Interleukin 2-dependent and interleukin 2-independent pathways of regulation of thymocyte function by interleukin 6

Interleukin 6 Antagonists in Severe COVID-19 Disease: Cardiovascular and Respiratory Outcomes

BACKGROUND

Inhibitors of interleukin 6 [IL-6] have been utilized to treat severe COVID-19 disease. Their immunosuppressive or immunomodulating impact may be beneficial in COVID-19.

OBJECTIVES

To discuss the role of IL-6 inhibitors and assess various trials conducted to evaluate the efficacy of IL-6 inhibitors in COVID-19 disease.

SUMMARY

Two of the most common causes of mortality in COVID-19-infected critically ill individuals are acute respiratory distress syndrome (ARDS) and multiorgan failure. Increased levels of inflammatory cytokines suggest that a cytokine storm, also known as cytokine release syndrome (CRS), is involved in the etiology of COVID-19. Most tissue damage, sepsis, and pulmonary and cardiovascular problems are caused mainly by the host defense system. Therefore, regulating this inflammatory cascade using immunomodulators is a prudent strategy. Although corticosteroids, as immunomodulators, are routinely used in COVID-19 management, interleukin (IL) inhibitors, especially IL-6 inhibitors, are also tested in many trials. Many studies have demonstrated that IL-6 inhibitors improve disease outcomes and decrease mortality, whereas others have shown that they are ineffective. In this paper, we briefly examined the role of IL-6 in COVID-19 pathogenesis and trials that support or refute the use of IL-6 inhibitors in treating COVID-19 disease.

RESULTS

Though mixed results are coming from trials regarding the adjuvant use of IL-6 inhibitors and standard anti-viral therapy with dexamethasone, a consensus favors using IL-6 inhibitors in severely ill COVID-19 patients regardless of the outcome.

Contribution of Interleukin-6 to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology, manifesting in patients as tissue fibrosis, endothelial dysfunction, and inflammation. The disease is characterized by autoantibodies, a hallmark of autoimmunity. Various cytokines and growth factors are elevated in the systemic circulation and fibrotic lesions of patients with SSc. In particular, several studies over the past 2 decades have shown that interleukin-6 (IL-6) appears to be involved in the pathogenesis of SSc. Based on the association between aberrant IL-6 production and tissue fibrosis in patients with SSc, the anti-IL-6 receptor antibody, tocilizumab, is being investigated in clinical trials. This article reviews the biological features of IL-6 and the IL-6 receptor; the role of IL-6 in the pathogenesis of SSc; and the potential for IL-6 inhibition to be used in the treatment of patients with SSc.

Inhibition of U937 Cytokine Secretion by HIV-1 gp120 C4-Derived Peptide Constructs

Lipopolysaccharide (LPS) stimulation of the human promyelomonocytic cell line U937 results in interleukin 6 and interleukin 10 secretion. Modulation of cytokine secretion in response to LPS may be possible through binding of ligands to surface receptors. A peptomer, containing multiple repeat units of the CD4-binding C4 region of HIV-1 gp120, and the monomeric C4 peptide each were investigated for their ability to affect LPSinduced IL-6 and IL-10 secretion. The peptomer inhibited IL-6 and IL-10 secretion, while the monomer inhibited only IL-6 secretion. Larger CD4-binding proteins, specifically gp120 and Leu3A, a CD4-directed monoclonal antibody, had no effect on the LPS response. PMA differentiation to downregulate CD4 expression did not reverse the inhibitory effect of the peptomer or peptide, suggesting a CD4-independent effect. Bioactivity changed markedly with different constructs in the presence of IFN. with reversal or enhancement of the IL-10 response but not IL-6 production. These results suggest that truncation of a larger polypeptide may result in constructs with novel binding capabilities and bioactivities not seen in parent proteins.

Suppressor of cytokine signaling 4 (SOCS4) protects against severe cytokine storm and enhances viral clearance during influenza infection

Suppressor of cytokine signaling (SOCS) proteins are key regulators of innate and adaptive immunity. There is no described biological role for SOCS4, despite broad expression in the hematopoietic system. We demonstrate that mice lacking functional SOCS4 protein rapidly succumb to infection with a pathogenic H1N1 influenza virus (PR8) and are hypersusceptible to infection with the less virulent H3N2 (X31) strain. In SOCS4-deficient animals, this led to substantially greater weight loss, dysregulated pro-inflammatory cytokine and chemokine production in the lungs and delayed viral clearance. This was associated with impaired trafficking of influenza-specific CD8 T cells to the site of infection and linked to defects in T cell receptor activation. These results demonstrate that SOCS4 is a critical regulator of anti-viral immunity.

The suppressor of cytokine signaling proteins are key regulators of immunity. As yet there is no described biological role for SOCS4, despite its broad expression in cells of the immune system. Given the important role of other SOCS proteins in controlling the immune response, we have generated SOCS4-mutant mice and used a mouse influenza infection model to investigate the biological function of SOCS4. We demonstrate that mice lacking SOCS4 rapidly succumb to infection with a pathogenic H1N1 influenza virus and are hypersusceptible to infection with the less virulent H3N2 strain. This is the first demonstration of a functional phenotype in SOCS4-deficient mice. Our study reveals that in SOCS4-deficient animals, there is a dysregulated pro-inflammatory cytokine and chemokine production in the lungs and delayed viral clearance. This is associated with impaired trafficking of virus-specific CD8 T cells to the site of infection and linked to defects in T cell receptor activation. These results demonstrate that SOCS4 is a critical regulator of anti-viral immunity. Understanding the regulation of the inflammatory response to influenza is particularly relevant given the current climate concerning pandemic influenza outbreaks.

Estimation of the potential antitumor activity of microencapsulated Lactobacillus acidophilus yogurt formulation in the attenuation of tumorigenesis in Apc(Min/+) mice

There is a strong correlation between orally administered probiotics and suppression of the low-grade inflammation that can lead to restoration of normal local immune functions. We studied the potential immunomodulatory and antitumorigenic properties of microencapsulated probiotic bacterial cells in a yogurt formulation in Min mice carrying a germline APC mutation. Daily oral administration of microencapsulated Lactobacillus acidophilus bacterial cells in the yogurt formulation mice resulted in significant suppression of colon tumor incidence, tumor multiplicity, and reduced tumor size. Results show that oral administration of microencapsulated L. acidophilus contributed to the stabilization of animal body weight and decreased the release of bile acids. Histopathological analyses revealed fewer adenomas in treated versus untreated animals. Furthermore, treated animals exhibited fewer gastrointestinal intra-epithelial neoplasias with a lower grade of dysplasia in detected tumors. Results suggest that oral administration of microencapsulated probiotic L. acidophilus exerts anti-tumorous activity, which consequently leads to reduced tumor outcome.

