IL-23 is increased in dendritic cells in multiple sclerosis and down-regulation of IL-23 by antisense oligos increases dendritic cell IL-10 production

IL-23 is a heterodimeric cytokine comprising a p19 subunit associated with the IL-12/23p40 subunit. Like IL-12, IL-23 is expressed predominantly by activated dendritic cells (DCs) and phagocytic cells, and both cytokines induce IFN-gamma secretion by T cells. The induction of experimental autoimmune encephalitis, the animal model of multiple sclerosis (MS), occurs in mice lacking IL-12, but not in mice with targeted disruption of IL-23 or both IL-12 and IL-23. Thus, IL-23 expression in DCs may play an important role in the pathogenesis of human autoimmune diseases such as MS. We quantified the expression of IL-23 in monocyte-derived DCs in MS patients and healthy donors and found that DCs from MS patients secrete elevated amounts of IL-23 and express increased levels of IL-23p19 mRNA. Consistent with this abnormality, we found increased IL-17 production by T cells from MS patients. We then transfected monocyte-derived DCs from healthy donors with antisense oligonucleotides specific for the IL-23p19 and IL-12p35 genes and found potent suppression of gene expression and blockade of bioactive IL-23 and IL-12 production without affecting cellular viability or DCs maturation. Inhibition of IL-23 and IL-12 was associated with increased IL-10 and decreased TNF-alpha production. Furthermore, transfected DCs were poor allostimulators in the MLR. Our results demonstrate that an abnormal Th1 bias in DCs from MS patients related to IL-23 exists, and that antisense oligonucleotides specific to IL-23 can be used for immune modulation by targeting DC gene expression.     

Endotoxin fails to induce IFN-gamma in endotoxin-tolerant mice: deficiencies in both IL-12 heterodimer production and IL-12 responsiveness

Mice exposed to sublethal endotoxemia develop short-term endotoxin tolerance, a state characterized by decreased monokine production and enhanced protection against endotoxic lethality. We confirmed that TNF-alpha production is markedly impaired in endotoxin-tolerant mice and additionally found 2- to 6-fold decreases in serum IFN-gamma in these animals following endotoxin challenge. The IFN-gamma deficiency of endotoxin tolerance correlated with 8-fold decreases in the bioactive p40/p35 heterodimeric form of IL-12. In contrast, total circulating IL-12 p40 was reduced by only 30-50%. Endotoxin-tolerant mice were less responsive to IL-12 than control mice, as evidenced by 3-fold lower levels of IFN-gamma inducible in vivo when rIL-12 was administered at the time of endotoxin challenge. Similarly, spleen cell cultures of endotoxin-tolerant mice produced 3-fold less IFN-gamma in the presence of optimal concentrations of both IL-12 and IL-18. Finally, levels of IL-12R beta 2 subunit mRNA and the percent composition of NK lymphocytes in the spleen were both decreased in endotoxin-tolerant mice relative to controls. We conclude that endotoxin-tolerant mice are profoundly impaired in their ability to produce IFN-gamma in response to endotoxin and that this is associated with acquired defects in both the production of circulating IL-12 heterodimer response and the response to IL-12 by NK cells.     

IL-23 provides a limited mechanism of resistance to acute toxoplasmosis in the absence of IL-12

IL-23 and IL-12 are heterodimeric cytokines which share the p40 subunit, but which have unique second subunits, IL-23p19 and IL-12p35. Since p40 is required for the development of the Th1 type response necessary for resistance to Toxoplasma gondii, studies were performed to assess the role of IL-23 in resistance to this pathogen. Increased levels of IL-23 were detected in mice infected with T. gondii and in vitro stimulation of dendritic cells with this pathogen resulted in increased levels of mRNA for this cytokine. To address the role of IL-23 in resistance to T. gondii, mice lacking the p40 subunit (common to IL-12 and IL-23) and mice that lack IL-12 p35 (specific for IL-12) were infected and their responses were compared. These studies revealed that p40(-/-) mice rapidly succumbed to toxoplasmosis, while p35(-/-) mice displayed enhanced resistance though they eventually succumbed to this infection. In addition, the administration of IL-23 to p40(-/-) mice infected with T. gondii resulted in a decreased parasite burden and enhanced resistance. However, the enhanced resistance of p35(-/-) mice or p40(-/-) mice treated with IL-23 was not associated with increased production of IFN-gamma. When IL-23p19(-/-) mice were infected with T. gondii these mice developed normal T cell responses and controlled parasite replication to the same extent as wild-type mice. Together, these studies indicate that IL-12, not IL-23, plays a dominant role in resistance to toxoplasmosis but, in the absence of IL-12, IL-23 can provide a limited mechanism of resistance to this infection.     

