Endogenous peroxidase and pseudoperoxidase activity is found in many frozen, formalin-fixed paraffin-embedded tissue sections and cell smears. Peroxidase is most commonly found in red blood cells, myoglobin in muscle cells, cytochrome in granulocytes, and monocytes, liver and kidney. The presence of endogenous peroxidase activity gives false results when using peroxidase based Immunohistochemistry technique. For frozen tissue sections eg. Peripheral blood, bone marrow, fixation should be done with acetone/methanol.
Endogenous Alkaline Phosphatase (AP) is present in number of cells and tissues including epithelium of the bladder, the lamina propia of ovary, kidney, salivary glands (1), neutrophilic segmented cells, neutrophilic band cells, neutrophilic metamyelocytes, and may also be present in leukemic cells of chronic and acute granulocytes leukemia, and some neutrophilic leukemoid reactions (2). AP is also found in brush borders of epithelial cells of small intestine (3) and placenta (4). Elias (5) has shown that endogenous AP can be inhibited by Levamisole without significantly reducing specific staining of antigenic sites.References:
- Ponder, BA, Wilkinson, M. J. Histochem Cytochem. 29(8)981, 1981
- Seiverd CE Hematology for Medical technologies, Seiverd CE editor, Philadelphia: Lea and Febiger, 1972
- Uchida, T etal Advances in Immunohistochemistry, De Lellis,RA editor, Masson Publishing, 185, 1985
- Groote, GD etal Clin. Chem. 29(1), 115,1983
- Elias JM, Immunohistochemical methods: endogenous AP activity. Immunopathology A practical approach to diagnostic. Chicago: Ascp press, 49, 1990
- Deparaffinizate the tissue as described in your protocol.
- Add few drops of endoblocking solution for 5-10 minutes at 37ºC, or 10-15 minutes at room temperature.
- Proceed with the protocol.