Lymphocyte/macrophage interactions: biomaterial surface-dependent cytokine, chemokine, and matrix protein production

The role of lymphocytes in the biological response to synthetic polymers is poorly understood despite the transient appearance of lymphocytes at the biomaterial implant site. To investigate cytokines, chemokines, and extracellular matrix (ECM) proteins produced by lymphocytes and macrophages in response to biomaterial surfaces, human peripheral blood monocytes and lymphocytes were co-cultured on polyethylene terephthalate (PET)-based material surfaces displaying distinct hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic chemistries. Antibody array screening showed the majority of detected proteins are inflammatory mediators that guide the early inflammatory phases of wound healing. Proteomic ELISA quantification and adherent cell analysis were performed after 3, 7, and 10 days of culture. IL-2 and IFN-gamma were not detected in any co-cultures suggesting lack of lymphocyte activation. The hydrophilic/neutral surfaces increased IL-8 relative to the hydrophobic PET surface (p < 0.05). The hydrophilic/anionic surfaces promoted increased TNF-alpha over hydrophobic and cationic surfaces and increased MIP-1beta compared to hydrophobic surfaces (p < 0.05). Since enhanced macrophage fusion was observed on hydrophilic/anionic surfaces, the production of these cytokines likely plays an important role in the fusion process. The hydrophilic/cationic surface promoted IL-10 production and increased matrix metalloproteinase (MMP)-9/tissue inhibitor of MMP (TIMP) relative to hydrophilic/neutral and anionic surfaces (p < 0.05). These results suggest hydrophilic/neutral and anionic surfaces promote pro-inflammatory responses and reduced degradation of the ECM, whereas the hydrophilic/cationic surfaces induce an anti-inflammatory response and greater MMP-9/TIMP with an enhanced potential for ECM breakdown. The study also underscores the usefulness of protein arrays in assessing the role of soluble mediators in the inflammatory response to biomaterials.

Immunomodulatory Activities of HERBSnSENSES™Cordyceps—in Vitroandin VivoStudies

The commercially available HERBSnSENSEStrade mark Cordyceps (HSCS) belongs to a cultivated strain of Cordyceps sinensis whose immunomodulatory activities has been renowned in traditional Chinese medicine (TCM) for centuries. The present report is the first that describes its immunomodulatory features through a series of in vitro and in vivo experiments. We measured, in peripheral blood mononuclear cells the in vitro effects of HSCS on the gene expression of cytokines and cytokine receptors, cytokine release, and surface expression of cytokine receptors using cDNA expression array, cytometric bead array (CBA), and immunoflorescence staining, respectively, as well as macrophage phagocytosis and monocyte production of H2O2 using flow cytometry. Sixty female BALB/c mice were fed with either HSCS (40 mg/kg/day) or water consecutively for 14 days. Proliferation, cytokine liberation, and CD3/4/8 expression of splenic cells were measured using 5-bromo-2'-deoxyuridine proliferation ELISA, CBA, and cytometry immunoflorescence staining, respectively. In vitro results demonstrated that HSCS induced the production of interleukin(IL)-1beta, IL-6, IL-10 and tumor necrosis factor alphaalpha from PBMC, augmented surface expression of CD25 on lymphocytes, and elevated macrophage phagocytosis and monocyte production of H2O2. In vivo results showed that HSCS did not induce splenomegaly and cytokine overliberation. Our results possibly provide the biochemical basis for future clinical trials.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

Proinflammatory cytokine responses induced by influenza A (H5N1) viruses in primary human alveolar and bronchial epithelial cells

Background

Fatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia. We previously demonstrated that patients with H5N1 disease had unusually high serum levels of IP-10 (interferon-gamma-inducible protein-10). Furthermore, when compared with human influenza virus subtype H1N1, the H5N1 viruses in 1997 (A/Hong Kong/483/97) (H5N1/97) were more potent inducers of pro-inflammatory cytokines (e.g. tumor necrosis factor-a) and chemokines (e.g. IP-10) from primary human macrophages in vitro, which suggests that cytokines dysregulation may play a role in pathogenesis of H5N1 disease. Since respiratory epithelial cells are the primary target cell for replication of influenza viruses, it is pertinent to investigate the cytokine induction profile of H5N1 viruses in these cells.

Methods

We used quantitative RT-PCR and ELISA to compare the profile of cytokine and chemokine gene expression induced by H5N1 viruses A/HK/483/97 (H5N1/97), A/Vietnam/1194/04 and A/Vietnam/3046/04 (both H5N1/04) with that of human H1N1 virus in human primary alveolar and bronchial epithelial cells in vitro.

Results

We demonstrated that in comparison to human H1N1 viruses, H5N1/97 and H5N1/04 viruses were more potent inducers of IP-10, interferon beta, RANTES (regulated on activation, normal T cell expressed and secreted) and interleukin 6 (IL-6) in primary human alveolar and bronchial epithelial cells in vitro. Recent H5N1 viruses from Vietnam (H5N1/04) appeared to be even more potent at inducing IP-10 than H5N1/97 virus.

Conclusion

The H5N1/97 and H5N1/04 subtype influenza A viruses are more potent inducers of proinflammatory cytokines and chemokines in primary human respiratory epithelial cells than subtype H1N1 virus. We suggest that this hyper-induction of cytokines may be relevant to the pathogenesis of human H5N1 disease.

Autonomic innervation of immune organs and neuroimmune modulation

1. Increasing evidence indicates the occurrence of functional interconnections between immune and nervous systems, although data available on the mechanisms of this bi-directional cross-talking are frequently incomplete and not always focussed on their relevance for neuroimmune modulation. 2. Primary (bone marrow and thymus) and secondary (spleen and lymph nodes) lymphoid organs are supplied with an autonomic (mainly sympathetic) efferent innervation and with an afferent sensory innervation. Anatomical studies have revealed origin, pattern of distribution and targets of nerve fibre populations supplying lymphoid organs. 3. Classic (catecholamines and acetylcholine) and peptide transmitters of neural and non-neural origin are released in the lymphoid microenvironment and contribute to neuroimmune modulation. Neuropeptide Y, substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide represent the neuropeptides most involved in neuroimmune modulation. 4. Immune cells and immune organs express specific receptors for (neuro)transmitters. These receptors have been shown to respond in vivo and/or in vitro to the neural substances and their manipulation can alter immune responses. Changes in immune function can also influence the distribution of nerves and the expression of neural receptors in lymphoid organs. 5. Data on different populations of nerve fibres supplying immune organs and their role in providing a link between nervous and immune systems are reviewed. Anatomical connections between nervous and immune systems represent the structural support of the complex network of immune responses. A detailed knowledge of interactions between nervous and immune systems may represent an important basis for the development of strategies for treating pathologies in which altered neuroimmune cross-talking may be involved.

