Each primary antibody identifies and attaches to a specific target (antigen).
The epitope is the region of the antigen that is the “landing site” for the antibody.
Antibodies historically have been categorized as monoclonal or polyclonal. Antibodies used in clinical applications are most commonly monoclonal antibodies raised in mice or polyclonal antibodies raised in rabbits. Monoclonal rabbit antibodies are a relatively new variation now available for use in clinical applications. The antibody is produced by exposing the host animal to an antigen and then harvesting and purifying the antibody. Though typically the host is a mouse or rabbit, hosts can also be sheep, guinea pigs, or other animal species.
Image: Adenovirus infected liver demonstrated with mouse IgG1 monoclonal antibody cocktail of clones 2/6 and 20/11. DAB chromogen.