Crafoord Prize Lecture

Crafoord Prize Lectures
Lund University May 13, 2009

How extensive the view from a mountain top is!: A story of interleukin 6
Toshio Hirano

See Crafoord Days 2009 and Crafoord Prize Lectures 2009 at
http://www.crafoordprize.se/events/crafoorddays20082009.4.2f692b3510dbfce339680003937.html

Laboratory of Developmental Immunology, Graduate School of Frontier Biosciences, Graduate School of Medicine and WPI Immunology Frontier Research Center, Osaka University and Laboratory of Cytokine Signaling, RIKEN Research Center for Allergy and Immunology, Japan

Your Majesties, President of the Academy, members of the Crafoord Family, members of the Academy, ladies and gentlemen, it is my great honor to be awarded the 2009 Crafoord Prize in Polyarthritis jointly with Professor Charles Dinarello and Professor Tadamitsu Kishimoto by the Royal Swedish Academy of Sciences. At this special occasion, I would like to express my sincere thanks to Dr. Bo Sundqvist, President of the Academy, Dr. Gunnar Öquist, permanent secretary of the Academy, Dr. Catharina Svanborg, chairman of the prize committee. I also express my sincere thanks to the Academy and the Crafoord Foundation and members of the Crafoord Family, in particular Ms. Ebba Fischer, chairman of the Crafoord Foundation. I thank all my colleagues, without whose collaboration and help it would not have been possible for us to isolate interleukin 6 and clarify its properties and roles in inflammatory diseases. And I would not be standing here today without the support of my wife, Chiyoko Hirano. I thank my dear daughters, Yuko and Yoko. While my father is no longer with us, I know he is watching me with great pleasure. Although, my 92 year old mother is not here today, I know this award pleased her very much.

We do not know what the view from a mountain top will be. It is easy to find out if we check a guide before climbing. But in real life, as we know, there are no guides for all the mountains we have to climb. Life creates many challenges and it is not until we have reached one summit that we can see what lies before us. It may be
a breathtaking view of the ocean. It may be a straight road showing us the correct direction to go in. We may even see a delightful view of a city, like Granada in Spain as shown in this picture, which my uncle in law painted to celebrate my prize award. Or we may see many more mountains, new challenges to be climbed. Only the one who stands on the top of the mountain can know what this view is, how extensive it is, how beautiful it is and what it will lead to.

Today’s View

Today, we know that human beings cannot survive without an immune system. The history of humankind is the history of fighting against a variety of infectious diseases, such as the black plaque, cholera, smallpox, influenza, tuberculosis and so on. An epidemic of infectious diseases often determines which country finally wins a battle. We have won the battle against a variety of infectious diseases since Edward Jenner discovered that cowpox induced protection against human smallpox in 1796. This procedure is called “vaccination”. We are, however, still fighting against a variety of infectious diseases caused by a newly generated microorganisms. A patient with severe combined immunodeficiency syndrome, which is caused by the loss of function mutation of interleukin-2 receptor gamma chain essential for lymphocyte development, suffers severe infectious diseases. Thus it is out of question that we human beings cannot survive on the earth without the immune system. However, immune responses often bring disadvantages to human beings. There are several autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus, type 1 diabetes mellitus, Graves’ disease, multiple sclerosis and so on. Both genetic and environmental factors are involved in causing autoimmune diseases. Autoimmune diseases are caused by the attack of immune system against self-antigen, resulting in self-destruction. T lymphocytes, B lymphocytes, macrophages and antigen presenting dendritic cells are major players in the immune system. They interact with each other to initiate immune responses against pathogens and even self-components of our body. Cytokines, such as interleukin 1 and 6, which are soluble factors produced by immune cells, play crucial roles in immune responses and abnormal production of cytokine or their abnormal functions are involved in several autoimmune diseases including RA. Now we know that there are a lot of cytokines and inhibitors of these cytokines, including IL-1, IL-6 and TNFα which are beneficial for autoimmune diseases, in particular RA.

