Radioimmunology
Radioimmunology is a laboratory technique that uses the principles of radioimmunoassay (RIA) and immunoradiometric assay (IRMA) to measure the concentration of antigens or antibodies in a biological sample. These assays rely on the specific binding of an antibody to its corresponding antigen. In a typical RIA, a known amount of radiolabeled antigen is mixed with a sample containing an unknown amount of the same antigen and a limited amount of antibody. The unlabeled antigen in the sample competes with the radiolabeled antigen for binding to the antibody. After incubation, the antibody-bound antigen is separated from the free antigen, and the radioactivity of either the bound or free fraction is measured. The amount of radioactivity is inversely proportional to the concentration of the unlabeled antigen in the sample.
IRMA, on the other hand, uses an excess of antibody. In this assay, a known amount of