Immunochemical characterization of prostatic acid phosphatase with monoclonal antibodies

Hybridoma-derived monoclonal antibodies to human PAP have been produced by fusion of mouse myeloma cells [P3 x 63 Ag 8.653] with spleen cells from mice immunized with purified PAP. One hundred fifty-six out of 252 clones were found to produce antibodies against PAP. These monoclonal antibodies were classified into four different subclasses as IgM [3 clones], IgG2a [2 clones], IgG3 [1 clone], and IgG1 (150 clones] with k-chains. Four monoclonal antibodies, IgG1, IgG2 a, IgG3, and IgM, were selected from the 156 hybridoma clones for immunologic characterization. Results from a binding assay suggested that monoclonal anti-PAP antibodies IgG1 and IgM recognized two distinct antigenic determinants of the PAP molecule, while the hybridoma IgG2a and IgG3 antibodies recognized another antigenic determinant. The specificity of these four hybridoma anti-PAP antibodies has been evaluated by the immunohistochemical method and competitive-binding assay. Monoclonal antibodies IgG2a and IgG3 as well as polyclonal xenoantibodies were found to react with PAP as well as with nonprostatic acid phosphatases; and antibodies IgG1 and IgM reacted more specifically with PAP. These results indicated that monoclonal anti-PAP antibodies IgG1 and IgM possessed a higher specificity for human PAP in comparison with monoclonal antibodies IgG2a, IgG3, and xenoantibodies. The monoclonal anti-PAP IgG1 and IgM antibodies may be useful in delineating antigenic structure of the PAP molecule, as well as in the refinement of serologic determination and immunocytochemical study of PAP in human prostate cancer.