Immunohistochemical detection of early myocardial infarction. An evaluation of antibodies against the terminal complement complex (C5b-9).

Antibodies (abs) against the terminal complement complex (C5b-9) were used on routinely processed post mortem myocardial tissue in parallel with conventional staining methods. Both monoclonal and polyclonal abs were tested using the avidin biotin peroxidase complex (ABC), alkaline phosphatase anti-alkaline phosphatase (APAAP) methods and an ab-bridge with alkaline phosphatase. Enhancement of the diaminobenzene (DAB) end product with cobalt-nickel (ABC method) was also done. The polyclonal ab gave the most satisfactory results and the alkaline phosphate conjugated ab-bridge had a slight advantage over the ABC method. Cobalt-nickel enhancement of DAB improved the visualization, but with higher background staining. APAAP was the least satisfactory method. Comparing the immunohistochemical method with the conventional staining methods, the former showed positive reaction in 97% of areas of coagulation necrosis and in 65% of contraction band necrosis. On the other hand coagulation necrosis was seen in 44% and contraction band necrosis in 68% of C5b-9 positive areas indicating that C5b-9 abs react with ischemically damaged myocytes before visible alterations are seen in hematoxilin-eosin staining. Moreover, using C5b-9 abs, it seems possible to exclude agonal/artefactual contraction bands which show a negative reaction. Immunohistochemical detection of C5b-9, using an adequate technique could increase the possibility to demonstrate early ischemic myocardial damage.