A novel immunohistochemical method for evaluation of antibody specificity and detection of labile targets in biological tissue.

Immunohistochemistry is a key tool for analyzing target molecule localization within tissues. However, accurate results require an antibody that can distinguish between similar compounds. We present a simple immunohistochemical method that can also be used to rapidly evaluate antibodies' specificities. We demonstrate this technique with serotonin, an extremely labile compound. Serotonin (5-hydroxytryptamine, 5HT) is an important neurotransmitter regulating normal cognition and several mental disorders, as well as tumor growth, cardiopathology, and embryogenesis. Immunohistochemical detection of serotonin is commonly used as a neuronal cell marker and to provide crucial information on serotonin's role as an embryonic morphogen. It is necessary to be able to distinguish serotonin from closely related molecules with significantly different biological activity. Using our method, we identify antibodies that are specific for serotonin and show that some commercial 5HT antibodies often used to identify serotonergic cells in published papers are not 5HT-specific. These data demonstrate the necessity of specifically testing antibodies (especially in areas of high clinical relevance such as 5HT). We also illustrate detection of serotonergic cells in embryonic tissue using our technique. This method offers a number of general advantages for testing specificity of antibodies to any biological molecule, and helps avoid false positives and negatives during immunohistochemistry.