Temperature alters lipopolysaccharide-induced cytokine secretion by RAW 264.7 cells

Local and systemic temperature change is associated with the immune response to infection, but the role of temperature remains poorly understood. To study the effect of temperature on macrophage activation by lipopolysaccharide (LPS), RAW 264.7 cells were incubated with LPS at different temperatures and secretion of three cytokines was measured. Incubation at 31 degrees C increased tumour necrosis factor (TNF) secretion when compared with 37 degrees C, while cells exposed at 39 degrees C secreted less TNF. Interleukin-6 (IL-6) secretion was less at 31 degrees C than at 37 degrees C and remained unchanged at 39 degrees C. Interleukin-10 secretion was depressed on either side of 37 degrees C. Only IL-6 secretion was sensitive to preincubation temperature effects. The kinetics of cytokine secretion and steady-state mRNA analysis indicated potentially different mechanisms of temperature regulation for TNF and IL-6.

Induction of cytokine production by different Staphylococcal strains

In light of the important role of cytokines in the pathogenesis of bacterial infections, we analyzed the cytokine production induced by different Staphylococcus aureus (S. aureus), S. epidermidis and S. saprophyticus strains in human mononuclear cells (MNCs). MNCs secreted high amounts of interleukin-1beta (IL-1beta) and IL-6 proteins in responses to stimulation with all three species of Staphylococci. Interestingly, a large majority of the S. aureus strains induced significantly higher IL-12 and interferon (IFN) titers than did the S. epidermidis and S. saprophyticus strains. The RNase protection assay revealed high increases in IL-1alpha, IL-1 beta, IL-1 receptor antagonist, IL-6 and IL-12 p40 transcript levels in MNCs stimulated with Staphylococci. All of the tested Staphylococcal strains proved highly efficient in mediating the induction of these genes. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis indicated considerable increases in IFNA transcript levels in MNCs stimulated with S. aureus strains, while only a very weak expression was stimulated by S. epidermidis and S. saprophyticus. These results confirm that heat-killed Staphylococci exert strong immunomodulatory effects, and suggest that the contribution of T-helper 1 (Th(1)) cells to the immune response may be much extensive in infections caused by S. aureus strains, due to their high IL-12p70 and IFN-alpha-inducing activities.

In vitro cytokine production and proliferation of T cells from patients with anti-proteinase 3- and antimyeloperoxidase-associated vasculitis, in response to proteinase 3 and myeloperoxidase

OBJECTIVE

To investigate in vitro proliferative responses of CD4+ T cells and generation of specific cytokines induced by stimulation of peripheral blood mononuclear cells (PBMCs) from patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis with the autoantigens proteinase 3 (PR3) and myeloperoxidase (MPO).

METHODS

PBMCs from vasculitis patients with PR3 ANCA or MPO ANCA and from healthy controls were stimulated for 7 days with PR3, MPO, or control stimuli. Proliferation of CD4+ T cells was assessed by flow cytometry, using the proliferation marker Ki-67. Levels of the pro-proliferative cytokines interleukin-2 (IL-2) and IL-6 and of the Th1 and Th2 cytokines interferon-gamma (IFN gamma) and IL-10 in culture supernatants were determined.

RESULTS

PR3 and MPO induced proliferative responses in CD4+ T cells from individual patients with ANCA-associated vasculitides and healthy controls in vitro. Neither PR3 nor MPO elicited significant IL-2 production. Levels of IL-6 were highest after stimulation with PR3 but low after stimulation with MPO, independent of study group. Stimulation with PR3, and to a lesser extent with MPO, induced a Th2 cytokine milieu, characterized by high production of IL-6 and IL-10 and low production of IFN gamma in patients and controls.

CONCLUSION

PR3 and MPO promote proliferation of CD4+ T cells from patients with ANCA-associated vasculitides, but also cross-stimulate T cells from healthy individuals. Strong IL-10 production elicited by PR3 in vitro may act as an inhibitory signal for T cell proliferation and may have an important immunoregulatory function in vivo.

The paradigm of IL-6: from basic science to medicine

IL-6 is a pleiotropic cytokine with a wide range of biological activities in immune regulation, hematopoiesis, inflammation, and oncogenesis. Its activities are shared by IL-6-related cytokines such as leukemia inhibitory factor and oncostatin M. The pleiotropy and redundancy of IL-6 functions have been identified by using a unique receptor system comprising two functional proteins: an IL-6 receptor (IL-6R) and gp130, the common signal transducer of cytokines related to IL-6. Signal transduction through gp130 is mediated by two pathways: the JAK-STAT (Janus family tyrosine kinase-signal transducer and activator of transcription) pathway and the Ras mitogen-activated protein kinase pathway. The negative regulators of IL-6 signaling have also been identified, although the physiological roles of the molecules are not yet fully understood. The pathological roles of IL-6 have also been clarified in various disease conditions, such as inflammatory, autoimmune, and malignant diseases. On the basis of the findings, a new therapeutic approach to block the IL-6 signal using humanized anti-IL-6R antibody for rheumatoid arthritis, Castleman's disease, and multiple myeloma has been attempted.

Polymorphonuclear leukocyte rigidity is defective in patients with chronic renal failure

BACKGROUND

The purpose of the study was to investigate the rigidity of polymorphonuclear leukocytes (PMNs) in non-dialysed chronic renal failure (CRF) and haemodialysis (HD) patients.

METHODS

PMN rigidity as well as tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) plasma levels were assessed in 10 early-stage CRF, 10 late-stage non-HD, and 10 HD patients, before and during dialysis. In HD patients both cellulose acetate and polysulphone membranes were used. Ten healthy subjects served as controls. Rigidity was tested by counting the deformability in morphologically passive PMNs by the micropipette method. Cytokine levels were measured by enzyme-linked immunosorbent assay.

