Interleukin (IL)-1 is a proinflammatory cytokine that plays important roles in inflammation, host defense, and the neuro-immuno-endocrine network. IL-1 receptor antagonist (ra) is an endogenous inhibitor of IL-1 and is supposed to regulate IL-1 activity. However, its pathophysiological roles in a body remain largely unknown. To elucidate the roles of IL-1ra, IL-1ra–deficient mice were produced by gene targeting, and pathology was analyzed on different genetic backgrounds. We found that all of the mice on a BALB/cA background, but not those on a C57BL/6J background, spontaneously developed chronic inflammatory polyarthropathy. Histopathology showed marked synovial and periarticular inflammation, with articular erosion caused by invasion of granulation tissues closely resembling that of rheumatoid arthritis in humans. Moreover, elevated levels of antibodies against immunoglobulins, type II collagen, and double-stranded DNA were detected in these mice, suggesting development of autoimmunity. Proinflammatory cytokines such as IL-1β, IL-6, and tumor necrosis factor α were overexpressed in the joints, indicating regulatory roles of IL-1ra in the cytokine network. We thus show that IL-1ra gene deficiency causes autoimmunity and joint-specific inflammation and suggest that IL-1ra is important in maintaining homeostasis of the immune system. Possible involvement of IL-1ra gene deficiency in RA will be discussed.

Interleukin (IL)-1 is a major mediator of inflammation and exerts pleiotropic effects on the neuro-immuno-endocrine system. To elucidate pathophysiological roles of IL-1, we have first produced IL-1α/β doubly deficient (KO) mice together with mice deficient in either the IL-1α, IL-1β, or IL-1 receptor antagonist (IL-1ra) genes. These mice were born healthy, and their growth was normal except for IL-1ra KO mice, which showed growth retardation after weaning. Fever development upon injection with turpentine was suppressed in IL-1β as well as IL-1α/β KO mice, but not in IL-1α KO mice, whereas IL-1ra KO mice showed an elevated response. At this time, expression of IL-1β mRNA in the diencephalon decreased 1.5-fold in IL-1α KO mice, whereas expression of IL-1α mRNA decreased >30-fold in IL-1β KO mice, suggesting mutual induction between IL-1α and IL-1β. This mutual induction was also suggested in peritoneal macrophages stimulated with lipopolysaccharide in vitro. In IL-1β KO mice treated with turpentine, the induction of cyclooxygenase-2 (EC 1.14.99.1) in the diencephalon was suppressed, whereas it was enhanced in IL-1ra KO mice. We also found that glucocorticoid induction 8 h after turpentine treatment was suppressed in IL-1β but not IL-1α KO mice. These observations suggest that IL-1β but not IL-1α is crucial in febrile and neuro-immuno-endocrine responses, and that this is because IL-1α expression in the brain is dependent on IL-1β. The importance of IL-1ra both in normal physiology and under stress is also suggested.

IL-17 is a T cell-derived, proinflammatory cytokine that is suspected to be involved in the development of various inflammatory diseases. Although there are elevated levels of IL-17 in synovial fluid of patients with rheumatoid arthritis, the pathogenic role of IL-17 in the development of rheumatoid arthritis remains to be elucidated. In this report, the effects of IL-17 deficiency were examined in IL-1 receptor antagonist-deficient (IL-1Ra ؊/؊ ) mice that spontaneously develop an inflammatory and destructive arthritis due to unopposed excess IL-1 signaling. IL-17 expression is greatly enhanced in IL-1Ra ؊/؊ mice, suggesting that IL-17 activity is involved in the pathogenesis of arthritis in these mice. Indeed, the spontaneous development of arthritis did not occur in IL-1Ra ؊/؊ mice also deficient in IL

The cytokine interleukin-1 (IL-1) has been strongly implicated in the pathogenesis of ischemic brain damage. Evidence to date suggests that the major form of IL-1 contributing to ischemic injury is IL-1␤ rather than IL-1␣, but this has not been tested directly.The objective of the present study was to compare the effects of transient cerebral ischemia [30 min middle cerebral artery occlusion (MCAO)] on neuronal injury in wild-type (WT) mice and in IL-1␣, IL-1␤, or both IL-1␣ and IL-1␤ knock-out (KO) mice.Mice lacking both forms of IL-1 exhibited dramatically reduced ischemic infarct volumes compared with wild type (total volume, 70%; cortex, 87% reduction). Ischemic damage compared with WT mice was not significantly altered in mice lacking either IL-1␣ or IL-1␤ alone. IL-1␤ mRNA, but not IL-1␣ or the IL-1 type 1 receptor, was strongly induced by MCAO in WT and IL-1␣ KO mice.Administration (intracerebroventricularly) of recombinant IL-1 receptor antagonist significantly reduced infarct volume in WT (-32%) and IL-1␣ KO (-48%) mice, but had no effect on injury in IL-1␤ or IL-1␣/␤ KO mice.These data confirm that IL-1 plays a major role in ischemic brain injury. They also show that chronic deletion of IL-1␣ or IL-1␤ fails to influence brain damage, probably because of compensatory changes in the IL-1 system in IL-1␣ KO mice and changes in IL-1-independent mediators of neuronal death in IL-1␤ KO mice.

