4] Analytical immunology

Abstract

Publisher Summary Immunoassays are based on the specific recognition by antibodies of a small number of amino acids (epitopes) in an antigen. This immunological discrimination that can be used to determine, either antigen or the antibody concentration, is the basis for modern analytical immunology. The human immune system has the potential to generate 10 million different combinations of immunoglobulin specificities, each of which may complex with an antigen in a different way. The discussion here focuses on the general aspects of antigen–antibody binding that are common to most immunocomplexes. The lock-and-key model proposed in 1900 to represent the antibody–antigen binding is still accepted, although it is important to consider the surface topology of each molecular species involved in describing the specific chemical interactions. Knowledge of the steric aspects of antibody–antigen interaction at the molecular level can be obtained by crystallographic studies in some cases. In others, it must be combined with additional biochemical and immunological information. Improvements in antibody selectivity, antibody, and tracer labeling, antibody immobilization, detection, and automation of immunoassays, together with the enhanced selectivity and sensitivity, provided by integrating separation systems into the assay, have enormously increased the value of immunoassays. The large number of variations on this technique has proved to be quite useful in quantitating an analyte in a sample, determining its purity, discriminating the variants of the target substance formed during its production, and in performing real-time monitoring of the biomolecules.