Characterization of human sperm cell surface components

Localization of wheat germ agglutinin lectin receptors on human sperm by fluorescence microscopy: utilization of different fixatives

Wheat germ agglutinin (WGA) and Concanavalin A (Con A) seem to be the most widely studied of the lectins used to investigate sperm surface receptors. It has been reported that WGA receptors on human sperm membranes may be closely related to male fertility and that WGA receptor deficiency may cause human infertility. Although these claims may not be negated, there are many discrepancies in current literature regarding the localization and detection of human sperm WGA receptors. These discrepancies are probably the result of variations in the pretreatment of sperm before fixation and sperm-lectin interaction. This study investigated the effect of different fixation procedures on the localization of human sperm WGA receptors on normal spermatozoa. Comparative studies were performed on spermatozoa separated by wash-swim-up and fixed with 4% formaldehyde, 95% ethanol, or Bouin's solution, or nonfixed (air-dried) using fluorescein isothiocyanate-conjugated WGA. There were significant differences (p < .01) in the % WGA receptor localization following the different fixation procedures on samples receiving the same treatment previous to fixation. The different fixatives affect the plasma membrane to different degrees, resulting in an alteration of lectin receptor localization. To allow a better comparison and understanding of results, a standardized preparation procedure is recommended during studies using lectins as molecular probes. The results suggest than an aldehyde fixative may be the fixative of choice for sperm membrane studies.

Identification of human sperm antigens reacting with antisperm antibodies from sera and genital tract secretions

OBJECTIVE

To identify sperm antigens reacting with antisperm antibodies relevant in human infertility.

DESIGN

The reactions of separated sperm antigens with antibodies present in sera and genital tract secretions from infertile and fertile females and males were examined by immunoblotting techniques.

SETTING

The patients were followed in an outpatient setting of a hospital clinic.

PATIENTS

One hundred consecutive infertile males and females, referred for determinations of antisperm antibodies, comprised the study group. Fifty hospital and faculty employees with proven fertility served as a control group.

RESULTS

A high proportion of sera from fertile and infertile humans contained antibodies reacting with at least one sperm antigen. However, two discrete bands of antigenic proteins with molecular weights of 44 and 72 kd reacted significantly more frequently with serum antibodies from infertile females than from fertile females. No apparent correlation could be demonstrated between any particular antigen and serum antibodies from infertile males. Nevertheless, antigenic proteins of 62 kd were identified as the major sperm antigens reacting with antibodies present in seminal plasmas from infertile males.

CONCLUSIONS

The major sperm antigens reacting with systemic antibodies differ from the antigens recognized by local antisperm antibodies. Sperm antigens exhibiting relative molecular weights of 62 kd are major antigens reactive with local antisperm antibodies from infertile humans.

The effects of antibody sperm-egg interaction

Previous studies have shown that high titers of antisperm antibodies are correlated with low fertility. Furthermore, immunosuppressive therapy enhances pregnancy in some individuals. Serum tests, however, provide only an indirect measure of a potential pool of antisperm antibodies. When men have antibodies, direct measurement of the percent of sperm that are entirely antibody bound is a more appropriate approach. Antibodies can affect fertilization at many sites. Since sperm are composed of numerous antigens, many antibodies can develop but not all of them will interfere with infertility. Better tests are necessary to define which antibodies may affect fertility. To do that requires the development of better antigens. Use of monoclonal antibodies allows a framework for such further modifications.

Characterization of human sperm plasma membrane: glycolipids and polypeptides

The plasma membranes from ejaculated human spermatozoa were removed by nitrogen cavitation (600 PSI for 10 min) and isolated by centrifugation followed by a discontinuous sucrose density gradient centrifugation. Glycolipid analysis of the plasma membrane revealed a three-fold enrichment in gangliosides: GM3 and GD1a/GD1b and neutral glycolipids: globoside and sulfatide as compared to that of whole human sperm. Two dimensional electrophoresis of human sperm plasma membranes revealed about 75 polypeptides. Several of these polypeptides were similar in migration and in display of shape and color to that found in boar sperm plasma membranes.

Multiple actions of a novel vaginal contraceptive compound, ORF 13904

ORF 13904, a sulfonated polystyrene polymer possessing potent vaginal contraceptive activity, was tested in vitro and in vivo to investigate its mechanism of action. Observations of rabbit spermatozoa when mixed with the compound in buffered saline confirmed that the compound is not spermicidal and showed that the cells rapidly and irreversibly agglutinate. Seminal plasma did not compromise the effects of the drug, but rather enhanced them. When spermatozoa were suspended in solutions containing ORF 13904 and then washed thoroughly to remove excess drug, human spermatozoa could not penetrate bovine cervical mucus in vitro and rabbit spermatozoa could not achieve fertilization after artificial insemination in vivo, suggesting that the drug either adheres to the sperm surface or irreversibly compromises sperm function. Biochemical analysis showed that ORF 13904 is also a potent acrosin inhibitor. These experiments suggest that ORF 13904 has several mechanisms of action, including the ability to agglutinate spermatozoa, alter sperm-cervical mucus interaction, and inhibit sperm acrosin.

