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Biomedical subjects

M Feldmann

Publications and source records attributed to M Feldmann.

At least 145 records · Page 8Linked to original sources
PubMed1995

Beneficial effects of tumour necrosis factor-alpha (TNF-alpha) blockade in rheumatoid arthritis (RA)

The biological properties of TNF-alpha make it a candidate therapeutic target in RA. Our studies have demonstrated that TNF-alpha and its receptors are up-regulated and co-expressed in the synovium and cartilage-pannus junction of RA joints. Neutralizing TNF-alpha antibodies reduce the production of the many pro-inflammatory cytokines, including IL-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF), produced by mononuclear cells from RA in culture. When injected into DBA/1 mice with collagen-induced arthritis and TNF-alpha transgenic mice with arthritis, anti-TNF MoAbs decrease inflammatory damage of joints. Clinical trials employing cA2, a chimaeric anti-TNF-alpha MoAb, in open-label and randomized placebo-controlled studies have demonstrated a dose-dependent efficacy with impressive improvement in disease activity and acute-phase responses lasting several weeks. We conclude that TNF-alpha is a critical mediator of inflammation in RA, and is an important therapeutic target in this disease.

Antibodies, Monoclonal↗
PubMed1995

TNF inhibitors are produced spontaneously by rheumatoid and osteoarthritic synovial joint cell cultures: evidence of feedback control of TNF action.

We have proposed the hypothesis that tumour necrosis factor alpha (TNF-alpha) has a pivotal role in the pathogenesis of rheumatoid arthritis, based on in vitro observations that in RA synovial joint cell cultures removal of TNF-alpha, inhibited other potentially pathogenic cytokines such as the equally proinflammatory cytokine interleukin 1 (IL-1) and the macrophage activating factor, GM-CSF. Here we describe that in both rheumatoid (RA) and osteoarthritic (OA) synovial cultures there is a homeostatic mechanism to regulate the activities of TNF-alpha. This concept is based on several observations. First in these synovial joint cell cultures the substantial discrepancy between the levels of bioactive and immunoreactive TNF-alpha indicates the presence of an inhibitor. Second, TNF binding proteins are produced spontaneously, which are the soluble variants of surface p75 and p55 TNF receptor. The amount of soluble TNF receptors (sTNF-R) produced varied between cultures; p75 sTNF-R was more abundant than p55 sTNF-R (as detected by ELISA), and both were produced at higher levels by RA synovial joint cells in culture, compared to OA cultures. These TNF binding proteins act as endogenous inhibitors of TNF-alpha, since blocking their activity in synovial joint cell culture supernatants with MoAb to p55 and p75 sTNF-R enhanced their cytotoxic activity in the TNF bioassay. The regulation of production of these sTNF-R in synovial joint cell cultures is important as the balance between TNF-alpha and sTNF-R production may determine the outcome of the inflammatory process.

Arthritis, Rheumatoid↗
PubMed1995

Monoclonal anti-TNF alpha antibody as a probe of pathogenesis and therapy of rheumatoid disease.

