Expression Of TNFRII Research Articles

Supraoptimal peptide-major histocompatibility complex causes a decrease in bc1-2 levels and allows tumor necrosis factor alpha receptor II-mediated apoptosis of cytotoxic T lymphocytes.

Cytotoxic T lymphocytes (CTLs) are primary mediators of viral clearance, but high viral burden can result in deletion of antigen-specific CTLs. We previously reported a potential mechanism for this deletion: tumor necrosis factor (TNF)-alpha-mediated apoptosis resulting from stimulation with supraoptimal peptide-major histocompatibility complex. Here, we show that although death is mediated by TNF-alpha and its receptor (TNF-RII), surprisingly neither the antigen dose dependence of TNF-alpha production nor that of TNF-RII expression can account for the dose dependence of apoptosis. Rather, a previously unrecognized effect of supraoptimal antigen in markedly decreasing levels of the antiapoptotic protein Bc1-2 was discovered and is likely to account for the gain in susceptibility or competence to sustain the death signal through TNF-RII. This decrease requires a signal through the TCR, not just through TNF-RII. Although death mediated by TNF-RII is not as widely studied as that mediated by TNF-RI, we show here that it is also dependent on proteolytic cleavage by caspases and triggered by a brief initial encounter with antigen. These results suggest that determinant density can regulate the immune response by altering the sensitivity of CTLs to the apoptotic effects of TNF-alpha by decreasing Bc1-2 levels.

Enhanced expression and shedding of tumor necrosis factor (TNF) receptors from mononuclear leukocytes in human heart failure.

TNFalpha exerts its functions by engaging two receptors (TNF-RI and TNF-RII). The extracellular parts of the receptors are proteolytically shed to the soluble forms by a matrix metalloproteinase-like enzyme (sTNF-RI and sTNF-RII). The soluble TNF receptors can neutralize TNFalpha activities. Circulating levels of both sTNF-RI and sTNF-RII are elevated in patients with congestive heart failure (CHF). It remains unclear how a large amount of sTNF-RI and sTNF-RII is mobilized into the circulation. Mononuclear leukocytes were obtained from 14 controls and 21 patients with CHF. TNF-RII of the cells from CHF patients was upregulated in the cell-surface expression and mRNA transcripts. Besides enhanced shedding of TNF-RII on the cells from CHF patients with phorbol myristate acetate (PMA), sera from CHF induced shedding of TNF-RII on the cells from normal volunteers. Thus, the enhancement of both expression and shedding of TNF-RII may be related to increased circulating levels of the soluble TNF receptor in patients with CHF. The presence of CHF may affect the regulation of TNF receptors, which may modulate the responsiveness to TNFalpha in the tissues of patients with CHF.

Shedding of tumour necrosis factor receptors from purified villous term trophoblasts and cytotrophoblastic BeWo cells.

Within the placenta tumour necrosis factor-alpha (TNF-alpha) and its surface receptors TNF-RI and -RII have been detected on villous cyto- and syncytiotrophoblast and a role in trophoblast function/differentiation and turnover has been suggested. Here, we show for the first time that purified villous trophoblasts and cytotrophoblastic BeWo cells extensively shed TNF receptors, suggesting that release of these soluble proteins is an inherent property of trophoblasts. In supernatants of purified villous trophoblasts, TNF-RI and -RII increased from undetectable levels to 307 pg/ml and 484 pg/ml, respectively, within 12 h of cultivation. In BeWo cells, 26 pg/10(5) cells and 54 pg/10(5) cells of soluble TNF-RI and -RII, respectively, accumulated within 24 h of culturing. While forskolin did not alter TNF-RI expression, TNF-RII mRNA, protein and secretion were selectively up-regulated in these choriocarcinoma cells suggesting that elevation of cAMP levels could modulate cellular events by TNF-RII-mediated signal transduction. Interleukin-1, which greatly enhances TNF-alpha release from trophoblast cells, did not alter shedding of both receptors from villous trophoblasts or BeWo cells. Secretion of TNF receptors from the trophoblast may explain the high levels of soluble TNF-binding proteins in urine of pregnant women and could play a role in regulating TNF-alpha activity in the placental villus or protection against the cytotoxic effects of the cytokine.

