Characterization of human sperm antigens reacting with sperm antibodies from autologous serum and seminal plasma in an infertile population.

Immunoblotting techniques were used to characterize the reactivity of human sperm antigens with sperm antibodies from an infertile population. Sperm antigens of each individual were tested with autologous sperm antibodies present in serum and seminal plasma in order to construct a preliminary map of the antigens of the infertile spermatozoon and to compare the qualitative differences in the antigenic profile between fertile and infertile subjects. A total of 61 infertile males, comprising 51 subjects having poor semen quality and 10 subjects with no abnormalities in semen analysis, entered the study; 55 subjects with proven fertility served as controls. Infertile subjects often showed specific immunoreactivity to 50-, 55-, 57-, 62-, and 72-kDa proteins in serum and to 57- and 62-kDa proteins in seminal plasma. As to comparison of immunoreactivities between fertile and infertile individuals, the sperm antigens may be divided into three groups. Group 1 antigens (50-, 69-, and 72-kDa proteins) were recognized by sperm antibodies present in both populations; group 2 antigens (57- and 62-kDa proteins), by sperm antibodies typical of the infertile population; group 3 antigens (45-, 55-, and 85-kDa proteins), by sperm antibodies typical of the fertile population. This classification shows that the infertile spermatozoon differs substantially at the immunogenic level from the fertile spermatozoon. The group 2 antigens seem to be involved in a relevant step in the reproductive process and hence have been termed "fertility-related antigens."