An anti-IL-12p40 antibody down-regulates type 1 cytokines, chemokines, and IL-12/IL-23 in psoriasis

Psoriasis is characterized by activation of T cells with a type 1 cytokine profile. IL-12 and IL-23 produced by APCs are essential for inducing Th1 effector cells. Promising clinical results of administration of an Ab specific for the p40 subunit of IL-12 and IL-23 (anti-IL-12p40) have been reported recently. This study evaluated histological changes and mRNA expression of relevant cytokines and chemokines in psoriatic skin lesions following a single administration of anti-IL-12p40, using immunohistochemistry and real-time RT-PCR. Expression levels of type 1 cytokine (IFN-gamma) and chemokines (IL-8, IFN-gamma-inducible protein-10, and MCP-1) were significantly reduced at 2 wk posttreatment. The rapid decrease of these expression levels preceded clinical response and histologic changes. Interestingly, the level of an anti-inflammatory cytokine, IL-10, was also significantly reduced. Significant reductions in TNF-alpha levels and infiltrating T cells were observed in high responders (improvement in clinical score, > or =75% at 16 wk), but not in low responders. Of importance, the levels of APC cytokines, IL-12p40 and IL-23p19, were significantly decreased in both responder populations, with larger decreases in high responders. In addition, baseline levels of TNF-alpha significantly correlated with the clinical improvement at 16 wk, suggesting that these levels may predict therapeutic responsiveness to anti-IL-12p40. Thus, in a human Th1-mediated disease, blockade of APC cytokines by anti-IL-12p40 down-regulates expression of type 1 cytokines and chemokines that are downstream of IL-12/IL-23, and also IL-12/IL-23 themselves, with a pattern indicative of coordinated deactivation of APCs and Th1 cells.     

Mice lacking bioactive IL-12 can generate protective, antigen-specific cellular responses to mycobacterial infection only if the IL-12 p40 subunit is present.

Recent evidence suggests that absence of the IL-12p40 subunit is more detrimental to the generation of protective responses than is the absence of the p35 subunit. To determine whether this is the case in tuberculosis, both p35 and p40 knockout mice were infected with Mycobacterium tuberculosis. Mice lacking the p40 subunit were highly susceptible to increased bacterial growth, exhibited reduced production of IFN-gamma, and had increased mortality. In contrast, mice lacking the p35 subunit exhibited a moderate ability to control bacterial growth, were able to generate Ag-specific IFN-gamma responses, and survived infection longer. The superior Ag-specific responses of the p35 gene-disrupted mice, when compared with the p40 gene-disrupted mice, suggest that the p40 subunit may act other than as a component of IL-12. A candidate molecule capable of driving the protective responses in the p35 gene-disrupted mice is the novel cytokine IL-23. This cytokine is composed of the IL-12 p40 subunit and a p19 subunit. In support of a role for this cytokine in protective responses to M. tuberculosis, we determined that the p19 subunit is induced in the lungs of infected mice.     