Past view

What did I know 37 years ago when I graduated from Osaka University Medical School in 1972? We already knew that the interaction of immune cells, such as T lymphocyes, B lymphocytes and macrophages are required for immune responses. In response to antigenic stimulation such as pathogens, immune cells produce several soluble factors, now called cytokines, and these soluble factors are required for immune responses. For example, antigenic stimulation induces the differentiation of B lymphocytes into immunoglobulin-producing plasma cells under the help of T lymphocytes. In 1971 and 1972, M. Dutton and both Schimpl and Wecker, respectively reported the presence of soluble factors, which could replace the helper functions of T lymphocytes and thereby they called it T cell replacing factor (TRF). However, the molecular natures of these soluble factors were completely unknown. Immunologists called each factor by his/her own name based on the biological activity he/she examined, and thereby there were a lot of names corresponding to the numbers of immunologists.
I wished to study Immunology and in 1973 I applied to the visiting fellowship at National Institutes of Health, in The Unites States and participated in the laboratory of Immunology being supervised by Dr. Albert A. Nordin at The Gerontology Research Center, which is now called The National Institute on Aging in Baltimore. In Baltimore, I first met Dr. Kishimoto and Dr. Takatsu, both of whom were members of Dr. Kimishige Ishizaka’s laboratory at John Hopkins University and since then I have learned a lot from them. My encounter with Dr. Kishimoto has very much influenced my life as an immunologist. But at that time I did not know my future. After three years research on the regulation of cytotoxic T cell differentiation and soluble factors involved in this process at Dr. Nordin’s Lab, NIH, I returned to Osaka University Medical School in 1976 and thereafter moved to Osaka Prefectural Habikino Hospital in 1978, which is now called Osaka Prefectural Medical Center for Respiratory and Allergic Diseases. I saw many patients with tuberculous pleurisy there.

A steep mountain path

I found that the purified protein derivative (PPD)-stimulated pleural effusion cells of patients with pulmonary tuberculosis produce soluble factors capable of inducing immunoglobulin production in B cells (1). Since this activity seemed to be very strong and large amounts of lymphocytes (up to 1 X 109/patient) could be obtained from one patient I thought it might be possible to purify the active factors. Then I decided to isolate this active factor and started its purification together with Dr. Tsuyoshi Teranishi in 1978. We found that the fractions corresponding to the molecular weight of 22KDa and the isoelectric point of 5 contained factors acting on B cell lines transformed by Epstein-Barr virus to induce immunoglobulin production. These biological activity and physicochemical properties of the soluble factors, at that time we called TRF-like factor or BCDFII, are the same as those of cyotkine, which is now called interleukin 6 (2). Therefore, for me, interleukin 6 is a gift from patients with tuberculosis (Fig. 1). I moved to Kumamoto University Medical School as an Associated Professor of the late Professor Kaoru Onoue in 1980 and there I continued purification and characterization of this factor. Then I moved to Osaka University as an Associate Professor at Professor Kishimoto’s lab in early 1984 and finally succeeded in its purification and determined its N-terminal 14 amino acid sequence at the end of 1984. I had a prospective view for the next year and really enjoyed the New Year Holidays with a big dream. However, reality was much harder than I expected. Our several trials to clone the cDNA encoding this active molecule completely failed in 1985. This raised the doubt that the sequence we determined might be incorrect or it might be the sequence of the other proteins co-purified with the active molecule. This worry gave me severe arrhythmia, which disturbed my sleep at the end of 1985. A medical checkup showed that my arrhythmia was just psychogenic but not pathogenic. Then I decided to purify the molecule again utilizing 100 liters of newly obtained culture supernatants. We obtained several fragments of the purified protein and their partial amino acid sequences in March, 1986. Then I started cloning the cDNA. We used three probes corresponding to three selected fragments of the purified proteins. I believed that this way would be surer than the way I took using only one probe corresponding to the N-terminal amino acid sequences in 1985.

Figure 1. Interleukin6 is a gift from patients with tuberculosis.
I worked in Osaka Prefectural Habikino Hospital where I saw many patients with tuberculous pleurisy and we found pleural effusion cells when stimulated with purified protein derivative (PPD) produced factors being able to induce immunoglobulin production in B lymphocytes in 1978. We started isolating these factors and we found one of active factors had similar biological activity and physicochemical properties with those of a cytokine, now called interleukin 6. Therefore, for me, interleukin 6 is a gift from patients with tuberculosis.

