Impaired antibody diffusion within the cytoplasmic membrane-fibrous sheath interspace of the human sperm tail

Monoclonal and polyclonal antibodies specific for the fibrous sheath (FS) were used to assess their diffusion within the subcytoplasmic membrane space of the human sperm tail. Using indirect immunofluorescence (IIF) and immunogold electron microscopy (IEM), the staining of the entire FS with these antibodies was observed only when the spermatozoa were completely demembranated by detergents or dried onto slides. Partial damage to sperm cytoplasmic membranes by freezing and thawing resulted in segmental staining of the FS. The IEM of such spermatozoa with the antibodies revealed the distribution of gold particles on the FS in denuded areas only and adjacent segments which retained their cytoplasmic membrane were not stained. These results indicate that partial disruption of the sperm plasma membranes does not lead to free diffusion of antibodies within the cytoplasmic membrane-FS interspace. This property appears to be unique to sperm cells and is due to their specialized structural organization.