Design of human interleukin‐4 antagonists inhibiting interleukin‐4‐dependent and interleukin‐13‐dependent responses in T‐cells and B‐cells with high efficiency

Abstract

Human interleukin‐4 possesses two distinct sites for receptor activation. A signalling site, comprising residues near the C‐terminus on helix D, determines the efficacy of interleukin‐4 signal transduction without affecting the binding to the interleukin‐4 receptor α subunit. A complete antagonist and a series of low‐efficacy agonist variants of human interleukin‐4 could be generated by introducing combinations of two or three negatively charged aspartic acid residues in this site at positions 121, 124, and 125. One of the double variants, designated [R121D,Y124D]interleukin‐4, with replacements of both Arg121 and Tyr124 by aspartic acid residues was completely inactive in all analysed cellular responses. The loss of efficacy in [R121D,Y124D]interleukin‐4 is estimated to be larger than 2000‐fold. Variant [R121D,Y124D]interleukin‐4 was also a perfect antagonist for inhibition of interleukin‐13‐dependent responses in B‐cells and the TF‐1 cell line with a Ki value of approximately 100 pM. In addition, inhibition of both interleukin‐4‐induced and interleukin‐13‐induced responses could be obtained by monoclonal antibody X2/45 raised against interleukin‐4Rex, the extracellular domain of the interleukin‐4 receptor α subunit. These results indicate that efficient interleukin‐4 antagonists can be designed on the basis of a sequential two‐step activation model. In addition, the experiments indicate the functional participation of the interleukin‐4 receptor α subunit in the interleukin‐13 receptor system. Copyright © 1994, Wiley Blackwell. All rights reserved