Co-localization of the inositol 1,4,5-trisphosphate receptor and calreticulin in the equatorial segment and in membrane bounded vesicles in the cytoplasmic droplet of human spermatozoa.

Modulation of the intracellular calcium concentration within mammalian spermatozoa is important in several pre-fertilization events including hyperactivated motility and the acrosome reaction. To identify calcium binding proteins (CBP) potentially regulating these processes, a (45)Ca overlay technique was employed on 2-D blots of human sperm extracts. Microsequencing by Edman degradation and CAD mass spectrometry identified a relatively abundant 60.5 kDa CBP with a pI of 4.2 as calreticulin (CRT). Immunofluorescent labelling with anti-CRT antibodies localized CRT to the acrosome, with highest fluorescence in the equatorial segment, and in the cytoplasmic droplets of 94 and 48% of human spermatozoa respectively. Double immunolabelling experiments demonstrated co-localization of CRT and the inositol 1,4,5-trisphosphate receptor (IP(3)R) in the acrosome, in the equatorial segment, and vesicular structures in the cytoplasmic droplets of the neck region. Electron microscopic immunogold labelling localized CRT to the equatorial segment of acrosome-reacted spermatozoa and to membrane-enclosed vesicles within the cytoplasmic droplet of both acrosome-intact and acrosome-reacted spermatozoa. Localization of the IP(3) receptor to the CRT-containing vesicles, in the sperm neck and to the acrosome, suggests that capacitative calcium entry in human spermatozoa may be regulated from these putative calcium storage sites.

Differential extraction and enrichment of human sperm surface proteins in a proteome: identification of immunocontraceptive candidates.

The objective of this study was to discover previously unknown human sperm surface proteins that may be candidate contraceptive vaccinogens. To this end, methods of concentrating human sperm proteins for microsequencing by mass spectrometry were used, which increased the likelihood of identifying surface proteins. Vectorial labeling, differential extraction and two-dimensional (2-D) gel electrophoresis were employed to identify and isolate proteins accessible at the cell surface. Percoll harvested or swim-up sperm were either solubilized directly or solubilized after surface labeling with sulfo-succinimidyl-6-(biotinamido)hexanoate (sulfo-NHS-LC-biotin). Comparisons were made of proteins extracted with four lysis buffers: (i) Celis buffer containing 9.8 M urea and 2% Igepal CA-630; (ii) 1% Triton X (TX)-100; (iii) 1.7% TX-114 followed by phase partitioning; or (iv) 1 M NaCl. Blots of proteins separated by high-resolution 2-D electrophoresis were probed with avidin and antibodies to known proteins specific for three domains: the sperm surface (SAGA-1), the acrosome (SP-10), and the cytoskeleton (alpha-tubulin). Celis buffer (45 min) extracted proteins from all three major compartments. However, a 20-s extraction in Celis buffer enriched for several proteins and enabled the identification of several novel peptides by mass spectrometry. Mild extraction with TX-100 or 1 M NaCl solubilized mainly membrane and acrosomal proteins, but not cytoskeletal proteins. Comparison of biotinylated proteins extracted by each method showed that the major vectorially labeled proteins solubilized by Celis buffer were also solubilized by TX-100, TX-114, and 1 M NaCl. Extraction with TX-114 followed by phase-partitioning significantly enriched hydrophobic surface proteins and aided resolution and isolation. Eight protein spots microsequenced following all these extraction methods proved to be novel sperm molecules.

Proteomics--post-genomic cartography to understand gene function.

The completion of the genomic sequences of numerous organisms from human and mouse to Caenorhabditis elegans and many microorganisms, and the definition of their genes provides a database to interpret cellular protein-expression patterns and relate them to protein function. Proteomics technologies that are dependent on mass spectrometry and involve two-dimensional gel electrophoresis are providing the main window into the world of differential protein-expression analysis. In this article, the limitations and expectations of this research field are examined and the future of the analytical needs of proteomics is explored.

Differential nuclear localization of the cancer/testis-associated protein, SPAN-X/CTp11, in transfected cells and in 50% of human spermatozoa.

