Rheumatoid arthritis (RA) is a chronic infl ammatory disease of synovial joints that is associated with cartilage and bone destruction. Death Receptor 3 (DR3), a tumor necrosis factor (TNF) receptor superfamily member, has recently been associated with the pathogenesis of RA. We demonstrate that absence of DR3 confers resistance to the development of adverse bone pathology in experimental antigen-induced arthritis (AIA). DR3 ko mice exhibited a reduction in all histopathological hallmarks of AIA but, in particular, failed to develop subchondral bone erosions and were completely protected from this characteristic of AIA. In contrast, TNF-like protein 1A (TL1A), the ligand for DR3, exacerbated disease in a dose-and DR3-dependent fashion. Analysis of osteoclast number within AIA joint revealed a reduction in areas susceptible to bone erosion in DR3 ko mice, whereas in vitro osteoclastogenesis assays showed that TL1A could directly promote osteoclastogenesis in mouse and man. Treatment with antagonistic anti-TL1A mAb protected animals in a systemic model of RA disease collagen-induced arthritis. We therefore conclude that the DR3 -TL1A pathway regulates joint destruction in two murine models of arthritis and represents a potential novel target for therapeutic intervention in infl ammatory joint disease.

The cytokine IL-6 controls the survival, proliferation and effector characteristics of lymphocytes through activation of the transcription factors STAT1 and STAT3. While STAT3 activity is an ever-present feature of IL-6 signaling in CD4 + T cells, prior T-cell receptor activation limits the IL-6 control of STAT1 in effector and memory populations. Here we show that STAT1 phosphorylation in response to IL-6 was regulated by protein tyrosine phosphatases (PTPN2, PTPN22) expressed in response to the activation of naïve CD4 + T cells. Transcriptomic and chromatin immunoprecipitation-sequencing of IL-6 responses in naïve and effector memory CD4 + T cells showed how the suppression of STAT1 activation shaped the functional identity and effector characteristics of memory CD4 + T cells. Thus, protein tyrosine phosphatases induced by activation of naïve T cells determined the way activated or memory CD4 + T cells sensed and interpreted cytokine signals.

Tumor necrosis factor (TNF)-like cytokine (TL1A) is a T-cell costimulator that bolsters cytokine-induced activation through death receptor 3 (DR3). To explore the relationship between T-cell activation and TL1A responsiveness, flow cytometry profiled DR3 expression in resting and activated T cells. In human CD4+ T cells, DR3 was induced rapidly following activation and expressed prominently by interleukin (IL)-17-secreting T cells (Th17). Splenic T cells from wild-type and DR3-deficient mice showed that TL1A activation of DR3 inhibits Th17 generation (81±2.6% at 100 ng/ml TL1A) from naive T cells. This response was not associated with suppression of T-cell proliferation. Using neutralizing antibodies or T cells derived from genetically modified mice, TL1A inhibition of Th17 development was found to be independent of IL-2, IL-27, γIFN, IFNAR1, and STAT1. Under suboptimal TCR activation, TL1A continued to block IL-17A secretion, however, the reduced threshold of TCR engagement was now linked with an increase in TL1A-driven proliferation. In contrast, fully committed Th17 cells displayed an altered TL1A responsiveness and in the absence of TCR costimulation supported the maintenance of T cell IL-17A expression. Consequently, TL1A orchestrates unique outcomes in naive and effector T-helper cells, which may affect the proliferation, differentiation and maintenance of Th17 cells in peripheral compartments and inflamed tissues.—Jones, G. W., Stumhofer, J. S., Foster, T., Twohig, J.P., Hertzog, P., Topley, N., Williams, A. S., Hunter, C. A., Jenkins, B. J., Wang, E. C. Y., Jones, S. A. Naive and activated T cells display differential responsiveness to TL1A that affects Th17 generation, maintenance, and proliferation.

Death receptor 3 (DR3, TNFRSF25), the closest family relative to tumor necrosis factor receptor 1, promotes CD4(+) T-cell-driven inflammatory disease. We investigated the in vivo role of DR3 and its ligand TL1A in viral infection, by challenging DR3-deficient (DR3(KO)) mice and their DR3(WT) littermates with the β-herpesvirus murine cytomegalovirus or the poxvirus vaccinia virus. The phenotype and function of splenic T-cells were analyzed using flow cytometry and molecular biological techniques. We report surface expression of DR3 by naive CD8(+) T cells, with TCR activation increasing its levels 4-fold and altering the ratio of DR3 splice variants. T-cell responses were reduced up to 90% in DR3(KO) mice during acute infection. Adoptive transfer experiments indicated this was dependent on T-cell-restricted expression of DR3. DR3-dependent CD8(+) T-cell expansion was NK and CD4 independent and due to proliferation, not decreased cell death. Notably, impaired immunity in DR3(KO) hosts on a C57BL/6 background was associated with 4- to 7-fold increases in viral loads during the acute phase of infection, and in mice with suboptimal NK responses was essential for survival (37.5%). This is the first description of DR3 regulating virus-specific T-cell function in vivo and uncovers a critical role for DR3 in mediating antiviral immunity.

