The sera of 60 homosexual males were examined for the presence of antibodies to sperm using an indirect immunobead test (IBT). Six of 60 (10%) had antibodies of IgG isotype; in addition two of the six had antibodies of IgA isotype. The presence of antibodies was associated with the practice of unprotected receptive anal intercourse in the previous six months. Antibodies were not found in homosexual men who were celibate, or who practised only oral intercourse during the same period. There was no correlation between the presence of anti-sperm antibodies and antibodies to human immunodeficiency virus (HIV), or numbers of T lymphocytes. These preliminary results lend support to the hypothesis that antigen presentation in the lower gut may be a source of sensitisation against sperm. The possibility that anti-sperm antibodies may be a marker of receptive anal intercourse merits further investigation.
PIP: It has been suggested that the introduction of spermatozoa to the rectum leads to the development of a humoral immune response. The immunobead method was used to investigate antisperm antibody titre and prevalence and their relation to HIV status in 60 homosexual men attending the Royal Melbourne Hospital (Australia) HIV/AIDS clinic as part of an ongoing epidemiologic study. On the basis of their sexual practices in the preceding 6 months, the men were categorized into four groups: Group 1--unprotected oral intercourse only (n = 13), Group 2--unprotected oral and anal intercourse (n = 39), Group 3--unprotected anal intercourse only (n = 2), and Group 4--celibate (n = 6). Antibodies to sperm were found in the sera of 6 men (10%), all of whom were from Groups 2 and 3. Thus, the prevalence of antisperm antibodies in men who had practiced unprotected anal receptive intercourse in the preceding 6 months was 17%. Antibodies were of the IgG and IgA isotypes. There was no correlation between the presence of antisperm antibodies and antibodies to HIV or numbers of T lymphocytes. 30 men, including 2 of the 6 men with antisperm antibodies, were HIV-positive. These preliminary findings lend support to the hypothesis that antigen presentation in the lower gut may be a source of sensitization against sperm. They further suggest a possible role for antisperm antibodies as a marker of receptive anal intercourse.