Presence of immunoglobulin binding factor on human sperm surface as sperm coating antigen

The presence of IgBF as a sperm-coating antigen was demonstrated by showing that anti-IgBF antibodies agglutinate and immobilize human sperm and by localizing IgBF on sperm surface by immunofluorescence staining. Several components interacting with sperm immobilizing antibodies, known to be involved in infertility, are sperm-coating antigens. Anti-IgBF antibody in vitro did not block the ability of human sperm to penetrate human zona pellucida and zona-free hamster egg. Anti-IgBF activity of sera obtained from infertile women did not correlate with the titers of anti-sperm antibodies measured by the sperm immobilization test. IgBF is a sperm-coating antigen and may play a role in suppressing antibody production against alloantigenic sperm in the female reproductive tract.