Immunoselective adsorption processes exploit biospecific interactions between antibodies and their corresponding antigens in order to separate pure high-value bioactive products from biological sources (for example, blood, food materials, and products of genetically engineering organisms). Enzymes, hormones, vaccines, interferons, and antibodies have been purified by using immunoselective adsorption processes. The purified products find applications in therapeutics, diagnostic tests, drug targeting, food immunoassays, research, and clinical examinations, and as ligands for the preparation of highly selective immunoadsorbents. Immunoassays are rapidly becoming important for the detection and quantification of components in foods such as additives, fungal and bacterial contaminants, antinutritional factors, pesticide residues, and hormones. Purified antibodies have potential use in infant formulas to prevent intestinal infections.