Cancer-testis antigens (CTAs) represent potential targets for cancer immunotherapy because these proteins are widely distributed in tumors but not in normal tissues, except testes. In this paper, we identify homology of the CTA CTp11 with SPAN-X (sperm protein associated with the nucleus mapped to the X chromosome). On two-dimensional Western blots of human sperm extracts, SPAN-X antibodies recognized 19 spots ranging from 20 to 23 kDa with isoelectric points from 5.0 to 5.5. Differential extraction of spermatozoa demonstrated that the SPAN-X protein is highly insoluble. Only 50% of ejaculated spermatozoa exhibited SPAN-X immunofluorescent staining. Dual localization of the sex chromosomes and the SPAN-X protein demonstrated that an equal number of X- and Y-bearing spermatozoa exhibited SPAN-X staining. In transfected mammalian CV1 cells, the SPAN-Xa and SPAN-Xb proteins were localized to the nucleus and cytoplasm, respectively, by indirect immunofluorescence. On immunoblots of CV1 cells, the SPAN-Xa protein migrated at 15-20 kDa, whereas the SPAN-Xb protein migrated at a higher molecular weight of 21-22 kDa. The SPAN-X protein was ultrastructurally associated with nuclear vacuoles and the redundant nuclear envelope. SPAN-X is the first protein specifically localized to these poorly characterized structures of the mammalian sperm nucleus and provides a unique biochemical marker for investigation of their function in spermatozoa as well as the role of SPAN-X/CTp11 in human tumors.

Anti-sperm antibodies from infertile patients and their cognate sperm antigens: a review. Identity between SAGA-1, the H6-3C4 antigen, and CD52.

PROBLEM: The correlation of anti-sperm antibodies (ASA) with some instances of unexplained infertility implicates a role for these antibodies in blocking fertilization. Improved diagnosis and treatment of immunologic infertility, as well as a more complete understanding of the mechanism behind this phenomenon, are dependent on the identification and characterization of relevant sperm antigens. METHOD OF STUDY: In this article, we review literature on methods employed to identify sperm antigens using anti-sperm polyclonal and monoclonal antibodies from infertile patients and vasectomized men. Particular focus is given to approaches using human and mouse monoclonal antibodies to define the SAGA-1 human sperm antigen. RESULTS: ASA present in sera and genital tract secretions from infertile patients and vasectomized men have been employed in a variety of methods to identify sperm antigens. In an alternate approach, a monoclonal antibody (mAb), H6-3C4, was immortalized from the lymphocytes of an infertile woman who exhibited sperm-immobilizing titers. Subsequently, the sperm-agglutinating, murine S19 mAb was shown to react with the H6-3C4 cognate antigen. The H6-3C4 S19 cognate antigen, designated Sperm Agglutination Antigen-1 (SAGA-1), was characterized as a polymorphic, highly acidic, GPI-anchored glycoprotein on the surface of human spermatozoa. Purification with the S19 mAb followed by microsequencing demonstrated that the SAGA-1 core peptide is identical to CD52, a glycoprotein on the surface of human lymphocytes. Immunoblot analysis demonstrated that these two glycoproteins differed in carbohydrate composition. Thus, sperm SAGA-1 and lymphocyte CD52 represent glycoforms, glycoproteins with the same core peptide but with different carbohydrate structures. CONCLUSIONS: Autoimmunity to the SAGA-1 and/or CD52 glycoforms may lead to infertility. Structural and immunologic differences between these glycoproteins may be important factors in the etiology of immunologic infertility and other autoimmune disorders.

PI-PLC releases a 25-40 kDa protein cluster from the hamster oolemma and affects the sperm penetration assay.

The effects of phosphatidylinositol-specific phospholipase C (PI-PLC) on human sperm-hamster oocyte interaction were investigated to determine whether PI-PLC cleavable glycosylphosphatidyinositol (GPI)-anchored proteins are involved in sperm-egg binding and fusion. Two-dimensional electrophoresis was then utilized to visualize proteins released from hamster oocytes following PI-PLC treatment. For the binding and fusion assay, either spermatozoa or eggs were treated with 1 IU/ml PI-PLC for 30 min and washed prior to gamete co-incubation. Treatment of human spermatozoa with PI-PLC significantly (P

FSP95, a testis-specific 95-kilodalton fibrous sheath antigen that undergoes tyrosine phosphorylation in capacitated human spermatozoa.

