TL1A-DR3 Plasma Levels Are Predictive of HIV-1 Disease Control, and DR3 Costimulation Boosts HIV-1-Specific T Cell Responses.

Relative control of HIV-1 infection has been linked to genetic and immune host factors. In this study, we analyzed 96 plasma proteome arrays from chronic untreated HIV-1-infected individuals using the classificatory random forest approach to discriminate between uncontrolled disease (plasma viral load [pVL] >50,000 RNA copies/ml; CD4 counts 283 cells/mm3, n = 47) and relatively controlled disease (pVL <10,000 RNA copies/ml; CD4 counts 657 cells/mm3, n = 49). Our analysis highlighted the TNF molecule's relevance, in particular, TL1A (TNFSF15) and its cognate DR3 (TNFSRF25), both of which increased in the relative virus control phenotype. DR3 levels (in plasma and PBMCs) were validated in unrelated cohorts (including long-term nonprogressors), thus confirming their independence from CD4 counts and pVL. Further analysis in combined antiretroviral treatment (cART)-treated individuals with a wide range of CD4 counts (137-1835 cells/mm3) indicated that neither TL1A nor DR3 levels reflected recovery of CD4 counts with cART. Interestingly, in cART-treated individuals, plasma TL1A levels correlated with regulatory T cell frequencies, whereas soluble DR3 was strongly associated with the abundance of effector HLA-DR+CD8+ T cells. A positive correlation was also observed between plasma DR3 levels and the HIV-1-specific T cell responses. In vitro, costimulation of PBMC with DR3-specific mAb increased the magnitude of HIV-1-specific responses. Finally, in splenocytes of DNA.HTI-vaccinated mice, costimulation of HTI peptides and a DR3 agonist (4C12) intensified the magnitude of T cell responses by 27%. These data describe the role of the TL1A-DR3 axis in the natural control of HIV-1 infection and point to the use of DR3 agonists in HIV-1 vaccine regimens.

The TL1A-DR3 Axis Selectively Drives Effector Functions in Human MAIT Cells.

Mucosal-associated invariant T (MAIT) cells are semi-invariant T cells specifically recognizing riboflavin derivatives that are synthesized by many bacteria and fungi presented by MHC class I-related MR1 molecules. Accumulating evidence, however, indicates that MAIT cell functions are inducible by cytokine stimuli in the absence of TCR ligation, identifying MAIT cells as innate sentinels in inflammatory environments. In this study, we demonstrate that death receptor 3 (DR3), a member of the TNFR superfamily, is ex vivo expressed and predominantly upregulated on the surface of human MAIT cells by innate cytokine stimulation. In turn, the DR3 ligand TNF-like protein 1A (TL1A) licenses innate TNF-α production in the absence of cognate triggers, being sufficient to promote activation of primary endothelial cells in vitro. TL1A further amplifies synthesis of IFN-γ and granzyme B in the presence of otherwise weak innate stimuli and strongly augments polyfunctionality. Mechanistically, TL1A potentiates T-bet expression, early NF-κB, and late p38 MAP kinase phosphorylation, with the latter being indispensable for TNF-α production by MAIT cells. Of note, endogenous TL1A is also rapidly released from PBMC cultures in response to bacterial triggering, thereby equally augmenting Ag-specific MAIT cell effector functions. In summary, to our knowledge, we identify a new inflammatory mechanism in MAIT cells linking the DR3/TL1A axis with amplification of TCR-dependent and -independent effector functions, particularly inducing excessive innate TNF-α production. Given that both TL1A and TNF-α are abundantly present at sites of chronic inflammation, the contribution of MAIT cells in such scenarios needs to be determined.

T cell expression of IL-18R and DR3 is essential for non-cognate stimulation of Th1 cells and optimal clearance of intracellular bacteria.

