CHARACTERIZATION OF FERTILIZATION-BLOCKING MONOCLONAL-ANTIBODY 1G12 WITH HUMAN SPERM-IMMOBILIZING ACTIVITY

A mouse hybridoma (1G12) producing sperm-immobilizing MoAb to human sp erm was established and characterized in order to study the antigens r elevant to sperm immobilization by antibodies. MoAb 1G12 had strong sp erm-immobilizing and agglutinating activities and also showed a fertil ization-blocking activity on in vitro fertilization tests. The antibod y absorption experiments showed that MoAb 1G12 reacted not only to eja culated sperm but also human seminal plasma, suggesting that the corre sponding antigen might be a sperm coating antigen. The MoAb also react ed with peripheral blood lymphocytes. In histochemical studies, the ep ithelia of corpus epididymis were most strongly stained. Ejaculated sp erm were stained with a granular pattern for their entire surface by i mmunofluorescence. MoAb 1G12 recognized polymorphic glycoproteins of 1 5-25 kD in the ejaculated sperm extract in Western blot analysis. Afte r deglycosilation of the sperm extract, only a single staining band of under 15 kD was detected by MoAb 1G12. This suggests that the antigen epitope recognized by MoAb 1G12 might be a peptide of the core portio n of the glycoprotein. MoAb 1G12 might be a useful tool for studying t he mechanism of egg-sperm interaction, and also be applied to identify ing the corresponding antigen by using gene technology.