Protein tyrosine phosphorylation has been associated with both capacitation and motility of mammalian sperm. During capacitation, human spermatozoa undergo tyrosine phosphorylation of a characteristic set of proteins, only one of which has thus far been cloned and localized. We report here the sequence of a fibrous sheath protein of 95 kDa (FSP95) that undergoes tyrosine phosphorylation during capacitation of human spermatozoa and has similarity to sperm A-kinase anchor proteins (AKAPs). FSP95 is both auto- and iso-antigenic in humans as it is recognized by sera containing antisperm antibodies from infertile men and women. The 853-residue protein has a calculated molecular weight of 94.6 kDa and an isoelectric point (pI) of 6.0, and it contains multiple potential phosphorylation sites for protein kinase C and casein kinase II as well as one potential tyrosine kinase phosphorylation site at amino acid 435. The sequence has amino acid homology to mouse sperm fibrous sheath AKAP82 (pro-mAKAP82, 34% identity) and to human sperm fibrous sheath AKAP82 (pro-hAKAP82, 32% identity). The gene encoding FSP95 has 5 exons separated by 4 introns and is located on chromosome 12 at locus p13.3. Northern analysis detected a single transcript of approximately 3.0 kilobases, and Northern dot blot analysis of 50 human tissues revealed FSP95 mRNA expression only in testis. By employing sperm immobilization, indirect immunofluorescence, and immunoelectron microscopy with antisera to purified recombinant FSP95, the protein was localized to the ribs of the fibrous sheath in the principal piece of the sperm tail. FSP95 is the second fibrous sheath protein to be cloned, sequenced and localized in human spermatozoa.

N-linked glycan of a sperm CD52 glycoform associated with human infertility.

In a benchmark study, Isojima and colleagues established H6-3C4, the first successful heterohybridoma immortalized from the peripheral blood lymphocytes of an infertile woman who exhibited high sperm-immobilizing antibody titers. The present report demonstrates the identity between the glycoprotein antigens recognized by the human H6-3C4 monoclonal antibody (mAb) and the murine S19 mAb, generated in our laboratory to sperm agglutination antigen-1 (SAGA-1). Both mAb's recognize N-linked carbohydrate epitopes on the 15-25 kDa, polymorphic SAGA-1 glycoprotein that is localized to all domains of the human sperm surface. Treatment with phosphatidylinositol-specific phospholipase C demonstrated that SAGA-1 is anchored in the sperm plasmalemma via a GPI-lipid linkage. Immunoaffinity purification and microsequencing indicated that the core peptide of the SAGA-1 glycoprotein is identical to the sequence of CD52, a GPI-anchored lymphocyte differentiation marker implicated in signal transduction. Comparison of anti-SAGA-1 and anti-CD52 immunoreactivities revealed that the sperm form of CD52 exhibits N-linked glycan epitopes, including the epitope recognized by the infertility-associated H6-3C4 mAb, which are not detected on lymphocyte CD52. Thus, the two populations of the CD52 glycoprotein on lymphocytes and spermatozoa represent glycoforms, glycoprotein isoforms with the same core amino acid sequence but different carbohydrate structures. Furthermore, mAb's to the unique carbohydrate epitopes on sperm CD52 have multiple inhibitory effects on sperm function, including a cytotoxic effect on spermatozoa in the presence of complement. These results are the first to implicate unique carbohydrate moieties of a sperm CD52 glycoform as target epitopes in the anti-sperm immune response of an infertile woman. Furthermore, localization of CD52 on all domains of the sperm surface coupled with the multiple sperm-inhibitory effects of antibodies to its unique carbohydrate moieties suggest opportunities for immunocontraceptive development.

Post-obstruction rat sperm autoantigens identified by two-dimensional gel electrophoresis and western blotting.

Although antisperm autoantibody responses to obstruction of the male reproductive system have been documented, information on the nature of the cognate sperm autoantigens has been limited. In the present study, the patterns of sperm autoantigens recognized by sera from rats after obstruction of the vas deferens or epididymis were studied by high resolution two-dimensional (2-D) gel electrophoresis and western blotting. Comparisons of patterns of autoantigens stained on 2-D western blots of sera from prepubertal vasectomy, prepubertal epididymal ligation and adult vasectomy groups revealed both similarities and differences. Sera from sham-operated animals showed no detectable reaction or much lighter staining of a small number of spots. Visualization of sperm autoantigens on 2-D western blots supported the hypothesis that there is a relatively small set of sperm proteins that can be regarded as dominant post-obstruction sperm autoantigens because they are recognized by multiple post-obstruction sera. The 2-D analysis revealed previously undetected distinctions in the autoantigens recognized after adult and prepubertal vasectomy, as well as variations with the site of obstruction. These differences in the response may be due in part to changes in antigens of spermatozoa in different parts of the tract and at different ages, as well as variations in exposure of sperm cell proteins to the immune system resulting from the sites of spermatic granulomas. Preparative 2-D gels and western blotting with post-obstruction sera are now being used to identify specific sperm autoantigens by microsequencing of selected proteins.

