IMMUNOHISTOCHEMISTRY OF TARTRATE-RESISTANT ACID-PHOSPHATASE - ASSESSMENT OF STEAM HEAT FOR EPITOPE ENHANCEMENT AND COMPARISON OF B-5 AND FORMALIN FIXATION

Tartrate-resistant acid phosphatase (TRAP) is an important cell marker in both hematology and bone pathology. Cytochemical stains for TRAP a ctivity are used to identify leukemic cells of hairy cell leukemia, in flammatory or activated macrophages, and bone resorbing osteoclasts. A monoclonal antibody to TRAP (9C5) was developed for immunohistochemic al identification of these and other TRAP-expressing cells in paraffin sections. In our continuing efforts to maximize the sensitivity and s pecificity of 9C5 for diagnostic and investigational purposes, we cond ucted studies to compare steam to microwave irradiation for heat induc ed epitope retrieval (HIER) and to compare formalin fixation to B-5 fi xation. We found that a simple and inexpensive household vegetable ste amer provided equivalent or superior HIER for demonstration of TRAP wi th 9C5 in a variety of tissues. We also found no significant differenc es in immunoreactivity or nuclear detail between formalin and B-5 fixe d bone marrow biopsy sections. These findings may also apply to other antigens of diagnostic importance. We concluded that the high quality immunohistochemistry in hematopoietic and other tissues can be achieve d with inexpensive and reproducible steam HIER and that use of mercury -containing B-5 can be discontinued to increase the safety of the labo ratory and decrease negative environmental impact.