Standing at the top of the mountain

After 8 years of steep climbing, the summit suddenly came into view. 11 am Sunday morning May 25th 1986 I obtained the clone, which bound all three probes.

It was in my hand. It was not a dream. It was a reality.

I was very confident that I had finally cloned the cDNA encoding the molecule, which we called “BSF-2” at that time, which we previously called BCDF, BCDFII or TRF-like factor. Nucleotide sequence of the cDNA showed that BSF-2 is synthesized as a precursor consisting of 212 amino acids and is processed into a mature form consisting of 184 amino acids. We published the result in the November issue of Nature, 1986 (3). To my surprise, the sequence we reported was found to be identical to that of interleukin 1-induced 26kDa protein reported by Hageman and Fiers in the Sept. issue of Eur. J. Biochemisty and that of interferon beta 2 reported by Zilberstein and Revel in the Oct. issue of EMBO J. These results revealed that all these molecules are identical. The January issue of Science, 1988 reported that orphan interferon had found a new home; Uncertainties about the role of interfero-β2 were being resolved as researchers found that it had numerous activities in the body’s defenses. Furthermore, the plasmacytoma/hybridoma/myeloma growth factor and the hepatocyte stimulating factor which regulates the biosynthesis of a variety of acute-phase proteins, were also found to be identical to this factor. Therefore, the nomenclature meeting chaired by Dr. W. E. Paul, which was held in New York on Dec. 14, 1988 proposed the name of “interleukin-6” for this molecule (4). Thus, the name “interleukin-6” was born!
I could finally see an extensive prospect from the top of the mountain after more than 8 years steep climb since I began isolating the factor capable of inducing immunoglobulin production in B cells in 1978. We wished to isolate a factor acting on B cells to induce immunoglobulin production, calling this factor a variety of names, such as TRF-like factor, BCDF, BCDFII, BSF-2 and so on. However, once we cloned the factor, we saw that this factor, given a new name “interleukin-6 (IL-6)”, acts on not only B cells, but also a variety of cells and tissues. It acts on hepatocyte to induce a variety of acute phase proteins; it activates osteoclasts to destroy bones; it is a growth factor for myeloma and plasmacytoma; it increases platelet, and it even induces fever and cachexia. IL-6 is now known to be a multifunctional cytokine that plays roles in the immune response, inflammation, hematopoiesis in the endocrine and nervous systems (Fig. 2) (4, 5).

Figure 2. The name of “interleukin 6”, which has multiple functions, was born.
Our study together with other studies showed that BSF-2 was identical with interferon-β2, 26kDa protein, plasmacytoma/hybridoma/myeloma growth factor and hepatocyte stimulating factor. The nomenclature meeting proposed the name of “interleukin-6” for this molecule in 1988. Thus, the name of “interleukin-6” was born. IL-6 is now known to be a multifunctional cytokine that plays roles in the immune response, inflammation, hematopoiesis, in the endocrine and nervous systems.

Anyway, once a ligand, such as IL-6 was cloned, it was not so difficult for us to isolate its receptor in the late 1980s. In fact, we cloned the cDNA encoding IL-6 receptor utilizing expression cloning, which was just introduced by Brian Seed and his colleagues (6). Then we cloned a signal transuding receptor subunit, gp130 (7). We showed that IL-6 receptor is composed of two subunits, one is an IL-6 specific subunit, alpha chain and the other is a signal transducer, gp130. (see Fig. 4). Furthermore, it was found that gp130 is not only a receptor subunit for IL-6, but also a signal transducer for other cytokines, such as IL-11, OSM, LIF, CT-1, CNTF, IL-27 and so on. The view I saw at the top of the mountain was far beyond my expectation. However, this was not the end of the story but just a beginning. Later, I saw another view from the top of the next mountain.

A beautiful view came next.

