Species specificity of monoclonal antibodies to human tartrate-resistant acid phosphatase.

Tartrate-resistant acid phosphatase (TRAP) is expressed abundantly by osteoclasts and is required for bone resorption. This enzyme is emerging as an important biomarker in bone pathology, both for histochemical identification of osteoclasts and as a serum marker of osteoclast activity and increased bone turnover. Rat and mouse models are becoming popular systems for studying osteoclast development, bone physiology and morphogenesis, and bone diseases such as osteoporosis. We have developed two unique antibodies to human TRAP purified from hairy cell leukemia spleen. Both antibodies (9C5 and 14G6) are suitable for immunohistochemistry of osteoclasts and macrophages. Only one (14G6) is capable of immunoprecipitating active TRAP from human cell lysates. Antibody 9C5 reacts with a denatured epitope of TRAP while antibody 14G6 probably reacts with a native, conformational determinant. The high degree of homology among TRAPs of various species predicts that these antibodies should be suitable for work in experimental animals as well as humans. Immunohistochemical staining, electrophoretic analyses, immunoprecipitation and immunoblotting assays of human rat and mouse TRAP were carried out to test the validity of these antibodies as cell markers in rodents. Both antibodies were suitable for immunohistochemistry in all species. Antibody 9C5 was suitable for immunoblotting of denatured TRAP of all species tested. Antibody 14G6 reacted with the native TRAP of humans only and failed to immunoprecipitate mouse or rat TRAP activity. Although TRAP is a phylogenetically conserved protein, subtle, species-specific determinants exist. Care should be exercised when anti-TRAP antibodies are used for immunoassay in experimental animals.