Monoclonal antibodies to human prostatic acid phosphatase: probes for antigenic study

Hybrid cell lines producing monoclonal antibodies against human prostatic acid phosphatase [PAPase; orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2) were prepared by the fusion of mouse myeloma cells with the spleen cells of PAPase-immunized BALB/c mice. Approximately 23% of the hybrid cells initially plated after cell fusion produced specific antibodies: 34 microcultures were cloned, and 8 eventually yielded stable cell lines. The monoclonal antibodies produced by these eight hybridomas were characterized for their isotypes, isoelectric points, concentrations, and affinities. All of the eight monoclonal antibodies exhibited strict specificity for PAPase as determined by radioimmunoassay and immunohistochemical methods. These antibodies were used as probes for the antigenic mapping of this enzyme, and three nonoverlapping determinants were recognized. Further binding studies with PAPase fragments, generated by cleavage with a submaxillaris protease, showed that those three determinants are clustered on one fragment of PAPase. These monoclonal antibodies may be useful in refinement of clinical immunoassays of PAPase or immunohistological study of PAPase-synthesizing cells.