Th1 cells can be activated by TCR-independent stimuli, but the importance of this pathway in vivo and the precise mechanisms involved require further investigation. Here, we used a simple model of non-cognate Th1 cell stimulation in Salmonella-infected mice to examine these issues. CD4 Th1 cell expression of both IL-18R and DR3 was required for optimal IFN-γ induction in response to non-cognate stimulation, while IL-15R expression was dispensable. Interestingly, effector Th1 cells generated by immunization rather than live infection had lower non-cognate activity despite comparable IL-18R and DR3 expression. Mice lacking T cell intrinsic expression of MyD88, an important adapter molecule in non-cognate T cell stimulation, exhibited higher bacterial burdens upon infection with Salmonella, Chlamydia or Brucella, suggesting that non-cognate Th1 stimulation is a critical element of efficient bacterial clearance. Thus, IL-18R and DR3 are critical players in non-cognate stimulation of Th1 cells and this response plays an important role in protection against intracellular bacteria.

Shared αß TCR Usage in Lungs of Sarcoidosis Patients with Löfgren's Syndrome.

Sarcoidosis is a granulomatous disease that primarily affects the lungs and is characterized by an accumulation of CD4+ T cells in the bronchoalveolar lavage (BAL). Previous work has indicated that HLA-DRB1*03:01+ (DR3+) patients diagnosed with the acute form of the disease, Löfgren's syndrome (LS), have an accumulation of CD4+ T cells bearing TCRs using TRAV12-1 (formerly AV2S3). However, the importance of these α-chains in disease pathogenesis and the paired TCRß-chain remains unknown. This study aimed to identify expanded αßTCR pairs expressed on CD4+ T cells derived from the BAL of DR3+ LS patients. Using a deep-sequencing approach, we determined TCRα- and TCRß-chain usage, as well as αßTCR pairs expressed on BAL CD4+ T cells from LS patients. TRAV12-1 and TRBV2 (formerly BV22) were the most expanded V region gene segments in DR3+ LS patients relative to control subjects, and TRAV12-1 and TRBV2 CDR3 motifs were shared among multiple DR3+ LS patients. When assessing αßTCR pairing, TRAV12-1 preferentially paired with TRBV2, and these TRAV12-1/TRBV2 TCRs displayed CDR3 homology. These findings suggest that public CD4+ TCR repertoires exist among LS patients and that these T cells are recognizing the putative sarcoidosis-associated Ag(s) in the context of DR3.

Effect of infusion of monoclonal antibodies to tumour necrosis factor-receptor super family 25 on graft rejection in allo-immune mice receiving autologous marrow transplantation.

Significant barriers to transplantation exist for individuals who are pre-sensitized to donor antigen and have high titres of donor-reactive antibody. We report the effect of autologous bone marrow transplantation (BMTx) after myeloablation in pre-sensitized mice along with the use of monoclonal antibodies (mAbs) to tumour necrosis factor-receptor super family 25 (TNFRSF25), expressed on regulatory T (Treg) cells. C57BL/6 mice, which had been sensitized earlier with BALB/c skin allografts, received secondary BALB/c grafts after the primary grafts had been rejected. Subsequently, recipient mice underwent myeloablation with cyclophosphamide and busulphan and were injected with T-cell-depleted bone marrow from CD45.1 congenic donors (BMTx). Recipient mice underwent immunosuppressive treatment with rapamycin. A subgroup of mice was also treated with mAbs to TNFRSF25. Control mice were pre-sensitized mice that received cyclophosphamide and busulphan followed by rapamycin. BMTx-treated mice had significantly prolonged skin graft survival versus control mice. These mice also showed attenuated donor-specific mixed lymphocyte co-culture responses relative to controls, increased splenic Treg cells and markedly diminished serum anti-donor IgG. Infusion of anti-TNFRSF25 mAbs further augmented graft survival and increased graft-infiltrating Treg cells. These mAbs also expanded murine and human Treg cells in vitro with the capacity to attenuate mixed lymphocyte co-cultures using fresh peripheral blood mononuclear cells. Overall, this study delineates the roles of autologous BMTx and anti-TNFRSF25 mAbs in expanding Treg cells and attenuating alloimmune responses in pre-sensitized mice.

Treatment with agonistic DR3 antibody results in expansion of donor Tregs and reduced graft-versus-host disease.

