By
From the * R.W. Johnson Pharmaceutical Research Institute, San Diego, California 92121; and the R.W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey 08869
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Interleukin (IL)-1 is a proinflammatory cytokine with pleiotropic effects in inflammation. IL-1
binding to its receptor triggers a cascade of signaling events, including activation of the stress-activated mitogen-activated protein (MAP) kinases, c-Jun NH2-terminal kinase (JNK) and p38
MAP kinase, as well as transcription factor nuclear factor B (NF-
B). IL-1 signaling results in
cellular responses through induction of inflammatory gene products such as IL-6. One of the
earliest events in IL-1 signaling is the rapid interaction of IL-1 receptor-associated kinases,
IRAK and IRAK-2, with the receptor complex. The relative roles of IRAK and IRAK-2 in
IL-1 signaling pathways and subsequent cellular responses have not been previously determined. To evaluate the importance of IRAK in IL-1 signaling, IRAK-deficient mouse fibroblast cells were prepared and studied. Here we report that IL-1-mediated activation of JNK,
p38, and NF-
B were all reduced in embryonic fibroblasts deficient in IRAK expression. In
addition, IL-6 production in response to IL-1 was also dramatically reduced in IRAK-deficient embryonic fibroblasts and in skin fibroblasts prepared from IRAK-deficient mice. Our results
demonstrate that IRAK plays an essential proximal role in coordinating multiple IL-1 signaling
pathways for optimal induction of cellular responses.
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Interleukin 1 (IL-1 and IL-1
) plays an important role
in inflammation, acting locally and systemically to induce
other proinflammatory cytokines, chemotactic factors, adhesion molecules, acute phase proteins, and fever (1). Animals that lack expression of IL-1 or IL-1 receptor have reduced inflammatory responses (2). Cellular responses to
IL-1 are mediated by a cascade of intracellular signaling events including activation of the stress-activated mitogen-activated protein (MAP)1 kinases, c-Jun NH2-terminal kinase (JNK) and p38, as well as transcription factor nuclear
factor
B (NF-
B) (6). Upon IL-1 binding, IL-1 receptor
type I forms a complex with IL-1 receptor accessory protein (7). IL-1 receptor-associated serine/threonine kinase (IRAK), and a recently identified homologue, IRAK-2,
are rapidly recruited to this receptor complex via the adaptor protein MyD88 (10). IRAK becomes phosphorylated and subsequently interacts with TRAF6, a member of
the TNF receptor-associated factor (TRAF) family (13,
14). TRAF6 has been implicated in activation of both JNK
and NF-
B (14, 15). TRAF6 associates with NF-
B-inducing kinase (NIK), a MAP 3 kinase-related protein that is
essential for TNF-
- and IL-1-mediated NF-
B activation
but has no effect on the activation of JNK or p38 (15).
NIK interacts with and may directly activate the recently
identified kinases of NF-
B inhibitor (I
B; 18-20). I
B kinases are responsible for activation of NF-
B via phosphorylation of its inhibitory partners, the I
B proteins,
leading to their degradation by proteasomes (21).
IRAK and IRAK-2 are homologous to Pelle, a Drosophila protein kinase identified genetically to be important
in dorsal-ventral pattern formation and in pathogen resistance (22, 23). Pelle is essential for the activation of Dorsal,
an NF-B-like protein which is mediated by Toll, an IL-1
receptor homologue in Drosophila (24). The rapid IL-1-dependent association of IRAK and IRAK-2 with the
IL-1 receptor complex and their homology to Pelle suggest that IRAK and/or IRAK-2 may serve important functions
in initiating IL-1 signaling. However, the roles of IRAK
and IRAK-2 in activation of the multiple downstream IL-1
signaling pathways have not previously been determined.
To dissect the role of IRAK in IL-1 signaling pathways, we
disrupted the IRAK gene by homologous recombination and prepared IRAK-deficient fibroblasts. IL-1-induced activation of JNK, p38, and transcription factor NF-
B, and
subsequent induction of IL-6 was analyzed in IRAK-deficient cells.
![]() |
Materials and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Preparation of IRAK Antibody.
Polyclonal rabbit antiserum to IRAK was raised against a peptide (Bio-Synthesis, Inc., Lewisville, TX) corresponding to the COOH-terminal amino acids (657-677) of mouse IRAK protein (25).Disruption of the IRAK Gene and Generation of IRAK-deficient Mice.