IL-23 enhances the inflammatory cell response in Cryptococcus neoformans infection and induces a cytokine pattern distinct from IL-12

IL-23, a heterodimeric cytokine composed of the p40 subunit of IL-12 and a novel p19 subunit, has been shown to be a key player in models of autoimmune chronic inflammation. To investigate the role of IL-23 in host resistance during chronic fungal infection, wild-type, IL-12- (IL-12p35-/-), IL-23- (IL-23p19-/-), and IL-12/IL-23- (p40-deficient) deficient mice on a C57BL/6 background were infected with Cryptococcus neoformans. Following infection, p40-deficient mice demonstrated higher mortality than IL-12p35-/- mice. Reconstitution of p40-deficient mice with rIL-23 prolonged their survival to levels similar to IL-12p35-/- mice. IL-23p19-/- mice showed a moderately reduced survival time and delayed fungal clearance in the liver. Although IFN-gamma production was similar in wild-type and IL-23p19-/- mice, production of IL-17 was strongly impaired in the latter. IL-23p19-/- mice produced fewer hepatic granulomata relative to organ burden and showed defective recruitment of mononuclear cells to the brain. Moreover, activation of microglia cells and expression of IL-1beta, IL-6, and MCP-1 in the brain was impaired. These results show that IL-23 complements the more dominant role of IL-12 in protection against a chronic fungal infection by an enhanced inflammatory cell response and distinct cytokine regulation.     

IL-23 compensates for the absence of IL-12p70 and is essential for the IL-17 response during tuberculosis but is dispensable for protection and antigen-specific IFN-gamma responses if IL-12p70 is available

IL-12p70 induced IFN-gamma is required to control Mycobacterium tuberculosis growth; however, in the absence of IL-12p70, an IL-12p40-dependent pathway mediates induction of IFN-gamma and initial bacteriostatic activity. IL-23 is an IL-12p40-dependent cytokine containing an IL-12p40 subunit covalently bound to a p19 subunit that is implicated in the induction of CD4 T cells associated with autoimmunity and inflammation. We show that in IL-23 p19-deficient mice, mycobacterial growth is controlled, and there is no diminution in either the number of IFN-gamma-producing Ag-specific CD4 T cells or local IFN-gamma mRNA expression. Conversely, there is an almost total loss of both IL-17-producing Ag-specific CD4 T cells and local production of IL-17 mRNA in these mice. The absence of IL-17 does not alter expression of the antimycobacterial genes, NO synthase 2 and LRG-47, and the absence of IL-23 or IL-17, both of which are implicated in mediating inflammation, fails to substantially affect the granulomatous response to M. tuberculosis infection of the lung. Despite this redundancy, IL-23 is required to provide a moderate level of protection in the absence of IL-12p70, and this protection correlates with a requirement for IL-23 in the IL-12p70-independent induction of Ag-specific, IFN-gamma-producing CD4 T cells. We also show that IL-23 is required for the induction of an IL-17-producing Ag-specific phenotype in naive CD4 T cells in vitro and that absence of IL-12p70 promotes an increase in the number of IL-17-producing Ag-specific CD4 T cells both in vitro and in vivo.     

Ubiquitous transgenic expression of the IL-23 subunit p19 induces multiorgan inflammation, runting, infertility, and premature death

p19, a molecule structurally related to IL-6, G-CSF, and the p35 subunit of IL-12, is a subunit of the recently discovered cytokine IL-23. Here we show that expression of p19 in multiple tissues of transgenic mice induced a striking phenotype characterized by runting, systemic inflammation, infertility, and death before 3 mo of age. Founder animals had infiltrates of lymphocytes and macrophages in skin, lung, liver, pancreas, and the digestive tract and were anemic. The serum concentrations of the proinflammatory cytokines TNF-alpha and IL-1 were elevated, and the number of circulating neutrophils was increased. In addition, ubiquitous expression of p19 resulted in constitutive expression of acute phase proteins in the liver. Surprisingly, liver-specific expression of p19 failed to reproduce any of these abnormalities, suggesting specific requirements for production of biologically active p19. Bone marrow transfer experiments showed that expression of p19 by hemopoietic cells alone recapitulated the phenotype induced by its widespread expression, pointing to hemopoietic cells as the source of biologically active p19. These findings indicate that p19 shares biological properties with IL-6, IL-12, and G-CSF and that cell-specific expression is required for its biological activity.     