Patients with cardiac myxoma show a variety of autoimmune symptoms, such as hypergammaglobulinemia, the presence of autoantibodies and an increase in acute phase proteins, all of which disappeared after the resection of the tumor cells, suggesting that cardiac myxoma cells may induce autoimmunity. We found that cardiac myxoma cells produce IL-6 (8). This was the first suggestive evidence indicating that IL-6 might be involved in autoimmune diseases. Important findings came next. We found that a large amount of IL-6 is present in the synovial fluids of patients with RA (9), suggesting the involvement of IL-6 in RA for the first time. RA is a chronic polyarthritis and one of the autoimmune diseases. Both genetic and environmental factors are involved, but its etiology is unknown. Since patients with RA show a variety of symptoms, such as polyclonal plasmacytosis accompanied with production of rheumatoid factor, increase of acute phase proteins, enhanced bone resorption activity and increase of platelet and so on, all of which do not apparently have any relationship with each other. However, if one considers the multiple functions of IL-6, this puzzle would be resolved. This led me to speculate that the cause, which triggers the dysregulation of IL-6 gene expression or abnormal IL-6 function is intimately related to the cause inducing RA (5, 10).
I was appointed as a Professor of Osaka University Medical School on November 1st, 1989. In early 1990s, I proposed a working hypothesis of possible mechanisms involved in certain autoimmune diseases, chronic inflammatory proliferative disease (CIPD) like RA where IL-6 is suggested to play a role (5,10). In the hypothesis illustrated in Fig. 3, the constitutive activation of a set of transcription factors, such as NF-kB, is the central factor governing the onset as well as the progression of the disease. In the initial phase, the activation of the transcription factors is induced by a variety of stimuli, including infection, stimulation with foreign materials, and injury. This initial stimulation induces inflammation that activates a set of transcription factors, leading to the expression of various genes encoding cellular proteins, including IL-6 and other cytokines, MHC molecules, adhesion molecules, various autoantigens, and several transcription factors. Thus expressed, autoantigens could be recognized by autoreactive T-cells in the context of the MHC molecules. These activated autoreactive T-cells also induce the inflammatory response. Since the first phase could occur in non-immune cells or tissues, my hypothesis indicated that the interaction between the non-immune system and immune system plays a critical role in autoimmune diseases and CIPD.

Figure 3. A working hypothesis of possible mechanisms involved in autoimmune diseases, chronic inflammatory proliferative disease (CIPD) like RA
The constitutive activation of a set of transcription factors, such as NF-kB, is the central factor governing the onset as well as the progression of autoimmune diseases and CIPD. In the initial phase, the activation of the transcription factors is induced by a variety of stimuli, including infection, stimulation with foreign materials, and injury. This initial stimulation induces inflammation that activates a set of transcription factors, leading to the expression of various genes encoding cellular proteins, such as IL-6 and other cytokines, MHC molecules, adhesion molecules, giving rise to the activation of immune system. Since the first phase could be induced in non-immune cells or tissues, this hypothesis suggested the interaction between the non-immune and immune system plays a critical role in autoimmune diseases and CIPD.

To understand the molecular mechanisms of IL-6 actions, we investigated signal transduction pathways through the IL-6 receptor. We showed IL-6 induces two major signal transduction pathways, the Stat3 signal and the SHP2/Gab/MAPK signal in a manner dependent on the YxxQ motif and the Y759 of gp130, respectively (11-14). Then, I wished to clarify the in vivo roles of each of the two signals of gp130. For this, we generated a series of knock-in mouse lines in which the gp130-mediated SHP2 or Stat3 signal is selectively disrupted (15). To make the SHP2 signal-deficient mice (F759 mice), we mutated Y759 of gp130 to phenylalanine. F759 mice show enhanced STAT3 activation through gp130 since Y759 is required for SOCS3-mediated negative feedback mechanisms. The most intriguing finding is that F759 mice, which show enhanced STAT3 activation by IL-6, spontaneously develop RA-like joint disease (F759 arthritis) (Fig. 4) (16). This is the first definitive evidence showing that IL-6 is critically involved in spontaneous autoimmune disease and shows that an abnormal IL-6 signal can induce autoimmune disease like RA. F759 arthritis is late onset, symmetrical and progressive like human RA. F759 mice show a variety of immunological abnoramlities, including hypergammaglobulinemia, production of autoantibodies, increase of memory activated T cells and so on. Then, we have tried to clarify molecular and immunological mechanisms. Both genetic and environmental factors are involved in autoimmune diseases. In F759 mice, point mutation of gp130 leading to the enhanced activation of STAT3 by IL-6 is one of the examples of the genetic factor. Then we asked a question: does HTLV-1 infection as an environmental factor have any effect on F759 arthritis? Iwakura and his colleagues showed that HTLV-1 env-pX transgenic mice, a model of HTLV-1 infection, developed arthritis in certain genetic backgrounds. Then we asked if HTLV-1 has any effect on arthritis in C57BL/6 backgrounds. We found HTLV-1 pX enhanced F759 arthritis (17). F759 mutation enhances STAT3 activation by IL-6, while HTLV-1 activates NF-kB, suggesting that both STAT3 and NF-kB are involved in F759 arthritis. Thus F759 mice are a new animal model of RA.

