The present disclosure is directed to high-affinity immunopolymers for use in a variety of immunoassays and other techniques. The immunopolymers comprise a plurality of antibodies, a plurality of coupling proteins, and a plurality of detectable labels. The plurality of antibodies and plurality of coupling proteins are associated by a high-efficiency conjugation moiety, and may be used in highly multiplexed assays. Methods of preparing the high-affinity immunopolymers are provided. Also disclosed are methods of detecting an antigen that include reacting an antigen with a high-affinity immunopolymer of the disclosure. Reagent mixtures and methods for quantitative immunochemical assays are also provided. The mixtures and methods may include the high-affinity immunopolymers disclosed herein.