Role of Th1 and Th2 cytokines in BCG-induced IFN-gamma production: cytokine promotion and simulation of BCG effect

Induction of a T-helper-type 1 (Th1) immune response is indispensable for successful treatment of superficial bladder cancer with BCG. In this study possible involvement of various cytokines in BCG action as well as their potential roles in enhancing and mimicking BCG effect were explored. In immunocompetent cell cultures, IFN-gamma, a major Th1 cytokine, appears to be a late responsive cytokine to BCG stimulation. Its induction requires involvement of various endogenously produced Th1 and Th2 cytokines. Functional abolishment of any one of these cytokines (IL-2, IL-6, IL-12, IL-18, GMCSF, TNF-alpha, or IFN-alpha, except IL-10) by neutralizing antibodies leads to reduced IFN-gamma production (19-82% inhibition in mouse and 44-77% inhibition in human systems, respectively). In mice cytokines IL-2, IL-12, IL-18, and GMCSF are observed to synergize with BCG for IFN-gamma production, whereas in human cytokines IL-2, IL-12, TNF-alpha, and IFN-alpha exhibit similar synergistic effects. Rational combinations of these Th1-stimulating cytokines (IL-12 plus IL-18 in mice and IL-2 plus IL-12 in humans, respectively) dramatically up-regulate IFN-gamma production that is incomparably superior to BCG for induction of this cytokine. These results suggest that combined Th1-stimulating cytokines and combinations of BCG plus selected Th1-stimulating cytokines are rational candidates for further study in the treatment of bladder cancer patients.     

IL-12Rbeta2-deficient mice of a genetically resistant background are susceptible to Leishmania major infection and develop a parasite-specific Th2 immune response

The cytokine IL-12 plays a critical role in inducing the production of IFN-gamma from T and NK cells and in the polarization of T cells towards the Th1 phenotype. IL-12 is comprised of two subunits (IL-12p40 and IL-12p35) that together form the biologically active p70 molecule, and IL-12 functions via binding to a heterodimeric receptor (IL-12Rbeta1 and IL-12Rbeta2). Previous studies utilizing mice deficient for either the IL-12 cytokine or the IL-12-induced signaling molecule STAT4 have established a critical role for IL-12 during infection with Leishmania major. However, these studies warrant careful re-interpretation in light of the recent discovery of the IL-12-related cytokine, IL-23, which utilizes the IL-12p40 chain in combination with an IL-12p35-related molecule, called p19, and a receptor comprised of the IL-12Rbeta1 chain plus a unique chain referred to as IL-23R. We analyzed the course of L. major infection in mice deficient for the IL-12-specific IL-12Rbeta2 subunit in order to assess the role of IL-12 signaling without disruption of the IL-23 pathway. After infection with L. major, IL-12Rbeta2KO mice of a resistant background (C57Bl/6) developed large cutaneous lesions similar to those developed by susceptible BALB/c mice. Draining lymph node cells from L. major-infected IL-12Rbeta2KO mice released the Th2 cytokines IL-4 and IL-5 after in vitro stimulation with Leishmania lysate but were completely devoid of IFN-gamma, consistent with a default towards a strong parasite-specific Th2 response. L. major-infected IL-12Rbeta2KO mice were also devoid of parasite-specific IgG2a antibodies, and interestingly, their footpad lesions ulcerated earlier than those of susceptible BALB/c mice.     

