Immunohistochemistry of Tartrate-Resistant Acid Phosphatase: Assessment of Steam Heat for Epitope Enhancement and Comparison of B-5 and Formalin Fixation

Abstract

Tartrate-resistant acid phosphatase (TRAP) is an important cell marker in both hematology and bone pathology. Cytochemical stains for TRAP activity are used to identify leukemic cells of hairy cell leukemia, inflammatory or activated macrophages, and bone resorbing osteoclasts. A monoclonal antibody to TRAP (9C5) was developed for immunohistochemical identification of these and other TRAP-expressing cells in paraffin sections. In our continuing efforts to maximize the sensitivity and specificity of 9C5 for diagnostic and investigational purposes, we conducted studies to compare steam to microwave irradiation for heat induced epitope retrieval (HIER) and to compare formalin fixation to B-5 fixation. We found that a simple and inexpensive household vegetable steamer provided equivalent or superior HIER for demonstration of TRAP with 9C5 in a variety of tissues. We also found no significant differences in immunoreactivity or nuclear detail between formalin and B-5 fixed 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 achieved with inexpensive and reproducible steam HIER and that use of mercury-containing B-5 can be discontinued to increase the safety of the laboratory and decrease negative environmental impact. (The J Histotechnol 20:303, 1997)