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Biomedical subjects

M Feldmann

Publications and source records attributed to M Feldmann.

479 records · Page 27Linked to original sources
PubMedDate not supplied

Specific T helper and suppressor cells and factors induced in vitro to the hapten NP.

Nitrophenyl (NP)-specific helper cells and suppressor cells were induced in vitro using NP-T4 bacteriophage as antigen. These cells could mediate their effects also by secreted effector molecules, helper and suppressor factors. The function of both NP-specific helper and suppressor cells was abolished by treatment with anti-Thy1.2 plus C', but they were not retained on nylon wool columns, suggesting that NP-specific helpers and suppressors were T cells. The membrane phenotype of both NP-specific helper and suppressor cells was found to be Ly1+2+I-J+(I-A-). The secreted effector molecules, helper and suppressor factors which mediate helper or suppressor function, bound to NP immunoadsorbents and are NP-specific in their function. They do not have conventional Ig determinants, but both bear determinants coded by the I-J subregion of H-2. The unusual phenotype of NP-specific helper and suppressor cells is discussed, as is the potential use of these hapten-specific T cells and their secreted effector molecules in increasing our understanding of T-cell receptors, effector molecules and the fine specificity of the interacting network in the regulation of immune responses.

Animals↗
PubMedDate not supplied

Targeting TNF alpha for the therapy of rheumatoid arthritis.

Our pre-clinical studies have demonstrated a pathogenic role for TNF alpha in RA. Firstly, TNF alpha and its receptors are upregulated and co-expressed in the synovium and cartilage-pannus junction of RA joints. Secondly, mononuclear cells from RA joints maintained in culture produce many cytokines with pro-inflammatory activity, including TNF alpha. Neutralizing TNF alpha antibodies in vitro reduces the production of these pro-inflammatory cytokines, including IL-1, IL-8, and GM-CSF. Thirdly, when injected into arthritic DBA/l mice with collagen-induced arthritis, monoclonal anti-TNF antibodies decrease inflammatory damage of joints. Clinical trials employing cA2, a monoclonal chimeric anti-TNF alpha antibody, 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↗
PubMedDate not supplied

p55 and p75 tumor necrosis factor receptors are expressed and mediate common functions in synovial fibroblasts and other fibroblasts.

There is increasing evidence that TNF-alpha is a cytokine of major importance in the pathogenesis of rheumatoid arthritis. Since TNF-alpha mediates its effects via high affinity receptors, we were interested in investigating their expression and function in cells from rheumatoid tissue. Synovial fibroblasts derived from rheumatoid synovial tissue are stimulated by TNF-alpha to proliferate and release cytokines, prostaglandins, proteases and protease inhibitors. We have evaluated through which receptor stimulation of DNA synthesis and the release of the proinflammatory agents, IL-6, IL-8 and PGE2 are induced. It was found that rheumatoid synovial fibroblasts express both the p55 and p75 TNF receptor, in a ratio of 4:1. TNF-alpha-stimulated synovial fibroblast DNA synthesis and the release of IL-6, IL-8 and PGE2 was inhibited by antagonist monoclonal antibodies against either the p55 or the p75 TNF receptor, although the blockade of the p55 TNF receptor had a more potent effect than inhibition of the p75 TNF receptor alone. Similarly, specific monoclonal antibodies, agonistic for either the p55 or p75 TNF receptor stimulated synovial fibroblast DNA synthesis, as well as IL-6, IL-8 and PGE2 release. Both p55 and p75 TNF receptors on dermal and gingival fibroblasts were also involved in TNF-alpha-mediated DNA synthesis and IL-6, IL-8 and PGE2 release, although differences in the levels of DNA synthesis and release of inflammatory cytokines and PGE2 were observed between the three fibroblast types.

Antibodies, Monoclonal↗
PubMedDate not supplied

TNF-alpha in rheumatoid arthritis and prospects of anti-TNF therapy.