Figure 4. Dysregulation of IL-6 signaling spontaneously induces RA-like arthritis with age.
IL-6 receptor is composed of two subunits, one is an IL-6 specific subunit, alpha chain and the other is a signal transducer, gp130. IL-6 induces two major signaling pathways, one is mediated by STAT3 and the other SHP2/GAB through tyrosine residues of go130 with YxxQ motif and tyrosine 759 of gp130, respectively. F759 mice, which express mutated gp130 (Y759F) defective of SOCS3-mediated negative feedback, spontaneously develop RA-like arthritis with age.

Using studies of bone-marrow transplantation and various knock-out strains, we demonstrated that F759 arthritis is CD4 T cell-dependent, and interestingly, the gp130 F759 mutation is necessary in cells of a non-hematopoietic origin. In response to IL-6 stimulation, these non-hematopoietic cells from F759 mice show an enhanced production of T-cell survival factor, IL-7, leading to the activation of CD4 T cells by homeostatic proliferation. This homeostatic proliferation of CD4 T cells is important for the development of F759 arthritis (18). Thus our results show that the interaction between the non-immune system and immune system plays a critical role in causing autoimmune F759 arthritis and suggested the important role of the non-immune system in causing autoimmune diseases in general (see Fig. 5). It was recently found that IL-6 together with TGFβ induces TH17, which has been considered to play a pivotal role in causing autoimmune diseases and inflammation, indicating that IL-6 is located upstream of IL-17. In fact, we showed that gp130 and Stat3 in T cells are essential for TH17 development (19). In addition, we found that IL-6 is not only an IL-17 inducing factor, but also a target gene of IL-17 in non-immune cells including fibroblast cells. Importantly, IL-6 is a critical downstream target gene of IL-17 for F759 arthritis. An intriguing finding we made was that IL-17-induced IL-6 gene expression through NF-kB activation is augmented in the presence of IL-6. This synergistic induction of IL-6 is mediated through an interaction between NF-kB and STAT3. IL-6 can induce TH17 cells to produce IL-17 and therefore once an IL-6 positive feedback loop is initiated in non-immune cells, enhanced IL-6 production results in the enhanced TH17 development, giving rise to further enhanced production of IL-6. We named this positive loop the “IL-6 amplifier” (see Fig. 5) (20). More importantly, “IL-6 amplifier” in type1 collagen positive non-immune tissues is required for autoimmune arthritis in F759 mice.
“IL-6 amplifier” is induced by the interaction between the immune system and non-immune system where both NF-kB and STAT3 activation has occurred. “IL-6 amplifier” is enhanced in F759 mice where IL-6-mediated STAT3 activation is enhanced due to the lack of negative feedback through SOCS3. Consistent with this scenario, HTLV1-p40Tax capable of activating NF-kB enhances F759 arthritis. We showed that MOG-specific TH17-induced experimental autoimmune encephalomyelitis (EAE) is dependent on STAT3 in type 1 collagen positive non-immune tissue. Collectively, we hypothesized that any event, including antigen-specific T cells, virus infection, injury and physical stimulation capable of activating IL-6 amplifier through either STAT3 activation or NF-kB activation or both plays a critical role in causing autoimmune diseases. This scenario might be applied in general autoimmune models (Fig.5). Thus, I would like to remind you of my old hypothesis (see Fig. 3), which I proposed in the early 1990s and suggested that the interaction between the non-immune system and immune system through the activation of several transcription factors is critically involved in autoimmune diseases and chronic inflammatory proliferative diseases.