Rheumatoid arthritis is a common cause of chronic disability for which current therapies are of limited value in controlling the disease process and outcome. Our initial approach to understanding the pathogenesis of RA and defining a novel therapeutic target was to investigate the role of cytokines by blocking their action with antibodies on cultured synovial-derived mononuclear cells in vitro. These investigations suggested that neutralization of TNF alpha with antibodies significantly inhibited the generation of other pro-inflammatory cytokines also over-produced, such as, IL-1, GM-CSF, IL-6 and IL-8. The implication that blockade of a single cytokine, TNF alpha might have far-reaching effects on multiple cytokines and thereby exert significant anti-inflammatory and protective effects on cartilage and bone of joints, was tested in arthritic DBA/1 mice immunized with collagen II. Impressive amelioration of joint swelling and joint erosions in this model encouraged clinical trials with a monoclonal anti-TNF alpha antibody. The cA2 chimeric anti-TNF alpha high-affinity antibody was initially tested in an open-label study at a dose of 20 mg/kg on 20 patients, with substantial and universal benefit. Subsequently, a randomized placebo-controlled double-blind trial was performed on 73 patients comparing a single intravenous injection of placebo (0.1% human serum albumin) with two doses of cA2. Using a composite disease activity index, at 4 weeks post infusion, 8% of patients receiving placebo improved compared with 44% receiving 1 mg/kg cA/2 and 79% receiving 10 mg/kg. Between 2 to 4 repeated cycles of cA2 were administered to 7 patients and all patients showed improvement of a similar magnitude with each cycle. These data support our proposition that TNF alpha is implicated in the pathogenesis of RA, and is thus a key therapeutic target. Monoclonal anti-TNF alpha antibodies control disease flares and are candidate agents for longer-term control of RA, although repeated therapy with cA2 is associated with anti-idiotypic responses in 50% of patients and a trend toward shortening of the duration of response. In the DBA/1 arthritic mice, synergy of action of anti-TNF and anti-CD4 is observed together with suppression of an anti-globulin response, indicating one way in which benefit might be augmented in the future.

Animals↗
PubMed1995

Identification of thyroid stimulating hormone receptor-specific T cells in Graves' disease thyroid using autoantigen-transfected Epstein-Barr virus-transformed B cell lines.

The importance of thyrotropin receptor (TSHR) agonist antibodies in the manifestations of Graves' disease (GD) is recognized. There are, however, no convincing reports of TSHR-specific T cells. We have previously cloned T cells specific for thyroglobulin and thyroid peroxidase (TPO) from GD lymphoid infiltrates and used autologous EBV-transformed B cell lines (EBVL) transfected with an expression vector encoding TPO to efficiently detect TPO-specific T cells. Here we used EBVL transfected with TSHR to seek TSHR-specific T cells in the GD infiltrates, after cloning the in vivo activated T cells without antigen. 3 out of 30 clones responded vigorously and reproducibly to EBVL-TSHR, with a mean stimulation index > 7. Their release of IL-2, IL-4, and IL-10 after stimulation with soluble anti-CD3 and phorbol ester was indistinguishable from the other clones from this thyroid. However, they produced relatively little IFN gamma (median IL-4/IFN gamma ratio of 0.80) compared with the other clones (median IL-4/IFN gamma ratio 0.06). Thus, this new potent method of antigen presentation, using autoantigen-transfected EBVL, has permitted the first unequivocal identification of TSHR T cells in GD thyroid, with distinct Th0/Th2 characteristics, unlike previously cloned TPO-responsive cells which have Th1 characteristics.

Antigen Presentation↗
PubMed1995

Successful therapy of collagen-induced arthritis with TNF receptor-IgG fusion protein and combination with anti-CD4.

We have previously shown that anti-tumour necrosis factor (TNF) monoclonal antibody (mAb) ameliorates established collagen-induced arthritis and that the efficacy of this form of treatment can be enhanced by concurrent anti-CD4 treatment. Here we assess the efficacy of a human p55 TNF receptor-IgG fusion protein (p55-sf2), given alone or with anti-CD4 mAb. TNF receptor-IgG fusion protein (100 micrograms) suppressed paw swelling and limb recruitment in established arthritis and reduced the incidence of erosions in the proximal interphalangeal joints from 92% to 50%, which was comparable to 41% erosions using anti-TNF mAb. Methylprednisolone acetate (4.2 mg/kg/week) reduced clinical signs of inflammation in a manner comparable to TNF blockade but had little effect on the incidence of erosions. Co-administration of anti-CD4 and TNF receptor-IgG led to an even greater therapeutic effect than TNF receptor-IgG alone, with the incidence of erosions being reduced from 100% to 17%. Serological analyses showed that the beneficial effects of anti-CD4 and TNF receptor-IgG could be partly explained by the ability of anti-CD4 to prevent a neutralizing antibody response. These results confirm the importance of TNF in destructive inflammatory arthritis and demonstrate the feasibility of therapeutically targeting TNF with a form of TNF receptor. Finally, the findings confirm the beneficial effects of TNF-targeted therapy coupled with anti-CD4 therapy.

