title: Non-immune IgG binding to the surface of spermatozoa by disulphide rearrangement.
abstract: The mechanism whereby immunoglobulin binds to the surface of spermatozoa was investigated. IgG reacts with spermatozoa non-specifically via the Fc portion of the molecule, while both IgM and IgA are completely unreactive. This selective binding of IgG is non-competitive, resistant to heat, proteases and non-ionic detergents and is not mediated by an Fc receptor on the sperm surface. Instead, evidence is presented that IgG covalently binds to spermatozoa by an exchange reaction between labile disulphides on both the sperm surface and IgG-Fc. It is calculated that there are 3 X 10(11) exchangeable disulphide bonds per bull spermatozoon.
mesh_terms: D000818:Animals; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane / Q000276:immunology; D004220:Disulfides / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology*; D008297:Male; D010447:Peptide Hydrolases; D011961:Receptors, Fc / Q000502:physiology; D013094:Spermatozoa / Q000276:immunology*
chemical_list: D004220:Disulfides; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D011961:Receptors, Fc; D010447:Peptide Hydrolases