Burnet proposed in the 1950's that the immune system is engaged in identifying and destroying abnormal cancerous cells. This process, termed immune surveillance, has been at the centre of intense debate for decades. Results using immunodeficient mice lend support to the immune surveillance hypothesis. We surmised that immune surveillance would be hampered by the inhibitory effect of naturally occurring FoxP3 þ regulatory T cells, a population of T cells shown to be present at an increased frequency in a variety of human tumours. The carcinogen, methylcholanthrene was injected subcutaneously into mice and the steady development of fibrosarcomas was observed over approximately 200 days. These fibrosarcomas were strikingly infiltrated with FoxP3 þ regulatory T cells implying that these cells impinge upon immune-mediated rejection of the tumour. This was confirmed by partial ablation of FoxP3 þ regulatory T-cell activity, which resulted in a marked reduction in tumour incidence. The reduction of tumour incidence was ablated in mice that lacked interferon gamma. These data offer strong support for the concept of immune surveillance and indicate that this process is limited by the inhibitory effect of FoxP3 þ regulatory T cells.

ObjectiveTo investigate the role of death receptor 3 (DR-3) and its ligand tumor necrosis factor–like molecule 1A (TL1A) in the early stages of inflammatory arthritis.MethodsAntigen-induced arthritis (AIA) was generated in C57BL/6 mice deficient in the DR-3 gene (DR3−/−) and their DR3+/+ (wild-type) littermates by priming and intraarticular injection of methylated bovine serum albumin. The joints were sectioned and analyzed histochemically for damage to cartilage and expression of DR3, TL1A, Ly-6G (a marker for neutrophils), the gelatinase matrix metalloproteinase 9 (MMP-9), the aggrecanase ADAMTS-5, and the neutrophil chemoattractant CXCL1. In vitro production of MMP-9 was measured in cultures from fibroblasts, macrophages, and neutrophils following the addition of TL1A and other proinflammatory stimuli.ResultsDR3 expression was up-regulated in the joints of wild-type mice following generation of AIA. DR3−/− mice were protected against cartilage damage compared with wild-type mice, even at early time points prior to the main accumulation of Teff cells in the joint. Early protection against AIA in vivo correlated with reduced levels of MMP-9. In vitro, neutrophils were major producers of MMP-9, while neutrophil numbers were reduced in the joints of DR3−/− mice. However, TL1A neither induced MMP-9 release nor affected the survival of neutrophils. Instead, reduced levels of CXCL1 were observed in the joints of DR3−/− mice.ConclusionDR-3 drives early cartilage destruction in the AIA model of inflammatory arthritis through the release of CXCL1, maximizing neutrophil recruitment to the joint and leading to enhanced local production of cartilage-destroying enzymes.

Death receptor 3 is a proinflammatory member of the immunomodulatory tumor necrosis factor receptor superfamily, which has been implicated in several inflammatory diseases such as arthritis and inflammatory bowel disease. Intriguingly however, constitutive DR3 expression has been detected in the brains of mice, rats, and humans, although its neurological function remains unknown. By mapping the normal brain expression pattern of DR3, we found that DR3 is expressed specifically by cells of the neuron lineage in a developmentally regulated and region-specific pattern. Behavioral studies on DR3-deficient (DR3 ko ) mice showed that constitutive neuronal DR3 expression was required for stable motor control function in the aging adult. DR3 ko mice progressively developed behavioral defects characterized by altered gait, dyskinesia, and hyperactivity, which were associated with elevated dopamine and lower serotonin levels in the striatum. Importantly, retrograde tracing showed that absence of DR3 expression led to the loss of corticostriatal innervation without significant neuronal loss in aged DR3 ko mice. These studies indicate that DR3 plays a key nonredundant role in the retention of normal motor control function during aging in mice and implicate DR3 in progressive neurological disease.

Tumor necrosis factor receptor superfamily (TNFRSF) members were initially identified as immunological mediators, and are still commonly perceived as immunological molecules. However, our understanding of the diversity of TNFRSF members' roles in mammalian physiology has grown significantly since the first discovery of TNFRp55 (TNFRSF1) in 1975. In particular, the last decade has provided evidence for important roles in brain development, function and the emergent field of neuronal homeostasis. Recent evidence suggests that TNFRSF members are expressed in an overlapping regulated pattern during neuronal development, participating in the regulation of neuronal expansion, growth, differentiation and regional pattern development. This review examines evidence for non-immunological roles of TNFRSF members in brain development, function and maintenance under normal physiological conditions. In addition, several aspects of brain function during inflammation will also be described, when illuminating and relevant to the non-immunological role of TNFRSF members. Finally, key questions in the field will be outlined.