Mouse IRAK clones were isolated from a 129/Ola mouse genomic library. A 7-kb BamHI-EcoRI DNA fragment covering the first 9 exons of the mouse IRAK gene was used to prepare the knockout construct. A cassette containing a neomycin resistance gene was used to replace a 940-bp region covering exon 5 to exon 7 of the gene. A herpes simplex-thymidine kinase cassette was placed at the 3' end of the construct. The DNA construct was introduced into E14 embryonic stem cells by electroporation. Cells were cultured in the presence of 400 µg/ml G418 and 0.2 µM gancyclovir. Embryonic stem cells with the disrupted gene were detected by PCR and then confirmed by Southern hybridization using a DNA probe flanking the 3' end of the construct. Chimeric mice were generated from embryos injected with embryonic stem cells. Germline mice were obtained from breeding of chimeric male mice with C57BL/6J females. Germline female mice heterozygous for the disrupted IRAK gene were identified by PCR. IRAK-deficient male mice carrying only the disrupted IRAK gene were obtained from cross-breeding of heterozygous female mice with wild-type littermates.Preparation of Embryonic Fibroblasts and Skin Fibroblasts.
To prepare embryonic fibroblasts (EFs), embryonic stem cells with the disrupted IRAK gene were injected into C57BL/6J blastocysts and transferred to pseudopregnant mice. Embryos at day 15 of gestation were harvested. Fibroblast cell suspensions were prepared by trypsin treatment of the minced embryonic tissues. Fibroblasts derived from embryonic stem cells were enriched by culturing in DMEM with 10% FCS and 1 mg/ml G418. Fibroblasts after 3-4 wk of culture with G418 were used in these studies. Control EF cells with the wild-type IRAK gene were prepared from embryos of CD8-deficient mice (26). To prepare skin fibroblasts (SFs), mouse body skin was shaved, cut into small pieces, and then subjected to trypsin treatment. SFs in cell suspensions were cultured in DMEM with 10% FCS.Cell Stimulation.
Control and IRAK-deficient cells (9 × 105/ plate) were plated overnight in 100-mm cell culture plates with DMEM containing 5% FCS. EF cells were kept in the presence of 200 µg/ml G418. Before each experiment, cells were starved in serum-free DMEM for 4 h. The cells were then stimulated with IL-1In Vitro Kinase Assay.
After stimulation, cells were lysed in NP-40 lysis buffer (20 mM Hepes, pH 7.5, 150 mM NaCl, 1% NP-40, and 1 mM Na3VO4) containing EDTA-free complete protease inhibitor cocktail (Boehringer Mannheim Corp., Indianapolis, IN), centrifuged at 16,000 g for 10 min, and precleared twice with 50 µl of GammaBind G-Sepharose slurry (Pharmacia Biotech, Piscataway, NJ). MAP kinases were immunoprecipitated with 50 µl GammaBind G-Sepharose slurry and 2 µg polyclonal rabbit antibody, specific for the 20 COOH-terminal residues of p38Western Blotting.
Western blot analyses were carried out as previously described (27). For detection of IRAK and INF-B Mobility Shift Assay.
Northern Blot Analysis and IL-6 ELISA.
For IL-6 mRNA detection, EF cells cultured in 100-mm plates were treated with IL-1 ![]() |
Results and Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
To investigate whether IRAK is indispensable for IL-1 signaling pathway, IRAK-deficient mouse primary EF cells were prepared from mouse embryos injected with embryonic stem cells carrying a disrupted IRAK gene as described in Materials and Methods. The IRAK gene was disrupted by deletion of exons 5-7, which encode the NH2-terminal portion of the kinase domain, subdomains I-V, including conserved amino acids involved in ATP binding (Fig. 1 A). The deletion was confirmed by Southern hybridization (Fig. 1 B). Detection of only the disrupted IRAK allele in male embryonic stem cells suggests that the mouse IRAK gene is located on the X chromosome. Consistent with our finding, the human IRAK gene was also reported to be on the X chromosome (EMBL/GenBank'DDBJ accession number U52112). The absence of IRAK protein in EF cells containing the disrupted IRAK allele was demonstrated by immunoblotting with an anti-IRAK antiserum (Fig. 1 C). The lack of IRAK expression in IRAK-deficient EF cells enabled us to evaluate the importance of IRAK in IL-1 signaling.