RESULTS

PMN rigidity was significantly increased in end-stage CRF patients regardless of HD but not in early-stage CRF. In HD patients PMN rigidity increased significantly 60 min after initiation of HD. There was an increase of TNF-alpha and IL-1beta levels in end-stage non-HD and HD patients and a further increase at 60 min after initiation of HD. The percentage of morphologically activated PMNs was increased only during dialysis. The nature of the HD membrane had no influence on rigidity, PMN activation, or cytokine production.

CONCLUSIONS

The results indicate that PMN rigidity is defective in end-stage chronic CRF patients and is further increased 60 min after initiation of HD, regardless of the nature of the HD membrane used. PMN activation, increased TNF-alpha and IL-1beta levels, or a direct PMN impairment may cause the observed cell rigidity.

Anti-interleukin 6 receptor antibody treatment in rheumatic disease

Interleukin 6 (IL6) is a pleiotropic cytokine with a wide range of biological activities. IL6 transgene into mice gives rise to the abnormalities such as hypergammaglobulinaemia, thrombocytosis, infiltration of inflammatory cells into the tissues, mesangial cell proliferation of the kidney as well as splenomegaly and lymphadenopathy, which are predictable by the biological functions of IL6 shown in vitro. Continuous overproduction of IL6 is observed in patients with some immune-inflammatory diseases such as Castleman's disease and rheumatoid arthritis that are frequently associated with similar abnormalities to those of IL6 transgenic mice, strongly suggesting the involvement of IL6 in the human diseases. Successful treatment of the model animals for immune-inflammatory diseases with anti-IL6 receptor (IL6R) antibody thus indicates the possible application of IL6 blocking agents to treat the IL6 related immune-inflammatory diseases of humans. In this review, the new therapeutic strategy for Castleman's disease and RA using humanized antibody to human IL6 receptor, MRA, is discussed.

Divergent cell-specific effects of activin-A on thymocyte proliferation stimulated by phytohemagglutinin, and interleukin 1beta or interleukin 6 in vitro

Activin-A is a member of the transforming growth factor-beta (TGF-beta) cytokine family. Based on studies in several cell systems, activin-A has been postulated to be a specific inhibitor of the actions of the inflammatory cytokine, interleukin 6. In cultures of adult rat thymocytes, activin-A inhibited sub-optimal phytohemagglutinin-induced and interleukin 1beta-stimulated proliferation, as measured by [(3)H]-thymidine incorporation in vitro. In contrast with TGF-beta1, which exerted similar inhibitory effects on thymocyte proliferation, activin-A activity was reduced by increasing the concentration of phytohemagglutinin or addition of the reducing agent, beta-mercaptoethanol. Both activin-A and TGF-beta1 inhibited the in vitro production of interleukin 6 by thymocytes in the presence of phytohemagglutinin and interleukin 1beta. In the presence of exogenous interleukin 6, however, both activin-A and TGF-beta1 stimulated thymocyte proliferation. These data suggest that activin-A inhibits thymocyte growth and differentiation, at least in part, by inhibiting endogenous production of interleukin 6, but stimulates thymocyte growth when exogenous interleukin 6 is present in vitro. These data indicate that activin interacts with other cytokines to exert complex regulation of T cell development, and is not an inhibitor of interleukin 6 action in all cell systems.

Catecholamines and lipopolysaccharide synergistically induce the release of interleukin-6 from thymic epithelial cells

The thymus as the major site of T-cell development is exposed to circulating hormones as well as to neurotransmitters released from peripheral nerves. We investigated the influence of catecholamines on the synthesis of interleukin-1 (IL-1) and IL-6 by cultured rat thymic epithelial cells. Basal or lipopolysaccharide (LPS)-stimulated production of IL-1 was not affected by catecholamines. Release of IL-6 was stimulated only scarcely by catecholamines or tumor necrosis factor-alpha (TNF-alpha) and moderately by LPS alone. However, co-stimulation with adrenaline, noradrenaline, or the beta-adrenoceptor agonist isoproterenol (isoprenaline) had an additive (TNF-alpha) or synergistic (LPS) effect on IL-6 release. The synergistic effect was dose-dependent on catecholamine or LPS concentrations. It was mediated by beta-adrenoceptors that are linked to elevation of intracellular cAMP levels, since it was promoted by beta-adrenoceptor agonists and could be blocked by beta-adrenoceptor antagonists. Co-incubation of LPS with agents directly raising cAMP-levels like forskolin or dibutyryl cAMP yielded even stronger IL-6 induction. After co-stimulation IL-6 mRNA was first detected after 3-4 h and a constant increase of IL-6 bioactivity in the culture supernatant was measured for up to 48 h. Since IL-6 is an important factor for thymocyte differentiation and proliferation, the findings demonstrate an influence of neuronal or hormonal catecholamines on the thymic microenvironment that is created by thymic epithelial cells.

Elevated serum levels of the soluble form of gp130, the IL-6 signal transducer, in HTLV-1 infection and no involvement of alternative splicing for its generation

By using an ELISA, increased levels of the soluble form (sgp130) of gp130, the IL-6 signal transducer, were detected in the sera of various HTLV-1-associated conditions (HC, ATL, HAM) as compared to normal healthy individuals. Sgp130 levels seemed to be correlated with disease severity. The 94 KD of sgp130 was specifically precipitated in the sera of HTLV-1-infected patients as revealed by Western blot analysis. A reverse transcriptase (RT)-polymerase chain reaction (PCR) method was used to detect the message for transmembrane (TM) lacking gp130 in mRNA isolated from peripheral blood mononuclear cells (PBMCs) of patients infected with or without HTLV-1 and those of various hematopoietic cell lines. Two PCR products, 648 and 507 bp were observed in the PBMCs from HTLV-1-infected patients. But the 507 by PCR product was not detected in the PBMCs from normal healthy individuals and HTLV-1-positive cell lines although the 648 bp product was equally expressed. A nucleotide sequence analysis of the 507 bp fragment showed deletion of the 141 bp at the region spanning from nucleotide 1702 (G) to 1842 (T) of the 648 bp product that matched completely with a conventional gp130 molecule. This deleted region was located upstream of the transmembrane (TM) domain, but not within the TM region itself. However, no frame shift was observed. These results indicate that the generation of sgp130 may not be due to an alternative splicing mechanism.

