CD161 DEFINES EFFECTOR T CELLS THAT EXPRESS LIGHT AND RESPOND TO TL1A-DR3 SIGNALING

Effects of dioscin from Dioscorea nipponica on TL1A/DR3 and Th9 cells in a collagen-induced arthritis mouse model

Rheumatoid arthritis (RA) is a systemic autoimmune disease, and TL1A and its receptor DR3 play important roles in its pathogenesis. Th9 cells are involved in RA development. Dioscin from Dioscorea nipponica (DDN) has a therapeutic effect on RA, but its effect on TL1A/DR3 and Th9 cells remains unclear. A collagen-induced arthritis (CIA) model was established in DBA/1 mice, and the therapeutic effects of DDN were determined using pathological sections and arthritis index scores. Western blotting and PCR were used to detect TL1A, DR3, PU.1, TGF-β and IRF-4. Enzyme-linked immunosorbent assay was used to detect the expression of TL1A and IL-9 in the serum. Immunofluorescence was used to detect the localization and expression of TL1A, DR3, and PU.1 in synovial tissue. Flow cytometry was used to detect TL1A and DR3 expression in different immune cells and Th9 cells. DDN ameliorated bone destruction, inflammatory cell infiltration, synovial inflammation, cartilage tissue destruction, and proteoglycan loss. DDN downregulated TL1A, DR3, and PU.1 in the synovium of the lymph nodes and spleen and TL1A and IL-9 in the serum. DDN decreased the number of TL1A-expressing APCs and macrophages, DR3-expressing CD4 + T cells, and Th9 cells. Th9 cell differentiation-related factors TGF-β and IRF-4 were also inhibited by DDN. We conclude that DNN inhibited the expression of TL1A/DR3 in CIA mice and suppressed the expression of the Th9 cell-specific transcription factor PU.1, Th9 cell number, and IL-9 secretion. DDN inhibited the function of Th9 cells by targeting TGF-β and IRF-4 in the TL1A/DR3 pathway, thereby reducing inflammation.

Immunobiology and conflicting roles of the human CD161 receptor in T cells

Human C-type lectin-like CD161 is a type-II transmembrane protein expressed on the surface of various lymphocytes across innate and adaptive immune systems. CD161+ T cells displayed enhanced ability to produce cytokines and were shown to be enriched in the gut. Independently of function, CD161 was used as marker of innate-like T cells and marker of IL-17-producing cells. The function of CD161 is still not fully understood. In T cells, CD161 was proposed to act as co-signalling receptor that influence T-cell receptor-dependent responses. However, conflicting studies were published demonstrating lack of agreement over the role of CD161 during T-cell activation. In this review, we outline phenotypical and functional consequences of CD161 expression in T cells. We provide critical discussion over the most pressing issues including in depth evaluation of the literature concerning CD161 putative co-signalling properties.

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.

TCR and Inflammatory Signals Tune Human MAIT Cells to Exert Specific Tissue Repair and Effector Functions

MAIT cells are an unconventional T cell population that can be activated through both TCR-dependent and TCR-independent mechanisms. Here, we examined the impact of combinations of TCR-dependent and TCR-independent signals in human CD8+ MAIT cells. TCR-independent activation of these MAIT cells from blood and gut was maximized by extending the panel of cytokines to include TNF-superfamily member TL1A. RNA-seq experiments revealed that TCR-dependent and TCR-independent signals drive MAIT cells to exert overlapping and specific effector functions, affecting both host defense and tissue homeostasis. Although TCR triggering alone is insufficient to drive sustained activation, TCR-triggered MAIT cells showed specific enrichment of tissue-repair functions at the gene and protein levels and in in vitro assays. Altogether, these data indicate the blend of TCR-dependent and TCR-independent signaling to CD8+ MAIT cells may play a role in controlling the balance between healthy and pathological processes of tissue inflammation and repair.

The Anatomical Location Shapes the Immune Infiltrate in Tumors of Same Etiology and Affects Survival

PURPOSE

The tumor immune microenvironment determines clinical outcome. Whether the original tissue in which a primary tumor develops influences this microenvironment is not well understood.

EXPERIMENTAL DESIGN

We applied high-dimensional single-cell mass cytometry [Cytometry by Time-Of-Flight (CyTOF)] analysis and functional studies to analyze immune cell populations in human papillomavirus (HPV)-induced primary tumors of the cervix (cervical carcinoma) and oropharynx (oropharyngeal squamous cell carcinoma, OPSCC).