|
JNK and p38 are strongly activated by IL-1, TNF-,
cell stress, and LPS (29). JNK phosphorylates the transactivation domain of c-Jun, which is involved in the activation
of activator protein 1-dependent genes, including genes involved in inflammatory responses (29). p38 is also involved in activation of gene expression and protein synthesis
during inflammation, including IL-1-induced IL-6 and prostaglandin synthesis (34). The proximal events responsible for IL-1-induced JNK and p38 activation are only partially
understood. We therefore compared IL-1-induced activation of JNK and p38 in IRAK-deficient and control EF cells.
JNK activity was measured by in vitro kinase assays of JNK
immunoprecipitates, using c-Jun as substrate. Activation of
JNK was reduced in IRAK-deficient cells by two- to threefold at all concentrations of IL-1 tested, although not completely eliminated (Fig. 2). This defect in JNK activation was
IL-1 specific, since TNF-
-induced JNK activity was comparable in control and IRAK-deficient cells. Activation of
p38 was measured in p38 immunoprecipitates using MAPKAPK-2 as a substrate. IL-1-induced activation of p38 was
also reduced in IRAK-deficient cells compared with control
cells, by three- to fivefold at all concentrations of IL-1 tested.
In contrast, TNF-
-induced p38 activity was similar in control and IRAK-deficient cells (Fig. 2). These results demonstrate that IL-1-induced JNK and p38 activities are both specifically reduced in IRAK-deficient cells, and implicate
IRAK as the most proximal signaling component in the activation of the JNK and p38 pathways.
|
IL-1 and TNF- are the
two most efficient activators of the NF-
B family of transcription factors (21, 35). NF-
B remains in an inactive
state when sequestered by I
B in the cytoplasm. Phosphorylation of I
B by I
B kinases leads to ubiquitination and
subsequent degradation of I
B by proteasomes (18).
Released NF-
B is then translocated to the nucleus, where
it binds to regulatory sites in NF-
B-induced genes (21).
I
B levels in IRAK-deficient cells and control cells treated
with IL-1 were determined by immunoblotting with an
I
B-
-specific antibody. At concentrations of IL-1 ranging from 10 pg/ml to 1 ng/ml, I
B degradation was significantly less in IRAK-deficient cells as compared with control cells (Fig. 3 A). However, at 10 ng/ml IL-1, I
B-
was degraded almost completely in both IRAK-deficient
and control cells. IL-1 induction of the NF-
B pathway
was further investigated by examining NF-
B DNA-binding activity in nuclear extracts (Fig. 3 B). Significant reduction in NF-
B activation was observed in IRAK-deficient
cells at low IL-1 concentrations. Consistent with the results in
I
B degradation, NF-
B activation was comparable in control and IRAK-deficient cells at high IL-1 concentrations.
|
IL-1 signaling triggers cellular responses through the induction of various inflammatory gene products (1). IL-6 is strongly induced by IL-1 via
activation of transcription factors including NF-B and activator protein 1, which bind to the enhancer elements of
the IL-6 gene promoter (6). IL-6 in turn plays a crucial role
in inflammation by mediating acute phase reactions (36). To determine whether the observed defects in IL-1-activated signaling result in impaired cellular responses, IL-6
induction in response to IL-1 was measured. Levels of IL-6
mRNA induced by various concentrations of IL-1 were
significantly lower in IRAK-deficient EF cells compared with control cells (Fig. 4 A). Similar decreases were also
found in IL-6 secreted from IRAK-deficient cells compared with control cells (Fig. 4 B, top), and at various times
after IL-1 treatment (data not shown). In three independent experiments, IL-6 induction by IL-1 was reduced by
three- to sixfold. Thus, the reduced IL-1 signaling in
IRAK-deficient cells results in decreased IL-6 production. To confirm the defects in IL-1 signaling and cellular response observed in IRAK-deficient EF cells, SF cells were
obtained from mice deficient in IRAK expression, as described in Materials and Methods. Consistent with the observation in EF cells, IL-1-induced IL-6 production was
significantly decreased in IRAK-deficient SF cells compared with SF cells prepared from wild-type mice (Fig. 4 B,
bottom). IL-1-induced JNK activation and I
B degradation were also found to be defective in IRAK-deficient SF cells
(data not shown).
