By
From the Department of Biological Sciences, Columbia University, New York 10027
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Binding sites for the nuclear factor (NF)-B transcription factor have been identified within
control regions of many genes involved in inflammatory and immune responses. Such
B sites
are often found adjacent to those of interferon (IFN)-
-inducible transcription factors, suggesting a requirement for multiple signaling pathways for gene regulation. Using fibroblasts from
RelA (p65)-deficient mice generated by gene targeting, we have investigated the role of this
subunit of NF-
B in gene activation by microbial lipopolysaccharide, tumor necrosis factor
,
and in possible synergism with the IFN-
-signaling pathway. Our results indicate not only that
RelA is required for activation of key genes involved in adaptive (acquired) immune responses,
including major histocompatibility complex class I, CD40, and the Fas death receptor, but also
that both NF-
B-inducing signals and IFN-
are necessary for maximal activation. In contrast, neutrophil-specific chemokine genes KC and MIP-2, which can function as nonspecific mediators in innate immune responses, were strongly induced by RelA in the absence of IFN-
.
Our results show that RelA plays a critical role in activation of immune system genes in response to nonspecific stimuli and demonstrate a novel proapoptotic function for this protein in
Fas-induced cell death.
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Innate immune responses are dependent on the presence of receptors that are capable of recognizing highly conserved features present on microorganisms (1, 2). Thus, LPS present in cell walls of gram-negative bacteria is recognized by cell surface receptors present on many different types of cells, and viral products such as double-stranded (ds)RNA molecules can activate intracellular kinases (1, 2). As a result of interaction of host cells with these foreign substances, defense mechanisms may be initiated to neutralize the invading infectious agents. Such innate defense mechanisms have been highly conserved. Thus, both plants and animals possess such mechanisms and in some cases may even use similar mediators (3, 4). In contrast, an adaptive immune response exists only in vertebrates and is dependent on the presence of antigen receptors displayed on specialized cells of the immune system. However, an effective adaptive response in vertebrates generally requires participation of innate response mediators. Signals produced by the innate immune system may provide information about the origin or harmfulness of foreign substances and thus determine the kind of adaptive response that is generated (1, 2).
Microbial LPS and viral dsRNA are potent inducers of
nuclear factor (NF)-B transcription factors, which have
been implicated in regulation of host defense mechanisms
in diverse species ranging from insects to mammals (3). Although NF-
B can be activated in response to both nonspecific and antigen-specific signals generated during an
immune response in vertebrates, only nonspecific signals may be inducers of NF-
B proteins in insects (5, 6), which lack an adaptive immune system. The possible involvement
of NF-
B factors in both innate and adaptive responses
suggests they may function as an important link between
these two systems. NF-
B proteins exist as dimers which
typically reside in an inactive form in the cytoplasm complexed with the inhibitory I
B proteins (3, 7). Treatment
of cells with inducers of NF-
B results in phosphorylation
and degradation of I
B proteins, which allows free NF-
B
proteins to translocate to the nucleus and regulate the expression of target genes (7). Activation of NF-
B target genes often occurs within minutes of receiving an inducing
signal, making this system optimally responsive to many
harmful stimuli, including invading microbes, DNA damaging agents, and oxidative stress (3, 7). The predominant
dimeric form of NF-
B in most cells is a complex of a 50-kd protein (p50) and a 65-kd protein called RelA or p65
(7). However, studies on mice deficient in p50 and RelA
have revealed distinct functions for these proteins (8, 9) and
have identified a requirement for RelA for embryonic survival (9, 10). Gene disruption of other members of the NF-
B
family, p52, c-Rel, and RelB, have indicated key roles for these proteins in various tissues (11).
