Anti-sperm IgA antibodies against the equatorial segment of the human spermatozoon are associated with impaired sperm penetration and subfertility.

OBJECTIVE

To determine the prevalence of antibodies directed against the equatorial segment of the spermatozoon in (a) serum in both sexes in relation to age and fertility status and (b) semen of infertile men with tail-to-tail sperm agglutination in relation to in vitro sperm penetration capacity.

MATERIAL

Serum samples were obtained from 30 neonates, 11 prepubertal children, 30 adolescents, 60 adults aged 20-50 years, and 60 adults over the age of 70. Semen samples were obtained from 62 men with normal sperm counts and sperm morphology but with tail-to-tail agglutination.

METHODS

Sperm antibodies were demonstrated with an immunoperoxidase assay. Sperm penetration capacity was measured with a modified Kremer capillary test.

RESULTS

Serum anti-sperm antibodies were absent in children but appeared in teen-age boy (10%) and in adult men (20%) and women (30%). Lower prevalence of serum anti-sperm antibodies was noted for old individuals of both sexes (6-10%). Among individuals with a history of infertility, a significantly higher frequency of anti-sperm antibody-positive men (P < .001) and (P < .05) was found as compared to fertile controls. Presence of IgA antibodies bound to the equatorial segment of spermatozoa was associated with impaired in vitro sperm penetration capacity. No IgG or IgM anti-sperm antibodies bound to the equatorial segment were demonstrable.

CONCLUSIONS

Seminal IgA antibodies bound to sperm are associated with impaired sperm penetration.