Figure 5. The interaction between the non-immune and immune system through an “IL-6 amplifier” plays a role in autoimmune diseases and CIPD.
“IL-6 amplifier”, which is dependent on NF-kB and STAT3 plays an important role in causing F759 arthritis. It is speculated that any event, any reagent, any pathogen, capable of chronically activating either or both NF-kB and STAT3 plays a role in RA and this scenario might be applied in autoimmune diseases and CIPD in general.

How extensive the view from a mountain top is!

Now, I am standing on top of the mountain and I can finally enjoy the view. 37 years ago when I graduated Osaka University Medical School in 1972 I could not have imagined it. I have discovered one of essential factors involved in the immune system, IL-6. It is the multifunctional cytokines which are involved not only in the immune system, but also in inflammation, hematopoietic system, nervous system and even in early development of our body. 37 years ago, I did not imagine how autoimmune diseases could develop and how RA occurs. Now I can see part of these mechanisms and how autoimmune diseases develop and how IL-6 is involved. Dysregulation of the IL-6 signaling pathway spontaneously induces autoimmune arthritis in mice (F759 arthritis). Furthermore, we found the presence of an “IL-6 amplifier” which is critically involved in F759 arthritis. These facts led me to speculate that any event, any reagent, any pathogen capable of chronically activating either or both NF-kB and STAT3 plays a role in RA and this scenario might be applied to autoimmune diseases in general. Anti-IL-6 receptor antibody treatment, which inhibits IL-6 function, has been found to be beneficial for many patients. Thus our basic studies during the last 30 years contributed toward an understanding of the immunological mechanisms of RA and paved the way to develop a new drug beneficial for patients with RA and hopefully other autoimmune diseases and inflammatory diseases.

Finally, I would like to acknowledge many people. First of all, I acknowledge the late Professors Yuichi Yamamura and Kaoru Onoue, Professor Sohei Kondo, Dr. Albert A. Nordin and Professor Tadamitsu Kishimoto all of whom are my mentors. I also express my special thanks to Professors Kiyoshi Takatsu, Tadatsugu Taniguchi and Takeshi Watanabe for their valuable advice and encouragement. I also wish to thank many friends and colleagues, Drs Tetsuya Taga, Kiyoshi Yasukawa, Katsuhiko Yamasaki, Tsuyoshi Teranishi, Shizuo Akira, Atsushi Muraguchi, Hitoshi Kikutani, Kazuyuki Yoshizaki, and Yoichiro Iwakura. Finally I acknowledge the many people in my laboratory, including Drs Koichi Nakajima, Tadashi Matsuda, Katsuhiko Ishihara, Masahiko Hibi, Tsuneyasu Kaisho, Yojiro Yamanaka, Toshiyuki Fukada, Keigo Nishida, Motoyuki Ito, Takuya Ohtani, Toru Atsumi, Satoru Yamasaki, Shinichiro Sawa, Daisuke Kamimura, Hideyuki Ogura, Yukihisa Sawa and Masaaki Murakami and many other colleagues.

I am very grateful to the Royal Swedish Academy of Sciences and the Crafoord Foundation. Finally, I would like to express my sincere thanks to Ms. Elin Mellqvist for her perfect arrangement of the Crafoord Days 2009.