Among the best characterized endogenously produced
inducers of NF-B in mammals are the proinflammatory
cytokines TNF-
and IL-1 (3). These cytokines can be
produced by nonspecific mechanisms such as macrophage
activation after phagocytosis or exposure to microbial products such as LPS. In addition, interaction of macrophages with the T cell-derived cytokine IFN-
can also result in
production of TNF-
and IL-1. Activation of NF-
B by
these cytokines may activate expression of genes involved
in regulation of an inflammatory response (3). Indeed, our
previous studies with RelA
/
mice have shown that RelA
is required for the activation of GM-CSF and I
B genes in
fibroblasts treated with TNF-
(9). Recent studies have
also shown that this subunit of NF-
B can inhibit TNF-
-induced cell death, an adaptation that may allow TNF-
-responsive cells to function without induction of cell
death (15). Such an antiapoptotic function of RelA is likely
the result of activation of genes that inhibit TNF-
-induced
cell death.
Many genes containing potential NF-B binding elements have been identified (7). Interestingly, such genes
often contain binding sites for other transcription factors as
well, including AP-1, NF-IL6, and members of the IFN-
-activated factors, signal transducer and activator of transcription (STAT)1 and IFN-regulatory factor (IRF)-1 (16).
Thus, transcription factor interactions within control regions may be used for optimal regulation of gene expression, as demonstrated biochemically for the IFN-
gene
(17). Of particular interest are synergistic interactions between TNF-
-inducible and IFN-
-inducible factors.
These two cytokines cooperate to activate many target
genes, and such cooperation is often manifested in functional interactions between monocytes/macrophages (source of TNF-
) and T lymphocytes (source of IFN-
) in inflammatory and immune responses.
Although NF-B factors have been implicated in regulation of many important genes, the relatively ubiquitous nature of these proteins has precluded determination of specific contributions of different subunits in gene activation.
One approach to determine the function of individual subunits is gene targeting in embryonic stem cells. Using this
approach, we have now analyzed the role of the RelA subunit in activation of genes containing
B-like binding sites
in fibroblasts, cells that not only are important for production of chemokines and cytokines but which also function as target cells for cytotoxic T cells and in some cases as
APCs (18). We find that RelA activation by LPS or TNF-
and activation of the IFN-
pathway are both required for
activation of key genes involved in adaptive immune responses. In contrast, RelA activation alone is sufficient for
potent activation of genes involved in innate responses.
Our results indicate a dual role for RelA in regulation of
genes involved in both kinds of immune responses and in
potentiating adaptive responses by nonspecific stimuli.
![]() |
Materials and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Cell Culture and Treatments.
Mouse embryonic fibroblasts (MEFs) derived from RelA-deficient mice (9) were cultivated in DMEM supplemented with 10% calf serum and antibiotics. MEFs were stimulated in the presence of 10 ng/ml of TNF-Antibodies.
mAb against Fas receptor (Jo2) and PE-conjugated hamster Jo2 were purchased from PharMingen. Jo2 was used at 1 µg/ml for Fas-induced cell killing.Northern Blot Analysis.
RNA was isolated from cells grown under normal conditions (untreated cells) or stimulated for 6 h with LPS and/or cytokines. Total RNA was extracted using the TRIzol reagent (Molecular Research Center) as recommended by the manufacturer. 10 µg of total RNA was size fractionated on denaturing formaldehyde gels for 4-5 h and transferred overnight to a nylon membrane. Different mRNAs were detected by hybridization to specific 32P probes (reverse transcription PCR products from mouse fibroblast cDNA) in the presence of salmon sperm DNA (Sigma) for 1 h at 68°C. Final washes (twice for 15 min) were performed in 0.2% SSC, 0.1% SDS at 25°C. RNA loading was controlled by normalization to aFlow Cytometric Analysis.
Cells were treated with LPS and/or cytokines, harvested, and stained with PE-conjugated hamster anti-murine Fas mAb Jo2 for 30 min on ice. Cells were washed twice, fixed in 4% paraformaldehyde, and analyzed using a Becton Dickinson flow cytometer.Analysis of Fas-mediated Cell Death.
