Monoclonal antibodies (Mab) produced from one of the hybridomas (B11C8) which were established by cell fusion of mouse myeloma cells (P3UI) with spleen cells from a mouse immunized with porcine zona pellucida (ZP) were characterized and their inhibitory effect on in vitro fertilization of porcine oocytes by boar spermatozoa was studied. B11C8 Mab was IgG2a and reacted tissue-specifically and species-specifically to porcine ZP. It formed an immune precipitin line against heat solubilized porcine ZP in Ouchterlony's double immunodiffusion test, suggesting that multiple antigen epitopes corresponding to B11C8 Mab were expressed on one antigen molecule. The binding site of the antigen corresponding to the Mab seems to be composed of a peptide-carbohydrate mixed portion. B11C8 Mab, either divalent (IgG) or univalent (Fab) antibody, showed a strong inhibitory effect on the binding of boar spermatozoa to porcine oocytes. This suggests that B11C8 Mab possibly recognized some antigen molecule related to the sperm receptors on porcine ZP.