References

1) Hirano, T., T. Teranishi, H. Toba, N. Sakaguchi, T. Fukukawa, and I. Tsuyuguchi. Human helper T cell factor(s) (ThF). I. Partial purification and characterization. J.Immunol. 126:517-522, 1981
2) Teranishi, T., T. Hirano, N. Arima, and K. Onoue. Human helper Tcell factor(s) (ThF). II. Induction of IgG production in B lymphoblastoid cell lines and identification of T cell replacing factor-(TRF) like factor(s). J. Immunol. 128:1903-1908, 1982.
3) Hirano, T., K. Yasukawa, H. Harada, T. Taga, Y. Watanabe, T. Matsuda, S. Kashiwamura, K. Nakajima, K. Koyama, A. Iwamatu, S. Tsunasawa, F. Sakiyama, H. Matsui, Y. Takahara, T. Taniguchi, and T. Kishimoto. Complementary DNA for a novel human inteleukin (BSF-2) that induces B lymphocytes to produce immunoglobulin. Nature 324:73-76, 1986
4) Sehgal, P. B., Grienger, G., and Tosato, G. (editors) Regulation of the Acute Phase and Immune Responses: Interleukin-6. Ann New York Acad Sci 557, 1-583, 1989
5) Hirano, T. Interleukin 6 and its receptor: Ten years later. Int. Reviews of Immunology 16: 249-284, 1998
6) Yamasaki, K., T. Taga, Y. Hirata, H. Yawata, Y. Kawanishi, B. Seed, T. Taniguchi, T. Hirano, and T. Kishimoto. Cloning and expression of human interleukin 6 ( BSF-2/IFNb2 ) receptor. Science 241:825-828, 1988
7) Hibi, M., M. Murakami, M. Sito, T. Hirano, T. Taga and T. Kishimoto. Molecular cloning and expression of an IL-6 signal transducer, gp130. Cell 63:1149-1157, 1990.
8) Hirano, T., T. Taga, K. Yasukawa, K. Nakajima, N. Nakano, F. Takatsuki, M. Shimizu, A. Murashima, S. Tsunasawa, F. Sakiyama, and T. Kishimoto. Human B cell differentiation factor defined by an anti-peptide antibody and its possible role in autoantibody production. Proc. Natl. Acad. Sci. USA. 84:228-231, 1987
9) Hirano, T., T. Matsuda, M. Turner, K. Sato, G. Buchan, B. Tang, N. Miyasaka, M. Shimizu, R. Maini, M. Feldmann, and T. Kishimoto. Excessive production of interleukin 6/B cell stimulatory factor-2 in rheumatoid arthritis. Eur. J. Immunol. 18:1797-1801, 1988
10) Hirano, T. Interleukin-6 and its relation to inflammation and disease. Clinical Immunol. Immunopathol. 62:S60-S65, 1992
11) Yamanaka, Y., K. Nakajima, T. Fukada, M. Hibi, and T. Hirano. Differentiation and growth arrest signals generate through the cytoplasmic region of gp130 that is essential for Stat3 activation. EMBO J. 15:1557-1565, 1996
12) Nakajima, K., Y. Yamanaka, K. Nakae, H. Kojima, N. Kiuchi, M. Ichiba, T. Kitaoka, T. Fukada, M. Hibi and T. Hirano. A central role for Stat3 in IL-6-induced regulation of growth and differentiation in M1 leukemia cells. EMBO J. 15:3651-3658, 1996
13) Fukada, T., M. Hibi, Y. Yamanaka, M. Takahashi-Tezuka, Y. Fujitani, T. Yamaguchi, K. Nakajima, and T. Hirano, Two signals are necessary for cell proliferation induced by a cytokine receptor gp130: involvement of STAT3 in anti-apoptosis. Immunity 5: 449-460, 1996
14) Kamimura, D., Ishihara, K., and Hirano, T. IL-6 signal transduction and its physiological roles:The signal orchestration model. Reviews of Physiology, Biochemistry and Pharmacology, 149:1-38, 2003
15) Ohtani, T., K. Ishihara, T. Atsumi, K. Nishida, Y. Kaneko, T. Miyata, S. Itoh, M. Narimatsu, H. Maeda, T. Fukada､, M. Itoh, H. Okano, M. Hibi and T. Hirano. Dissection of signaling cascades through gp130 in vivo: Reciprocal roles for STAT3- and SHP2-mediated signals in immune responses. Immunity, 12: 95-105, 2000
16) Atsumi, T., K. Ishihara, D. Kamimura, H. Ikushima, T. Ohtani, S. Hirota, H. Kobayashi, S-.J. Park, Y. Saeki, Y. Kitamura, and T. Hirano. J. Exp. Med. 196:979-990, 2002
17) Ishihara, K., S. Sawa, H. Ikushima, S. Hirota, T. Astumi, D. Kamimura, S.-J. Park, M. Murakami, Y. Kitamura, Y. Iwakura, and T. Hirano. The point mutation of Y759 of the IL-6 family receptor gp130 synergizes with HTLV-1 pX in promoting RA-like arthritis. Int. Immunol. 16: 455-465, 2004
18) Sawa, S., D. Kamimura, G.-H. Jin, H. Morikawa, H. Kamon, M. Nishihara, K. Ishihara, M. Murakami, and T. Hirano. Autoimmune arthritis associated with mutated IL-6 receptor gp130 is driven by STAT3/IL-7-dependent homeostatic proliferation of CD4+ T cells. J. Exp. Med. 203:1459-1470, 2006
19) Nishihara, M., H. Ogura, N. Ueda, M. Tsuruoka, C. Kitabayashi, F. Tuji, H. Aono, K. Ishihara, E. Huseby, U. A.K.Betz, M. Murakami and T. Hirano. IL-6-gp130-STAT3 in T cells directs the development of IL-17+T helper cells with a minimum effect on that of Treg in the steady state. Int. Immunol. 19(6): 695-702, 2007
20) Ogura, H., M. Murakami, Y. Okuyama, M. Tsuruoka, C. Kitabayashi, M. Kanamoto, M. Nishihara, Y. Iwakura and T. Hirano. Interleukin-17 promotes autoimmunity by triggering a positive feedback loop via interleukin-6 induction. Immunity, 29:628-636, 2008

