Expression of 20 KD homologous restriction factor of complement on myocardial cells: an immunohistochemical study using acetone-fixed and paraffin-embedded tissues.

Expression of 20 KD homologous restriction factor of complement (HRF20) (CD59) in normal human heart was immunohistochemically examined with monoclonal antibody (MAb) 1F5. HRF20 was clearly demonstrated on the cell surface membrane and intercalated discs of myocardial cells throughout the ventricular walls. Therefore, this factor may protect normal cardiomyocytes from complement deposition, which has been demonstrated on infarcted cardiomyocytes. Expression of HRF20 was also observed on endothelial cells of the endocardium and on blood vessels, including arteries, capillaries, and veins, and on the Schwann-cell sheath of peripheral nerve fibers. In the present study, we found that the epitopes of HRF20 were well preserved for immunohistochemistry even in acetone-fixed and paraffin-embedded tissues, as well as in frozen tissues that have been conventionally used for HRF20. This method using paraffin sections allows for easier staining and greater accuracy in histological examination.