Polyclonal antibodies are produced by immunizing animals. The animals used most commonly for the production of antibodies are rats, rabbits, goats, sheep and horses.
The desired antigen is repeatedly injected into the animal at specific time intervals. This process is called immunization. After a few weeks, the polyclonal antiserum can be collected. The antibodies obtained react to the antigen used, but the epitopes recognized by the individual antibodies on the antigen may be different. polyclonal antibodies are often used as secondary antibodies against the actual detection antibody (e.g. with the ELISA technique). In general, polyclonal antibodies are less expensive than monoclonal antibodies.