The paucity of regulatory T cells (Tregs) limits clinical translation to control aberrant immune reactions including graft-versus-host disease (GVHD). Recent studies showed that the agonistic antibody to DR3 (αDR3) expanded CD4(+)FoxP3(+) Tregs in vivo. We investigated whether treating donor mice with a single dose of αDR3 could alleviate acute GVHD in a MHC-mismatched bone marrow transplantation model. αDR3 induced selective proliferation of functional Tregs. CD4(+) T cells isolated from αDR3-treated mice contained higher numbers of Tregs and were less proliferative to allogeneic stimuli. In vivo GVHD studies confirmed that Tregs from αDR3-treated donors expanded robustly and higher frequencies of Tregs within donor CD4(+) T cells were maintained, resulting in improved survival. Conventional T cells derived from αDR3-treated donors showed reduced activation and proliferation. Serum levels of proinflammatory cytokines (IFNγ, IL-1ß, and TNFα) and infiltration of donor T cells into GVHD target tissues (gastrointestinal tract and liver) were decreased. T cells from αDR3-treated donors retained graft-vs-tumor (GVT) effects. In conclusion, a single dose of αDR3 alleviates acute GVHD while preserving GVT effects by selectively expanding and maintaining donor Tregs. This novel strategy will facilitate the clinical application of Treg-based therapies.

The TNF-family receptor DR3 is essential for diverse T cell-mediated inflammatory diseases.

DR3 (TRAMP, LARD, WSL-1, TNFRSF25) is a death-domain-containing tumor necrosis factor (TNF)-family receptor primarily expressed on T cells. TL1A, the TNF-family ligand for DR3, can costimulate T cells, but the physiological function of TL1A-DR3 interactions in immune responses is not known. Using DR3-deficient mice, we identified DR3 as the receptor responsible for TL1A-induced T cell costimulation and dendritic cells as the likely source for TL1A during T cell activation. Despite its role in costimulation, DR3 was not required for in vivo T cell priming, for polarization into T helper 1 (Th1), Th2, or Th17 effector cell subtypes, or for effective control of infection with Toxoplasma gondii. Instead, DR3 expression was required on T cells for immunopathology, local T cell accumulation, and cytokine production in Experimental Autoimmune Encephalomyelitis (EAE) and allergic lung inflammation, disease models that depend on distinct effector T cell subsets. DR3 could be an attractive therapeutic target for T cell-mediated autoimmune and allergic diseases.

The TNF-family ligand TL1A and its receptor DR3 promote T cell-mediated allergic immunopathology by enhancing differentiation and pathogenicity of IL-9-producing T cells.

The TNF family cytokine TL1A (Tnfsf15) costimulates T cells and type 2 innate lymphocytes (ILC2) through its receptor DR3 (Tnfrsf25). DR3-deficient mice have reduced T cell accumulation at the site of inflammation and reduced ILC2-dependent immune responses in a number of models of autoimmune and allergic diseases. In allergic lung disease models, immunopathology and local Th2 and ILC2 accumulation is reduced in DR3-deficient mice despite normal systemic priming of Th2 responses and generation of T cells secreting IL-13 and IL-4, prompting the question of whether TL1A promotes the development of other T cell subsets that secrete cytokines to drive allergic disease. In this study, we find that TL1A potently promotes generation of murine T cells producing IL-9 (Th9) by signaling through DR3 in a cell-intrinsic manner. TL1A enhances Th9 differentiation through an IL-2 and STAT5-dependent mechanism, unlike the TNF-family member OX40, which promotes Th9 through IL-4 and STAT6. Th9 differentiated in the presence of TL1A are more pathogenic, and endogenous TL1A signaling through DR3 on T cells is required for maximal pathology and IL-9 production in allergic lung inflammation. Taken together, these data identify TL1A-DR3 interactions as a novel pathway that promotes Th9 differentiation and pathogenicity. TL1A may be a potential therapeutic target in diseases dependent on IL-9.

Human group3 innate lymphoid cells express DR3 and respond to TL1A with enhanced IL-22 production and IL-2-dependent proliferation.