Human sperm proteome: immunodominant sperm surface antigens identified with sera from infertile men and women.

The objective of this study was to identify those immunodominant sperm antigens recognized by antisperm antibodies (ASA) in the serum samples of infertile men and women. High-resolution two-dimensional gel electrophoresis was employed to separate human sperm proteins using isoelectric focusing or nonequilibrium pH gradient electrophoresis, followed by PAGE. Serum samples from 15 infertile male subjects and 6 infertile female subjects that contained ASA as assayed by the immunobead binding test (IBT) were analyzed by Western blotting followed by enhanced chemiluminescence (ECL). Serum samples from 10 fertile subjects (5 males and 5 females) that were ASA negative by IBT were used as controls. The ECL blots were analyzed by computer scanning to compare the immunoreactivity between serum samples from fertile and infertile subjects and to identify the antigens unique to the sera of the infertile subjects; 98 sperm auto- and iso-antigenic protein spots were recognized by sera from infertile males and females but not from fertile subjects. Based on vectorial labeling with 125I at the sperm surface, a subset of 6 auto- and iso-antigens was identified as possibly relevant to antibody-mediated infertility.

Treatment of mouse oocytes with PI-PLC releases 70-kDa (pI 5) and 35- to 45-kDa (pI 5.5) protein clusters from the egg surface and inhibits sperm-oolemma binding and fusion.

The effect of phosphatidyinositol-specific phospholipase C (PI-PLC) on mouse sperm-egg interaction was investigated in this study to determine if glycosyl-phosphatidylinositol (GPI)-anchored proteins are involved in mammalian fertilization. When both sperm and zona-intact oocytes were pretreated with a highly purified preparation of PI-PLC and coincubated, there was no significant effect on sperm-zona pellucida binding; however, fertilization was reduced from 59.6% (control group) to 2.8% (treatment group). A similar reduction in fertilization rates was found when zona-intact oocytes were treated with PI-PLC and washed prior to incubation with untreated sperm. The effect of PI-PLC on sperm binding and fusion with zona-free oocytes was then investigated. Treatment of sperm with PI-PLC had no significant effect on sperm-egg binding or fusion. However, treatment of eggs with PI-PLC significantly reduced sperm-egg binding and fusion from 6.2 bound and 2.1 fused sperm per egg in the control group to 2.1 bound and 0.02 fused sperm per egg in the treatment group. This decrease in sperm-egg binding and fusion depended on the dose of PI-PLC employed, with a maximal inhibitory effect on binding and fusion at 5 and 1 U/ml, respectively. PI-PLC-treated oocytes could be artificially activated by calcium ionophore, demonstrating that the oocytes were functionally viable following treatment. Furthermore, treatment of oocytes with PI-PLC did not reduce the immunoreactivity of the non-GPI-anchored egg surface integrin, alpha6beta1. Taken together, these observations support the hypothesis that PI-PLC affects fertilization by specifically releasing GPI-anchored proteins from the oolemma. In order to identify the oolemmal GPI-anchored proteins involved in fertilization, egg surface proteins were labeled with sulfo-NHS biotin, treated with PI-PLC, and analyzed by two-dimensional gel electrophoresis followed by avidin blotting. A prominent high-molecular-weight protein cluster (approximately 70 kDa, pI 5) and a lower molecular weight (approximately 35-45 kDa, pI 5.5) protein cluster were released from the oolemmal surface as a result of PI-PLC treatment. It is likely that these GPI-anchored egg surface proteins are required for sperm-egg binding and fusion.

Biochemical characterization of sperm agglutination antigen-1, a human sperm surface antigen implicated in gamete interactions.

The anti-sperm monoclonal antibody (mAb) S19 was previously demonstrated to agglutinate human spermatozoa, inhibit sperm penetration of cervical mucus, and inhibit sperm-zona pellucida binding. These results implicated the cognate S19 antigen, designated sperm agglutination antigen-1 (SAGA-1), in gamete interactions and identified SAGA-1 as an attractive candidate for immunocontraceptive development. In the present study, evaluation of sperm agglutination with video microscopy showed that the S19 mAb rapidly and completely agglutinated human spermatozoa in a "tangled" pattern of agglutination. One- and two-dimensional immunoblot analyses identified SAGA-1 as a highly acidic, polymorphic sperm protein with an apparent molecular mass of 15-25 kDa and an isoelectric point of 2.5-3.0. Periodate treatment abolished this immunoreactivity, demonstrating that the S19 mAb reacted with a carbohydrate epitope and indicating that SAGA-1 is a glycoprotein. Absence of S19 immunoreactivity in postvasectomy seminal fluid implicated the testis, epididymis, and/or proximal vas deferens in the expression of SAGA-1. In solubility and phase partitioning assays, SAGA-1 was extracted from spermatozoa in Triton X-114 and exhibited the hydrophobic characteristics of integral and glycosylphosphatidyl inositol-anchored membrane proteins. These results identify SAGA-1 as a hydrophobic, highly acidic sperm glycoprotein that is localized on the entire sperm surface and has potential significance as a target for antibodies that inhibit sperm function and gamete interactions.

