title: Molecular and biological properties of an interleukin-1 receptor immunoadhesin.
abstract: Overproduction of the cytokine interleukin 1 (IL-1) is an important factor in the pathogenesis of several autoimmune and inflammatory disease. To develop a recombinant inhibitor of IL-1 with an extended pharmacologic half-life, we constructed an IL-1 receptor immunoadhesin (IL-1R-IgG), by fusing the extracellular domain of the type IL-1 receptor with the hinge and Fc regions of human IgG1 heavy chain. Transfected human 293 cells express IL-1R-IgG as a secreted, disulfide-bonded homodimer. The secreted protein contains an intact antibody Fc region, as indicated by immunoblotting, and a functional IL-1 receptor region, as indicated by ligand-blotting. Saturation binding analysis indicates an equilibrium dissociation constant (KD) of 350 pM for the binding of IL-1R-IgG to its ligand, IL-1 beta. Kinetic analysis of the binding reveals an off rate of 0.1 min-1 and an on rate of 1.5 x 10(8) min-1 M-1, yielding a calculated KD of 770 pM. These binding properties are similar to those of cell-surface type I IL-1 receptor. IL-1R-IgG is capable of inhibiting the biological activity of IL-1 beta in vitro, as evidenced in a thymocyte proliferation assay. Pharmacokinetic analysis in mice indicates that IL-1R-IgG has a terminal half-life of 91 hr in the blood circulation. This half-life is markedly longer than the values reported for other recombinant inhibitors of IL-1 such as the IL-1 receptor antagonist or soluble IL-1 receptor. Thus, IL-1R-IgG may be useful for investigating the interaction of IL-1 with its receptor and the role of IL-1 in disease, as well as for potential intervention in pathological situations involving overproduction of IL-1.
authors.affiliation: Department of Molecular Biology, Genentech, Inc., South San Francisco, CA 94080.
authors.forename: R M
authors.initials: RM
authors.lastname: Pitti
authors.forename: S A
authors.initials: SA
authors.lastname: Marsters
authors.forename: M
authors.initials: M
authors.lastname: Haak-Frendscho
authors.forename: G C
authors.initials: GC
authors.lastname: Osaka
authors.forename: J
authors.initials: J
authors.lastname: Mordenti
authors.forename: S M
authors.initials: SM
authors.lastname: Chamow
authors.forename: A
authors.initials: A
authors.lastname: Ashkenazi
mesh_terms: D000818:Animals; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry*; D007375:Interleukin-1 / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D017472:Receptors, Interleukin-1 / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology
chemical_list: D015815:Cell Adhesion Molecules; D007074:Immunoglobulin G; D007375:Interleukin-1; D017472:Receptors, Interleukin-1; D011993:Recombinant Fusion Proteins