Death receptor 3 (DR3, TNFRSF25) is expressed by activated lymphocytes and signaling by its ligand, TL1A, enhances cytokine expression and proliferation. Recent studies show that DR3 is also present on murine type 2 innate lymphoid cells (ILC2s). Here, we show that DR3 is expressed by IL-22-producing human group 3 innate lymphoid cells (ILC3s). Stimulation of ILC3s with exogenous TL1A alone had no impact on cytokine production or proliferation. Addition of TL1A to IL-1ß + IL-23 significantly enhanced the amount IL-22 produced by ILC3s as well as the percentage IL-22- and IL-8-producing cells. Addition of TL1A to IL-1ß + IL-23 also augmented ILC3 proliferation. Mechanistically, this occurred through the upregulation of CD25 and responsiveness to IL-2 stimulation. The combination of TL1A, IL-1ß+ IL-23, and IL-2 expanded ILC3s while IL-1ß+ IL-23 did not increase proliferation above controls. After 2 weeks of expansion, ILC3s maintained their phenotype, transcription factor expression, and function (IL-22 production). These findings identify DR3 as a costimulatory molecule on ILC3s that could be exploited for ex vivo expansion and clinical use.

Biologics beyond TNF-α inhibitors and the effect of targeting the homologues TL1A-DR3 pathway in chronic inflammatory disorders.

A number of anti-tumor necrosis factor alpha (TNF-α) biologics have been developed in recent years, such as adalimumab, etanercept, and infliximab for the treatment of chronic inflammatory disorders like rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and psoriasis and several other novel drugs that target TNF-α signaling are still being developed. Indeed, blockade of this pathway seems so important amongst immune-targets that TNF-α targeted therapies will continue to have a significant role in the treatment of chronic inflammation. However, up to 40% of RA and IBD patients do not respond to anti-TNF-α treatment and one possible explanation may be the heterogeneity of chronic inflammatory diseases and a dominance of other significant TNF family members. Indeed, polymorphisms in the TNF family member, TL1A gene, is associated with the development of IBD and increased serum concentrations of TL1A has been demonstrated in patients with various chronic inflammatory disorders. Here, we describe the current knowledge of TL1As immunobiology and present results from human disease, animal models, and pre-clinical intervention studies that point toward development of anti-TL1A therapy as a highly promising strategy for treatment of chronic inflammatory disorders.

The molecular basis for development of proinflammatory autoantibodies to progranulin.

Recently we identified in a wide spectrum of autoimmune diseases frequently occurring proinflammatory autoantibodies directed against progranulin, a direct inhibitor of TNFR1 & 2 and of DR3. In the present study we investigated the mechanisms for the breakdown of self-tolerance against progranulin. Isoelectric focusing identified a second, differentially electrically charged progranulin isoform exclusively present in progranulin-antibody-positive patients. Alkaline phosphatase treatment revealed this additional progranulin isoform to be hyperphosphorylated. Subsequently Ser81, which is located within the epitope region of progranulin-antibodies, was identified as hyperphosphorylated serine residue by site directed mutagenesis of candidate phosphorylation sites. Hyperphosphorylated progranulin was detected exclusively in progranulin-antibody-positive patients during the courses of their diseases. The occurrence of hyperphosphorylated progranulin preceded seroconversions of progranulin-antibodies, indicating adaptive immune response. Utilizing panels of kinase and phosphatase inhibitors, PKCß1 was identified as the relevant kinase and PP1 as the relevant phosphatase for phosphorylation and dephosphorylation of Ser81. In contrast to normal progranulin, hyperphosphorylated progranulin interacted exclusively with inactivated (pThr320) PP1, suggesting inactivated PP1 to cause the detectable occurrence of phosphorylated Ser81 PGRN. Investigation of possible functional alterations of PGRN due to Ser81 phosphorylation revealed, that hyperphosphorylation prevents the interaction and thus direct inhibition of TNFR1, TNFR2 and DR3, representing an additional direct proinflammatory effect. Finally phosphorylation of Ser81 PGRN alters the conversion pattern of PGRN. In conclusion, inactivated PP1 induces hyperphosphorylation of progranulin in a wide spectrum of autoimmune diseases. This hyperphosphorylation prevents direct inhibition of TNFR1, TNFR2 and DR3 by PGRN, alters the conversion of PGRN, and is strongly associated with the occurrence of neutralizing, proinflammatory PGRN-antibodies, indicating immunogenicity of this alternative secondary modification.

TL1A and DR3, a TNF family ligand-receptor pair that promotes lymphocyte costimulation, mucosal hyperplasia, and autoimmune inflammation.