|
Taken together, our data demonstrate that IRAK plays an important role in activating multiple IL-1 signaling pathways that lead to the induction of IL-1-responsive gene products such as IL-6. In the absence of IRAK, induction of JNK and p38 activities was significantly reduced at all concentrations of IL-1 tested, although not completely eliminated. Our results suggest that IRAK is required for optimal induction of JNK and p38 kinases and that loss of its function cannot be completely compensated for by IRAK-2 or other related kinases. Activation of JNK and p38 have been reported to be mediated by cascades of upstream kinases including MAP-2, MAP-3, and MAP-4 kinases (29). It remains to be determined at which levels within these cascades IRAK may act to induce JNK and p38 activity.
In contrast to the effects on JNK and p38, defects in NF-B
activation in IRAK-deficient cells could be overcome by
high concentrations of IL-1. Our interpretation is that related kinases such as IRAK-2 may be able to fully activate
the NF-
B pathway under these conditions. However, induction of cellular response to IL-1, such as IL-6 production, is dramatically reduced in IRAK-deficient cells even at high IL-1 concentrations. This suggests that activation of NF-
B alone is not sufficient for optimal induction of
IL-1-mediated cellular responses. Induction of IL-6 and
other IL-1-responsive gene products may be mediated synergistically by multiple pathways, including activation of
NF-
B, and JNK/p38-mediated pathways. In the case of
IL-6 secretion, the dramatic decrease in its induction by IL-1
in IRAK-deficient cells, even in the presence of full activation of NF-
B DNA-binding activity, may result from decreased activation of JNK/p38-dependent signaling pathways. This possibility is supported by a recent report that
p38 and other MAP kinases are involved in TNF-induced
IL-6 gene expression via modulation of transactivation potential of NF-kB without affecting its DNA binding activity (37).
Our observation of significant reduction in multiple signaling pathways and in IL-6 production induced by IL-1 in IRAK-deficient cells suggests that inhibitors of IRAK or IRAK-related kinases may be therapeutically useful for the treatment of IL-1-mediated inflammatory diseases.
![]() |
Footnotes |
---|
Address correspondence to Wai-Ping Fung-Leung, 3535 General Atomics Court, R.W. Johnson Pharmaceutical Research Institute, San Diego, CA 92121. Phone: 619-450-2016; Fax: 619-450-2070; E-mail: wleung @prius.jnj.com, or to Crafford A. Harris, 1000 Route 202 South, R.W. Johnson Pharmaceutical Research Institute, Raritan, NJ 08869. Phone: 908-704-4558; Fax: 908-526-7118; E-mail: charris{at}prius.jnj.com
Received for publication 5 March 1998 and in revised form 14 April 1998.
We thank G. Olini, Julie Culver, and Michelle Courtney for their excellent technical assistance. We also thank Jonathan Sprent, Avery August, Linda Joliffe, Lars Karlsson, and Michael Jackson for helpful discussions.
Abbreviations used in this paper
EF, embryonic fibroblast;
IB, inhibitor of
NF-
B;
IRAK, interleukin 1 receptor-associated kinase;
JNK, c-Jun NH2-terminal kinase;
MAP, mitogen-activated protein kinase;
MAPKAPK2, MAP kinase-activated protein kinase 2;
NF-
B, nuclear factor
B;
SF, skin fibroblast;
TRAF, TNF receptor-associated factor.
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
1. |
Dinarello, C.A..
1996.
Biologic basis for interleukin-1 in disease.
Blood.
87:
2095-2147
|
2. | Glaccum, M.B., K.L. Stocking, K. Charrier, J.L. Smith, C.R. Willis, C. Maliszewski, D.J. Livingston, J.J. Peschon, and P.J. Morrissey. 1997. Phenotypic and functional characterization of mice that lack the type I receptor for IL-1. J. Immunol. 159: 3364-3371 [Abstract]. |
3. | Labow, M., D. Shuster, M. Zetterstrom, P. Nunes, R. Terry, E.B. Cullinan, T. Bartfai, C. Solorzano, L.L. Moldawer, R. Chizzonite, and K.W. Mclntyre. 1997. Absence of IL-1 signaling and reduced inflammatory response in IL-1 type I receptor-deficient mice. J. Immunol. 159: 2452-2461 [Abstract]. |
4. |
Leon, L.R.,
C.A. Conn,
M. Glaccum, and
M.J. Kluger.
