Tocilizumab inhibits signal transduction mediated by both mIL-6R and sIL-6R, but not by the receptors of other members of IL-6 cytokine family

Int Immunopharmacol. 2005 Nov;5(12):1731-40. doi: 10.1016/j.intimp.2005.05.010.


To characterize the biological activity of tocilizumab, a humanized anti-human interleukin-6 receptor (IL-6R) monoclonal antibody, we examined its binding activity to both soluble IL-6R (sIL-6R) and membrane bound IL-6R (mIL-6R) and its neutralizing activity to other IL-6 family cytokines. ELISA assay demonstrated that tocilizumab bound to sIL-6R and inhibited IL-6 binding to sIL-6R in a dose-dependent manner. The dissociation constant (Kd value) for IL-6R was determined to be 2.54+/-0.12 nmol/L by Scatchard analysis. In addition, tocilizumab had the ability to dissociate IL-6 and sIL-6R from their preformed complex. The immune complex of tocilizumab and sIL-6R did not transmit signaling. Moreover, tocilizumab suppressed the IL-6/sIL-6R complex-induced proliferation of human gp130-transfected cell, BAF-h130. In addition, tocilizumab had the ability to bind to human IL-6R expressing COS-7 cells and to suppress the growth of the IL-6-dependent myeloma cell line, KPMM2. Finally, to analyze the specificity of this antibody, the effects on signal transduction of IL-6 family cytokines such as interleukin-11 (IL-11), oncostatin M (OSM), leukemia inhibitory factor (LIF), and ciliary neurotrophic factor (CNTF) were examined using murine transfectant cell lines (BaF/IL-6R, BaF/IL-11R, BaF/OSMR, BaF/LIFR and BaF/CNTFR) that proliferate depending on IL-6, IL-11, OSM, LIF and human CNTF, respectively. Tocilizumab inhibited the proliferation of BaF/IL-6R induced by IL-6, but did not inhibit the proliferation of BaF/IL-11R, BaF/OSMR, BaF/LIFR and BaF/CNTFR cells induced by their corresponding cytokines. These lines of evidence indicate that tocilizumab is able to bind to both sIL-6R and mIL-6R and to inhibit IL-6 binding to its receptors, leading to the blockade of the IL-6 signaling through both sIL-6R and mIL-6R, but not block the signaling of other IL-6 family cytokines.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology*
  • Antibodies, Monoclonal, Humanized
  • COS Cells
  • Cell Proliferation / drug effects
  • Chlorocebus aethiops
  • Cytokines / immunology*
  • Cytokines / metabolism
  • Dose-Response Relationship, Drug
  • Humans
  • Interleukin-6 / immunology
  • Interleukin-6 / metabolism
  • Protein Binding
  • Receptors, Cytokine / immunology
  • Receptors, Cytokine / metabolism
  • Receptors, Interleukin-6 / immunology*
  • Receptors, Interleukin-6 / metabolism
  • Signal Transduction / drug effects*
  • Signal Transduction / immunology
  • Transfection


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Cytokines
  • Interleukin-6
  • Receptors, Cytokine
  • Receptors, Interleukin-6
  • tocilizumab