DR3 (TNFRSF25) is a member of the tumor necrosis factor receptor (TNFR) superfamily expressed primarily on lymphocytes and is a receptor for the TNF family cytokine TL1A (TNFSF15). DR3 costimulates T-cell activation, but it is unique among these receptors in that it signals through an intracytoplasmic death domain and the adapter protein TRADD (TNFR-associated death domain). TL1A costimulates T cells to produce a wide variety of cytokines and can promote expansion of activated and regulatory T cells in vivo. Studies in mice deficient in DR3 or TL1A or in animals treated with antibodies that block the activity of TL1A have revealed a specific role for DR3 in enhancing effector T-cell proliferation at the site of tissue inflammation in autoimmune disease models. DR3 appears to be required in autoimmune disease models dependent on a variety of different T-cell subsets and also invariant natural killer T (iNKT) cells. Chronic expression of TL1A induces a distinct interleukin-13-dependent pathology in the small intestine marked by goblet cell hyperplasia and other features associated with allergic and anti-parasitic responses. These studies suggest that TL1A may be a viable target for therapies designed to inhibit the T-cell-dependent component of diverse autoimmune diseases.

TL1A increased the differentiation of peripheral Th17 in rheumatoid arthritis.

The interaction between TNF-like protein 1A (TL1A) and its receptors, death receptor-3 (DR3) may be involved in the pathogenesis of rheumatoid arthritis (RA) through the regulation of Th17. Our data here showed that TL1A could significantly promote Th17 differentiation and RORc mRNA expression from naive T cells and enhance IL-17A level in cell supernatant in RA patients. Anti-TNF-α treatment had suppressive effects on TL1A-mediated Th17 differentiation and RORc mRNA expression. In addition, The percentage of peripheral CD4+DR3+T cells of RA was significantly higher than that of healthy controls (HC), and this increased percentage of CD4+DR3+T cells was obviously up-regulated when stimulated with anti-CD3 and anti-CD28 antibody in RA patients. However, anti-CD3 and anti-CD28 antibody stimulation did not increase the percentage of CD4+DR3+IL-17A+T cells in RA patients. These results suggested that TL1A could promote Th17 differentiation in RA via the activation of RORc, and this effect may be mediated by the binding of TL1A with DR3.

[Frequency of the occurrence of spliced variants of the messenger RNA DR3/LARD in herpesviral infection].

Analysis of frequency of the occurrence of membrane and soluble forms of the mRNA DR3/LARD in blood in herpesviral infection of various etiology was studied. Four forms of the mRNA DR3/LARD were detected with various frequencies in blood cells of healthy volunteers. Patients with herpesviral infection of various etiology were studied using RT-PCR. Two forms encoded membrane molecules (mRNA LARD 1a, mRNA DR3beta) and two other forms accorded soluble forms of receptor (mRNA LARD 3, mRNA soluble DR3beta). It was revealed that the frequency of the occurrence of mRNA soluble DR3beta form decreased in patients with the varicella zoster virus (VZV) infection in comparison with healthy volunteers. However, the patients with the Epstein-Barr virus (EBV) and cytomegalovirus (CMV) infection did not display significant change in occurrence of mRNA soluble DR3beta form. As a whole, changes in frequency of occurrence of spliced variants of mRNA DR3/LARD are directed toward modulation of apoptosis and restraint antiviral immune response.

Anti-TL1A monoclonal antibody modulates the dysregulation of Th1/Th17 cells and attenuates granuloma formation in sarcoidosis by inhibiting the PI3K/AKT signaling pathway.