Low molecular weight proteins in human seminal plasma electrophoretical evidence of their vesicular origin

The protein composition of seminal plasma (SP), two-fractions split ejaculates and expressed prostatic secretions (EPS) from healthy and fertile donors or from infertile patients has been analyzed under proteolysis-blocking and denaturing conditions by 5-20% gradient SDS-PAGE. EPS protein patterns were found to be strikingly similar, both in protein types and concentrations. The same was true for the SP samples. Co-electrophoresis and comparison of the patterns obtained allowed to identify a medium-sized protein (MW 75-80,000 daltons) and low-MW proteins (MW 10-25,000 daltons) as of vesicular origin. Furthermore, prostatic and vesicular proteins were found to migrate into different zones of the gels, giving raise to an unexpected MW "complementarity". A similar finding was obtained by comparing the protein spectra of fluid from vesicular massage (EVS), EPS and SP from a man with moderate asthenozoospermia. However, analysis of nine other EVS samples by the same electrophoretical technique revealed that the majority of them were (sometimes heavily) contaminated by prostatic proteins. It was concluded that SDS-PAGE on gradient gels is of help to distinguish and characterize the proteins secreted by the two major male accessory glands. Such a finding has both research and clinical applications.

Identification of mammalian sperm surface antigens: II. Characterization of an acrosomal cap protein and a tail protein using monoclonal anti-mouse sperm antibodies

Monoclonal anti-mouse sperm antibodies have been produced by fusing mouse myeloma cells with spleen cells from rats immunized with epididymal sperm of C3H mice, Immunoprecipitation and immunoperoxidase techniques showed that one such monoclonal antibody, AMS IV-33, recognized a 200 000 dalton protein localized on the acrosomal cap of the sperm cell. Two other monoclonal antibodies AMS IV-54 and -76, reacted with a 68 000 dalton component on the surface of the sperm tail. Both antigenic targets were species specific and were present in about equal amounts on sperm from several different strains of mice. The tail protein was sperm specific, whereas the antibody reacting with the acrosomal cap protein also appeared to react somewhat with antigens present in other mouse tissues.

High-resolution protein patterns of human expressed prostatic secretion: a new tool for the diagnosis of prostatitis

Expressed prostatic secretions (EPS) obtained from 62 infertile and urological patients have been analyzed for their protein content by sodium dodecylsulfate electrophoresis and isoelectrofocusing. Independent cytological and bacteriological screening on the same EPS samples was carried out to detect prostatic inflammation. EPS from both urological and infertile patients without inflammation had simple and characteristic protein patterns. Important qualitative and quantitative differences in the protein composition of EPS from patients with severe dysspermia or prostatic inflammation were found. The comparison of EPS protein patterns with those of seminal plasma obtained from the same patients led to the detection of a characteristic group of low-molecular-weight bands that were not of prostatic origin.

Surface components of ejaculated chimpanzee sperm

Surface components of ejaculated chimpanzee sperm were radiolabeled by enzymatic iodination with lactoperoxidase and Na125I. The sperm were lysed and the labeled components analyzed on SDS-7.5% polyacrylamide gels. Electrophoresis of solubilized radioactivity resolved four components with approximate molecular weights of 72,000, 49,000, 25,000 and 17,000 daltons. To identify components, which might be adsorbed to the chimpanzee sperm surface from seminal secretions, seminal plasma was labeled. Electrophoresis of labeled seminal plasma resolved three components with approximate molecular weights of 63,000, 26,000, and 17,000 daltons, two of which comigrated with a labeled sperm surface component.

Immunological identification of lactoferrin as a shared antigen on radioiodinated human sperm surface and in radioiodinated human seminal plasma

After lactoperoxidase-catalyzed iodination of either human sperm surface or human seminal plasma, a 72-76 kdalton component was resolved on SDS-7.5% polyacrylamide gels. The approximate molecular weight of this component was consistent with that of human lactoferrin, a major sperm-coating antigen. Immunoprecipitation of labeled sperm surface and of labeled seminal plasma with specific anti-human lactoferrin antibody identified lactoferrin as a constituent of this 72-76 kdalton component both on human sperm surface and in human seminal plasma. These data show that components which have been inferred to be shared because of similarities in biochemical characteristics also contain immunologically identical components.

Characterization of radiolabeled components of human sperm surface and seminal plasma

Externally oriented components on the human sperm cell surface and components in human seminal plasma were labeled by enzymatic iodination with lactoperoxidase and [¹²⁵I] NaI. SDS-7.5% PAGE of labeled sperm surface resolved one minor and four major components with approximate molecular weights of 92, 72, 46, 30, and 20K daltons, respectively. SDS-7.5% PAGE of labeled seminal plasma resolved five components with approximate molecular weights of 74, 51, 43, 28, and 20K daltons. Three of the five moieties seen on the sperm surface and in seminal plasma were similar in molecular weight. This suggested that these surface components were adsorbed from seminal secretions. Because the iodination procedure used labels both proteins and lipids, labeled sperm surface and labeled seminal plasma were subjected to isopycnic density gradient centrifugation to identify the chemical composition of the radioiodinated components. With human sperm surface, two areas of radioactivity were resolved in CsCl gradients, one corresponding to protein and the other to lipid. With human seminal plasma, only one area of radioactivity, corresponding to protein, was identified. Electrophoretic analysis of each peak of radioactivity obtained from the gradients demonstrated that all of the sperm surface and four of five seminal plasma components were in the protein fractions. All three of the seminal plasma components which correspond to sperm surface components were recovered in the protein fraction. This observation supports our hypothesis that some of the proteins labeled on the human sperm cell surface are adsorbed from seminal secretions.