Impairment of antigen-specific antibody production in transgenic mice expressing a dominant-negative form of gp130

gp130 is a common signal-transducing receptor component for the interleukin 6 family of cytokines functioning in, for example, immune, hematopoietic, and nervous systems. In this study, to investigate the physiological functions of gp130 and to determine the pathological consequences of impaired gp130 signals, we have generated transgenic mice expressing a cytoplasmically truncated form of mouse gp130. Expression of this form of gp130 in lymphocytes significantly suppressed interleukin 6-induced tyrosine phosphorylation of endogenous gp130 and a downstream signaling molecule, signal transducer and activator of transcription 3, indicating that this form has a dominant negative function. In spite of the impaired gp130 signals, the development of lymphocytes in the transgenic mice appeared normal in terms of surface marker phenotypes. These mice, however, exhibited severe defects in antigen-specific antibody production of most immunoglobulin isotypes other than IgM after immunization with 2,4-dinitrophenol-conjugated ovalbumin. These results demonstrate in vivo that gp130 is essential for antigen-specific antibody production.

Analysis of lymphoproliferative cytokines produced by thymic myoid cells

Lymphoproliferative activities produced by cloned thymic myoid cell 871207B were analysed by immunological and biochemical methods. The lymphoproliferative activities were separated into two fractions by DEAE-Sepharose CL-6B chromatography: one is in the fraction passed through the column and the other in the fraction eluated from the column with a low concentration of NaCl. The eluated fraction induced the proliferation of interleukin-1 (IL-1)-dependent D10N4 M cells. This activity was abrogated by an anti-IL-1 alpha antibody, but not an anti-IL-1 beta antibody. Expression of IL-1 alpha mRNA was also detected in 871207B cells. The thymocyte proliferative activity found in the fraction passed through the DEAE-Sepharose column was further separated into three fractions by heparin-Sepharose column chromatography: (1) the fraction passed through the column, (2) the fraction weakly bound to the column, and (3) the fraction firmly bound to the heparin column. The fraction passed through the heparin column sustained the growth of IL-6-dependent MH60.BSF-2 cells. IL-6-specific mRNA was found in 871207B cells. The thymocyte proliferative activity of the fraction firmly bound to the heparin column was neutralized with an anti-IL-7 antibody. The biological activity of the fraction weakly bound to the column remained to be elucidated. These results suggest that thymic myoid cells produce IL-1 alpha, IL-6, IL-7 and unidentified lympho-stimulatory factors, all of which play significant roles in many steps of T-cell development in the thymus.

IL-6 cytokine family and signal transduction: a model of the cytokine system

The interleukin 6 (IL-6) cytokine family, which includes IL-6, leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor (CNTF), IL-11 and cardiotrophin-1 (CT-1), exhibits pleiotropy and redundancy in biological activities. The IL-6 family cytokines exhibit a helical structure. Their receptors belong to the type 1 cytokine receptor family. The receptors of the IL-6 family cytokines share a receptor subunit, which explains one of the mechanisms of functional redundancy. In this review, we describe the general features of the IL-6 cytokine family and its signal transduction mechanisms. Many functional properties of the IL-6 family of cytokines and their receptors are general features of the cytokine system.

Bacterial stimulators of macrophages

Our current understanding of the interaction between bacteria and macrophages, cells of the immune system that play a major role in the defense against infection, is summarized. Cell-surface structures of Gram-negative and Gram-positive bacteria that account for these interactions are described in detail. Besides surface structures, soluble bacterial molecules, toxins that are derived from pathogenic bacteria, are also shown to modulate macrophage functions. In order to affect macrophage functions, bacterial surface structures have to be recognized by the macrophage and toxins have to be taken up. Subsequently, signal transduction mechanisms are initiated that enable the macrophage to respond to the invading bacteria. To destroy bacteria, macrophages employ many strategies, among which antigen processing and presentation to T cells, phagocytosis, chemotaxis, and different bactericidal mechanisms are considered to be the main weapons.

Interleukin-6 response to laparoscopic and open colectomy

PURPOSE

It has been postulated that cortisol and interleukin-6 play a significant role in the modulation of the early inflammatory response following surgical intervention. There are no available data on the normal responses of these mediators following major laparoscopic procedures. The purpose of this study was to assess changes in cortisol (by fluorescence polarization immunoassay), interleukin-6 (by enzyme-linked immunoassay), and interleukin-1 (by enzyme-linked immunoassay) after elective laparoscopic colon resections.

METHODS

All patients undergoing colon resection between February 1, 1992 and April 30, 1992 were eligible for study. Selection of laparoscopic (N = 12) vs. open (N = 41) resection was determined by the attending surgeon. All patients received a standard general anesthetic with endotracheal intubation. Cortisol, interleukin-6, and interleukin-1 were measured at preinduction, 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours after the induction. Interleukin-6 and interleukin-1 were additionally measured at 12 hours, 24 hours, and 72 hours after induction. Comparisons were made between the laparoscopic patients (N = 12) and age, sex, and operation-matched open patients (N = 12).

RESULTS

Cortisol levels rose in the early postoperative period in both open and laparoscopic groups with no significant differences occurring between the cohorts at any of the measured time intervals. The interleukin-6 levels of the laparoscopic cohort (N = 12) were significantly lower than those of the open cohort (N = 12) between 3 and 24 hours postinduction (P < 0.05). Interleukin-1 levels remained undetectable in virtually all patients irrespective of operative technique or postoperative interval. There was no correlation between peak interleukin-6 levels and operative times (laparoscopic, r = 0.31; open, r = 0.36) or blood loss (laparoscopic, r = 0.10; open, r = 0.20).

CONCLUSION

The results indicate that laparoscopic colon resections do not appear to alter cortisol or interleukin-1 responses when compared with open colon resection. There is, however, a significant blunting of the interleukin-6 response associated with the use of laparoscopic techniques for colectomy compared with standard laparotomy.

