngeneic
leukemia EL4; in some cases, PO showed higher specific and nonspecific
CTL activity compared with B/6 mice (Table III). However, the nonspecific activity
against the allogeneic L1210 leukemia of DBA/2
(H-2d) mice was CD95-dependent, because only the
CD95-transfected L1210 cells (LF+) were
lysed.
|
|
The induction of adaptive tumor immunity in PO mice combined with
the nonspecific lysis of CD95-expressing targets (Tables I and III,
respectively) implied a CD95L/CD95-based mechanism against the tumor.
Surprisingly, using a CD95 mAb (Jo2; Phar-Mingen), we detected
virtually no cell-surface CD95 on cultured D122 and 39.5 cells. To
resolve this enigma, we tested the hypothesis that cell-surface CD95
expression was up-regulated on tumor cells upon their injection in
vivo. Indeed, we found that D122 and 39.5 tumors grown in vitro and
expressing little CD95 underwent massive CD95 up-regulation when
injected into PO mice (Table IV). This
unexpected finding prompted us to test CD95 expression on a series of
other tumors that were injected into both syngeneic and allogeneic
recipients. As with D122 and 39.5, a moderate to marked enhancement of
CD95 expression in a series of otherwise low CD95-expressing cells
(L1210, LF-, BW, P815) was found (Table IV). Hence, CD95 up-regulation upon in
vivo inoculation appears to be a more general phenomenon, a finding
relevant to our understanding of CD95 expression and function in tumor
immunity.
|
). The reversibility of
Fas-expression was rigorously proven by showing that the CFSE-labeled,
high (up-regulated) Fas-expressing cells down-regulated their surface
Fas upon culturing (and dividing) in vitro (Table V). RT-PCR performed
with RNA from CFSE-labeled, sorted cells indicated that the up- and
down-regulated cell-surface Fas expression upon in vivo and in vitro
growth, respectively, correlated well with the amount of Fas mRNA
detected (Fig. 1).
|
|
To test the hypothesis that CD95 up-regulation plays a role in
tumor immune surveillance, we monitored the growth of
LF+ and LF- in syngeneic
(perforin-expressing) DBA/2 mice. The LF+ and
LF- cells were derived from leukemia L1210 of
DBA/2 mice and were then transfected with CD95-overexpression
(LF+) and antisense constructs
(LF-), respectively (17, 18). Fig. 2 shows surface CD95 expression on in
vitro-cultured LF+ and LF-
cells; whereas 77% (76–96% in eight experiments) of
LF+ expressed CD95, only 2.2% of
LF- expressed it, consistent with their
differential apoptotic response to the CD95 Ab Jo2 and to PO CTL (Table VI). Note that immunization of PO mice
with either LF+ or LF-
resulted in CTLs that lysed LF+ but not
LF- (Table VI). The induction of PO CTL by
LF-, and its eventual rejection, supports the
notion of CD95 up-regulation. This has been confirmed by FACS (Tables
IV and V) and by lymphocytotoxicity of in vivo-grown D122 (Table III) and LF- (Table VI) found to be more
sensitive to apoptotic lysis than cultured cells.
|
|
,
A and B), despite the fact that CD95 expression
per se had no effect on the tumor doubling time measured in vitro (Fig. 3C). Interestingly, enhanced CD95 expression on
LF- in vivo was detected before the onset of
tumor growth and an inverse expression pattern of CD95 was found with
the slower growing CD95-expressing (LF+) tumors
(data not shown). Hence, CD95 up-regulation upon in vivo inoculation of
LF- cells appears to have profound consequences
on their susceptibility to CD95-based apoptosis as well as in vivo
growth.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
).
Simultaneously, we have confirmed reduced NK cell activity in PO mice
(Table II) and consequently an impaired ability to control the growth
of RMA-S cells (MHC nonexpressing (syngeneic) leukemia RBL-5) (data not
shown), as previously reported (24). Hence, while
perforin-expressing immune effector cells appear to play an obligatory
role against some tumors, a CTL-mediated CD95/CD95L-based mechanism
appears to be involved in immunity against certain tumors.
CD95 is a membrane-anchored protein that can bring about apoptosis upon
cross-linking by certain CD95 Abs or by the cell-bound or soluble
natural ligand CD95L (Table VI). The CD95 gene is defective in
lymphoproliferative (lpr) mice due to the insertion of a
retrotransposome that causes premature termination of CD95 mRNA
transcripts or a point mutation in its cytoplasmic death domain.
