Enhancement of human IL-4 activity by soluble IL-4 receptors in vitro

Eur J Immunol. 1999 Mar;29(3):864-71. doi: 10.1002/(SICI)1521-4141(199903)29:03<864::AID-IMMU864>3.0.CO;2-T.


The recombinant form of the extracellular domain of the IL-4 receptor (sIL-4R) is a potential candidate to neutralize IL-4; however, murine sIL-4R displayed both antagonistic and agonistic activity in vivo. Here we show that human recombinant sIL-4R induced the formation of complexed IL-4 in supernatants of activated T cells in a dose-dependent manner as measured by newly developed enzyme-linked immunosorbent assays. These IL-4/sIL-4R complexes liberated free IL-4 even after prolonged culturing. In contrast, in the absence of exogenously added sIL-4R, free IL-4 was rapidly consumed or proteolytically degraded in cultures of activated T cells. Thus, no IL-4 bioactivity could be determined in supernatants of T cells activated in the presence of IL-4 for 6 days. In contrast, the same cultures carried out in the presence of sIL-4R showed marked IL-4 bioactivity. While low concentrations of sIL-4R enhanced IL-4-driven inhibiton of IFN-gamma production by activated T cells, higher concentrations neutralized IL-4. Together, human sIL-4R, besides its activity as an antagonist to IL-4, also possesses protective and agonistic functions for IL-4, which may be relevant for clinical studies aiming to neutralize IL-4 in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cricetinae
  • Dose-Response Relationship, Drug
  • Endopeptidases / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Interleukin-4 / immunology*
  • Lymphocyte Activation
  • Mice
  • Receptors, Interleukin-4 / immunology*
  • Recombinant Proteins / immunology
  • Solubility
  • T-Lymphocytes / immunology


  • Receptors, Interleukin-4
  • Recombinant Proteins
  • Interleukin-4
  • Endopeptidases