Interleukin-6 exacerbates glomerulonephritis in (NZB x NZW)F1 mice

The ability of interleukin-6 (IL-6) to modulate immune parameters and mesangial cell function suggests a role for this cytokine in the development of autoimmune glomerulonephritis. This hypothesis was tested in 6-month-old female (NZB x NZW)F1 mice that were administered recombinant human IL-6 (rhIL-6) (50 and 250 micrograms/kg s.c.) for 12 weeks, resulting in an accelerated and severe form of membranoproliferative glomerulonephritis associated with marked upregulation of mesangial major histocompatibility complex class II antigen and glomerular ICAM-1 expression. To distinguish direct effects of rhIL-6 on the renal mesangium from those mediated through the immune system, (NZB x NZW)F1 mice were immunosuppressed with cyclosporin. Immunosuppression by cyclosporin inhibited the development of glomerulonephritis, decreased class II antigen expression, and abrogated IL-6-mediated effects. Administration of neutralizing anti-IL-6 antibody had no effect on the spontaneous development of glomerulonephritis in (NZB x NZW)F1 mice. This finding, together with undetectable IL-6 serum levels, makes a pathogenetic role of endogenously produced IL-6 in this disease model unlikely. In contrast to (NZB x NZW)F1 mice, parental NZW or BALB/c mice given high doses of rhIL-6 (500 micrograms/kg) or recombinant murine IL-6 (100 micrograms/kg) daily for 4 weeks failed to develop morphological or biochemical evidence of glomerulonephritis. Induction of acute phase proteins, anemia, thrombocytosis, and induction of renal class II antigen confirmed the biological activity of IL-6 in these mice. In conclusion, while non-nephritogenic in normal mice, IL-6 accelerates the development of the genetically determined glomerulonephritis of (NZB x NZW)F1 mice through effects mediated by a modulated immune system. Since neutralizing IL-6 antibody treatment did not prevent the development of glomerulonephritis, it is unlikely that increased IL-6 production plays a role in the pathogenesis of lupus nephritis.

Signal transduction through gp130 that is shared among the receptors for the interleukin 6 related cytokine subfamily

Interleukin 6 (IL-6) and related cytokines, such as leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor (CNTF) and IL-11 exhibit multiple functions and redundancy in biological activities and play important roles in the immune response, hematopoiesis, the nervous system and acute phase reactions. These IL-6 family cytokines exhibit a similar helical structure, and their receptors are structurally similar and constitute a cytokine receptor super family. In addition, a receptor subunit is shared among these IL-6 related cytokine subfamily receptors, contributing to one of the mechanisms of functional redundancy of cytokine activities and suggesting the presence of a common signal transduction pathway among these receptors. In this review, we describe the structure of the receptors for IL-6 and its related cytokine subfamily members. Furthermore, we propose a novel mechanism for the generation of cytokine diversity, i.e. the complex of a cytokine and one of its receptor subunits act as a novel cytokine on the cells that express the other receptor subunit(s) capable of acting as a receptor for the complex. Finally, we describe a Ras-independent novel signal transduction pathway that utilizes Jak tyrosine kinase family, Stat protein family and yet unidentified H-7-sensitive pathway. This signal transduction pathway is commonly generated through the receptors for a wide range of cytokines and growth factors.

Overexpression and characterization of recombinant human fusion protein IL-6/IL-2 (CH925)

An expression vector encoding the human recombinant fusion protein interleukin 6/interleukin 2 (IL-6/IL-2) was constructed. When a flexible linker had been synthesized and ligated with the IL-2 gene fragment by polymerase chain reaction (PCR) amplification, the IL-6 gene fragment was unidirectionally inserted into the upstream of the linker-IL-2 sequence. The molecule of the IL-6-linker-IL-2 fusion gene named E. coli DH5 alpha/pfIL-6/2 was cloned and identified by DNA sequencing. The expressed protein named as CH925 showed a strong band on SDS-PAGE and amounted to 32% of total cell protein, and its estimated molecular weight was about 37 kDa. The fusion protein purified by gel filtration and reversed-phase HPLC showed as almost homogeneous. CH925 possesses both IL-2 and IL-6 activities when assayed by CTLL2- and 7TD1-dependent cell lines, respectively. The specific activity of IL-2 was 2.1 x 10(6) U/mg while that of IL-6 was 2.3 x 10(8) U/mg. Our studies exhibited that CH925 exerted a significant augmentative effect on the growth of erythroid colony forming units (CFU-E), and synergized with erythropoietin (EPO) and/or IL-3 in a dose-dependent way. Our experimental results also showed CH925 at a low dose causing active lymphokine-activated killer (LAK) cell proliferation more vigorous than IL-2 and/or IL-6 (p < 0.001). CH925 is a novel fusion protein, being neither IL-6 nor IL-2, more potent than IL-2 and/or IL-6 and causing non-IL-2 and non-IL-6 functions of strong EPO-like and mild IL-3-like effects on erythroid progenitor cell growth. There is a potential for efficacious clinical application of CH925.

Endogenous IL-10 and IFN-gamma production controls thymic cell proliferation in mice acutely infected by Trypanosoma cruzi

Thymocytes from mice with experimental Trypanosoma cruzi infection respond poorly to Con-A stimulation. However, the proliferative capacity of these cells is not impaired, as demonstrated by the fact that at high doses, exogenous rIL-2 restores thymidine uptake. This finding could be explained either by insufficient IL-2 production or by the appearance of inhibitory factors during T. cruzi infection. This paper shows that in response to Con A, IL-2 production is decreased in the model. Furthermore, the whole profile of cytokine production is modified, with a striking increase in IL-10, IFN-gamma, IL-4, IL-5 and IL-6 production. The results indicate that IL-10 plus IFN-gamma are responsible for the decrease in the Con A-induced proliferation since a normal proliferative response as well as normal IL-2 production can be restored if both cytokines are neutralized by adding their monoclonal antibodies (MoAbs). Evidence is provided also for an enhanced non-specific cytotoxicity of thymic cells from infected mice that might involve IL-4, IL-5 and IL-6. This is the first study demonstrating an alteration of thymic cell function by T. cruzi infection which results from overstimulation of IL-10 and IFN-gamma production.

Interaction of IL-1 beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) in human T cells activated by murine antigens

We used a mixed leucocyte culture between human T cells and irradiated murine splenocytes which allowed us to distinguish between cytokine production from the responder and stimulator cells by the use of species-specific assays for mRNA up-regulation. Using this model of T cell activation by antigen, we studied the effects of human antigen-presenting cell-derived cytokines IL-1 beta, IL-6 and TNF-alpha on the activation of human T cell subsets. We show in this system that exogenously added IL-1 beta, IL-6 and TNF-alpha induces IL-2 receptor (R) up-regulation and IL-2 production, and proliferation by both CD4+ and CD8+ cells. The addition of IL-1 beta induces IL-6 mRNA, and anti-IL-1 antibodies or an IL-1R antagonist protein completely suppresses IL-6 and TNF-alpha supported proliferation. Similarly, addition of IL-6 or TNF-alpha induces up-regulation of IL-1 beta mRNA. However, anti-IL-6 and anti-IL-6R antibodies only partially block proliferation supported by IL-1 beta. These findings suggest that IL-6 and TNF-alpha will induce IL-2R up-regulation/IL-2 secretion via the induction of IL-1 beta production.