Distinct roles of lymphotoxin alpha and the type I tumor necrosis factor (TNF) receptor in the establishment of follicular dendritic cells from non-bone marrow-derived cells.

In mice deficient in either lymphotoxin alpha (LT-alpha) or type I tumor necrosis factor receptor (TNFR-I), organized clusters of follicular dendritic cells (FDC) and germinal centers (GC) are absent from the spleen. We investigated the role of LT-alpha and TNFR-I in the establishment of spleen FDC and GC structure by using reciprocal bone marrow (BM) transfer. When LT-alpha-deficient mice were reconstituted with wild-type BM, FDC organization and the ability to form GC were restored, indicating that the LT-alpha-expressing cells required to establish organized FDC are derived from BM. The role of LT-alpha in establishing organized FDC structure was further investigated by the transfer of complement receptor 1 and 2 (CR1/2)-deficient BM cells into LT-alpha-deficient mice. Organized FDC were identified with both the FDC-M1 and anti-CR1 monoclonal antibodies in these BM-chimeric mice, indicating that these cells were derived from the LT-alpha-deficient recipient. Thus, expression of LT-alpha in the BM-derived cells, but not in the non-BM-derived cells, is required for the maturation of FDC from non-BM precursor cells. In contrast, when TNFR-I-deficient mice were reconstituted with wild-type BM, they showed no detectable FDC clusters or GC formation. This indicates that TNFR-I expression on non-BM-derived cellular components is necessary for the establishment of these lymphoid structures. TNFR-I-deficient BM was able to restore FDC organization and GC formation in LT-alpha-deficient mice, indicating that formation of these structures does not require TNFR-I expression on BM-derived cells. The data in this study demonstrate that FDC organization and GC formation are controlled by both LT-alpha-expressing BM-derived cells and by TNFR-I-expressing non-BM-derived cells.

Interleukin-10 Upregulates Tumor Necrosis Factor Receptor Type-II (p75) Gene Expression in Endotoxin-Stimulated Human Monocytes

AbstractInterferon-γ (IFN-γ) upregulates expression of certain genes in monocytes, including cell-surface molecules such as HLA class II, B7, and ICAM-1. IFN-γ also potentiates production of cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-12. Conversely, IL-10 downregulates expression of many of these same genes and often antagonizes the effects of IFN-γ. IL-10 is known to inhibit TNF-α production in lipopolysaccharide (LPS)-stimulated monocytes; however, the effects of IL-10 on TNF receptor (TNF-R) expression are not well defined. We examined the effects of IL-10 on production of both membrane-associated (m) and soluble (s) TNF-R type II (sTNF-RII) by purified human CD14+ monocytes. We also compared the effects of IFN-γ and IL-10 on production of TNF-α and sTNF-RII by these cells. Monocytes constitutively expressed low levels of TNF-RII mRNA and mTNF-RII protein. LPS stimulation induced rapid, but transient loss (shedding) of mTNF-RII molecules and a delayed, but marked increase in TNF-RII mRNA levels. IL-10 increased expression of both mTNF-RII and sTNF-RII by LPS-stimulated monocytes, whereas IFN-γ decreased their expression. The increased levels of sTNF-RII in cultures of IL-10–treated monocytes correlated directly with increased levels of TNF-RII mRNA and inversely with the levels of TNF-α mRNA. The ability of IL-10 to upregulate TNF-RII gene expression was transcriptionally mediated because actinomycin D blocked this effect. Furthermore, IL-10 treatment did not alter the half-life of TNF-RII mRNA transcripts in LPS-stimulated monocytes. To further examine the mechanism by which IL-10 potentiates TNF-RII gene expression, a 1.8-kb fragment of the human TNF-RII promoter cloned into a luciferase expression vector (pGL2-basic) was transfected into the IL-10–responsive macrophage cell line, RAW264.7. Although IL-10 alone induced only minimal promoter activity in these cells, it markedly increased the LPS-induced response, providing further evidence that the ability of IL-10 to amplify TNF-RII gene expression is transcriptionally controlled. Together, these findings demonstrate that IL-10 coordinately downregulates expression of TNF-α and upregulates expression of TNF-RII, particularly the soluble form of this receptor, in monocytes.

