Simultaneous visualization of immunodetected antigens and tissue components revealed by non-enzymatic histochemical stains.

We explored the possibility of simultaneous application of histochemical and immunohistochemical staining techniques on the same paraffin-embedded human tissue section. Conventional histological stains (PAS, Alcian, Alcian-PAS, Van Gieson, Gomori silver impregnation, and Giemsa) were used in association with a battery of markers (keratins, leucocyte common antigen, S-100 protein, Factor VIII-related antigen) that are widely employed in diagnostic and experimental studies. We found that the best procedure was to perform immunostaining before the histochemical reaction, as this enables all the other possible combinations to be carried out. In addition, several detection systems, such as peroxidase-anti-peroxidase (PAP), alkaline phosphatase-anti-alkaline phosphatase (APAAP), and avidin-biotin complex (ABC), were tested and all gave consistent results. Some minor modifications of the histological staining methods were necessary, but the current immunohistochemical techniques could be used as established. Preliminary findings indicate that immunohistochemistry can be combined with histochemistry techniques by means of a relatively simple procedure whose only disadvantage is the time required to carry out the double staining.