The Effects of Patients' Sera with Sperm‐Immobilizing Antibodies on Sperm of the Japanese Monkey

In order to study the interspecies cross-reactivity of sperm-immobilizing antibodies found in sera of women who were infertile for unknown reasons, we used the sperm-immobilization test to examine the effects of patients' sera with or without sperm-immobilizing antibodies on the sperm of the Japanese monkey (Macaca fuscata). Fourteen of 17 antibody-positive sera and 7 of 14 antibody-negative sera showed sperm-immobilizing activity with regard to monkey sperm. The sperm-immobilizing antibody that was active against both human and monkey sperm could be absorbed only by sperm from each corresponding species. The periodate treatment of human or monkey sperm markedly diminished their antibody-absorbing capabilities. Human and mouse monoclonal antibodies having sperm-immobilizing activity with regard to human sperm showed no sperm-immobilizing activity with regard to monkey sperm. These results indicate that the sperm-immobilizing activity of the sera of infertile women against human and monkey sperm might be due to antibodies with different specificities, which recognize a unique carbohydrate antigen epitope expressed in the sperm of each species.