RESULTS

Despite the same etiology of these tumors, the composition and functionality of their lymphocytic infiltrate substantially differed. Cervical carcinoma displayed a 3-fold lower CD4:CD8 ratio and contained more activated CD8⁺CD103⁺CD161⁺ effector T cells and less CD4⁺CD161⁺ effector memory T cells than OPSCC. CD161⁺ effector cells produced the highest cytokine levels among tumor-specific T cells. Differences in CD4⁺ T-cell infiltration between cervical carcinoma and OPSCC were reflected in the detection rate of intratumoral HPV-specific CD4⁺ T cells and in their impact on OPSCC and cervical carcinoma survival. The peripheral blood mononuclear cell composition of these patients, however, was similar.

CONCLUSIONS

The tissue of origin significantly affects the overall shape of the immune infiltrate in primary tumors.

Tumor Necrosis Factor-like Cytokine TL1A and Its Receptors DR3 and DcR3: Important New Factors in Mucosal Homeostasis and Inflammation

Tumor necrosis factor (TNF)-like cytokine 1A (TL1A) is a member of the TNF superfamily of proteins (TNFSF15), which signals through association with death domain receptor 3 (DR3). Decoy receptor 3 (DcR3) competes with DR3 for TL1A binding and inhibits functional signaling. These proteins are significantly upregulated in inflamed intestinal tissues, and their pathogenetic importance for inflammatory bowel disease (IBD) is suggested by accumulating evidence. TL1A/DR3 induce costimulatory signals to activated lymphocytes, including the gut-specific populations of CD4+CD161+ and CD4+CCR9+ cells, affecting all major effector pathways and inducing the mucosal upregulation of Th1, Th2, and Th17 factors. They may also participate in mucosal homeostasis and defense against pathogens through their effects on the development and function of the recently described innate lymphoid cells. T-regulatory lymphocytes highly express DR3, and they respond to TL1A stimulation also. Mechanistic studies by transgenic expression of TL1A, deletion of TL1A or DR3, and therapeutic blockade by anti-TL1A antibodies all support the critical involvement of the corresponding pathways in the pathogenesis of chronic mucosal inflammation. Wide genome association studies have identified IBD-specific polymorphisms in TNFSF15 gene, which have functional implications and serve as poor prognostic factors. Recently, TL1A blockade in mice was presented as a unique pharmacological treatment for the reversal of established intestinal fibrosis. Finally, TL1A/DR3 signaling seems to critically participate in extraintestinal inflammatory conditions that are frequently associated with IBD as part of the gut-joint-skin-eye axis. These converging lines of evidence make TL1A/DR3 a suitable model for personalized approaches to IBD therapy.

The TNF-family cytokine TL1A: from lymphocyte costimulator to disease co-conspirator

Originally described in 2002 as a T cell-costimulatory cytokine, the tumor necrosis factor family member TNF-like factor 1A (TL1A), encoded by the TNFSF15 gene, has since been found to affect multiple cell lineages through its receptor, death receptor 3 (DR3, encoded by TNFRSF25) with distinct cell-type effects. Genetic deficiency or blockade of TL1A-DR3 has defined a number of disease states that depend on this cytokine-receptor pair, whereas excess TL1A leads to allergic gastrointestinal inflammation through stimulation of group 2 innate lymphoid cells. Noncoding variants in the TL1A locus are associated with susceptibility to inflammatory bowel disease and leprosy, predicting that the level of TL1A expression may influence host defense and the development of autoimmune and inflammatory diseases.

A major population of mucosal memory CD4+ T cells, coexpressing IL-18Rα and DR3, display innate lymphocyte functionality

Mucosal tissues contain large numbers of memory CD4(+) T cells that, through T-cell receptor-dependent interactions with antigen-presenting cells, are believed to have a key role in barrier defense and maintenance of tissue integrity. Here we identify a major subset of memory CD4(+) T cells at barrier surfaces that coexpress interleukin-18 receptor alpha (IL-18Rα) and death receptor-3 (DR3), and display innate lymphocyte functionality. The cytokines IL-15 or the DR3 ligand tumor necrosis factor (TNF)-like cytokine 1A (TL1a) induced memory IL-18Rα(+)DR3(+)CD4(+) T cells to produce interferon-γ, TNF-α, IL-6, IL-5, IL-13, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-22 in the presence of IL-12/IL-18. TL1a synergized with IL-15 to enhance this response, while suppressing IL-15-induced IL-10 production. TL1a- and IL-15-mediated cytokine induction required the presence of IL-18, whereas induction of IL-5, IL-13, GM-CSF, and IL-22 was IL-12 independent. IL-18Rα(+)DR3(+)CD4(+) T cells with similar functionality were present in human skin, nasal polyps, and, in particular, the intestine, where in chronic inflammation they localized with IL-18-producing cells in lymphoid aggregates. Collectively, these results suggest that human memory IL-18Rα(+)DR3(+) CD4(+) T cells may contribute to antigen-independent innate responses at barrier surfaces.