MEFs were cultured for 12 h in the presence or absence of LPS, TNF- ![]() |
Results and Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
The gene encoding for the MHC class I H-2 molecule can
be activated by TNF- and IFN-
(19). Although NF-
B
sites have been found within transcriptional control regions
of this gene (20, 21), the role of NF-
B proteins in its activation is not known. Furthermore, transcription factors
that do not belong to the NF-
B family have also been
shown to bind specifically to the MHC
B site (22).
Therefore, we wished to determine whether RelA participates in activation of this gene. To this end, primary MEFs
derived from RelA+/
or RelA
/
mice were first treated
with TNF-
or LPS. We have previously shown that LPS
is a potent inducer of NF-
B in MEFs, although the effect
of such treatment on gene induction was not determined (23). Treatments were carried out for 6 h, since this time
period is sufficient for maximal activation of the genes we
have studied and does not result in significant death of
RelA
/
MEFs by TNF-
. Northern blot analysis of RNA
obtained from TNF-
- or LPS-treated RelA+/
MEFs
showed a moderate increase in H-2 expression (two- to
threefold). However, this increase was significantly potentiated in the presence of IFN-
(10.5-fold with TNF-
). In
contrast, no induction of expression was seen in the
RelA
/
cells after TNF-
or LPS treatment, whereas
IFN-
-mediated activation of H-2 expression (threefold)
was unaltered in these cells (Fig. 1). These results demonstrate that RelA is required for activation of the H-2 gene
after TNF-
or LPS and for potentiation of expression in
the presence of IFN-
.
|
MHC class I is critical for the initial interaction between
T lymphocytes and target cells. We next tested whether
other genes functionally important in interactions between
T lymphocytes and target cells or APCs are also under
RelA control. The CD40 gene can be inducibly expressed
on APCs and is important for activation of both T cells
which express the CD40 ligand and the APCs (24). Once
again, TNF- or LPS treatment increased expression of
CD40 mRNA in RelA+/
MEFs, and the presence of
IFN-
synergistically increased the amount of CD40
mRNA. In contrast, RelA
/
MEFs showed virtually no
increase in the amount of CD40 mRNA in the presence of
TNF-
or LPS alone or in combination with IFN-
(Fig. 1).
Next we tested the effect of these inducers on expression
of the Fas death receptor. Coupling of Fas expressed on target cells with Fas ligand expressed on T cells generally results in apoptotic demise of the target cell (25). Fas expression is generally low in most cells, although certain cells
such as hepatocytes constitutively express high levels of Fas
(25). As shown in Fig. 1, Fas expression was dramatically
induced by TNF- plus IFN-
or LPS plus IFN-
(~10-fold), but less strongly by these inducers alone (2-3-fold).
Importantly, RelA
/
MEFs showed greatly diminished
induction of Fas mRNA (approximately twofold) under
the same conditions (Fig. 1). These results provide the first
direct proof for a role of NF-
B in regulation of the MHC
class I, CD40, and Fas death receptor genes, and suggest
that NF-
B may play a key role in activation of genes involved in specific immune responses by nonspecific stimuli
such as LPS. Activation of NF-
B by such stimuli may thus
allow synchronous expression of multiple genes that carry
out similar or complementary functions.
IFN- is a potent activator of macrophages, especially in
combination with LPS. Two genes critically involved in
macrophage function that can also be activated in fibroblasts are those encoding the inducible form of nitric oxide
synthase (iNOS) and the proinflammatory cytokine IL-6.
Therefore, we tested whether activation of these genes was
dependent on RelA. As above, both iNOS and IL-6 genes were potently induced by the combined effects of LPS and
IFN-
in RelA+/
MEFs (Fig. 2 A). Interestingly, activation of these genes was considerably less after TNF-
or
TNF-
and IFN-
treatment (Fig. 2 A). Induction was
again significantly reduced in RelA
/
MEFs (Fig. 2 A),
demonstrating that RelA is specifically required for activation of these genes. Next we tested the potential involvement of RelA in regulation of chemokine gene expression.
