Circulating human antisperm antibodies recognize prostasomes

PROBLEM: The presence of naturally occurring antisperm antibodies (ASA) is a well-known cause of infertility in men and women, but the antigens for these antibodies are usually poorly characterized. Prostasomes, organelles secreted by human prostatic acinar cells and expelled into the seminal plasma at ejaculation, can adhere to sperm cells. Thus, we have examined whether prostasomes could be an antigen for ASA. METHOD OF STUDY: We have studied the reactivity of chicken antiprostasome antibodies with sperm cells in an agglutination test and conversely the reactivity of serum positive for ASA from 20 infertile patients, with spermatozoa using flow cytometry and with purified prostasomes using enzyme-linked immunosorbent assay. RESULTS: The chicken antiprostasome antibody caused agglutination of sperm cells similarly to the agglutination observed with patients' sera. All of these patients' sera contained IgG antibodies against prostasomes. CONCLUSIONS: The high percentage of patients with antiprostasome antibodies in this study shows that prostasomes could be one of the major targets for ASA.