Characterization and isolation of a sperm-coating antigen from rabbit seminal plasma with capacity to block fertilization.

The relationship between the sperm-coating antigens of rabbit seminal plasma and the phenomenon of decapacitation was studied using agar-gel diffusion, immuno-electrophoresis, chromatography on Sephadex G-200, and polyacrylamide vertical gel electrophoresis. Interpretation of data obtained with these techniques led to the conclusion that a sperm-coating antigen of seminal plasma origin possessed biological activity for blocking fertilization. The sperm-coating antigen was a glycoprotein of approximately 170,000 molecular weight, migrated in an electric field similar to a serum slow \g=b\-globulinand was still present in the seminal fluid of vasectomized males. This sperm\x=req-\ coating antigen was absent from the inactive upper supernatant fluid fraction of seminal plasma after 4 hr of ultracentrifugation at 105,000 g and was present in the active ultracentrifugal pellet.