A new decalcifying technique for immunohistochemical studies of calcified tissue, especially applicable to cell surface marker demonstration.

We have developed a new decalcifying technique for use in light and electron microscopy studies utilizing immunohistochemical staining of calcified tissues. Specimens containing calcified tissues can be adequately decalcified at a pH of 7.1-7.4 and temperature of -5 degrees C, without freezing, by use of a solution containing EDTA, sodium hydroxide, and glycerol. In this study, Leu-2a, Leu-3a, Leu-4, Leu-7, Leu-12, Leu-14, Leu-M1, Leu-M2, Leu-M3, and HLA-DR-positive cells in destructive lesions of bone tissues from patients with rheumatoid arthritis and osteomyelitis were successfully detected immunohistochemically. Furthermore, the presence of HLA-DR antigen on the surface of the infiltrating cells in the same lesions could be demonstrated using the immunoelectron microscopic technique. The results reported here have not previously been obtainable using conventional decalcifying techniques.