Animals↗
PubMed1995

Human alpha beta T-cell receptor CD4-CD8 T-cell clones are predominantly Th0-like.

The cytokine production profile, focusing on interleukin-4 (IL-4), interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) of human CD4+, CD8+ and CD4- CD8- alpha beta T cells cloned from the peripheral blood of healthy individuals was compared. Solid-phase anti-CD3 stimulation of CD4- CD8- alpha beta T cell clones from one individual revealed a significantly increased frequency of IL-4-producing clones (81%), compared to CD4+ T cells (24%) or CD8+ (28%). All five CD4- CD8- alpha beta T-cell clones from two other individuals also produced IL-4. Clones that produced IFN-gamma with undetectable IL-4 production, thus being of the 'classical' Th1 phenotype, were infrequent in CD4- CD8- alpha beta T-cell clones (19%) compared to CD4+ (71%), and CD8+ clones (72%) cloned in OKT3, and CD4+ cells cloned in phytohaemaglutinin A (77%). Unlike previously reported studies with gamma delta cells, the alpha beta CD4- CD8- T cells produced IL-10 at appreciable frequency (38%) in PHA generated clones. The supernatants from anti-CD3 stimulated CD4- CD8- alpha beta T-cell clones contained sufficient IL-4 to activate B cells, enhancing CD23 and surface immunoglobulin M (IgM) expression and co-stimulating B-cell proliferation. These findings suggest that the function of CD4- CD8- alpha beta T cells is distinct from that of most CD4+ or CD8+ T cells.

B-Lymphocytes↗
PubMed1995

Soluble TNF receptor production by activated T lymphocytes: differential effects of acute and chronic exposure to TNF.

Soluble tumour necrosis factor receptors (sTNF-R) are up-regulated at sites of chronic inflammation such as rheumatoid synovial joints. The p75 sTNF-R is the more abundant, suggesting an important role for this TNF inhibitor in regulating TNF bioactivity in vivo. As the precise cellular source of these soluble receptors is not known, we investigated the production and regulation of sTNF-R by T lymphocytes, an abundant cell type in inflammatory infiltrates, which upon activation express high levels of p75 surface receptors. Using panels of T-cell lines and clones expressing high levels of p75 TNF-R, we found that p75 sTNF-R production upon stimulation is a feature common to all subsets of T cells, including cells of the CD4-CD8- double negative phenotype expressing either alpha beta or gamma delta T-cell receptors (TCR). In contrast, levels of p55 sTNF-R were only detected when T cells were stimulated at higher densities and by potent mitogens such as phorbol 12-myristate 13-acetate (PMA). Detailed kinetic analyses revealed that the production of p75 sTNF-R was biphasic, the first phase was activation dependent, occurring in the absence of detectable TNF, while the second phase of p75 sTNF-R production was regulated by cytokines such as TNF. Unlike short-term exposure to TNF which enhances sTNF-R production in vitro and in vivo, prolonged exposure of T lymphocytes to TNF suppressed p75 sTNF-R (but not p55 sTNF-R) production in a dose- and time-dependent fashion. These results suggest that in patients with chronic inflammatory disease, which are exposed to augmented levels of bioactive TNF for prolonged periods, the production of p75 sTNF-R may be impaired.

Clone Cells↗
PubMed1995

LPS-induced 111In-eosinophil accumulation in guinea-pig skin: evidence for a role for TNF-alpha.