Homozygous mutant mice develop lymphadenopathy and lupus-like
autoimmunity (25). Interestingly, a similar mutation in
the human CD95 homologue gene results in an autoimmune
lymphoproliferative syndrome (26). The emergence of tumor
cell resistance to Fas-based apoptosis may be fundamental to tumor
progression. Apoptosis-resistant human lymphoma cells have been
described; these express splicing variants of CD95, coding for
truncated CD95 that lacks the intracellular death domain of 80 aa
(27). Reduced CD95 expression or function has been found
in melanoma (9), colon cancer (28, 29), and
testicular cancer (30). In contrast, expression of CD95L
is up-regulated in some normal and malignant tissues (9, 10, 31). Hence, coordinate expression of CD95 and its ligand may be
an important factor in tumor growth and progression. Although Nagata
(8) extensively studied CD95 and showed that it plays a
role in immunoregulation and in some immunopathologies (liver, heart),
little has been known about the role of CD95 in tumor immunity and
immunosurveillance. Debatin et al. (32) established that
an externally administered CD95 Ab can retard the growth of certain
tumors, although CD95-Ab therapy of tumors seems unlikely because of
its severe side effects (mostly liver). In contrast, CD95-based
specific CTL/NK cell action may be an important and powerful immune
mechanism in controlling tumor growth metastases (11)
.
Down-regulation or lack of the CD95 protein in malignant cells may be a
primary mechanism in tumor escape from immune surveillance. Because
CD95 expression varies widely among tumors and within a given tumor,
studies on the regulation of CD95 expression in a well-defined in vivo
setting are important (33). We observed an unexpected
sharp up-regulation of CD95 expression on D122, as well as on its
H-2Kb-transfected clone, 39.5, upon inoculation
of the two tumors into susceptible PO mice (Table IV). We found a
similar up-regulation of CD95 expression in vivo with a series of other
common laboratory tumors (Tables IV and V) that express very little
cell-surface CD95, including the Fas antisense transfected
LF- cells. In vitro, the expression of the
normal Fas gene in LF- cells is likely to be
retarded by the Fas anti-sense transcripts; this appears to be
reversed under the in vivo conditions that favor the expression of the
normal gene, as reflected at both the protein and mRNA levels, as well
as by the enhanced susceptibility to Fas-based Ab and CTL-mediated
lysis. Up-regulated CD95 expression took place in the very same cells
injected in either PO or B/6 mice, and expression was down-regulated
upon returning to in vitro culture (Table V). Fig. 1 presents evidence
correlating the extent of Fas mRNA expression and up- and
down-regulation of surface membrane CD95 in LF-
cells shown in Tables IV and V. Whether the difference in Fas mRNA
expression are due to changes in transcription or also to an altered
half-life of the Fas message is not known at present. Moreover,
mRNA-based control of Fas expression may apply to some but not all
tumors. For example, in the human lung adenocarcinoma, Fas is
sequestered within the cytoplasm (34). It appears that the
failure to detect CD95 expression on in vitro-cultured tumor cells may
not indicate its absence in the tumor cells when placed in vivo. The
up-regulation of CD95 expression on the D122 and 39.5 as well as
LF- tumors upon inoculation in vivo, which
resulted in increased susceptibility to Fas-based lysis mediated by CTL
(Tables III and VI), supports the hypothesis that, at least in PO mice,
immunity against these tumors is CD95 based.
In a separate set of experiments, we found that the CD95-nonexpressing
tumor, LF- (CD95 anti-sense transfected),
had a clear growth advantage compared with its CD95-overexpressing
counterpart, LF+ (CD95 transfected), in vivo, but
not in vitro (Fig. 3). Paradoxically, the enhanced growth of
LF- (Fig. 3, A and B),
grown i.p. as well as s.c., occurred concurrently with the
up-regulation of CD95 expression; conversely, with the slower-growing
CD95-expressing tumor, LF+, we observed
down-regulated CD95 expression (data not shown). Importantly, both
tumors grew progressively in syngeneic (DBA/2) recipients (Fig. 3, A and B), eventually killing them. As a minimal
working hypothesis, we have postulated that the enhanced growth of
LF- in vivo was related to the lack of normal
CD95 gene expression. Consequently, tumor growth was not retarded by
CD95-based innate immunity (CTL NK cell-mediated). In fact,
LF+ cells showed a low susceptibility to natural
cytotoxicity (Fig. 3). While we are inclined to attribute the enhanced
growth of the LF- tumor to their (initial) low
level CD95 expression, which may help escape immune surveillance, it is
also possible that the growth advantage of LF-
over LF+ is due to a more complex interaction of
LF- cells with the in vivo environment. The
acquisition of CD95 upon progressive syngeneic growth of
LF- in vivo probably reflects the overall
effects of the natural and acquired immune responses against the tumor
and is likely to be mediated by cytokines (see below). However, with
LF+ cells, constitutive CD95 expression
presumably retards tumor growth at least initially by the innate immune
system (Fig. 3, A and B), resulting in the
partial deletion of high CD95-expressing LF+
cells (data not presented). However, this does not alter the fate of
the host with either tumor, because tumor growth overrides and
progressive growth follows, with the host eventually succumbing to the
tumor. Factors generated by innate and adaptive immunity, in response
to tumors, such as IFN-
and TNF-
, can bring about enhanced CD95
expression, and the combination of these cytokines synergistically
enhance CD95 expression (35, 36). Further studies on the
roles that cytokines play in the regulation of CD95 expression in
well-defined tumor settings in vivo are required because CD95
expression varies widely among tumors, even within a given tumor. The
present findings stress the need to scrutinize the regulation and
function of the CD95 system in tumor immunity in an in vivo setting.
