Immunology: Identification of human sperm surface glycoproteins by sperm membrane-specific autoantibodies

In order to identify the surface antigens of human spermatozoarecognized by the sera of immune infertile men, sperm membrane-specificantibodies were obtained from three serum samples exhibitinghigh titres of antibodies with different sperm-binding patterns.Serum antibodies were adsorbed onto normal motile spermatozoaand subsequently eluted from the sperm membrane. Using the immunoblottingtechnique under renaturating conditions, the sperm-eluted antibodieswere tested against an electro-phoretically fractionated spermmembrane preparation. A total of 15 protein bands ranging from110 to 16 kDa were defined, but the immunoblot profiles differedquantitatively and qualitatively from one serum to another.Only two polypeptides were recognized by the three sperm membrane-specificantibody preparations; one of 90 kDa and another of 110 kDa.Blots were also used for the affinodetection of specific oligosaccharideside chains. Three lectins were tested (concanavalin A, Pisumsativum, and wheat germ agglutinin). Of the 15 protein zonesrecognized by the antibodies, 11 bound at least one lectin andshould contain glycopeptides with oligosaccharides of four differenttypes: N-linked biantennary complex type, N-linked fucosylatedcomplex type, N-linked lactosaminyl complex type with terminalsialic acid and polysialyl type oligosaccharides. Further analysisof these glycoproteins will be pursued with sperm-associatedantibodies eluted from the ejaculates of infertile men in orderto define those with a potential role in the fertilization process.