Relation between antisperm antibodies and the rate of fertilization of human oocytes in vitro

To clarify further the role of antisperm antibodies in in vitro fertilization, the occurrence of antisperm antibodies on ejaculated sperm and in sera was determined by the immunobead binding assay in 67 couples after an unsuccessful in vitro fertilization cycle. Antisperm antibodies in maternal sera were associated with a failure of oocyte fertilization (P <0.02) or with fertilization of only 9–19% of the oocytes (P <0.01) in vitro. Antisperm antibodies were detected in sera from 13 of 24 women (54.2%) where no fertilization occurred, 9 of 14 women (64.3%) where less than 20% of the oocytes fertilized, and 3 of 19 women (15.8%) where greater than 40% of the oocytes fertilized. Antisperm antibodies in these sera were mostly IgG and directed against the sperm tail. Antibodies on the surface of ejaculated motile sperm were also associated with a low (9–19%) fertilization rate (P <0.01). Sperm-bound antibodies were detected in 2 of 24 men (8.3%) where no fertilization occurred, 5 of 14 men (35.7%) where less than 20% of the oocytes fertilized, and 0 of 19 men where fertilization was greater than 40%. Sperm-bound antibodies were mainly IgA and were tail-directed. Antisperm antibodies in sera of males were not related to the rate of fertilization. Antisperm antibodies were detected in female partners of 21 of 46 couples (45.7%) with unexplained infertility, 2 of 12 women (16.7%) with blocked tubes, 4 of 7 women (57.1%) with endometriosis, and 0 of 2 women with adrenal hyperplasia. There was no relation between the fertilization rate and the maternal age, number of oocytes harvested, or semen quality. We conclude that antisperm antibodies are present in sera from a high percentage of women with unexplained infertility and that antibodies reacting with sperm tails may directly interfere with fertilization in vitro or may be a surrogate marker for another factor that interferes with this event.