Legends for Figures

Figure 1. Interleukin6 is a gift from patients with tuberculosis.
I worked in Osaka Prefectural Habikino Hospital where I saw many patients with tuberculous pleurisy and we found pleural effusion cells when stimulated with purified protein derivative (PPD) produced factors being able to induce immunoglobulin production in B lymphocytes in 1978. We started isolating these factors and we found one of active factors had similar biological activity and physicochemical properties with those of a cytokine, now called interleukin 6. Therefore, for me, interleukin 6 is a gift from patients with tuberculosis.

Figure 2. The name of “interleukin 6”, which has multiple functions, was born.
Our study together with other studies showed that BSF-2 was identical with interferon-β2, 26kDa protein, plasmacytoma/hybridoma/myeloma growth factor and hepatocyte stimulating factor. The nomenclature meeting proposed the name of “interleukin-6” for this molecule in 1988. Thus, the name of “interleukin-6” was born. IL-6 is now known to be a multifunctional cytokine that plays roles in the immune response, inflammation, hematopoiesis, in the endocrine and nervous systems.

Figure 3. A working hypothesis of possible mechanisms involved in autoimmune diseases, chronic inflammatory proliferative disease (CIPD) like RA
The constitutive activation of a set of transcription factors, such as NF-kB, is the central factor governing the onset as well as the progression of autoimmune diseases and CIPD. In the initial phase, the activation of the transcription factors is induced by a variety of stimuli, including infection, stimulation with foreign materials, and injury. This initial stimulation induces inflammation that activates a set of transcription factors, leading to the expression of various genes encoding cellular proteins, such as IL-6 and other cytokines, MHC molecules, adhesion molecules, giving rise to the activation of immune system. Since the first phase could be induced in non-immune cells or tissues, this hypothesis suggested the interaction between the non-immune and immune system plays a critical role in autoimmune diseases and CIPD.

Figure 4. Dysregulation of IL-6 signaling spontaneously induces RA-like arthritis with age.
IL-6 receptor is composed of two subunits, one is an IL-6 specific subunit, alpha chain and the other is a signal transducer, gp130. IL-6 induces two major signaling pathways, one is mediated by STAT3 and the other SHP2/GAB through tyrosine residues of go130 with YxxQ motif and tyrosine 759 of gp130, respectively. F759 mice, which express mutated gp130 (Y759F) defective of SOCS3-mediated negative feedback, spontaneously develop RA-like arthritis with age.

Figure 5. The interaction between the non-immune and immune system through an “IL-6 amplifier” plays a role in autoimmune diseases and CIPD.
“IL-6 amplifier”, which is dependent on NF-kB and STAT3 plays an important role in causing F759 arthritis. It is speculated that any event, any reagent, any pathogen, capable of chronically activating either or both NF-kB and STAT3 plays a role in RA and this scenario might be applied in autoimmune diseases and CIPD in general.