Lipopolysaccharide (LPS) is a major component of the cell wall of Gram-negative bacteria with powerful pro-inflammatory activities. Although the mechanisms involved in LPS-induced neutrophil accumulation have been studied extensively, few reports have focused on the effects of LPS on eosinophil infiltration. In this study we have used an in vivo model of local 111In-eosinophil accumulation in the guinea-pig to investigate the mechanisms of LPS-induced eosinophilia. Using a 4-hr in vivo test period, the intradermal injection of LPS (50-1000 ng/site) led to a marked and dose-dependent accumulation of 111In-eosinophils into guinea-pig skin sites. Time-course experiments revealed that this cell infiltration was delayed in onset, becoming significant 1 hr after the intradermal administration of LPS. The slow development of the response and its sensitivity to the locally administered protein synthesis inhibitor, actinomycin D, suggested that the LPS-induced 111In-eosinophil accumulation in vivo is mediated by the generation of de novo proteins. The intravenous pretreatment of guinea-pigs with a soluble tumour necrosis factor-alpha (TNF-alpha) receptor fusion protein (TNFR-IgG, 1 mg/kg), potently inhibited the 111In-eosinophil accumulation induced by LPS. Our results demonstrate that LPS can induce 111In-eosinophil accumulation in vivo in guinea-pig skin, and that this process is mediated by TNF-alpha.

Animals↗
PubMed1995

Inhibition of transfer of collagen-induced arthritis into SCID mice by ex vivo infection of spleen cells with retroviruses expressing soluble tumor necrosis factor receptor.

Collagen-induced arthritis can be transferred into severe combined immunodeficiency (SCID) mice by spleen cells from diseased DBA/1 mice. The development of arthritis in SCID animals can be prevented by infection ex vivo of DBA/1 spleen cells with retroviruses expressing the monomeric soluble human p75 tumor necrosis factor (TNF) receptor (TNF-R). In addition, a vector engineered to express a polycystronic mRNA with TNF-R and the herpes simplex virus thymidine kinase (HSVtk) gene, while producing low levels of TNF-R, had a limited effect which could be blocked by treating the animals with ganciclovir. A retroviral vector expressing the HSVtk gene alone had no effect on this arthritis transfer model with or without ganciclovir. Serum levels of TNF-R did not correlate with clinical signs, however, lower anti-collagen antibody levels corresponded with lack of clinical symptoms. These results indicate that local production of cytokine inhibitor is essential for therapeutic purposes while systemic levels may not be required.

Animals↗
PubMed1994

Randomised double-blind comparison of chimeric monoclonal antibody to tumour necrosis factor alpha (cA2) versus placebo in rheumatoid arthritis.

Tumour necrosis factor alpha (TNF alpha) is a critical inflammatory mediator in rheumatoid arthritis, and may therefore be a useful target for specific immunotherapy. In support of this hypothesis, we previously observed beneficial responses in patients with active rheumatoid arthritis after open-label administration of a chimeric monoclonal antibody to TNF alpha (cA2). We now report the results of a four-centre, randomised double-blind trial of a single infusion of 1 or 10 mg/kg cA2 compared with placebo in 73 patients with active rheumatoid arthritis. The primary endpoint of the study was the achievement at week 4 of a Paulus 20% response, an amalgam of six clinical, observational, and laboratory variables. Intention-to-treat analysis of data from individual patients showed only 2 of 24 placebo recipients responding at this time, compared with 11 of 25 patients treated with low-dose cA2 (p = 0.0083) and 19 of 24 patients treated with high-dose cA2 (p < 0.0001). Over half of the high-dose cA2 patients responded by the more stringent 50% Paulus criteria at this time (p = 0.0005). The magnitude of these responses was impressive, with maximum mean improvements in individual disease-activity assessments, such as tender or swollen-joint counts and in serum C-reactive protein, exceeding 60% for patients on high-dose treatment. There were two severe adverse events. 1 patient on 1 mg/kg cA2 developed pneumonia ("possibly" treatment-related) and 1 on 10 mg/kg had a fracture ("probably not" treatment-related). The results provide the first good evidence that specific cytokine blockade can be effective in human inflammatory disease and define a new direction for the treatment of rheumatoid arthritis.

Adolescent↗
PubMed1994

Repeated therapy with monoclonal antibody to tumour necrosis factor alpha (cA2) in patients with rheumatoid arthritis.

