Abstract
The present study was conducted to examine whether there is any difference in the protein profiles of sperm membranes of fertile (n = 37) and infertile (n = 29) men. In the sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) procedure, the sperm extracts of fertile and infertile men showed 12-16 major and 8-14 minor common protein bands in various molecular regions. However, there was an additional band of ~78kD present in the sperm extracts of ~80% of infertile men that was absent in the sperm extracts of fertile men. In the remaining ~20% of the infertile men, it was of relatively weaker intensity. This band was present only in the sperm extracts and not in the seminal plasma, whether of fertile or infertile men, and was designated as the infertility-associated sperm protein (IASP).Antibodies to IASP specifically immunoprecipitated the ~78-kD protein from the sperm extracts of only infertile and not the fertile men. In the immunofluorescence technique, the anti-IASP antibodies reacted strongly with the head and/or midpiece regions of morphologically abnormal sperm and cross-reacted with a protein in the equatorial regions of morphologically normal sperm of fertile men. The IASP molecule and its antibodies may provide molecular tools to differentiate between the normal and abnormal sperm, and, thus, may be useful markers for the diagnosis of male-factor infertility.