Paradoxical anti-inflammatory actions of TNF-alpha: inhibition of IL-12 and IL-23 via TNF receptor 1 in macrophages and dendritic cells

IL-12 and TNF-alpha are central proinflammatory cytokines produced by macrophages and dendritic cells. Disregulation of TNF-alpha is associated with sepsis and autoimmune diseases such as rheumatoid arthritis. However, new evidence suggests an anti-inflammatory role for TNF-alpha. TNF-alpha-treated murine macrophages produced less IL-12p70 and IL-23, after stimulation with IFN-gamma and LPS. Frequency of IL-12p40-producing macrophages correspondingly decreased as measured by intracellular cytokine staining. IL-12p40 production was also inhibited in dendritic cells. TNFR1 was established as the main receptor involved in IL-12p40 regulation, because IL-12p40 levels were not affected by TNF-alpha in TNFR1(-/-)-derived macrophages. Macrophages activated during Listeria monocytogenes infection were more susceptible to inhibition by TNF-alpha than cells from naive animals, which suggests a regulatory role for TNF-alpha in later stages of infection. This nonapoptotic anti-inflammatory regulation of IL-12 and IL-23 is an important addition to the multitude of TNF-alpha-induced responses determined by cell-specific receptor signaling.     

Systemic administration of IL-23 induces potent antitumor immunity primarily mediated through Th1-type response in association with the endogenously expressed IL-12

IL-23, a cytokine, which is composed of the p40 subunit shared with IL-12 and the IL-23-specific p19 subunit, has been shown to preferentially act on Th1 effector/memory CD4+ T cells and to induce their proliferation and IFN-gamma production. The IL-23 is also reported to act on Th17-CD4+ T cells, which are involved in inducing tissue injury. In this study, we examined the antitumor effects associated with systemic administration of IL-23 and their mechanisms in mouse tumor system. Systemic administration of high-dose IL-23 was achieved using in vivo electroporation of IL-23 plasmid DNA into the pretibial muscles of C57BL/6 mice. The IL-23 treatment was associated with significant suppression of the growth of pre-existing MCA205 fibrosarcoma and prolongation of the survival of treated mice without significant toxicity when compared with those of the mice treated with EGFP. Although the therapeutic outcomes were similar to those with the IL-12 treatment, the IL-23 treatment induced characteristic immune responses distinctive to those of IL-12 treatment. The IL-23 administration even at the therapeutic levels did not induce detectable IFN-gamma concentration in the serum. In vivo depletion of CD4+ T cells, CD8+ T cells, or NK cells significantly inhibited the antitumor effects of IL-23. Furthermore, the CD4+ T cells in the lymph nodes in the IL-23-treated mice showed significant IFN-gamma and IL-17 response upon anti-CD3 mAb stimulation in vitro. These results and the ones in the IFN-gamma or IL-12 gene knockout mice suggest that potent antitumor effects of IL-23 treatment could be achieved when the Th1-type response is fully promoted in the presence of endogenously expressed IL-12.     

IL-12/23p40-dependent clearance of Anaplasma phagocytophilum in the murine model of human anaplasmosis

Human anaplasmosis is an emerging infectious disease transmitted by ticks that can be potentially fatal in the immunocompromised and the elderly. The mechanisms of defense against the causative agent, Anaplasma phagocytophilum, are not completely understood; however, interferon (IFN)-gamma plays an important role in pathogen clearance. Here, we show that IFN-gamma is regulated through an early IL-12/23p40-dependent mechanism. Interleukin (IL)-12/23p40 is regulated in macrophages and dendritic cells after activation by microbial agonists and cytokines and constitutes a subunit of IL-12 and IL-23. IL-12/23p40-deficient mice displayed an increased A. phagocytophilum burden, accelerated thrombocytopenia and increased neutrophil numbers in the spleen at day 6 postinfection. Infection of MyD88- and mitogen-activated kinase kinase 3 (MKK3)-deficient mice suggested that the early susceptibility due to IL-12/23p40 deficiency was not dependent on signaling through MyD88 or MKK3. The lack of IL-12/23p40 reduced IFN-gamma production in both CD4(+) and CD8(+) T cells although the effect was more pronounced in CD4(+) T cells. Our data suggest that the immune response against A. phagocytophilum is a multifactorial and cooperative process. The IL-12/23p40 subunit drives the CD4(+) Th1 immune response in the early phase of infection and IL-12/23p40-independent mechanisms ultimately contribute to pathogen elimination from the host.     

