The antigenic relatedness of proteins from human and simian prostate fluid

Two‐dimensional electophoretic analysis of human prostate fluid reveals an abundant protein migrating to a molecular weight of 15 kD and an isoelectric point of 5.5. Polyclonal antibodies were raised specifically to microgram quantities of electrophoresed, excised, and eluted PSP15 (prostate secretory protein). Western immunoblot analysis using these antibodies showed they ot only react to PSP¹⁵, but cross‐react with simian prostate and human seminal fluid proteins of similar molecular weights. Two‐dimensional gel immunoblots strongly suggest that the seminal protein and PSP15 are the same, thereby providing a more accessible source of the protein. The antibody to the human PSP¹⁵ cross‐reacted with neither prostate fluid from the ventral lobe of the rat prostate nor the prostate fluid from the beagle dog.