Our work has shown that TNF alpha is produced by cultured mononuclear cells from rheumatoid arthritis joints and appears to regulate the production of IL-1. Immunohistochemical examination has shown the presence of TNF alpha in the synovium, e.g. in the lining layer, some endothelial cells and most importantly, in the cells in the cartilage pannus junction. TNF receptors (both p55 and p75) have a similar distribution, thereby suggesting that TNF has the potential for autocrine and paracrine activity in the joint. The concept that TNF alpha is pathogenic in inflammatory arthritis has been validated by showing that neutralizing monoclonal anti-TNF antibodies significantly attenuate collagen-induced arthritis in mice. In preliminary trials in rheumatoid patients anti-TNF appears to have an impressive effect on indices of disease activity including C-reactive production and serum amyloid-A production. TNF alpha appears to be a relevant therapeutic target in rheumatoid disease.

Animals↗
PubMedDate not supplied

Modulation of proinflammatory cytokine release in rheumatoid synovial membrane cell cultures. Comparison of monoclonal anti TNF-alpha antibody with the interleukin-1 receptor antagonist.

While there is an extensive literature on cytokine regulation in vivo using human cell lines or peripheral blood monocytes, very little is known about cytokine regulation within the multicellular environment of inflammatory sites in vivo. We have previously shown that in rheumatoid synovial membrane cultures, a complex, but pathophysiologically relevant mixture of cells, the addition of a neutralizing anti TNF-alpha antibody inhibits the production of IL-1 and GM-CSF, indicating the presence of a cytokine 'cascade' in this inflammatory tissue. In this paper we demonstrate that the interactivities between cytokines in rheumatoid arthritis also extends to other cytokines, such as IL-6 and IL-8, and that within the IL-1 family it is IL-1 beta in particular which is downregulated by neutralizing TNF-alpha activity. The cytokine interactions are unidirectional, in that neutralization of TNF-alpha reduced IL-1 beta, IL-6 and IL-8 production, whereas treatment of the rheumatoid synovial membrane cells with a neutralizing concentration of the IL-1 receptor antagonist (IL-1ra) reduced IL-6 and IL-8 production but not TNF-alpha production. These results suggest a rationale for the profound anti-inflammatory effects and consequent clinical benefit noted in RA patients treated recently in clinical trials with a chimeric anti-TNF-alpha antibody in vivo.

Antibodies, Blocking↗
PubMedDate not supplied

Cytokine expression and networks in rheumatoid arthritis: rationale for anti-TNF alpha antibody therapy and its mechanism of action.

The cloning of cytokine cDNAs has permitted the analysis of cytokine expression in diseased sites such as rheumatoid joints. A very wide range of cytokines were detected, mostly with proinflammatory activities. From the analysis of cytokine regulation in rheumatoid joint cell cultures using neutralizing anti-cytokine antibodies, it was found that blockade of TNF alpha reduced the production of other proinflammatory cytokines. Hence TNF alpha was a potential therapeutic target. This concept was tested successfully in collagen induced arthritis in mice and led to clinical trials of anti-TNF alpha antibody in rheumatoid arthritis (RA) in humans. The mechanism of action of anti-TNF alpha will be discussed.

Animals↗
PubMedDate not supplied

Effect of blocking TNF on IL-6 levels and metastasis in a B16-BL6 melanoma/mouse model.

We studied the relationship between tumour necrosis factor (TNF) and interleukin 6 (IL-6) levels, and the metastatic process in C57BL/6 mice after intravenous inoculation of B16-BL6 melanoma cells. Bioactive TNF was not detectable in the sera of inoculated mice, but these animals did show higher TNF levels following intraperitoneal challenge with lipopolysaccharide (LPS) compared to control animals. Serum IL-6 levels were increased in inoculated animals. Injection of a hybrid molecule (p55-sf2) composed of the human p55 TNF receptor extracellular domain coupled to a human constant region backbone, decreased serum TNF (after LPS challenge) and IL-6 levels in inoculated animals. Lung metastases at 7-14 days were reduced, compared to human IgG-injected control animals, but this effect was lost at day 21 postinoculation. The results suggest that the reduction in the number of metastases may be related to the effect of blocking TNF activity.

Animals↗