1996.
IL-1 type I receptor mediates acute phase response to
turpentine, but not lipopolysaccharide, in mice.
Am. J. Physiol.
271:
R1668-R1675
|
5. |
Zheng, H.,
D. Fletcher,
W. Kozak,
M. Jiang,
K.J. Hofmann,
C.A. Conn,
D. Soszynski,
C. Grabiec,
M.E. Trumbauer,
A. Shaw, et al
.
1995.
Resistance to fever induction and impaired
acute phase response in interleukin-1![]() |
6. | Bankers-Fulbright, J.L., K.R. Kalli, and D.J. McKean. 1996. Interleukin-1 signal transduction. Life Sci. 59: 61-83 [Medline]. |
7. |
Wesche, H.,
C. Korherr,
M. Kracht,
W. Falk,
K. Resch, and
M.U. Martin.
1997.
The interleukin-1 receptor accessory
protein (IL-1RAcP) is essential for IL-1-induced activation
of interleukin-1 receptor-associated kinase (IRAK) and
stress-activated protein kinases (SAP kinases).
J. Biol. Chem.
272:
7727-7731
|
8. | Korher, C., R. Hofmeister, H. Wesche, and W. Falk. 1997. A critical role for interleukin-1 receptor accessory protein in interleukin-1 signaling. Eur. J. Immunol. 27: 262-267 [Medline]. |
9. |
Huang, J.,
X. Gao,
S. Li, and
Z. Cao.
1997.
Recruitment of
IRAK to the interleukin 1 receptor complex requires interleukin 1 receptor accessory protein.
Proc. Natl. Acad. Sci.
USA.
94:
12829-12832
|
10. |
Muzio, M.,
J. Ni,
P. Feng, and
V.M. Dixit.
1997.
IRAK
(Pelle) family member IRAK2 and MyD88 as proximal mediators of IL-1 signaling.
Science
278:
1612-1615
|
11. | Wesche, H., W.J. Henzel, W. Shillinglaw, S. Li, and Z. Cao. 1997. MyD88: an adapter that recruits IRAK to the IL-1 receptor complex. Immunity. 7: 837-847 [Medline]. |
12. |
Croston, E.,
Z. Cao, and
D.V. Goeddel.
1995.
NF-![]() |
13. | Cao, Z., W.J. Henzel, and X. Gao. 1996. IRAK: a kinase associated with the interleukin-1 receptor. Science. 271: 1128-1131 [Abstract]. |
14. | Cao, Z., J. Xiong, M. Takeuchi, T. Kurama, and D.V. Goeddel. 1996. TRAF6 is a signal transducer for interleukin-1. Nature. 383: 443-446 [Medline]. |
15. |
Song, H.Y.,
C.H. Regnier,
C.J. Kirschning,
D.V. Goeddel, and
M. Rothe.
1997.
Tumor necrosis factor (TNF)-mediated
kinase cascades: bifurcation of nuclear factor-![]() |
16. |
Malinin, N.L.,
M.P. Boldin,
A.V. Kovalenko, and
D. Wallach.
1997.
MAP3K-related kinase involved in NF-![]() |
17. |
Natoli, G.,
A. Costanzo,
F. Moretti,
M. Fulco,
C. Balsano, and
M. Levrero.
1997.
Tumor necrosis factor (TNF) receptor
1 signaling downstream of TNF receptor-associated factor 2. Nuclear factor ![]() ![]() ![]() |
18. |
DiDonato, J.A.,
M. Hayakawa,
D.M. Rothwarf,
E. Zandi, and
M. Karin.
1997.
A cytokine-responsive I![]() ![]() |
19. |
Woronicz, D.,
X. Gao,
Z. Cao,
M. Rothe, and
D.V. Goeddel.
1997.
I![]() ![]() ![]() ![]() ![]() |
20. |
Mercurio, F.,
H. Zhu,
B.W. Murray,
A. Shevchenko,
B.L. Bennett,
J.W. Li,
D.B. Young,
M. Barbosa,
M. Mann,
A. Manning, and
A. Rao.
1997.