Our in-vitro, animal, and early clinical data suggest that tumour necrosis factor alpha (TNF alpha) is an important target for specific biological therapy in rheumatoid arthritis. We report the results of repeated treatment with a chimeric monoclonal antibody to TNF alpha (cA2) in patients having disease flares. 7 patients originally enrolled in an open-label trial completed two to four cycles, each of which was followed by a good clinical response, with median improvements in the swollen-joint count and C-reactive protein exceeding 80%. cA2 may be useful therapy in the control of acute disease flares in rheumatoid arthritis and treatment programmes including cA2 may be effective in the long-term management of this disease.

Antibodies, Monoclonal↗
PubMed1994

Functional activities of receptors for tumor necrosis factor-alpha on human vascular endothelial cells.

Tumor necrosis factor-alpha (TNF-alpha) plays a critical role in the control of endothelial cell function and hence in regulating traffic of circulating cells into tissues in vivo. Stimulation of endothelial cells in vitro by TNF-alpha increases the surface expression of leukocyte adhesion molecules, enhances cytokine production, and induces tissue factor procoagulant activity. In the present study, we have examined the relative roles of the two cell surface receptors for TNF-alpha (p55 and p75) on endothelial cells, using antibodies with both agonistic and antagonistic activities. We report that anti-p55 receptor agonistic antibody Htr-9 induces the expression of tissue factor antigen and the release of interleukin-8 (IL-8) and granulocyte-macrophage colony-stimulating factor (GM-CSF). In contrast, there is very little or no activation of endothelial cell responses by an anti-p75 agonist. TNF-alpha-induced expression of tissue factor and adhesion molecules, and release of IL-8 and GM-CSF, are decreased by antibodies with antagonistic activities for either receptor, although the effect of anti-p55 antibodies is markedly greater than that of anti-p75 antibodies. The responses of endothelial cells to lymphotoxin/TNF-beta are significantly decreased by anti-p55 antagonists alone. Our data suggest that endothelial cell responses to TNF-alpha, such as expression of tissue factor and adhesion molecules for mononuclear cells, which may be important in the pathogenesis of atherosclerosis, are mediated predominantly, but not exclusively, by the p55 TNF receptor.

Antibodies↗
PubMed1994

Characterization of ligand binding by the human p55 tumour-necrosis-factor receptor. Involvement of individual cysteine-rich repeats.

Two soluble tumour-necrosis-factor-alpha(TNF)-binding proteins are derived from the extracellular domains of the p55 and p75 TNF receptors. They are considered to play a pivotal regulatory role in TNF-mediated inflammatory processes, including diseases such as rheumatoid arthritis, by competing with the cell surface receptors for TNF and lymphotoxin (LT, tumour-necrosis factor beta). The extracellular domains of the two receptors each contain four similar cysteine-rich repeats of about 40 amino acids, in common with several other cell surface proteins including the p75 nerve-growth-factor receptor and the CD40 and Fas antigens. The aim of this study was to characterize the involvement of the four cysteine-rich repeats of the human p55 TNF receptor in TNF and LT binding by both membrane-bound and soluble forms of the receptor. Individual repeats were systematically deleted by PCR mutagenesis and the variants transiently expressed in COS cells. Immunoprecipitated receptor variants exhibited the expected sizes on SDS/PAGE gels, and bound a panel of conformation-dependent anti-(TNF receptor) antibodies. Binding of TNF by the four soluble derivatives was compared with binding by the wild-type soluble receptor using a TNF-affinity column and a BIAcore Biosensor, by measurement of their ability to inhibit TNF cytotoxicity on WEHI cells, and 125I-TNF binding to U937 cells. delta 4, which lacks the fourth cysteine-rich repeat, bound TNF comparably with the full-length soluble receptor. TNF-binding affinity was unaltered by deletion of the fourth membrane-proximal cysteine-rich repeat, as determined by Scatchard analysis of the transmembrane derivatives. We conclude that the fourth cysteine-rich repeat is not required for TNF binding. In contrast, both the soluble and the transmembrane derivatives lacking any one of the first, second or third repeats failed to bind TNF. Although we cannot entirely exclude the possibility that this may be due to indirect conformational change, rather than the removal of essential epitopes, our results suggest that the first three repeats are each required for TNF binding by both the soluble and the cell-surface receptor.