Chemokines produced at sites of inflammation, often by fibroblasts, play an important role in both initiation and potentiation of an inflammatory response. Thus IFN-inducible protein (IP)-10, a chemokine specific for macrophages
and T lymphocytes (26), was also synergistically induced by
LPS or TNF-
and IFN-
in RelA+/
MEFs, and induction was reduced in RelA
/
MEFs (Fig. 2 A). Taken together, our results demonstrate that the RelA component
of NF-
B is important for gene induction by LPS and
TNF-
alone and for synergistic activation in the presence of IFN-
.
|
An inflammatory response can occur without the involvement of antigen-specific lymphocytes, often providing the first line of defense against invading pathogens. Key
leukocytes involved in such "immediate" responses are
neutrophils, which are attracted to infected or inflamed
sites by chemokines. Two such neutrophil-specific chemokines, KC (27) and macrophage-inflammatory protein
(MIP)-2 (28), were found to be potently induced by LPS
in RelA+/ MEFs (and to a lesser degree by TNF-
),
whereas induction was significantly reduced in RelA
/
MEFs (Fig. 2 B). Importantly, and in contrast to the examples described above, IFN-
neither induced expression of
these chemokines nor potentiated expression by LPS or
TNF-
treatments, in both RelA+/
and RelA
/
MEFs.
These results indicate a potentially dual role for RelA in
target gene regulation. In the absence of specific immune
effectors such as IFN-
produced by T cells, RelA alone
can function as a potent inducer of innate response genes,
e.g., neutrophil chemokines. However, IFN-
is required
for optimal induction by RelA of genes involved in an
adaptive immune response.
Interestingly, significant differences in induction of specific genes in response to LPS or TNF- and in synergy
with IFN-
were noticed. For example, although MHC
class I, CD40, and Fas were activated to a comparable extent by TNF-
or LPS, the induction of IP-10, KC, and
MIP-2 is dramatically more by LPS than by TNF-
. The
basis for such differences is presently unclear, but they indicate that different NF-
B inducers may activate distinct
heterodimers of RelA-containing complexes, and
B sites
in different genes may preferentially bind different heterodimers. Induction of iNOS expression in macrophages
requires c-Rel (29), suggesting that both RelA and c-Rel
are important for activation of this gene.
We next wished to determine the consequence of RelA-dependent activation of Fas expression on
induction of cell death by this receptor. First, we determined whether the observed induction of Fas mRNA correlated with increased surface expression of this molecule
after LPS, IFN-, or LPS plus IFN-
treatment of RelA+/
or RelA
/
MEFs. Only LPS was used as the NF-
B activator, since it results in potent induction of Fas mRNA in
RelA+/
cells in the presence of IFN-
and is not cytotoxic to RelA
/
cells. Combined treatment of RelA+/
MEFs with LPS and IFN-
resulted in an ~10-fold increase in Fas surface expression, as measured by FACS®
analysis, whereas LPS and IFN-
treatments alone resulted
in less significant increases (Fig. 3 A). In contrast, Fas expression was increased only twofold in RelA
/
cells after
LPS plus IFN-
treatment (Fig. 3 B). Thus, potent mRNA
induction of Fas results in increased cell surface expression of Fas in RelA+/
but not in RelA
/
MEFs. We have also
found that IFN-
treatment is moderately cytostatic to
both RelA+/
and RelA
/
cells (see Fig. 4, A and B, below); in RelA
/
cells, some cytotoxicity through likely
production of TNF-
or TNF-
was also noticed after
LPS and IFN-
treatment.