IKK-1 and IKK-2: cytokine-activated I![]() ![]() |
21. |
Baldwin, A.S. Jr..
1996.
The NF-![]() ![]() |
22. | Shelton, C.A., and S.A. Wasserman. 1993. Pelle encodes a protein kinase required to establish dorsoventral polarity in the drosophila embryo. Cell. 72: 515-525 [Medline]. |
23. | Lemaitre, B., E. Nicolas, L. Michaut, J.-M. Reichhart, and J.A. Hoffmann. 1996. The dorsoventral regulatory gene cassette spatzle/toll/cactus control the potent antifungal response in drosophila adults. Cell. 86: 973-983 [Medline]. |
24. | Belvin, M.P., and K.V. Anderson. 1996. A conserved signaling pathway: the Drosophila toll-dorsal pathway. Ann. Rev. Cell Dev. Biol. 12: 393-416 . [Medline] |
25. |
Trofimova, M.,
A.B. Sprenkle,
M. Green,
T.W. Sturgill,
M.G. Goebl, and
M.A. Harrington.
1996.
Developmental
and tissue-specific expression of mouse Pelle-like protein kinase.
J. Biol. Chem.
271:
17609-17612
|
26. | Fung-Leung, W.-P., M.W. Schilham, A. Rahemtulla, T.M. Kudig, M. Vollenweider, J. Potter, W. van Ewijk, and T.W. Mak. 1991. CD8 is needed for development of cytotoxic T cells but not helper T cells. Cell. 65: 443-449 [Medline]. |
27. |
Kanakaraj, P.,
B. Duckworth,
L. Azzoni,
M. Kamoun,
L.C. Cantley, and
B. Perussia.
1994.
Phosphatidylinositol-3 kinase
activation induced upon Fc![]() |
28. |
Trotta, R.,
P. Kanakaraj, and
B. Perussia.
1996.
Fc![]() ![]() |
29. | Su, B., and M. Karin. 1996. Mitogen activated protein kinase cascade and regulation of gene expression. Curr. Opin. Immunol 8: 402-411 [Medline]. |
30. | Pulverer, B.J., J.M. Kyriakis, J. Avruch, E. Nikolakaki, and J. Woodgett. 1991. Phosphorylation of c-jun mediated by MAP kinases. Nature. 353:670-674. |
31. |
Westwick, J.K.,
C. Weitzel,
A. Minden,
M. Karin, and
D.A. Brenner.
1994.
Tumor necrosis factor-![]() |
32. |
Raingeaud, J.,
S. Gupta,
J.S. Rogers,
M. Dickens,
J. Han,
R.J. Ulevitch, and
R.J. Davis.
1995.
Pro-inflammatory cytokines and environmental stress cause p38 mitogen-activated
protein kinase activation by dual phosphorylation on tyrosine
and threonine.
J. Biol. Chem.
270:
7420-7426
|
33. |
Bird, T.A.,
J.M. Kyriakis,
L. Tyshler,
M. Gayle,
A. Milne, and
G.D. Virca.
1994.
Interleukin-1 activates p54 mitogen-activated protein (MAP) kinase/stress-activated protein kinase by a pathway that is independent of p21ras, Raf-1, and
MAP kinase kinase.
J. Biol. Chem.
269:
31836-31844
|
34. | Ridley, S.H., S.J. Sarsfield, J.C. Lee, H.F. Bigg, T.E. Cawston, D.J. Taylor, D.L. DeWitt, and J. Saklatvala. 1997. Actions of IL-1 are selectively controlled by p38 mitogen-activated protein kinase. Regulation of prostaglandin H synthase-2, metalloproteinases, and IL-6 at different levels. J. Immunol 158: 3165-3173 [Abstract]. |
35. |
Osborn, L.,
S. Kunkel, and
G.J. Nabel.
1989.
Tumor necrosis
factor ![]() ![]() |
36. | Akira, S., and T. Kishimoto. 1992. IL-6 and NF-IL-6 in acute-phase response and viral infection. Immunol. Rev 127: 25-50 [Medline]. |
37. |
Berghe, W.V.,
S. Plaisance,
E. Boone,
K. De Bosscher,
M.L. Scmitz,
W. Fiers, and
G. Haegeman.
1998.
p38 and extracellular signal regulated kinase mitogen-activated protein kinase
pathways are required for nuclear factor-![]() |