Two-dimensional gel electrophoretic analysis of vectorially labeled surface proteins of human spermatozoa.

The objective of this study was to identify the repertoire of proteins exposed on the surface of ejaculated human spermatozoa. High-resolution two-dimensional gel systems for separation of human sperm and seminal plasma proteins were developed using both isoelectric focusing (IEF) and nonequilibrium pH gradient electrophoresis (NEPHGE) followed by polyacrylamide gel electrophoresis (IEF/PAGE, NEPHGE/PAGE). Proteins were visualized by silver staining of gels and by electroblotting followed by gold staining. The protein patterns were analyzed by computer after laser or camera scanning. One thousand three hundred ninety-seven sperm proteins with a molecular mass between 5 and 160 kDa and isoelectric points (pI) from 4 to 11 were catalogued from silver-stained gels loaded with approximately 0.25 mg of NP-40/urea extracts of sperm harvested by Percoll density gradient centrifugation, and 1191 proteins were resolved following extraction with SDS/3-[3-cholamidopropyl) dimethylammonio]-1-propane-sulfonate/urea. Analysis of seminal plasma proteins obtained from vasectomized patients revealed over 300 silver-stained proteins, which aided the identification of sperm-coating proteins acquired from secretions of the accessory sex organs. Sperm surface proteins accessible to vectorial labeling with 125I or N-hydroxysuccinimide biotin were identified; 181 protein spots were radiolabeled with 125I, while 228 protein spots were biotinylated, including several groups of protein isoforms. Cytoskeletal and intra-acrosomal control proteins were not iodinated or biotinylated, thus verifying the surface specificity of both labeling methods. Ninety-eight sperm surface proteins were labeled by both iodine and biotin, and 22 sperm surface proteins, representing five groups of protein isoforms, were shown to contain phosphotyrosine. A composite computer image showing the position of the dually vectorially labeled sperm surface proteins was constructed, together with a table of the proteins' molecular weight, pI, and relative concentration. In addition, novel isoforms of actin, beta-tubulin, PH-20, and several phosphotyrosine-containing proteins were identified in human sperm.

A novel negative imaging technique for accurate localization of stainable proteins on complex two-dimensional autoradiograms.

This paper describes a fast, simple, and accurate method for localization of protein antigens in complex two-dimensional (2-D) autoradiograms where the precise position and identity of the protein is required. The method involves the creation of negative images on an autoradiogram through arrangement of image-intensifying screens. By placing a chromogenically stained 2-D gel or blot between the intensifying screen and the film, photons emitted from the intensifying screen are obstructed by the stained spots, thus creating a negative image on the film. The technique can be used in autoradiograms of proteins labeled with either 32P or (125)I radioisotopes. The technique permits analysis of radiolabeled, gold-stained and immunoreacted proteins on a single film and offers versatility by combining analysis of total protein patterns with specific identification of radiolabeled and/or immunoreacted protein spots. The technique is especially useful when selecting a subset of specifically radiolabeled proteins from the total protein pattern in 2-D gels or membranes for microsequencing.

Immunological response in the primate oviduct to a defined recombinant sperm immunogen.

Assessment of immune responses in the oviduct is of importance in understanding reproductive tract responses to infections, vaccination against reproductive tract pathogens, or contraceptive immunogens. This review discusses a technique that permits repeated sampling of oviductal fluid from the same monkey at intervals spanning up to several years, and the analysis of antigen-specific immunoglobulins in the fluid. This technique is important to immunocontraceptive development because previous studies in primates have lacked information on oviductal immune responses and contraceptive efficacy may not correlate well with serum antibody titers. Thus, a reliable method of sampling oviductal fluid before and after immunization with a defined antigen is required to determine the quantity and type of local immune responses necessary to achieve contraceptive effects. Implantation of access ports proved useful for repeatedly aspirating oviductal fluid in vivo from cynomolgus monkeys that was free from artifactual contaminants and with no observable changes in the behavior or health of the animals. Subsequent assays of relative and absolute concentrations of antibodies in oviductal fluid and serum demonstrated the presence of IgA and IgG specific for the recombinant sperm immunogen SP-10 in fluid collected from the periovulatory oviduct of primates after intramuscular inoculations. The antibodies evoked by the recombinant sperm vaccinogen recognized the endogenous antigen target on both human and macaque sperm, lending support for the possibility of developing a contraceptive immunogen that prevents fertilization.

