title: Inhibition of human spermatozoon-oocyte interaction in vitro by monoclonal antibodies to CD46 (membrane cofactor protein).
abstract: CD46 (membrane cofactor protein) is a cell surface complement regulatory glycoprotein that facilitates enzymatic cleavage of complement component C3b; it is expressed by both human oocytes and acrosome-reacted spermatozoa. Murine anti-CD46 monoclonal antibody (mAb) has been reported to decrease significantly the ability of human spermatozoa to penetrate hamster oocytes. We have investigated the effect of purified anti-CD46 mAbs on spermatozoon-oocyte interaction in an autologous zona-free oocyte penetration test. Oocytes and/or spermatozoa were preincubated with either of two anti-CD46 murine mAbs, TRA.2.10 (a non-blocking mAb) and MH61 (a mAb that functionally blocks C3b-ligand binding activity), or a control isotype-matched mAb, in medium supplemented with human serum albumin. Preincubation of both spermatozoa and zona-free oocytes with TRA.2.10, but not MH61, caused a significant decrease in the number of oocytes showing sperm binding and pronuclear formation (9/23) compared with controls (21/26) in this complement component-depleted medium. This effect was not observed if oocytes or spermatozoa alone were preincubated. These data suggest that CD46 has a role in human spermatozoon-oocyte interaction at the level of the oocyte plasma membrane, and indicate that a novel function other than direct C3b binding could be involved.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Liverpool, UK.
authors.forename: C T
authors.initials: CT
authors.lastname: Taylor
authors.forename: M M
authors.initials: MM
authors.lastname: Biljan
authors.forename: C R
authors.initials: CR
authors.lastname: Kingsland
authors.forename: P M
authors.initials: PM
authors.lastname: Johnson
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D015703:Antigens, CD / Q000502:physiology*; D003165:Complement System Proteins / Q000502:physiology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D013084:Sperm-Ovum Interactions / Q000276:immunology* / Q000502:physiology*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C497857:CD46 protein, human; C497859:Mcp protein, mouse; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D003165:Complement System Proteins