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The use of ELISA to evaluate human antibody binding to epididymal sperm from different species
1Department of Biology, Laboratory of Reproductive Immunology, Medical Faculty, Sofia, Bulgaria.
Problem:
The impact of antibodies to epididymal sperm antigens in human infertility has been poorly understood. Cross-reactivity of human antibodies with animal epididymal sperm has been previously observed, however, only by means of qualitative methods. Moreover, it has been always compared to reactivity against human ejaculated rather than human epididymal sperm.
Method:
Following a screening study of 940 infertility patients, sperm agglutinating and immobilizing sera as well as sperm antibody negative controls were used to standardize an ELISA employing human ejaculated sperm. Nine sera positive in ELISA were further tested against epididymal human, guinea pig, rat, and hamster sperm. Differences among groups were evaluated by factorial analysis of variance (ANOVA).
Results:
The specificity and sensitivity of ELISA were shown to be 85.1% and 61.18%, respectively. Eight out of nine antisperm antibody-positive sera from infertile subjects reacted relatively stronger with epididymal than with ejaculated human sperm. All tested infertility sera showed strong although variable cross-reactivity with sperm from guinea pig, hamster, and rat.
Conclusion:
ELISA has definite potential in sperm antibody research, allowing quantitative assessment of the results and immotile sperm employment. The suggested predominant role of epididymal sperm antigens in immune responses related to fertility needs further investigation. Some of these antigens are obviously phylogenetically preserved, and possibly in a quantitative aspect present differently on epididymal spermatozoa from various mammalian species.