Antibodies, Monoclonal↗
PubMed1994

Transfection of thyroid autoantigens into EBV-transformed B cell lines. Recognition by Graves' disease thyroid T cells.

Autologous EBV-transformed B cell lines (EBVL) from a patient with Graves' disease (GD) were transfected with the expression vector pREP4 encoding thyroid peroxidase (TPO), the thyroid-stimulating hormone receptor (TSHR), or chloramphenicol acetyl transferase. The relevant proteins were expressed. The capacity of EBVL to present transfected Ag was assessed by using EBVL transfected with TPO (EBVL-TPO) to stimulate TPO-specific T cells cloned from autologous thyroid tissue; stimulation indices greater than 100 were consistently obtained, even at low APC:T cell ratios. EBVL-TPO and EBVL transfected with TSHR (EBVL-TSHR) were used to characterize the Ag specificity of five thyroid epithelial cell-specific T cell clones. Despite previous unresponsiveness to recombinant TPO or purified thyroglobulin, four of these clones responded vigorously to EBVL-TPO but none responded to EBVL-TSHR. Experiments were then performed to determine whether transfected EBVL were presenting endogenously synthesized TPO, or were taking up and reprocessing exogenous Ag shed from the surface of adjacent cells. The stimulatory capacity of EBVL-TPO was not transferable to untransfected EBVL by cell-free culture supernatant and to only a minor degree by EBVL-TPO-derived cell membrane fragments, indicating that the majority of the TPO presented by the transfected EBVL is endogenously synthesized. The clear and reproducible proliferative responses obtained illustrate the usefulness and potency of this method of Ag presentation to T cells. Because this system obviates the need for large numbers of autologous APC or purified recombinant Ag, it will be useful for obtaining autoantigen-reactive T cells and to help define the autoantigenic epitopes recognized.

Adult↗
PubMed1994

Immunoregulatory role of interleukin 10 in rheumatoid arthritis.

The presence and the role of interleukin 10 (IL-10), a potent cytokine synthesis inhibitory factor and antiinflammatory cytokine, were investigated in rheumatoid arthritis (RA). The expression of both mRNA and protein for IL-10 could be demonstrated in RA and osteoarthritis (OA) joints. Human IL-10 mRNA could be demonstrated by polymerase chain reaction amplification of cDNA made by reverse transcription of total RNA extracted directly from synovial tissue in five out of five RA and four out of five OA patients. IL-10 protein was demonstrated by specific immunoassay and immunohistology. IL-10 protein was spontaneously produced in all 11 RA and 17 OA synovial membrane cultures investigated, and this production was sustained for up to 5 d in culture in the absence of any extrinsic stimulation. IL-10 protein could also be detected by immunohistology in all five RA and four OA synovial membrane biopsies investigated, but not three normal synovial membranes. Immunohistology revealed that the IL-10 was localized to the synovial membrane lining layer and mononuclear cell aggregates. Immunofluorescence double staining revealed that the sources of IL-10 were monocytes in the lining layer, and T cells in the mononuclear cell aggregates. We found evidence that the IL-10 expression was functionally relevant, as neutralization of endogenously produced IL-10 in the RA synovial membrane cultures resulted in a two- to threefold increase in the protein levels of proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and IL-1 beta, although IL-6 and IL-8 levels were not affected. The addition of exogenous recombinant IL-10 to the RA synovial membrane cultures resulted in a two- to threefold decrease in the levels of TNF-alpha and IL-1 beta. IL-8 levels were reduced by day 5; however, IL-6 levels were not affected by exogenous IL-10. Neutralization of the endogenous IL-10 in two out of seven RA synovial membrane cultures resulted in the expression of detectable levels of interferon gamma (561-1,050 pg/ml). Taken together, the above findings suggest that IL-10 is spontaneously produced in RA and OA and is an important immunoregulatory component in the cytokine network of RA, regulating monocyte and in some cases T cell cytokine production.

