Identification of human sperm surface glycoproteins recognized by autoantisera from immune infertile men, women, and vasectomized men

To identify the surface antigens of human sperm recognized by antisera from immune infertility patients and vasectomized men, we labeled sperm surface proteins with ¹²⁵I- and used patient antisera for immunoprecipitation. Sera were studied from 27 infertile males, 18 infertile females, and 4 vasectomized males, each possessing anti-sperm antibodies detected by immunobead binding. Sera from different infertile males, different infertile females, and vasectomized males were remarkably similar in their surfce antigen recognition. The different sera specifically immunoprecipitated the same small group of ¹²⁵I-labeled surface proteins, which included polypeptides in the region 90 kDa, 40-45 kDa, and 26 kDa. Tretment with N-glycanase showed that the proteins of 90 kDa, 40-45 kDa, and 26 kDa were glycoproteins with N-linked carbohydrate. The immunoprecipitated ¹²⁵I-labeled proteins and the total extract of ¹²⁵I-labeled surface proteins were compared on two-dimensional (2D) gels. The results show the 90 k Da polypeptide is a major sperm surface component, whereas 40-50 kDa and 26 kDa polypeptides are minor components. The 2D gel comparison also indicates that 90 kDa, 40-45 kDa, and 26 kDa are a small subset of the total ensemble of sperm surfce proteins. Clinical data suggest antibodies to these few proteins interfere with sperm function.