Endogenous cytokines during a lethal infection with Listeria monocytogenes in mice

It has been demonstrated that endogenous cytokines including gamma interferon (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) play protective roles but that IL-4 and IL-10 play detrimental roles in nonlethal Listeria monocytogenes infection in mice. In this paper, we studied the roles of endogenous cytokines in a lethal infection with L. monocytogenes in mice. TNF-alpha and IL-6 titres in the bloodstreams, spleens and livers paralleled bacterial numbers in the organs, and both these cytokines and the bacterial numbers peaked just before the mice died. The high titres of TNF-alpha notably detected in the circulation in lethal infection were different from those in nonlethal infection. The maximum production of IFN-gamma was observed before the peaks of TNF-alpha and IL-6, and IFN-gamma almost disappeared from the bloodstreams and organs just before the mice died. No notable difference of IFN-gamma titres between lethal infection and nonlethal infection in the specimens obtained from mice was observed. IL-10 was also detected in the bloodstreams earlier than the peaks of TNF-alpha and IL-6 during lethal infection, while IL-4 was never detected in the sera. The administration of monoclonal antibodies (mAbs) against TNF-alpha, IFN-gamma, IL-6, IL-4 or IL-10 failed to rescue mice from lethal L. monocytogenes infection, whereas anti-TNF-alpha mAb and anti-IFN-gamma mAb prevented mice from lethality by high-dose endotoxin shock. These results suggest that lethality in L. monocytogenes infection might not be determined solely by these cytokines.     

Role of IL-12 receptor beta 1 in regulation of T cell response by APC in experimental autoimmune encephalomyelitis

IL-12 was thought to be involved in the development of experimental autoimmune encephalomyelitis (EAE), a Th1 cell-mediated autoimmune disorder of the CNS. However, we have recently found that IL-12 responsiveness, via IL-12Rbeta2, is not required in the induction of EAE. To determine the role of IL-12Rbeta1, a key subunit for the responsiveness to both IL-12 and IL-23, in the development of autoimmune diseases, we studied EAE in mice deficient in this subunit of IL-12R. IL-12Rbeta1(-/-) mice are completely resistant to myelin oligodendrocyte glycoprotein (MOG)-induced EAE, with an autoantigen-specific Th2 response. To study the mechanism underlying this Th2 bias, we cocultured purified CD4(+) T cells and APCs of MOG-immunized mice. We demonstrate that IL-12Rbeta1(-/-) APCs drive CD4(+) T cells of both wild-type and IL-12Rbeta1(-/-) mice to an Ag-induced Th2 phenotype, whereas wild-type APCs drive these CD4(+) T cells toward a Th1 type. IL-12Rbeta1(-/-) CD4(+) T cells, in turn, appear to exert an immunoregulatory effect on the capacity of wild-type APCs to produce IFN-gamma and TNF-alpha. Furthermore, decreased levels of IL-12p40, p35, and IL-23p19 mRNA expression were found in IL-12Rbeta1(-/-) APCs, indicating an autocrine pathway of IL-12/IL-23 via IL-12Rbeta1. IL-18 production and IL-18Ralpha expression are also significantly decreased in IL-12Rbeta1(-/-) mice immunized with MOG. We conclude that in the absence of IL-12Rbeta1, APCs play a prominent regulatory role in the induction of autoantigen-specific Th2 cells.     

IL-12p35-deficient mice are susceptible to experimental autoimmune encephalomyelitis: evidence for redundancy in the IL-12 system in the induction of central nervous system autoimmune demyelination