Sarcoidosis is a systemic granulomatous disease characterized by non-caseating epithelioid cell granulomas. One of its immunological hallmarks is the differentiation of CD4 + naïve T cells into Th1/Th17 cells, accompanied by the release of numerous pro-inflammatory cytokines. The TL1A/DR3 signaling pathway plays a crucial role in activating effector lymphocytes, thereby triggering pro-inflammatory responses. The primary aim of this investigation was to scrutinize the impact of anti-TL1A monoclonal antibody on the dysregulation of Th1/Th17 cells and granuloma formation in sarcoidosis. Initially, the abnormal activation of the TL1A/DR3 signaling pathway in pulmonary tissues of sarcoidosis patients was confirmed using qPCR and immunohistochemistry techniques. Subsequently, employing a murine model of sarcoidosis, the inhibitory effects of anti-TL1A monoclonal antibody on the TL1A/DR3 signaling pathway in sarcoidosis were investigated through qPCR, immunohistochemistry, and Western blot experiments. The influence of anti-TL1A monoclonal antibody on granulomas was assessed through HE staining, while their effects on sarcoidosis Th1/Th17 cells and associated cytokine mRNA levels were evaluated using flow cytometry and qPCR, respectively. Immunofluorescence and Western blot experiments corroborated the inhibitory effects of anti-TL1A monoclonal antibody on the aberrant activation of the PI3K/AKT signaling pathway in sarcoidosis. The findings of this study indicate that the TL1A/DR3 signaling pathway is excessively activated in sarcoidosis. Anti-TL1A monoclonal antibody effectively inhibit this abnormal activation in sarcoidosis, thereby alleviating the dysregulation of Th1/Th17 cells and reducing the formation of pulmonary granulomas. This effect may be associated with the inhibition of the downstream PI3K/AKT signaling pathway. Anti-TL1A monoclonal antibody hold promise as a potential novel therapeutic intervention for sarcoidosis.

Death receptor 3 is essential for generating optimal protective CD4⁺ T-cell immunity against Salmonella.

The TNF receptor superfamily member death receptor 3 (DR3) exacerbates Th2- and Th17-cell-mediated inflammatory and autoimmune conditions, yet no role in host defence has been reported. Here, we examined the role of DR3 during infection with Salmonella enterica serovar Typhimurium. Infection resulted in protracted expression of the DR3 ligand TL1A but not the related TNF superfamily proteins OX40L or CD30L. TL1A expression was localized to splenic F4/80(+) macrophages where S. enterica Typhimurium replicates, and temporally coincided with the onset of CD4(+) -cell expansion. To address the relevance of the TL1A-DR3 interaction, we examined immune responses to S. enterica Typhimurium in mice lacking DR3. Infected DR3(-/-) mice harboured reduced numbers of antigen-experienced and proliferating CD4(+) T cells compared with WT mice. Furthermore, the frequency of IFN-γ(+) CD4(+) T cells in DR3(-/-) mice was lower throughout the time of bacterial clearance. Importantly, bacterial clearance, which is dependent on Th1 cells, was also impaired in DR3(-/-) mice. This defect was intrinsic to CD4(+) T cells as evidenced by an increase in bacterial burden in RAG2-deficient mice receiving DR3(-/-) CD4(+) T cells compared with WT CD4(+) -cell recipients. These data establish for the first time a role for DR3 in a host defence response.

TNFRSF25 agonistic antibody and galectin-9 combination therapy controls herpes simplex virus-induced immunoinflammatory lesions.

Ocular infection with herpes simplex virus 1 (HSV-1) results in a chronic immunoinflamammtory reaction in the cornea, which is primarily orchestrated by CD4(+) T cells. Hence, targeting proinflammatory CD4(+) T cells or increasing the representation of cells that regulate their function is a relevant therapeutic strategy. In this report, we demonstrate that effective therapeutic control can be achieved using a combination of approaches under circumstances where monotherapy is ineffective. We use a convenient and highly effective monoclonal antibody (MAb) approach with MAbT25 to expand cells that express the tumor necrosis factor receptor superfamily member 25 (TNFRSF25). In naïve animals, these are predominantly cells that are Foxp3-positive regulatory T cells. MAbT25 treatment before or at the time of initial HSV infection was an effective means of reducing the severity of subsequent stromal keratitis lesions. However, MAbT25 treatment was not effective if given 6 days after infection since it expanded proinflammatory effector T cells, which also express TNFRSF25. Therefore, the MAbT25 procedure was combined with galectin-9 (Gal-9), an approach that compromises the activity of T cells involved in tissue damage. The combination therapy provided highly effective lesion control over that achieved by treatment with one of them. The beneficial outcome of the combination therapy was attributed to the expansion of the regulatory T cell population that additionally expressed activation markers such as CD103 needed to access inflammatory sites. Additionally, there was a marked reduction of CD4(+) gamma interferon-producing effector T cells responsible for orchestrating the tissue damage. The approach that we describe has potential application to control a wide range of inflammatory diseases, in addition to stromal keratitis, an important cause of human blindness.

