Intermediate filament proteins in human sperm heads

Monoclonal antibodies made against human sperm cells have been characterized with regard to binding patterns and molecular coordinates of the recognized antigens. Antibodies T5 and T6 gave uniform binding to the acrosomal cap in an intact cell, and decreased to equatorial segment binding in an 'acrosome-reacted' cell. Monoclonal antibody T15 gave the reverse: equatorial segment binding in intact cells and uniform acrosomal cap binding in reacted cells. From staining patterns on cultured cell lines, determination of molecular coordinates, immunoblots, and partial peptide analysis, we have determined that T15 is directed against the cytoskeletal protein, vimentin, while T5 and T6 recognize a keratin-like protein which may be unique to sperm cells. This is the first immunological and biochemical study to analyse both types of intermediate filament proteins in human sperm cells.