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