The tumor necrosis factor-like cytokine 1A/death receptor 3 cytokine system in intestinal inflammation.

PURPOSE OF REVIEW: Tumor necrosis factor (TNF)-like cytokine 1A (TL1A) associates with the death receptor 3 (DR3) on activated lymphocytes and induces proinflammatory signals. The decoy receptor 3 (DcR3) competes for TL1A binding and inhibits functional signaling. This review focuses on the role of the TL1A/DR3/DcR3 cytokine system in inflammatory bowel diseases (IBDs). RECENT FINDINGS: TL1A may induce IFN-γ-mediated and IL-17-mediated proinflammatory pathways in IBDs by acting on DR3-expressing, CD4(+)CD161(+) lymphocytes, which are substantially enriched at the inflamed intestinal mucosa. In addition, TL1A/DR3 signaling results in expansion of the Treg pool with concomitant and transient inhibition of their suppressive function. Constitutive expression of TL1A in transgenic mice was associated with small intestinal inflammation, which was accompanied by colonic fibrosis both spontaneously and under colitogenic conditions. Recent human studies demonstrated that soluble TL1A and DcR3 are present in the systemic circulation in patients with active IBD and decline after successful anti-inflammatory treatment. SUMMARY: TL1A/DR3 interactions may participate in the pathogenesis of chronic intestinal inflammation and offer novel therapeutic targets for patients with ulcerative colitis and Crohn's disease.

The adaptor protein TRADD is essential for TNF-like ligand 1A/death receptor 3 signaling.

TNFR-associated death domain protein (TRADD) is a key effector protein of TNFR1 signaling. However, the role of TRADD in other death receptor (DR) signaling pathways, including DR3, has not been completely characterized. Previous studies using overexpression systems suggested that TRADD is recruited to the DR3 complex in response to the DR3 ligand, TNF-like ligand 1A (TL1A), indicating a possible role in DR3 signaling. Using T cells from TRADD knockout mice, we demonstrate in this study that the response of both CD4(+) and CD8(+) T cells to TL1A is dependent upon the presence of TRADD. TRADD knockout T cells therefore lack the appropriate proliferative response to TL1A. Moreover, in the absence of TRADD, both the stimulation of MAPK signaling and activation of NF-κB in response to TL1A are dramatically reduced. Unsurprisingly, TRADD is required for recruitment of receptor interacting protein 1 and TNFR-associated factor 2 to the DR3 signaling complex and for the ubiquitination of receptor interacting protein 1. Thus, our findings definitively establish an essential role of TRADD in DR3 signaling.

Interleukin-32 enhances cytotoxic effect of natural killer cells to cancer cells via activation of death receptor 3.

Studies have demonstrated that the anti-tumour effect of natural killer (NK) cells is successful for patients with several cancers. Although interleukin-32 (IL-32) is endogenously expressed in NK cells, cytolytic function of NK cells against cancer cells has not been fully demonstrated. In the present study, we found that the growth of cancer cells was suppressed when colon cancer cells or prostate cancer cells were co-cultured with NK-92 cells, an NK cell line. We also found that the expression of tumour necrosis factor receptor 2 and death receptor 3 (DR3) was increased in PC3 cells, and the expression of FAS and DR3 was increased in SW620 cells by co-culture with NK-92 cells. However, cancer cell growth inhibition and IL-32 expression were abolished when cancer cells were co-cultured with NK cells transfected with small interfering (si) RNA of IL-32. DR3 expression was also diminished by co-culture with IL-32-specific siRNA-transfected NK-92 cells. Expression of APO3L, a ligand of DR3, was elevated in NK cells that were co-cultured with cancer cells. It was also found that expression of apoptosis-related proteins such as cleaved caspase-3 and bax was increased in cancer cells co-cultured with NK-92 cells, but their expression was abolished by co-culture with IL-32 siRNA-transfected NK-92 cells. Moreover, knockdown of DR3 in co-culture of NK-92 cells with cancer cells by siRNA or antibodies of DR3 and APO3L reversed the growth inhibitory effect of NK-92 cells. In conclusion, our study showed that IL-32 enhanced the cytotoxic effect of NK-92 cells on the cancer cells through activation of DR3 and caspase-3.