Monoclonal antibody labelling of human spermatozoa: an electron microscope study

The antigenic determinants recognized by six anti-human sperm monoclonal antibodies were localized at the subcellular level using an indirect peroxidase immunoelectron microscopic method. Labelling was performed using fresh spermatozoa, and after cell permeabilization (by osmotic shock or freeze-thawing) or detergent demembranation. Two antibodies bound to distinct regions of the plasma membrane, one over the acrosome and the other on the tail, but both also bound to intracellular sites on damaged cells. The internal organelles labelled by the other four antibodies were identified as the acrosomal membrane of the equatorial segment, structures in the connective piece, mitochondrial membranes and axonemal microtubules, respectively. These results are compared with those of a previous immunofluorescence study (Villarroya & Scholler, 1986) and the advantages of joint light and electron microscopy for sperm immunocytochemistry are discussed.