Abstract: Method and compositions are provided for performing homogeneous immunoassays. The method involves having a signal producing system, which provides a detectable signal, which system includes a macromolecular member. The determination of the analyte, which is a member of a specific binding pair consisting of a ligand and its homologous receptor, is performed by creating an extensive matrix in the assay medium by having in the assay medium in addition to the analyte, ligand labeled with one of the members of the signal producing system, antiligand either present as the analyte or added, a polyvalent receptor for antiligand, the macromolecular member of the signal producing system, and any additional members of the signal producing system. The labeled ligand, antiligand, and polyvalent receptor for the antiligand create a matrix which modulates, e.g. inhibits, the approach of the macromolecular member of the signal producing system to the labeled ligand.

Abstract: Novel immunoassays are provided employing discrete particulate reagents for determining an analyte which is a member of a specific binding pair-ligand and homologous receptor. The assay employs as a first reagent, a member of said pair bound to an insoluble particle (particle conjugate); as a second reagent, a label which is part of a signal producing system, bound to a member of said pair (signal label conjugate); and as a third reagent, a signal repressor comprising an insoluble particle, where the signal repressor is obstructed from interacting with said label of said signal label conjugate, when said signal label conjugate is bound to said particle conjugate.In performing the assay, the analyte, the reagents, and any ancillary materials are combined in an aqueous assay medium and the signal determined as compared to an assay medium having a known amount of analyte.

Abstract: Methods and reagents are provided for immunoassays employing as reagents a labelled receptor, where the label is capable of providing a detectable signal, and modifying reagents, capable of modifying the signal obtained from the label. When ligand (ligand analog for monoepitopic ligands) is present in the assay medium, a complex is formed which inhibits interaction between the label modifying reagent and the label. By measuring the signal obtained in the presence of a known amount of ligand in the assay medium and comparing that signal with the signal obtained with an unknown sample suspected of containing ligand, one can qualitatively or quantitatively determine the amount of ligand in the unknown. For determinating anti(ligand) the assay is carried out in substantially the same way, except a source of ligand or ligand analog must be provided.