Secondary Antibodies

Secondary antibodies allow the indirect detection of an antigen by binding to the constant region of the primary antibody. To achieve this, the secondary antibody needs to possess a reactivity to the species (e.g. mouse, rabbit or goat) and to the class (e.g. IgG or IgM) of the primary antibody. Secondary antibodies are often labeled with enzymes (e.g. alkaline phosphatases). They convert substrates into coloured products and this process can be analyzed photometrically. Besides the use of enzymes, the labeling of antibodies with fluorescent probes such as FITC or DyLight 488 is a widely used method.