Interleukin-18-receptor proteins

#1. Field of the Invention

#This invention relates to a novel receptor protein recognizing a specific cytokine, more particularly, to a novel protein composing interleukin-18 receptor (hereinafter abbreviated as “IL-18R”) or IL-18R protein, as well as to a monoclonal antibody specific to the IL-18R protein.

#2. Description of the Prior Art

#FIG. 1 shows that the monoclonal antibody MAb #117-10C binds to L428 cells and IL-18R while competing with IL-18.

#FIG. 2 is an image of intermediate tone given on display, which shows IL-18R on gel electrophoresis visualized by the Western blotting method using the monoclonal antibody MAb #117-10C.

#FIG. 3 shows the inhibitory action of the monoclonal antibody MAb #117-10C on the activity of IL-18.

#The symbol “117-VL-VH cDNA” means the cDNA which encodes the variable regions of both the heavy and light chains in the monoclonal antibody MAb #117-10C.

#The symbol “Pcmv” means the cytomegalo virus promotor.

#The IL-18R protein of this invention can be characterized by a property of recognizing IL-18. As to IL-18, those of human and mouse origins commonly consisting of 157 amino acids have been documented: Human IL-18 bears the amino acid sequence of SEQ ID NO:26 (where the amino acid with symbol “Xaa” represents either isoleucine or threonine), while mouse counterpart, the amino acid sequence of SEQ ID NO:27 (where the amino acid with symbol “Xaa” represents either methionine or threonine). The IL-18R protein has sites for recognizing and binding to IL-18. Binding of IL-18 to the sites expressed on immunocompetent cells can induce the production of IFN-γ in the cells. The IL-18R protein usually loses the property after being heated at 100° C. for 5 minutes. The IL-18R protein in an IL-18-bound form usually appears to have a molecular weight of about 50,000-200,000 daltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (hereinafter abbreviated as “SDS-PAGE”) in the presence of a reducing agent. The IL-18R protein may bear as partial amino acid sequence one or more amino acid sequences of SEQ ID NOs:3 to 10.