Secondary antibodies are polyclonal and monoclonal antibodies directed against an immunoglobulin (Ig) molecule. They are typically used in conjunction with an antigen specific primary antibody and are usually labeled to aid in detection.
Secondary antibodies are useful in numerous applications including -
Secondary antibodies are typically labeled with enzymes or fluorochromes which enable detection via colorimetric, chemiluminescent, and fluorescent technologies. For example, the enzymes horseradish peroxidase (HRP) and alkaline phosphatase (AP) are valuable in ELISA and western blot applications through both colorimetric and chemiluminescent platforms. Fluorochromes such as fluorescein (FITC), phycoerythrin (PE), and cyanine (CY) are essential in fluorescent based applications which include in flow cytometry, immunofluorescence microscopy, and multiplexing assays.
Secondary antibodies allow for flexibility in labeling and detection as well as increased sensitivity through the signal amplification.
Streptavidin and Neutralite Avidin Reagents
Streptavidin is a tetrameric bacterial protein isolated from Streptomyces avidinii. Neutralite Avidin is a deglycosylated avidin purified from egg white. Both exhibit an exceptionally strong affinity for biotin which makes them invaluable as second step reagents for biotinylated primary antibodies.