A soluble multimeric protein or polypeptide is disclosed that is able to inhibit interaction of leukocyte Fcγ receptors (FcγR) and immunoglobulin G (IgG). The protein or polypeptide comprises two or more linked Fc binding regions, at least one of which is derived from an FcγR type receptor and, particularly, FcγRIIa. Also described are polynucleotide molecules encoding the protein or polypeptide and the use thereof in methods of treating a subject for an immune-complex (IC)-mediated inflammatory disease.