Antibodies are proteins that specifically bind to particular molecules, such as proteins, peptides or hormones. Immuno-assays are biochemical assays that take advantage of the characteristics of the antibody-antigen interaction to detect or measure biological molecules. Immuno-assays use different labels to detect antibodies and antigens, most commonly enzymes (as in ELISA), but radioactive, fluorescent and DNA probes are also widely used. Due to the highly specific antibody-antigen binding, immuno-assays have high specificity and sensitivity.