Experimental autoimmune encephalomyelitis (EAE) serves as a model for multiple sclerosis and is considered a CD4(+), Th1 cell-mediated autoimmune disease. IL-12 is a heterodimeric cytokine, composed of a p40 and a p35 subunit, which is thought to play an important role in the development of Th1 cells and can exacerbate EAE. We induced EAE with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 (MOG(35-55)) in C57BL/6 mice and found that while IL-12p40-deficient (-/-) mice are resistant to EAE, IL-12p35(-/-) mice are susceptible. Typical spinal cord mononuclear cell infiltration and demyelination were observed in wild-type and IL-12p35(-/-) mice, whereas IL-12p40(-/-) mice had normal spinal cords. A Th1-type response to MOG(35-55) was observed in the draining lymph node and the spleen of wild-type mice. A weaker MOG(35-55)-specific Th1 response was observed in IL-12p35(-/-) mice, with lower production of IFN-gamma. By contrast, a Th2-type response to MOG(35-55) correlated with disease resistance in IL-12p40(-/-) mice. Production of TNF-alpha by microglia, CNS-infiltrating macrophages, and CD4(+) T cells was detected in wild-type and IL-12p35(-/-), but not in IL-12p40(-/-), mice. In addition, NO production was higher in IL-12p35(-/-) and wild-type mice than in IL-12p40(-/-) mice. These data demonstrate a redundancy of the IL-12 system in the induction of EAE and suggest that p40-related heterodimers, such as the recently cloned IL-23 (p40p19), may play an important role in disease pathogenesis.     

IFN-gamma is not induced through increased plasma concentrations of interleukin-12/interleukin-18 during human endotoxemia

Endotoxin administration to animals and humans is an accepted experimental model of Gram-negative sepsis, and endotoxin is believed to play a major role in triggering the activation of cytokines. In septic patients, the IL-12/IL-18/IFN-gamma axis is activated and correlates with mortality. Our aim was to investigate the effects of endotoxin administration in humans on the activation of the IL-12/IL-18/IFN-gamma axis. Seven healthy volunteers received E. coli endotoxin (O:113). Hemodynamics, temperature and the course of plasma concentrations of TNF-alpha, IL-1beta, IL-12, IL-18 and IFN-gamma were determined. Endotoxin administration resulted in the expected flu-like symptoms, a temperature of 38.8 +/- 0.3(o)C (p < 0.003), a decrease in mean arterial blood pressure of 14.8 +/- 1.8 mmHg (p < 0.0002) and an increase in heart rate of 27.5 +/- 4.8 bpm (p < 0.002) compared to baseline values. TNF-alpha increased from 16.6 +/- 8.2 to 927 +/- 187 pg/mL (p < 0.003). IL-1beta increased from 8.6 +/- 0.5 to 25.3 +/- 2.0 pg/mL (p < 0.0001). IL-12 showed no significant increase (8.2 +/- 0.2 to 9.3 +/- 0.8 pg/mL, p = 0.13), and all IL-18 measurements remained below the level of detection. In contrast, IFN-gamma showed an increase from 106.6 +/- 57.1 to 152.7 +/- 57.8 (p < 0.005). These results indicate that pathways other than the IL-12/IL-18 axis may induce IFN-gamma production in human endotoxemia.     

IL-23 is critical in the induction but not in the effector phase of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), a T cell-mediated inflammatory disease of the CNS, is a rodent model of human multiple sclerosis. IL-23 is one of the critical cytokines in EAE development and is currently believed to be involved in the maintenance of encephalitogenic responses during the tissue damage effector phase of the disease. In this study, we show that encephalitogenic T cells from myelin oligodendrocyte glycopeptide (MOG)-immunized wild-type (WT) mice caused indistinguishable disease when adoptively transferred to WT or IL-23-deficient (p19 knockout (KO)) recipient mice, demonstrating that once encephalitogenic cells have been generated, EAE can develop in the complete absence of IL-23. Furthermore, IL-12/23 double-deficient (p35/p19 double KO) recipient mice developed EAE that was indistinguishable from WT recipients, indicating that IL-12 did not compensate for IL-23 deficiency during the effector phase of EAE. In contrast, MOG-specific T cells from p19KO mice induced EAE with delayed onset and much lower severity when transferred to WT recipient mice as compared with the EAE that was induced by cells from WT controls. MOG-specific T cells from p19KO mice were highly deficient in the production of IFN-gamma, IL-17A, and TNF, indicating that IL-23 plays a critical role in development of encephalitogenic T cells and facilitates the development of T cells toward both Th1 and Th17 pathways.