Arthritis, Rheumatoid↗
PubMed1994

Synergy between anti-CD4 and anti-tumor necrosis factor in the amelioration of established collagen-induced arthritis.

Anti-CD4 treatment is reported to prevent collagen-induced arthritis if administered before the onset of clinical disease but has relatively little effect on established arthritis. In contrast, we have recently shown that anti-tumor necrosis factor alpha/beta (TNF) treatment reduces the severity of established arthritis. We now study the effect of combined administration of anti-CD4 monoclonal antibody (YTS 191.1.2/YTA 3.1.2) and anti-TNF monoclonal antibody (TN3-19.12) in established arthritis. Anti-CD4 treatment caused some reduction in paw-swelling but did not significantly prevent joint erosion. A suboptimal dose of anti-TNF alone had no significant effect on arthritis. In contrast, anti-CD4 plus suboptimal anti-TNF significantly reduced paw-swelling, limb involvement, and joint erosion. As previously reported, an optimal dose of anti-TNF alone inhibited paw-swelling, limb involvement, and joint erosion. However, optimal anti-TNF combined with anti-CD4 caused significantly greater reductions in paw-swelling and joint erosion than those achieved by optimal anti-TNF alone. Coadministration of anti-CD4 was also effective in preventing an antibody response to the hamster anti-TNF antibody, which may have implications for long-term therapy in human disease. Thus anti-CD4 acts synergistically with anti-TNF in ameliorating established collagen-induced arthritis and this combined therapeutic approach may provide effective long-term control of rheumatoid arthritis.

Animals↗
PubMed1994

Lymphotoxin acts as an autocrine growth factor for Epstein-Barr virus-transformed B cells and differentiated Burkitt lymphoma cell lines.

A critical event in B cell immortalization by Epstein-Barr virus (EBV) is the establishment of an autocrine loop where cells produce a growth factor which supports their own proliferation. We investigated the potential of lymphoblastoid cell lines (LCL) and Burkitt lymphoma (BL) cell lines to produce and respond to the cytotoxins, tumor necrosis factor-alpha (TNF-alpha) and lymphotoxin (LT). Transformation in vitro of peripheral blood B cells by EBV from seven different donors resulted in spontaneous production of both LT (11,542 pg/ml +/- 7546, mean +/- SD) and, to a lesser extent, TNF-alpha (197 pg/ml +/- 174). Similarly BL cell lines derived from in vivo transformation which developed a 'LCL-like' phenotype in vitro (group III) produced more LT (1990 pg/ml +/- 1740) than the 'group I' BL cell lines (< 40 pg/ml LT) which had maintained the original BL biopsy cell phenotype in vitro. Transformation of peripheral blood B cells to generate LCL also resulted in an increase in surface p75 (p < 0.02) and to a lesser extent p55 (not significant, ns) TNF receptor (TNF-R) expression. Similar increases in surface TNF-R (p75 p < 0.02, p55 ns) were observed on the 'group III' BL cell lines compared with the 'group I' BL cell lines. Proliferation of an LCL and a 'group III' BL cell line in vitro was via an autocrine loop since inhibition of LT reduced proliferation. This proliferation could also be blocked in the presence of the antagonistic anti-p55 TNF-R antibody, H398, but not the antagonistic antibody anti-p75 TNF-R antibody UTR-1. Furthermore, proliferation could be induced with the p55 agonistic antibody, HTR-9. In contrast to these observations with p55 TNF-R antibodies, two out of six of the 'group III' BL lines (Jijoye and Oba) only expressed the p75 TNF-R and proliferation of these cells could only be blocked by the antagonistic anti-p75 TNF-R antibody UTR-1. These data suggest that LT is an autocrine growth factor for lymphoblastoid cells, and BL cell lines which display an LCL phenotype. Furthermore, although both TNF-R are increased on the surface of these cells, this autocrine growth signal is mediated principally through binding to the p55 TNF-R.

B-Lymphocytes↗