|
|
We then tested whether cross-linking with the Fas-specific Jo2 antibody (30) resulted in death of RelA+/ or
RelA
/
fibroblasts. Significant cell death was observed in
RelA+/
cells by trypan blue staining when Jo2 was
added after LPS or IFN-
treatment, and combined treatment resulted in even greater killing (85% compared with
similar treatments without Jo2; Fig. 4 A). No cell death was
observed in the absence of LPS or IFN-
treatment. In
contrast, Fas-induced cell death was significantly reduced in
RelA
/
cells after LPS or combined treatment with LPS
and IFN-
(5% compared with similar treatments without
Jo2; Fig. 4 B). Our results indicate that the level of Fas expression may be critical in determining whether a cell will
undergo apoptosis after ligand binding, and that the RelA
component of NF-
B is required for activation of Fas expression and thus for induction of cell death by this receptor. Furthermore, activation of Fas expression appears to be
directly mediated by RelA, since consensus NF-
B binding sites have been found in the human Fas promoter (31)
and induction of Fas expression was found to be independent of new protein synthesis (data not shown).
Previous studies have demonstrated an antiapoptotic
function for RelA in TNF- and DNA damage-induced
cell death pathways (15, 32). However, the results presented here indicate that RelA is involved in regulation of
both proapoptotic and antiapoptotic genes. Recent studies
suggest that Fas expression may be responsible for tissue destruction in mouse autoimmune disease models for experimental autoimmune encephalomyelitis (EAE) and insulin-dependent diabetes (IDD) (35). Indeed, elevated Fas
expression has been found in
cells of the pancreas (36).
Our results indicate that Fas expression may be elevated by
cytokines such as IFN-
, TNF-
, TNF-
, and IL-1 produced by infiltrating T cells and macrophages. A role for
NF-
B in regulation of Fas expression suggests that inhibition of this transcription factor may have therapeutic potential for the treatment of autoimmune diseases.
![]() |
Footnotes |
---|
Address correspondence to Amer A. Beg, Department of Biological Sciences, Columbia University, 1110 Fairchild Center, 1212 Amsterdam Ave., New York, NY 10027. Phone: 212-854-5939; Fax: 212-854-5945; E-mail: aab41{at}columbia.edu
Received for publication 12 November 1998 and in revised form 27 January 1999.
We wish to thank P. Bruzzo for technical assistance and Dr. J. Manley for discussion and for comments on this manuscript. We are also indebted to Dr. D. Baltimore, in whose laboratory RelA-deficient mice were generated.
This work was supported by National Institutes of Health grant RO1 CA074982 to A.A. Beg.
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
1. | Medzhitov, R., and C.A. Janeway Jr.. 1997. Innate immunity: impact on the adaptive immune response. Curr. Opin. Immunol. 9: 4-9 [Medline]. |
2. | Medzhitov, R., and C.A. Janeway Jr.. 1997. Innate immunity: the virtues of a nonclonal system of recognition. Cell. 91: 295-298 [Medline]. |
3. | Ghosh, S., M.J. May, and E.B. Kopp. 1998. NF-kappa B and Rel proteins: evolutionarily conserved mediators of immune responses. Annu. Rev. Immunol. 16: 225-260 [Medline]. |
4. | Whitham, S., S.P. Dinesh-Kumar, D. Choi, R. Hehl, C. Corr, and B. Baker. 1994. The product of the tobacco mosaic virus resistance gene N: similarity to toll and the interleukin-1 receptor. Cell. 78: 1101-1115 [Medline]. |
5. | Ip, Y.T., M. Reach, Y. Engstrom, L. Kadalayil, H. Cai, S. Gonzalez-Crespo, K. Tatei, and M. Levine. 1993. Dif, a dorsal-related gene that mediates an immune response in Drosophila. Cell. 75: 753-764 [Medline]. |
6. | Ip, Y.T., and M. Levine. 1994. Molecular genetics of Drosophila immunity. Curr. Opin. Genet. Dev. 4: 672-677 [Medline]. |
7. |
Baeuerle, P.A., and
T. Henkel.
1994.
