Immunohistochemical characterization of 53 monoclonal antibodies to prostate-specific antigen.

Fifty-three antibodies submitted to the ISOBM TD-3 Workshop on the prostate specific antigen (PSA) were evaluated for their reactivity in frozen and formalin fixed tissue from benign hyperplastic prostate and salivary gland tissue. Only 13/53 antibodies showed clear reactivity in both frozen and paraffin sections, while some antibodies appeared to react only in formalin-fixed paraffin sections. Many antibodies showed extensive nonspecific reactivity in tissue sections. These results highlight the fact that the number of monoclonal antibodies suitable for immunohistochemical detection of PSA is still relatively limited.

Summary report of the TD-3 workshop: characterization of 83 antibodies against prostate-specific antigen.

Twelve research groups participated in the ISOBM TD-3 Workshop in which the reactivity and specificity of 83 antibodies against prostate-specific antigen (PSA) were investigated. Using a variety of techniques including cross-inhibition assays, Western blotting, BIAcore, immunoradiometric assays and immunohistochemistry, the antibodies were categorized into six major groups which formed the basis for mapping onto two- and three-dimensional (2-D and 3-D) models of PSA. The overall findings of the TD-3 Workshop are summarized in this report. In agreement with all participating groups, three main antigenic domains were identified: free PSA-specific epitopes located in or close to amino acids 86-91; discontinuous epitopes specific for PSA without human kallikrein (hK2) cross-reactivity located at or close to amino acids 158-163; and continuous or linear epitopes shared between PSA and hK2 located close to amino acids 3-11. In addition, several minor and partly overlapping domains were also identified. Clearly, the characterization of antibodies from this workshop and the location of their epitopes on the 3-D model of PSA illustrate the importance of selecting appropriate antibody pairs for use in immunoassays. It is hoped that these findings and the epitope nomenclature described in this TD-3 Workshop are used as a standard for future evaluation of anti-PSA antibodies.