Tumor necrosis factor-alpha and interleukin-1 alpha synergistically enhance phorbol myristate acetate-induced superoxide production by rat bone marrow-derived macrophages

Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha) are secreted by macrophages in response to endotoxin challenge. In addition, macrophages express receptors for both of these cytokines. Macrophage function can therefore be modulated by regulation of both cytokine production and receptor levels. We have initiated studies to investigate the effects of TNF-alpha and IL-1 alpha on macrophage function. Macrophages were obtained by in vitro differentiation of rat bone marrow cells. The biologic response to TNF-alpha and IL-1 alpha was assessed by measurement of superoxide production quantitated by the reduction of cytochrome c in response to phorbol myristate acetate. Macrophages were treated with endotoxin (LPS), TNF-alpha, and IL-1 alpha, alone and in combination. None of these agents was a primary stimulus for superoxide production. However, after treatment with endotoxin or TNF-alpha for 24 h, macrophages were primed for enhanced production of superoxide. The priming effect of LPS was due, at least in part, to endogenously produced TNF-alpha, since anti-murine TNF-alpha antibodies blocked the LPS-mediated priming by approximately 30%. IL-1 alpha did not prime macrophages, but treatment with IL-1 alpha followed by TNF-alpha or LPS resulted in enhanced superoxide production. IL-1 alpha treatment of macrophages resulted in an increase in TNF-alpha receptors, which might explain the synergistic priming of TNF-alpha and IL-1 alpha.

Production of natural killer cell activity-augmenting factor (interleukin-6) by human epiphyseal chondrocytes

OBJECTIVE

We sought to determine the capacity of human epiphyseal chondrocytes to modulate the cytotoxic activity of human natural killer (NK) cells by determining whether they release interleukin-6 (IL-6), a cytokine recently shown to stimulate NK cell activity.

METHODS

Conditioned medium from human epiphyseal chondrocyte cultures (Ch-CM) was tested for IL-6 activity using the B9 cell hybridoma assay. Its NK cell-stimulating capacity in the presence of K562 (myelogenous leukemia) cells or human chondrocytes was evaluated in a 4-hour 51Cr-release assay. Ch-CM-derived IL-6/NK cell-augmenting factor activity was partially purified by high-performance liquid chromatography (HPLC) gel filtration and Western blot.

RESULTS

Ch-CM contained an NK cell-augmenting factor (NKAF) which was blocked by IL-2 or IL-6 antibodies. Ch-CM did not contain detectable IL-2 activity, but it stimulated IL-2 production by human peripheral blood lymphocytes (PBL). This IL-2-inducing capacity was inhibited by IL-6 antibodies, indicating that chondrocytes release an IL-6-like activity. Ch-CM significantly enhanced the proliferation of IL-6-dependent B9 hybridoma cells, and Western blot analysis of Ch-CM revealed specific bands corresponding to those of highly purified IL-6. Upon HPLC gel filtration, chondrocyte NKAF copurified with chondrocyte IL-6. Pure IL-6 and chondrocyte IL-6 were tested for their ability to stimulate the cytotoxic activity of human PBL against chondrocytes. Both mediators significantly enhanced chondrocyte killing. Lysis of chondrocytes by PBL was mediated by NK cells, since depletion of CD16+ cells resulted in inhibition of the activity.

CONCLUSION

Thus, upon stimulation, chondrocytes produce IL-6 which, through IL-2 induction, augments the activity of NK cells against K562 target cells as well as against chondrocytes.

Neuromodulatory loop mediated by nerve growth factor and interleukin 6 in thymic stromal cell cultures

Neural crest cell derivatives have been suggested to be involved in thymus development. We established nonlymphoid thymic stromal cell cultures capable of supporting T-cell differentiation. In these nonlymphoid cell cultures, we identified cells with phenotypic and biochemical markers specific for neuronal cells. Neurofilament mRNA and 68- and 160-kDa neurofilament proteins, as well as 74-kDa synapsin I isoform, were expressed in many of the cultured cells. For example, neurofilament immunoreactivity was detected in 20-30% of the cells. To see whether thymic neuronal-like cells were involved in a neural differentiation pathway, we investigated the effect of nerve growth factor (NGF) and interleukin 6 (IL-6), two known neurotrophic factors. The expression of the above-described neural markers was enhanced by NGF and IL-6, which we report to be produced in an autocrine way by thymic stromal cell cultures. Finally, we found that IL-6 gene expression in these cell cultures was enhanced by NGF. Evidence is thus offered of a neuromodulatory loop within the thymic stromal cell population supported by local production of NGF and IL-6 and involving neural cell elements. Interestingly, IL-6, which is known to be implicated in thymocyte differentiation, also displays a neuromodulatory activity on thymic stromal cells, suggesting a multivalent role for this cytokine within the thymus.

Effects of acetate dialysate on transforming growth factor beta 1, interleukin, and beta 2-microglobulin plasma levels

To evaluate potential adverse effects of acetate use in hemodialysis (HD), we measured plasma interleukin (IL-1 alpha, IL-1 beta, IL-6), TNF alpha, TGF beta 1, and beta 2-microglobulin levels with ELISA assays in normal (N = 9), CRF (N = 6), CAPD (N = 7) and HD (N = 8) subjects and compared the effects of acetate (Ac) and acetate-free (Ac-free) dialysate. TGF beta 1 was the only cytokine consistently detected. Compared to normals (median 57, range 53 to 68 pg/ml, one undetected; N = 8), TGF beta 1 was higher in the CRF (75, 70 to 97 pg/ml, one undetected) and CAPD (75.5, 66 to 116 pg/ml, N = 6) groups (P less than 0.05), and was somewhat higher in the HD (68, 52 to 88 pg/ml) group (P less than 0.10). Acutely, TGF beta 1 pre-HD (70, 63 to 88 pg/ml) increased above normals post AcHD [79.5, 65 to 140 pg/ml uncorrected for ultrafiltration (UF)] and was higher after AcHD versus Ac-free HD both uncorrected (79.5, 65 to 140 pg/ml vs. 70, 52 to 86 pg/ml) and corrected for UF (68, 51 to 115 pg/ml vs. 57, 43 to 69 pg/ml; P less than 0.05). beta 2-microglobulin was not different after AcHD (81.2 +/- 8.0 mg/ml) versus Ac-free HD (72.5 +/- 6.9 mg/ml). Significantly lower serum inorganic phosphorus was also found four hours post-AcHD compared to four hours post-Ac-free HD (0.87 mmol +/- 0.10 SEM vs. 1.05 mmol +/- 0.07 SEM; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated circulating levels of interleukin-6 in patients with chronic renal failure