This information is relevant to adaptive tumor immunotherapy in
conjunction with cytokines, as well as to tumor vaccination programs.
The extent to which a given tumor may be subject to CD95 up-regulation
may, by itself, predict the success (or failure) of immunotherapy.
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Prof. Gideon Berke, Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel. E-mail address:
3 Abbreviations used in this paper: PO, perforin-deficient mice; PEL, peritoneal exudate lymphocytes; wt, wild type; CFSE, 5 [and 6]-carboxyfluorescein diacetate succinimidyl ester; NCS, newborn calf serum; DEPC, diethyl pyrocarbonate.
Received for publication March 19, 1999. Accepted for publication January 3, 2000.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
(TNF-) and/or interferon- (IFN-), resulting from down-modulation of Bcl-2 expression. Clin. Exp. Immunol. 111:211.[Medline]
This article has been cited by other articles:
|
|
 |
|
  Z. Su, J. Kuball, A.-P. Barreiros, D. Gottfried, E. A. Ferreira, M. Theobald, P. R. Galle, D. Strand, and S. Strand Nitric Oxide Promotes Resistance to Tumor Suppression by CTLs J. Immunol., April 1, 2006; 176(7): 3923 - 3930. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. C. Reed and M. Pellecchia Apoptosis-based therapies for hematologic malignancies Blood, July 15, 2005; 106(2): 408 - 418. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Hollenbaugh, J. Reome, M. Dobrzanski, and R. W. Dutton The Rate of the CD8-Dependent Initial Reduction in Tumor Volume Is Not Limited by Contact-Dependent Perforin, Fas Ligand, or TNF-Mediated Cytolysis J. Immunol., August 1, 2004; 173(3): 1738 - 1743. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Hayakawa, V. Screpanti, H. Yagita, A. Grandien, H.-G. Ljunggren, M. J. Smyth, and B. J. Chambers NK Cell TRAIL Eliminates Immature Dendritic Cells In Vivo and Limits Dendritic Cell Vaccination Efficacy J. Immunol., January 1, 2004; 172(1): 123 - 129. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Ruiz-Ruiz, G. Robledo, E. Cano, J. M. Redondo, and A. Lopez-Rivas Characterization of p53-mediated Up-regulation of CD95 Gene Expression upon Genotoxic Treatment in Human Breast Tumor Cells J. Biol. Chem., August 22, 2003; 278(34): 31667 - 31675. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Woolf, C. Xiao, O. Fainaru, J. Lotem, D. Rosen, V. Negreanu, Y. Bernstein, D. Goldenberg, O. Brenner, G. Berke, et al. Runx3 and Runx1 are required for CD8 T cell development during thymopoiesis PNAS, June 24, 2003; 100(13): 7731 - 7736. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Seki, A. D. Brooks, C. R. D. Carter, T. C. Back, E. M. Parsoneault, M. J. Smyth, R. H. Wiltrout, and T. J. Sayers Tumor-Specific CTL Kill Murine Renal Cancer Cells Using Both Perforin and Fas Ligand-Mediated Lysis In Vitro, But Cause Tumor Regression In Vivo in the Absence of Perforin J. Immunol., April 1, 2002; 168(7): 3484 - 3492. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Screpanti, R. P. A. Wallin, H.-G. Ljunggren, and A. Grandien A Central Role for Death Receptor-Mediated Apoptosis in the Rejection of Tumors by NK Cells J. Immunol., August 15, 2001; 167(4): 2068 - 2073. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. J. Topham, R. C. Cardin, J. P. Christensen, J. W. Brooks, G. T. Belz, and P. C. Doherty Perforin and Fas in murine gammaherpesvirus-specific CD8+ T cell control and morbidity J. Gen. Virol., August 1, 2001; 82(8): 1971 - 1981. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. K. Helmich and R. W. Dutton The Role of Adoptively Transferred CD8 T Cells and Host Cells in the Control of the Growth of the EG7 Thymoma: Factors That Determine the Relative Effectiveness and Homing Properties of Tc1 and Tc2 Effectors J. Immunol., June 1, 2001; 166(11): 6500 - 6508. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Zheng, F. Ouaaz, P. Bruzzo, V. Singh, S. Gerondakis, and A. A. Beg NF-{{kappa}}B RelA (p65) Is Essential for TNF-{{alpha}}-Induced Fas Expression but Dispensable for Both TCR-Induced Expression and Activation-Induced Cell Death J. Immunol., April 15, 2001; 166(8): 4949 - 4957. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Peng, J. C. Krauss, G. E. Plautz, S. Mukai, S. Shu, and P. A. Cohen T Cell-Mediated Tumor Rejection Displays Diverse Dependence Upon Perforin and IFN-{gamma} Mechanisms That Cannot Be Predicted From In Vitro T Cell Characteristics J. Immunol., December 15, 2000; 165(12): 7116 - 7124. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. E. Plautz, S. Mukai, P. A. Cohen, and S. Shu Cross-Presentation of Tumor Antigens to Effector T Cells Is Sufficient to Mediate Effective Immunotherapy of Established Intracranial Tumors J. Immunol., October 1, 2000; 165(7): 3656 - 3662. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