Complementary deoxyribonucleic acid cloning and characterization of mSP-10: the mouse homologue of human acrosomal protein SP-10.

Complementary DNA encoding the putative mouse homologue for human acrosomal protein SP-10, a candidate contraceptive vaccinogen, was cloned and sequenced. The entire open reading frame (amino acids 18 to 261) of the mouse SP-10 (mSP-10), with the exception of the signal peptide (amino acids 1 to 17), was placed under the influence of inducible T7 RNA polymerase/promoter system to overproduce recombinant protein (re-mSP-10) in Escherichia coli. A six-histidine tag, which was coexpressed at the carboxyl terminus of re-mSP-10, provided the means for purification of re-mSP-10 by immobilized metal chelation affinity chromatography technique. The level of purity of re-mSP-10 thus obtained was determined by 2-dimensional gel electrophoresis to be 98%. Immunoblotting with monoclonal and polyclonal antibodies previously generated against human or baboon SP-10 showed that mSP-10 shared significant antigenic similarity with its primate counterparts. The position of mSP-10 in the mouse genome was next mapped through segregation analysis of an interspecific backcross panel of 96 animals. Acrv1 (assigned gene symbol for mSP-10) was localized in the proximal portion of mouse chromosome 9 in a region that exhibits synteny with human 11q23, the region to which ACRV1 (gene symbol for human SP-10) was previously mapped. These characterizations by combined immunological and gene mapping techniques established the cloned mSP-10 to be the mouse homologue of SP-10.

Electrophoretic map of acidic and neutral human spermatozoal proteins.

A high resolution two dimensional electrophoretic technique (2-D), isoelectric focusing followed by polyacrylamide gel electrophoresis, for separation of neutral and acidic human spermatozoal proteins was established. Silver stained 2-D gels revealed over 260 proteins with Mr 20-200 kDa and pI between 4.5 and 7.8. Membrane proteins were radio-iodinated in their hydrophobic cores with the hydrophobic photoactivatable reagent 3 (trifluoromethyl)-3-(m-[125I]iodophenyl) diazirine (TID). Externally exposed carbohydrate side chains were radiolabelled by NaB(3H)4 reduction. 2-D lectin blotting was performed with horseradish peroxidase conjugated Concanavalin A (Con A), biotinylated Vicia faba agglutinin (VFA) and Solanum tuberosum agglutinin (STA). A map of 258 human spermatozoal proteins is presented and 48 TID-labelled proteins have been biochemically characterized.

The humoral autoimmune response to vasectomy described by immunoblotting from two-dimensional gels and demonstration of a human spermatozoal antigen immunochemically crossreactive with the D2 adhesion molecule.

The specificity of human serum antispermatozoal antibodies was analysed by immunoblotting after two-dimensional electrophoretic separation (IEF/PAGE) of human spermatozoal proteins. Spermatozoal proteins with Mr 20-200 kDa and pI between 4.5 and 7.8 were analysed for antigenicity. Fifteen sera (four female and 11 male) were analysed for antisperm IgG antibodies. Individual IgG binding patterns were observed. The antisperm antibody response to ligation of the vas deferens was described by immunoblotting analysis of sera taken pre- and post-operatively at regular intervals from three men undergoing vasectomy. The high resolution of spermatozoal antigens allowed a specific description of the humoral response to vasectomy. Both appearance and disappearance of spots were observed in the postoperative period, indicating induction of new antibody producing clones and binding of former free antibodies in circulating immunocomplexes. In one patient five glycosylated proteins induced an IgM response 2 weeks after vasectomy. Four of these autoantigens with Mr of 122 kDa, 119 kDa, 104 kDa and 77 kDa and pI of 5.9, 6.1, 7.7 and 6.0, respectively, have previously been shown to be intrinsic membrane proteins (Naaby-Hansen, (1990) J., Reprod. Immunol. 17). An observed immunochemical crossreactivity between the interneuronal adhesion molecule, D2-protein and an antigen extracted from human sperm and teratomas is discussed.