TL1A selectively enhances IL-12/IL-18-induced NK cell cytotoxicity against NK-resistant tumor targets.

INTRODUCTION: TL1A (TNFSF15) augments IFN-gamma production by IL-12/IL-18 responsive human T cells. Its ligand, death domain receptor 3 (DR3), is induced by activation on T and NK cells. Although IL-12/IL-18 induces DR3 expression on most NK cells, addition of TL1A minimally increases IFN-gamma production. METHODS: (51)Chromium release and flow cytometric analysis were used to determine whether the TL1A-DR3 pathway is implicated in tumor cell lysis. Our aim was to determine whether the TL1A-DR3 pathway is implicated in tumor cell lysis. RESULTS: TL1A had no additional effect on IL-12/IL-18-induced cytotoxicity against an NK-susceptible tumor (K562); however, it promoted cytotoxicity against NK-resistant targets susceptible to lysis only by activated NK cells. DISCUSSION: With IL-12/IL-18 activation, TL1A increased CD107a expression on NK cells which led to enhanced lysis of Daudi by PBMC and purified NK cells. To a lesser degree, TL1A increased lysis of colorectal adenocarcinoma epithelial derived lines (WiDr and SW837) by IL-12/IL-18-activated cells. CONCLUSION: TL1A increased cytotoxicity of IL-12/IL-18-activated NK cells against target cells dependent on NK activation for lysis and could function in vivo as a key co-activator of NK cytotoxicity.

The T cell costimulator TL1A is induced by FcgammaR signaling in human monocytes and dendritic cells.

The recently described TL1A/DR3 ligand/receptor pair mediates strong costimulation of Th1 cells. Activation of T and NK cells induces DR3 expression, permitting soluble recombinant TL1A to increase IFN-gamma production and proliferation of these cells. Gut T cells and macrophages express TL1A, especially in Crohn's disease (CD), and there is a strong association between CD and tl1a single nucleotide polymorphisms. Murine studies implicate TL1A in gut inflammation. To determine whether professional T cell-activating cells can express TL1A, fresh blood monocytes and monocyte-derived dendritic cells were stimulated with various activating ligands, including TLR agonists, IFN-gamma, and immune complexes. FcgammaR stimulation strongly induced TL1A mRNA in both cell types, which correlated with the detection of TL1A on the cell surface and in cell culture medium. TLR agonists capable of inducing IL-6 and TNF-alpha in monocytes and dendritic cells did not induce surface nor soluble TL1A. Furthermore, we demonstrate that TL1A production in monocytes leads to enhancement of T cell responses. The induction of TL1A on APCs via specific pathway stimulation suggests a role for TL1A in Th1 responses to pathogens, and in CD.

Dominant role for TL1A/DR3 pathway in IL-12 plus IL-18-induced IFN-gamma production by peripheral blood and mucosal CCR9+ T lymphocytes.

The TNF-like cytokine TL1A augments IFN-gamma production by anti-CD3 plus anti-CD28 and IL-12/IL-18-stimulated peripheral blood (PB) T cells. However, only a small subset of PB T cells respond to TL1A stimulation with IFN-gamma production. PB CCR9+ T cells represent a small subset of circulating T cells with mucosal T cell characteristics and a Th1/Tr1 cytokine profile. In the current study, we show that TL1A enhanced IFN-gamma production by TCR- or CD2/CD28-stimulated CCR9(+)CD4+ PB T cells. However, TL1A had the most pronounced effect on augmenting IFN-gamma production by IL-12/IL-18-primed CCR9(+)CD4+ PB T cells. TL1A enhanced both the percentage and the mean fluorescence intensity of IFN-gamma in CCR9(+)CD4+ T cells as assessed by intracellular cytokine staining. IL-12 plus IL-18 up-regulated DR3 expression in CCR9(+)CD4+ T cells but had negligible effect on CCR9(-)CD4+ T cells. CCR9(+)CD4+ T cells isolated from the small intestine showed a 37- to 105-fold enhancement of IFN-gamma production when TL1A was added to the IL-12/IL18 cytokine combination. Cell membrane-expressed TL1A was preferentially expressed in CCR9(+)CD4+ PB T cells, and a blocking anti-TL1A mAb inhibited IFN-gamma production by cytokine-primed CCR9(+)CD4+ T cells by approximately 50%. Our data show that the TL1A/DR3 pathway plays a dominant role in the ultimate level of cytokine-induced IFN-gamma production by CCR9+ mucosal and gut-homing PB T cells and could play an important role in Th1-mediated intestinal diseases, such as Crohn's disease, where increased expression of IL-12, IL-18, TL1A, and DR3 converge in the inflamed intestinal mucosa.

Potential role for TL1A, the new TNF-family member and potent costimulator of IFN-gamma, in mucosal inflammation.

TNF can potentiate IFN-gamma production by activated T cells and other members of the TNF-superfamily play key roles in this effect. A newly discovered TNF-superfamily cytokine (TL1A) could also be involved in initiating or promoting the Th1 response by enhancing IFN-gamma production. The purpose of this study was to assess the role of recombinant TL1A on IFN-gamma production by cultured PBMC and lamina propria LPMC and to determine whether TL1A expression is altered in inflammatory bowel disease. IFN-gamma, but not IL-4 or IL-10 production by PBMC and LPL, was dose-dependently augmented by TL1A (or by activation of its receptor, death domain receptor 3 [DR3], with specific mAb) independently of, but in synergy with, IL-12 and IL-18. T cell activating stimuli induced expression of TL1A on the cell membrane (mb-TL1A) in a fraction of peripheral blood (PB) T cells. In the intestinal mucosa, a fraction of lamina propria (LP) T cells, especially CD4+ cells, constitutively expressed mb-TL1A, and the fraction increased in mucosal inflammation. A higher fraction of cells also express the TL1A receptor DR3 in ulcerative colitis and Crohn's disease. TL1A transcript was several times more abundant in RNA from mucosal biopsies taken from inflamed Crohn's disease lesions than in those taken from uninvolved areas. Expression of TL1A and its receptor DR3 by lamina propria mononuclear cells (LPMC) could have significant influence on the severity of mucosal inflammation.