Cytokine response of B lymphocytes from splenic lymphoma with villous lymphocytes: correlation with TNF-RII (p75) and CD11c expression.

We studied the immunophenotype and the functional reactivity to cytokines of blood cells from eight patients with Splenic Lymphoma with Villous Lymphocytes (SLVL). Cells from all cases exhibited moderate to high levels of membrane immunoglobulin, CD22 and CD40 antigens and light chain restriction (kappa/lambda: 1.7/1). CD44, CD54 and CD11b expression was detected in all cases whereas CD11c was expressed in only four cases (50%). CD11c+ cells lacked CD21 and CD23 expression whereas CD11c cells expressed both these antigens. Cells from most patients (7/8) responded to IL2 whereas only four responded to IL4 and three to TNF alpha. The response to TNF alpha correlated with spontaneous TNF-RII and CD11c expression. Although two days of culture induced the TNF-RII expression in CD11c cells, they remained unresponsive to TNF alpha. These two groups of SLVL patients also differed by IL10 mRNA content: the former (CD11c+, TNF-RII+) contained TNF alpha and IL10 mRNA whereas the latter (CD11c, TNF-RII) lacked IL10 mRNA, even after two days of culture. There were thus two groups of SLVL patients: CD11c+ and CD11c, exhibiting different patterns of cytokine response and production. These groups may correspond to different cell origins or different progression stages of the disease.

Tumor Necrosis Factor-α (TNF-α) Inhibits Expression of Mouse Placental Lactogen-II Through TNF-α Type-I But Not Type-II Receptor

The aim of this study was to determine whether TNF-α inhibits mPL-II secretion through TNF-RI or TNF-RII, and to investigate the gestational profile of TNF-RI and TNF-RII gene expression. The mouse trophoblast cells from day 12 pregnancy were cultured with or without agonistic polyclonal antibodies directed against the individual TNF-α receptors, and mPL-II secretion in the medium was assessed by RIA. Anti-TNF-RI antibody significantly inhibited the dose- and time-dependent manner, but anti-TNF-RII antibody did not. Moreover, the TNF-RII antibody did not influence the inhibitory effect of the TNF-RI antibody on mPL-II secretion. TNF-RI antibody inhibited the mPL-II gene expression by Northern blot analysis. Amount of the gene expression of TNF-RI in the second half of pregnancy was higher than those in the first half of pregnancy both in vitro and in vivo, although the gene expression of TNF-RII was not detectable by Northern blot analysis using poly(A)+RNA. These results suggest that TNF-RI is a main receptor for TNF-α in mouse placenta and that TNF-α may have an important role in regulating mPL-II secretion after midpregnancy.

Role of tumor necrosis factor species in the sequence-dependent effects of interleukin-2--tumor necrosis factor immunotherapy in mice: implications for preclinical cytokine testing.

We previously demonstrated that recombinant human tumor necrosis factor (hTNF) is synergistic with human interleukin-2 (hIL-2) for in vivo regression of murine tumors. In mice, the timing of cytokine administration is critical in achieving synergy. Because hTNF exhibits negligible binding to the type II murine TNF receptor (TNF-R), we questioned whether murine TNF (mTNF) would have therapeutic benefits, scheduling requirements, and toxic effects similar to those of the hIL-2-hTNF combination. To evaluate the biological effects of TNF-R types I and II interaction, we directly compared the effects of mTNF and hTNF in combination with hIL-2 on in vivo tumor regression and in vitro activation of murine splenocytes. Our results demonstrate for the first time that (a) the cytokine combination hTNF-hIL-2 is consistently more efficacious than mTNF-hIL-2 in in vivo murine immunotherapy models; (b) the in vivo antitumor effects of hTNF-hIL-2 and not mTNF-hIL-2 are critically dependent upon cytokine scheduling; and (c) in vitro culture of splenocytes with mTNF-hIL-2 enhances cellular proliferation, Lyt 2, and TNF-RI expression compared with hTNF-hIL-2. Collectively, these studies extend the previous findings of species-specific mTNF-R responses and reveal that optimal scheduling and efficacy of TNF-hIL-2 combination therapy in murine tumor models is critically dependent upon the TNF species employed.