ANTIBODY-INDUCED CHANGES ON RABBIT SPERM SURFACE INHIBIT GAMETE INTERACTION

Interaction of specific ligands with cell surface molecules may induce reorganization of surface components. A monoclonal antibody (B-12) ag ainst sperm surface antigens of 40kDa size induced molecules on the pl asma membrane overlying the acrosome of rabbit sperm to cluster in sma ll aggregates at 0 degrees C (patching). At an elevated temperature of 37 degrees C these clusters of antigen antibody complexes collected i nto a large aggregate on one pole of the cell forming a cap (capping). This cap-like structure showed a reduction in size over a period of t ime and eventually disappeared from the sperm surface. Inhibition of c apping by sodium azide indicated that it is an energy-dependent proces s. Patching of antigens did not require energy. Involvement of sperm h ead cytoskeleton in the process of capping was evident from potentiati on of cap formation by cytoskeleton disrupting agents like cytochalasi n B and D. Patching of antigen antibody complexes was not affected by either of the agents. The loss of antigen antibody complexes from sper m surface was mainly due to shedding of the complexes in the surroundi ng media. Sperm with patches of antigen antibody complexes did not adh ere to oocytes. Sperm from the group where a majority of the sperm wer e denuded of the antigen antibody complexes also did not bind to oocyt es. (C) 1994 Wiley-Liss, Inc.