Soluble TNF-alpha receptors bind and neutralize over-expressed transmembrane TNF-alpha on macrophages, but do not inhibit its processing

J Leukoc Biol. 1999 Dec;66(6):1005-13. doi: 10.1002/jlb.66.6.1005.


Tumor necrosis factor alpha (TNF-alpha) is initially synthesized as a type II integral membrane protein (transmembrane TNF-alpha) after macrophage activation. In this study we have investigated some aspects of the regulation of expression and biological activity of transmembrane TNF-alpha by both soluble TNF-alpha receptors (sTNF-alphaR) and inhibitors of TNF-alpha processing. We show, using the technique of receptor-mediated ligand precipitation (RMLP), that a dimeric construct of the type I sTNF-alphaR binds to transmembrane TNF-alpha, expressed on the mouse macrophage cell line RAW264.7, under cell culture conditions. This interaction between sTNF-alphaR and transmembrane TNF-alpha does not prevent processing and release of soluble TNF-alpha. A specific hydroxamic acid-based inhibitor of processing, BB1101 (British Biotech), was found to increase the total cellular levels of whole-cell, 26-kDa, precursor TNF-alpha by 2.2-fold. However, the inhibitor increased the levels of precursor TNF-alpha present solely on the cell surface (i.e., transmembrane TNF-alpha) by 5.1- to 7.5-fold. This increase in the levels of transmembrane TNF-alpha on the activated human monocytoid cell line mono mac 6 was associated with a similar (6.7-fold) increase in TNF-alpha-mediated cytotoxicity toward the human adenocarcinoma cell line Colo 205, which is sensitive only to the transmembrane form of TNF-alpha. Mono mac 6 cells, expressing transmembrane TNF-alpha, were found to be killing the Colo 205 target cells through apoptosis. This cytotoxicity could be neutralized by pre-incubating the mono mac 6 cells with either sTNF-alphaR or polyclonal anti-TNF-alpha serum.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / immunology
  • Benzyl Compounds
  • Cell Line
  • Cells, Cultured
  • Cytotoxicity, Immunologic
  • Dexamethasone / pharmacology
  • Dimerization
  • Drug Combinations
  • Humans
  • Macrophage Activation / physiology
  • Macrophages / immunology
  • Macrophages / metabolism*
  • Mice
  • Neoplasm Proteins / metabolism*
  • Neoplasm Proteins / pharmacology
  • Pentoxifylline / pharmacology
  • Protein Processing, Post-Translational / immunology*
  • Receptors, Tumor Necrosis Factor / metabolism*
  • Receptors, Tumor Necrosis Factor / physiology
  • Receptors, Tumor Necrosis Factor, Type II
  • Solubility
  • Succinates
  • Tumor Cells, Cultured
  • Tumor Necrosis Factor Decoy Receptors
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors*
  • Tumor Necrosis Factor-alpha / biosynthesis
  • Tumor Necrosis Factor-alpha / metabolism*


  • BB 1101
  • Benzyl Compounds
  • Drug Combinations
  • Neoplasm Proteins
  • Receptors, Tumor Necrosis Factor
  • Receptors, Tumor Necrosis Factor, Type II
  • Succinates
  • Tumor Necrosis Factor Decoy Receptors
  • Tumor Necrosis Factor-alpha
  • Dexamethasone
  • Pentoxifylline