In a previous study, we demonstrated the presence of circulating interleukin-1 (IL-1) in long-term dialyzed patients and that of tumor necrosis factor alpha (TNF alpha) in both long-term and not yet dialyzed uremic patients. In the present study, we attempted to determine the respective influence of hemodialysis (HD) and uremia on the plasma level of interleukin-6 (IL-6), which shares several biological properties with IL-1 and TNF alpha, including the induction of the acute phase response of the inflammatory process. Forty-eight patients with end-stage renal failure, including 32 long-term HD patients and 16 chronic uremic patients undergoing their first dialysis session, were tested for plasma IL-6 using both biological and immunoreactive assays. Plasma IL-6 activity was significantly increased in patients with chronic renal failure (P less than 0.001) compared to its level in normal individuals. No difference was observed, however, between long-term and not yet dialyzed patients. In the patients with the most pronounced IL-6 activity, immunoreactive IL-6 levels between 60 and 150 pg/ml were detected. A monoclonal antibody (mAb) against human IL-6 inhibited the activity of plasma in the IL-6 bioassay, and a close correlation existed between the biological activity of IL-6 and its immunoreactive level. No change in plasma IL-6 was detected during the course of the first dialysis as well as subsequent sessions. Likewise, no influence of the nature (cellulosic or synthetic polyacrilonitrile) of the dialysis membrane equipping the dialyzer was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of interleukin-6 in patients with inflammatory bowel disease

The significance of interleukin-6 (IL-6) in patients with inflammatory bowel disease (IBD) was studied by measuring the IL-6 level in serum and colonic tissue by means of an enzyme-linked immunosorbent assay (ELISA), and by examining its localization using an immunohistochemical method. The serum IL-6 level reflected the degree of disease activity, and the extent of affected area, and was also correlated with the serum C-reactive protein (CRP) level. In the colonic mucosa of active IBD, the tissue IL-6 level was markedly elevated, and immunoreactive products of anti-IL-6 antibody were present in infiltrative mononuclear cells in the lamina propria. This indicates that IL-6 production in these cells is enhanced at the site of affected intestine. These results, together with its biological activity and the type of cell producing it, suggest that IL-6 is an available marker to assess disease conditions of IBD and that it might be also involved in the pathophysiology of IBD.

Induction of interleukin-1 and -6 in human gingival fibroblast cultures stimulated with Bacteroides lipopolysaccharides

Normal human gingival fibroblasts stimulated in vitro by lipopolysaccharides (LPS) from oral Bacteroides species produced cell-free and cell-associated thymocyte-activating factors (TAF). Neutralization assays using antisera to human interleukin-1 alpha (HuIL-1 alpha), HuIL-1 beta, and HuIL-6 revealed that cell-free TAF was attributable mainly to IL-1 beta and that IL-6 augmented the TAF activity of IL-1 beta in the culture supernatant. Another factor(s), however, may also be involved in cell-free TAF. By contrast, the active entity of cell-associated TAF was ascribed to IL-1 alpha alone. Furthermore, IL-6 was detected mainly in the supernatant of fibroblast cultures stimulated with Bacteroides LPS. Fibroblasts pretreated with natural human beta or gamma interferon, but not those pretreated with alpha interferon, synthesized higher levels of cell-associated IL-1 alpha in response to stimulation by Bacteroides LPS; however, no interferons exhibited direct IL-1-inducing activity or synergistic IL-1-inducing activity with LPS. Endogenously induced beta interferon was suggested to be necessary for fibroblasts to produce cell-associated IL-1 alpha in response to Bacteroides LPS.

The in vivo anti-tumor effect of human recombinant interleukin-6

Administration of recombinant interleukin-6 (IL-6) was found to induce in vivo generation of cytotoxic T lymphocytes (CTL) against syngeneic transplantable erythroleukemia (FBL-3) in lymph node cells and peritoneal exudate cells (PEC) in C57BL/6 mice. Furthermore, 15 out of 16 C57BL/6 mice injected with 5 x 10(6) viable FBL-3 cells survived on day 100 when they were treated with 5 x 10(4) U of recombinant IL-6 three times a day on days 1, 2, 3, 5, 7 and 9 after the inoculation of tumor cells (the cure rate was 94%). Cured mice could reject the tumor cells rapidly after the re-inoculation of a large number of live FBL-3 cells. In contrast, all normal mice died of tumor development by day 10. In these cured mice, FBL-3-specific CD4-8+ CTL cells were found to be generated in PEC, spleen and lymph node cells by either in vivo or in vitro re-stimulation with FBL-3 cells, but lymphokine-activated killer cells never developed. The results suggested that the anti-tumor effect of IL-6 was mediated by in vivo induction of tumor-specific CTL.

Role of interleukin-2 and interleukin-6 in the mitogen responsiveness of T cells from patients with 'common-variable' hypogammaglobulinaemia

We have assessed the ability of interleukin-2 (IL-2) and interleukin-6 (IL-6) to augment the proliferative response of T lymphocytes from 'common-variable' hypogammaglobulinaemia (CVH) patients and from normal controls, to the mitogens phytohaemagglutinin (PHA) and OKT3. We show that with cells from the control group and from those patients whose T cells respond to PHA within the control range, both IL-2 and IL-6 will significantly augment the response to OKT3. However, in those patients with a T cell defect in which the PHA response is below the control range, neither IL-2 nor IL-6 could restore the PHA or OKT3 response to normal. Responses to IL-2 or IL-6 alone were always in or above the control range.

Glucocorticoid up-regulation of high-affinity interleukin 6 receptors on human epithelial cells

Interleukin 6 (IL-6) is a potent pleiotropic cytokine, known, among others, to stimulate immunoglobulin production by B cells and to trigger acute-phase protein synthesis by hepatocytes. Similar to IL-1, it is produced by monocytes and macrophages following an inflammatory challenge. Analysis of IL-6 receptor (IL-6R) expression on different human cell lines indicates that dexamethasone could up-regulate the number of IL-6R on one epithelial cell line (UAC) and on two hepatoma cell lines (HepG2 and Hep3B). This effect was confirmed by Scatchard analysis of binding experiments, using [35S]methionine and [35S]cysteine metabolically labeled IL-6. It was confirmed at the level of mRNA expression by Northern blot analysis. These results provide evidence for a link between IL-6 and glucocorticoids. They could represent an example of a system in which one role of glucocorticoids is to define more accurately the target of cytokines, and they could explain, at least partly, the frequently observed synergy between IL-6 and glucocorticoids, notably in the case of hepatocytes.