TL1A synergizes with IL-12 and IL-18 to enhance IFN-gamma production in human T cells and NK cells.

TL1A, a recently described TNF-like cytokine that interacts with DR3, costimulates T cells and augments anti-CD3 plus anti-CD28 IFN-gamma production. In the current study we show that TL1A or an agonistic anti-DR3 mAb synergize with IL-12/IL-18 to augment IFN-gamma production in human peripheral blood T cells and NK cells. TL1A also enhanced IFN-gamma production by IL-12/IL-18 stimulated CD56(+) T cells. When expressed as fold change, the synergistic effect of TL1A on cytokine-induced IFN-gamma production was more pronounced on CD4(+) and CD8(+) T cells than on CD56(+) T cells or NK cells. Intracellular cytokine staining showed that TL1A significantly enhanced both the percentage and the mean fluorescence intensity of IFN-gamma-producing T cells in response to IL-12/IL-18. The combination of IL-12 and IL-18 markedly up-regulated DR3 expression in NK cells, whereas it had minimal effect in T cells. Our data suggest that TL1A/DR3 pathway plays an important role in the augmentation of cytokine-induced IFN-gamma production in T cells and that DR3 expression is differentially regulated by IL-12/IL-18 in T cells and NK cells.

Expression and regulation of the chemokine receptor CXCR3 on lymphocytes from normal and inflammatory bowel disease mucosa.

Chemokine receptors play an important role in the recruitment of activated T cells to inflammatory sites. The aim of this study was to analyze the expression of the chemokine receptor CXCR3 on T lymphocytes in intestinal lymphoid tissues and to document the altered disposition of these cells in patients with inflammatory bowel disease (IBD). The expression and regulation of CXCR3 on mucosal lymphoid tissue and peripheral blood lymphocytes (PBLs) were analyzed by flow cytometry and Northern blotting. The migration of lamina propria lymphocytes (LPLs) and PBLs to interferon (IFN)-gamma-inducible protein (IP)-10 (or CXCL10) was evaluated by chemotaxis assays. IFN-gamma and interleukin-4-producing T lymphocytes were quantitated by intracellular staining, and IFN-gamma was measured in culture supernatants by enzyme-linked immunosorbent assay. CXCR3 is expressed on the majority of CD4 lamina propria (LP) T cells and correlates with a T-helper (Th) type 1/Th-0 cytokine phenotype on LP and mesenteric lymph node (MLN) CD4 T lymphocytes. IP-10/CXCL10 is more chemotactic in vitro for both CD4 and CD8 T cells that have been isolated from the LP compared with peripheral blood. CXCR3 protein, but not messenger RNA, expression was lower in inflamed LPLs compared with uninvolved LPLs in patients with ulcerative colitis but not in those with Crohn's disease. However, CXCR3 was expressed on a higher percentage of MLN CD4 T cells isolated from inflamed intestinal tissue, and CXCR3 expression could be induced in vitro with T-cell activation in MLN CD4 T cells. In summary, most CXCR3 T lymphocytes in normal intestinal tissues are Th-1/Th-0 effector/memory cells. Activation-dependent receptor regulation and alteration in receptor-bearing cells, primarily in MLN draining inflamed intestinal tissue, suggest an important role for this T-cell subset in the pathogenesis of human IBD.

CC chemokine receptor 9 expression defines a subset of peripheral blood lymphocytes with mucosal T cell phenotype and Th1 or T-regulatory 1 cytokine profile.

The chemokine receptor CCR9 is expressed on most small intestinal lamina propria and intraepithelial lymphocytes and on a small subset of peripheral blood lymphocytes. CCR9-expressing lymphocytes may play an important role in small bowel immunity and inflammation. We studied the phenotype and functional characteristics of CCR9(+) lymphocytes in blood from normal donors. A subset of CCR9(+) T cells have a phenotype of activated cells and constitutively express the costimulatory molecules CD40L and OX-40. In contrast to CCR9(-), CCR9(+)CD4(+) peripheral blood T cells proliferate to anti-CD3 or anti-CD2 stimulation and produce high levels of IFN-gamma and IL-10. IL-10-producing cells were exclusively detected within the CCR9(+) subset of CD4(+) T cells by intracellular staining and were distinct from IL-2- and IFN-gamma-producing cells. Moreover, memory CCR9(+)CD4(+) lymphocytes respond to CD2 stimulation with proliferation and IFN-gamma/IL-10 production, whereas memory CCR9(-)CD4(+) cells were unresponsive. In addition, memory CCR9(+)CD4(+) T cells support Ig production by cocultured CD19(+) B cells in the absence of prior T cell activation or addition of exogenous cytokines. Our data show that the memory subset of circulating CCR9(+)CD4(+) T cells has characteristics of mucosal T lymphocytes and contains cells with either Th1 or T-regulatory 1 cytokine profiles. Studies on the cytokine profile and Ag specificity of this cell subset could provide important insight into small intestinal immune-mediated diseases and oral tolerance in humans.