The peroxidase-antiperoxidase (PAP) method and other all-immunologic detection methods

Immunoenzyme procedures take on many forms, including, simply, antibody coupled to enzyme. These direct techniques require the labeling of all the primary antibodies and can produce more background. A more economical method uses a secondary antibody or one that has the primary antibody as its antigen. Labeling this secondary antibody with enzyme provides detection for many primary antibodies directed against different antigens of interest. A more sensitive approach involves the use of antibodies directed against enzyme connected to same-species primary antibodies by a secondary linking antibody. This "all immunologic" technique is more sensitive and can result in less background than the covalently labeled methods. Finally, an immune polymer consisting of several secondary antibodies along with many enzyme molecules embedded on one long chain carbon polymer, can be used. This can provide a faster, more universal detection procedure with adequate sensitivity and specificity.