The alkaline phosphatase anti-alkaline phosphatase technique in dermatopathology

The APAAP technique is an unlabelled antibody bridge technique which can be used on either frozen or paraffinembedded sections. One applies first a monoclonal antibody, then a polyclonal bridge antibody, and finally a soluble complex of alkaline phosphatase and monoclonal mouse anti-alkaline phosphatase. Subsequently, the enzyme label is developed with a naphthol salt and new fuchsin as a dye. This technique was used in our laboratory on frozen and/or paraffin embedded sections by using 15 different monoclonal antibodies, which are commercially available. The reaction product was bright red and could easily be distinguished from the brown color of melanin, which makes the APAAP technique particularly suitable for dermatopathology.