Tumour necrosis factor superfamily members in the pathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the gastrointestinal tract of unclear aetiology of which two major forms are Crohn's disease (CD) and ulcerative colitis (UC). CD and UC are immunologically distinct, although they both result from hyperactivation of proinflammatory pathways in intestines and disruption of intestinal epithelial barrier. Members of the tumour necrosis factor superfamily (TNFSF) are molecules of broad spectrum of activity, including direct disruption of intestinal epithelial barrier integrity and costimulation of proinflammatory functions of lymphocytes. Tumour necrosis factor (TNF) has a well-established pathological role in IBD which also serves as a target in IBD treatment. In this review we discuss the role of TNF and other TNFSF members, notably, TL1A, FasL, LIGHT, TRAIL, and TWEAK, in the pathogenesis of IBD.

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.

SUSTAINED TL1A (TNFSF15) EXPRESSION ON BOTH LYMPHOID AND MYELOID CELLS LEADS TO MILD SPONTANEOUS INTESTINAL INFLAMMATION AND FIBROSIS

TL1A is a member of the TNF superfamily, and its expression is increased in the mucosa of inflammatory bowel disease patients. Moreover, patients with certain TNFSF15 variants over-express TL1A and have a higher risk of developing strictures in the small intestine. Consistently, mice with sustained Tl1a expression in either lymphoid or myeloid cells develop spontaneous ileitis and increased intestinal collagen deposition. Transgenic (Tg) mice with constitutive Tl1a expression in both lymphoid and myeloid cells were generated to assess their in vivo consequence. Constitutive expression of Tl1a in both lymphoid and myeloid cells showed increased spontaneous ileitis and collagen deposition than WT mice. T cells with constitutive expression of Tl1a in both lymphoid and myeloid cells were found to have a more activated phenotype, increased gut homing marker CCR9 expression, and enhanced Th1 and Th17 cytokine activity than WT mice. Although no differences in T cell activation marker, Th1 or Th17 cytokine activity, ileitis, or collagen deposition were found between constitutive Tl1a expression in lymphoid only, myeloid only, or combined lymphoid and myeloid cells. Double hemizygous Tl1a-Tg mice appeared to have worsened ileitis and intestinal fibrosis. Our findings confirm that TL1A-DR3 interaction is involved in T cell-dependent ileitis and fibrosis.

The delay in the development of experimental colitis from isomaltosyloligosaccharides in rats is dependent on the degree of polymerization

Background

Isomaltosyloligosaccharides (IMO) and dextran (Dex) are hardly digestible in the small intestine and thus influence the luminal environment and affect the maintenance of health. There is wide variation in the degree of polymerization (DP) in Dex and IMO (short-sized IMO, S-IMO; long-sized IMO, L-IMO), and the physiological influence of these compounds may be dependent on their DP.

Methodology/Principal Findings

Five-week-old male Wistar rats were given a semi-purified diet with or without 30 g/kg diet of the S-IMO (DP = 3.3), L-IMO (DP = 8.4), or Dex (DP = 1230) for two weeks. Dextran sulfate sodium (DSS) was administered to the rats for one week to induce experimental colitis. We evaluated the clinical symptoms during the DSS treatment period by scoring the body weight loss, stool consistency, and rectal bleeding. The development of colitis induced by DSS was delayed in the rats fed S-IMO and Dex diets. The DSS treatment promoted an accumulation of neutrophils in the colonic mucosa in the rats fed the control, S-IMO, and L-IMO diets, as assessed by a measurement of myeloperoxidase (MPO) activity. In contrast, no increase in MPO activity was observed in the Dex-diet-fed rats even with DSS treatment. Immune cell populations in peripheral blood were also modified by the DP of ingested saccharides. Dietary S-IMO increased the concentration of n-butyric acid in the cecal contents and the levels of glucagon-like peptide-2 in the colonic mucosa.

Conclusion/Significance

Our study provided evidence that the physiological effects of α-glucosaccharides on colitis depend on their DP, linkage type, and digestibility.

TNFSF15 Modulates Neovascularization and Inflammation

Tumor necrosis factor superfamily-15 (TNFSF15; also known as VEGI or TL1A) is a unique cytokine that functions in the modulation of vascular homeostasis and inflammation. TNFSF15 is expressed abundantly in established vasculature but is down-regulated at sites of neovascularization such as in cancers and wounds. TNFSF15 inhibits endothelial cell proliferation and endothelial progenitor cell differentiation. Additionally, TNFSF15 stimulates T cell activation, Th1 cytokine production, and dendritic cell maturation. Some of the functions of TNFSF15 are mediated by death receptor-3. We review the experimental evidences on TNFSF15 activities in angiogenesis, vasculogenesis, inflammation, and immune system mobilization.