THE ANTI-HUMAN PROSTASOME MAB 78 BINDS TO AN ANTIGEN DISTINCT FROM PSA AND PAP

Purpose: The characteristics of an antigen corresponding to a monoclon al antibody (mAb 78) against human prostasomes were compared with pros tate-specific antigen (PSA) and prostatic acid phosphatase (PAP). The correspondence of Ag 78 to two other prostate-derived antigens, prosta sin and peptide pGlu-Phe-Pro-NH2, were also considered. Materials and Methods: The immunoreactivity of mAb 78 and the cross-reactivity of mA b 78 with PSA and PAP were studied with immunohistochemical and enhanc ed chemiluminescence (ECL) Western blotting methods. Results: The mAb 78 did not bind to PSA blots, and anti-PSA antibody did not label pros tasome blots. Neither did PSA and PAP impede the binding of mAb 78 ont o prostasome blots nor to paraffin sections of prostate epithelium. Af ter Western blots, mAb 78 bound diffusely to a band with a molecular w eight of 35 kDa, but did not bind to PSA (33 kDa) or PAP (monomer 50 k Da, intact molecule 100 kDa) bands. From purified 35 kDa bands, three fractions were sequenced, which showed no similarities to PSA and PAP. Conclusions: The Ag 78 is different from PSA and PAP, and probably al so from prostasin and peptide pGlu-Phe-Pro-NH2. The mAb 78 can be used as a new marker for human prostasomes.