Th17 cells require IL-6 and TGFβ for lineage commitment and IL-23 for maintenance. Unexpectedly, naive IL-6−/− splenocytes stimulated with anti-CD3 and IL-23 produced normal amounts of IL-17 during the first 24 h of culture. These rapid IL-6-independent IL-17 producers were identified as predominantly DX5+ TCRβ+ NKT cells, and a comparable response could be found using the invariant NKT-specific ligand α-galactosylceramide. Human NKT cells also produced IL-17. NKT cells constitutively expressed IL-23R and RORγt. Ligation of either TCR or IL-23R triggered IL-17 production and both together had a synergistic effect, suggesting independent but convergent pathways. IL-17 production was not restricted to a particular subset of NKT cells but they were NK1.1 negative. Importantly, in vivo administration of α-galactosylceramide triggered a rapid IL-17 response in the spleen. These data suggest an important biological role for innate IL-17 production by NKT cells that is rapid and precedes the adaptive IL-17 response.

Fas ligand is a well-characterized apoptosis inducer. Here we demonstrate that Fas ligand induces the processing and secretion of interleukin-1beta (IL-1beta) in peritoneal exudate cells. This IL-1beta secretion is independent of IL-1beta converting enzyme (caspase 1), yet it is inhibited by caspase inhibitors, indicating that a caspase(s) in addition to IL-1beta converting enzyme can process IL-1beta. Inoculation of tumor cells expressing Fas ligand into wild-type mice induces a massive neutrophil infiltration that is, in contrast, suppressed in IL-1alpha/beta knockout mice. These results demonstrate a newly discovered role for Fas ligand in inflammation, and challenge the dogma that apoptosis does not induce inflammation.

A similar gene network was found to control chick myogenesis, in which Six1, Eya2 and Dach2 synergistically regulate the expression of myogenic genes such as myogenin and MyoD (Heanue et Six1 is a member of the Six family homeobox genes, which function as components of the Pax-Six-Eya-Dach gene network to control organ development. Six1 is expressed in otic vesicles, nasal epithelia, branchial arches/pouches, nephrogenic cords, somites and a limited set of ganglia. In this study, we established Six1-deficient mice and found that development of the inner ear, nose, thymus, kidney and skeletal muscle was severely affected. Six1-deficient embryos were devoid of inner ear structures, including cochlea and vestibule, while their endolymphatic sac was enlarged. The inner ear anomaly began at around E10.5 and Six1 was expressed in the ventral region of the otic vesicle in the wild-type embryos at this stage. In the otic vesicle of Six1-deficient embryos, expressions of Otx1, Otx2, Lfng and Fgf3, which were expressed ventrally in the wildtype otic vesicles, were abolished, while the expression domains of Dlx5, Hmx3, Dach1 and Dach2, which were expressed dorsally in the wild-type otic vesicles, expanded ventrally. Our results indicate that Six1 functions as a key regulator of otic vesicle patterning at early embryogenesis and controls the expression domains of downstream otic genes responsible for respective inner ear structures. In addition, cell proliferation was reduced and apoptotic cell death was enhanced in the ventral region of the otic vesicle, suggesting the involvement of Six1 in cell proliferation and survival. In spite of the similarity of otic phenotypes of Six1-and Shh-deficient mice, expressions of Six1 and Shh were mutually independent.

Summary Activated retina-specific T cells that have acquired the ability to break through the blood-retinal barrier are thought to be causally involved in autoimmune uveitis, a major cause of human blindness. It is unclear where these autoreactive T cells first become activated, given that their cognate antigens are sequestered within the immune privileged eye. We demonstrate in a novel mouse model of spontaneous uveitis that activation of retina-specific T cells is dependent on gut commensal microbiota. Retina-specific T cell activation involved signaling through the autoreactive T cell receptor (TCR) in response to non-cognate antigen in the intestine, and was independent of the endogenous retinal autoantigen. Our findings not only have implications for etiology of human uveitis, but also raise the possibility that activation of autoreactive TCRs by commensal microbes may be a more common trigger of autoimmune diseases than is currently appreciated.