Function and activation of NF-![]() |
8. |
Sha, W.C.,
H.C. Liou,
E.I. Tuomanen, and
D. Baltimore.
1995.
Targeted disruption of the p50 subunit of NF-![]() |
9. |
Beg, A.A.,
W.C. Sha,
R.T. Bronson,
S. Ghosh, and
D. Baltimore.
1995.
Embryonic lethality and liver degeneration in mice
lacking the RelA component of NF-![]() |
10. |
Doi, T.S.,
T. Takahashi,
O. Taguchi,
T. Azuma, and
Y. Obata.
1997.
NF-![]() |
11. |
Caamano, J.H.,
C.A. Rizzo,
S.K. Durham,
D.S. Barton,
C. Raventos-Suarez,
C.M. Snapper, and
R. Bravo.
1998.
Nuclear factor (NF)-![]() |
12. |
Franzoso, G.,
L. Carlson,
L. Poljak,
E.W. Shores,
S. Epstein,
A. Leonardi,
A. Grinberg,
T. Tran,
T. Scharton-Kersten,
M. Anver, et al
.
1998.
Mice deficient in nuclear factor (NF)-![]() |
13. |
Weih, F.,
D. Carrasco,
S.K. Durham,
D.S. Barton,
C.A. Rizzo,
R.-P. Ryseck,
S.A. Lira, and
R. Bravo.
1995.
Multiorgan inflammation and hematopoietic abnormalities in mice
with a targeted disruption of RelB, a member of the NF-![]() |
14. | Kontgen, F., R.J. Grumont, A. Strasser, D. Metcalf, R. Li, D. Tarlinton, and S. Gerondakis. 1995. Mice lacking the c-rel proto-oncogene exhibit defects in lymphocyte proliferation, humoral immunity, and interleukin-2 expression. Genes Dev. 9: 1965-1977 [Abstract]. |
15. |
Beg, A.A., and
D. Baltimore.
1996.
An essential role for NF-![]() ![]() |
16. |
Thanos, D., and
T. Maniatis.
1995.
NF-![]() |
17. | Thanos, D., and T. Maniatis. 1995. Virus induction of human IFN beta gene expression requires the assembly of an enhanceosome. Cell. 83: 1091-1100 [Medline]. |
18. | Kundig, T.M., M.F. Bachmann, C. DiPaolo, J.J. Simard, M. Battegay, H. Lother, A. Gessner, K. Kuhlcke, P.S. Ohashi, H. Hengartner, et al . 1995. Fibroblasts as efficient antigen-presenting cells in lymphoid organs. Science. 268: 1343-1347 [Medline]. |
19. | Ting, J.P., and A.S. Baldwin. 1993. Regulation of MHC gene expression. Curr. Opin. Immunol. 5: 8-16 [Medline]. |
20. | Baldwin, A.S. Jr., and P.A. Sharp. 1988. Two transcription factors, NF-kappa B and H2TF1, interact with a single regulatory sequence in the class I major histocompatibility complex promoter. Proc. Natl. Acad. Sci. USA. 85: 723-727 [Abstract]. |
21. |
Kieran, M.,
V. Blank,
F. Logeat,
J. Vandekerckhove,
F. Lottspeich,
O. Le Bail,
M.B. Urban,
P. Kourilsky,
P.A. Baeuerle, and
A. Israël.
1990.
The DNA binding subunit of NF-![]() |
22. | Baldwin, A.S. Jr., K.P. LeClair, H. Singh, and P.A. Sharp. 1990. A large protein containing zinc finger domains binds to related sequence elements in the enhancers of the class I major histocompatibility complex and kappa immunoglobulin genes. Mol. Cell. Biol. 10: 1406-1414 [Medline]. |
23. | Beg, A.A., W.C. Sha, R.T. Bronson, and D. Baltimore. 1995. Constitutive NF-kappa B activation, enhanced granulopoiesis, and neonatal lethality in I kappa B alpha-deficient mice. Genes Dev. 9: 2736-2746 [Abstract]. |
24. | van Kooten, C., and J. Banchereau. 1997. Functional role of CD40 and its ligand. Int. Arch. Allergy Immunol. 113: 393-399 [Medline]. |
25. | Nagata, S., and P. Golstein. 1995. The Fas death factor. Science. 267: 1449-1456 [Medline]. |
26. | Baggiolini, M., B. Dewald, and B. Moser. 1997. Human chemokines: an update. Annu. Rev. Immunol. 15: 675-705 [Medline]. |
27. |
Frevert, C.W.,
S. Huang,
H. Danaee,
J.D. Paulauskis, and
L. Kobzik.
1995.
Functional characterization of the rat chemokine KC and its importance in neutrophil recruitment in a rat
model of pulmonary inflammation.
J. Immunol.
154:
335-344
|
28. | Driscoll, K.E., D.G. Hassenbein, B.W. Howard, R.J. Isfort, D. Cody, M.H. Tindal, M. Suchanek, and J.M. Carter. 1995. Cloning, expression, and functional characterization of rat MIP-2: a neutrophil chemoattractant and epithelial cell mitogen. J. Leukocyte Biol. 58: 359-364 [Abstract]. |
29. | Grigoriadis, G., Y. Zhan, R.J. Grumont, D. Metcalf, E. Handman, C. Cheers, and S. Gerondakis. 1996. The Rel subunit of NF-kappaB-like transcription factors is a positive and negative regulator of macrophage gene expression: distinct roles for Rel in different macrophage populations. EMBO (Eur. Mol. Biol. Organ.) J. 15: 7099-7107 [Abstract]. |
30. | Ogasawara, J., R. Watanabe-Fukunaga, M. Adachi, A. Matsuzawa, T. Kasugai, Y. Kitamura, N. Itoh, T. Suda, and S. Nagata. 1993. Lethal effect of the anti-Fas antibody in mice. Nature. 364: 806-809 [Medline]. |
31. | Behrmann, I., H. Walczak, and P.H. Krammer. 1994. Structure of the human APO-1 gene. Eur. J. Immunol. 24: 3057-3062 [Medline]. |
32. |
Wang, C.Y.,
M.W. Mayo, and
A.S. Baldwin Jr..
1996.
TNF- and cancer therapy-induced apoptosis: potentiation by
inhibition of NF-![]() |
33. |
Van Antwerp, D.J.,
S.J. Martin,
T. Kafri,
D.R. Green, and
I.M. Verma.
1996.
Suppression of TNF-![]() ![]() |
34. |
Liu, Z.G.,
H. Hsu,
D.V. Goeddel, and
M. Karin.
1996.
Dissection of TNF receptor 1 effector functions: JNK activation
is not linked to apoptosis while NF-![]() |
35. | Kang, S.M., D.B. Schneider, Z. Lin, D. Hanahan, D.A. Dichek, P.G. Stock, and S. Baekkeskov. 1997. Fas ligand expression in islets of Langerhans does not confer immune privilege and instead targets them for rapid destruction. Nat. Med. 3: 738-743 [Medline]. |
36. | Chervonsky, A.V., Y. Wang, F.S. Wong, I. Visintin, R.A. Flavell, C.A. Janeway Jr., and L.A. Matis. 1997. The role of Fas in autoimmune diabetes. Cell. 89: 17-24 [Medline]. |
37. | Waldner, H., R.A. Sobel, E. Howard, and V.K. Kuchroo. 1997. Fas- and FasL-deficient mice are resistant to induction of autoimmune encephalomyelitis. J. Immunol. 159: 3100-3103 [Abstract]. |
38. |
Benoist, C., and
D. Mathis.
1997.
Cell death mediators in
autoimmune diabetes![]() |