Anti-tubulin beta 4A (TBB4A) antibody immobilized sperm in a complement-dependent manner in humans.

Sperm-immobilizing antibodies (SI-Abs) are detected in the sera of 3 % of infertile women. SI-Abs are occasionally produced as allogeneic antibodies against sperm, causing immune infertility. SI-Abs inhibit the passage of sperm through the female reproductive tract. Research on anti-sperm antibodies (ASA) remains of great importance for population control. We aimed to identify the antigens recognized by SI-Abs and elucidate the pathogenesis of immune infertility. Twelve sperm-immobilization test (SIT)-positive and fourteen SIT-negative sera were analyzed by two-dimensional electrophoresis and western blotting. Antigenic materials were extracted from well-motile sperm prepared using 0.1 % sodium dodecyl sulfate. In total, 22 different spots were detected in the 12 positive sera. Among these, three positive serum samples showed two positive signals with similar migration patterns. The significant positive spots were Mr: 49 K, pI: 5.1 and Mr: 51 K, pI: 5.6. All these positive spots were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS); tubulin beta-4A (TBB4A) was identified from the spot Mr: 49 K, pI: 5.1. TBB4A is a major component of tubulin and constitutes the axoneme in the sperm tail and the centrosome in the sperm neck; it is generally located inside the cell. An authentic antibody against TBB4A showed a positive reaction in the sperm neck and tail regions in an immunofluorescence study. This antibody also inhibited sperm motility in a complement-dependent manner. Sperm membrane permeability reportedly changes during swimming and capacitation. We identified TBB4A as an antigenic molecule recognized by SI-Abs, which may be relevant to immunological contraception in the future.

Advancements in the detection and implications of sperm-immobilizing antibodies in female infertility.

This review highlights over five decades of research on sperm-immobilizing antibodies (SI-Abs), which are crucial for understanding female infertility due to their effects on sperm motility and fertilization. Since the 1960s, Isojima et al. have made significant strides, notably with the Sperm Immobilization Test (SIT), which revolutionized the quantification of SI-Abs and their roles in infertility. Drawing from a comprehensive PubMed search on "the sperm immobilization test" and "sperm immobilizing antibody," our review underscores the critical insights gained into SI-Abs' impact on reproductive functions. SI-Abs result from the body's response to sperm antigens, potentially leading to infertility by affecting post-intercourse sperm function. However, the presence of anti-sperm antibodies does not guarantee infertility, indicating a complex relationship between these antibodies and reproductive outcomes. Isojima et al.'s pioneering studies paved the way for SIT and sperm immobilization titer (SI50), tools that have clarified the link between SI-Abs and infertility, focusing on disrupted sperm mobility and fertilization as key infertility mechanisms. Clinically, interventions such as in-vitro fertilization (IVF), which bypasses or eliminates SI-Abs, have improved pregnancy rates, whereas Freund's complete adjuvant therapy has deepened our understanding of infertility mechanisms. The SI50 value is crucial for predicting fertility treatment success and guiding therapeutic decisions based on antibody levels. In summary, the evolution of SI-Abs research has provided new hope for addressing infertility, significantly enriching the field of reproductive immunology, and highlighting the need for ongoing investigation.

Characterization of a spontaneously occurring self-reactive antibody against sperm in mice.

We previously established a spontaneously occurring monoclonal antibody, namely Ts3, that was reactive to sperm from an aged male mouse. The present study investigated the characteristic properties and reproductive functions of Ts3. Immunofluorescent staining revealed that Ts3 reacted to epididymal sperm, and the corresponding antigen was located in the midpiece and principal piece. Immunohistochemistry revealed positive reactions in the germ cells and Sertoli cells in the testis, the epithelial cells in the epididymis and vas deferens. Through western blotting with two-dimensional electrophoresis, we demonstrated that Ts3 reacted with four spots, which were around Mr ∼25,000-60,000 and pI 5-6. MALDI-TOF/TOF mass spectrometry identified outer dense fiber 2 (ODF2) as a candidate for Ts3. ODF2 is a cytoskeletal structural component located in the midpiece and principal piece of the flagella of mammalian sperm. This was validated with the result of immunofluorescent staining, suggesting that ODF2 was the main target antigen for Ts3. Sperm immobilization test showed that Ts3 possessed sperm immobilizing activity. Furthermore, Ts3 impaired early embryo development but not in vitro fertilization. These results suggest that ODF2 plays an important role in both sperm function and early embryonic development.

Sex difference in anti-sperm antibodies.

Background: Some diseases have sex differences. There have been no reports on the relationship between anti-sperm antibodies (ASA) and sex differences. Methods: ASA are detected by sperm-immobilization test using patients' sera in women. In men, the ASA testing is generally performed by direct-immunobead test. Main findings: Sperm-immobilizing antibodies in women inhibit sperm migration in their genital tract and exert inhibitory effects on fertilization. ASA bound to sperm surface in men also show inhibitory effect on sperm passage through cervical mucus. The fertilization rate of IVF significantly decreased when sperm were coated with higher numbers of ASA. For women with the antibodies, it is important to assess individual patients' SI50 titers. In patients with continuously high SI50 titers, pregnancy can be obtained only by IVF. For men with abnormal fertilizing ability by ASA, it is necessary to select intracytoplasmic sperm injection. Production of sperm-immobilizing antibodies is likely to occur in women with particular HLA after exposure to sperm. The risk factors for ASA production in men are still controversial. Conclusion: Attention to sex differences in specimens, test methods and the diagnosis of ASA should be paid. For patients with ASA, treatment strategies have been established by considering sex difference for each.

Toward a Practical Impedimetric Biosensor: A Micro-Gap Parallel Plate Electrode Structure That Suppresses Unexpected Device-to-Device Variations.

We propose a rational electrode design concept for affinity biosensors based on electrochemical impedance spectroscopy to substantially suppress unexpected device-to-device variations. On the basis that the uniformity of the current distribution affects the variation, a novel micro-gap parallel plate electrode (PPE) was developed, where two planar electrodes with edges covered with a SiO2 layer were placed face to face. The structure provides a uniform current distribution over the planar electrode surface and maximizes the contribution of the planar electrode surface to sensing. For a comparative study, we also fabricated a micro-structured interdigitated electrode (IDE) that has been widely adopted for high-sensitivity measurement, although its current is highly concentrated on the electrode edge corner. Protein G (PrG) molecules were immobilized on both electrodes to prepare an immunoglobulin G (IgG) biosensor on which the specific binding of PrG-IgG can occur. We demonstrated that the IgG sensor with the PPE has small device-to-device variations, in strong contrast to the sensor with the IDE having large device-to-device variations. The results indicate that the current distribution on the electrode surface is important to fabricating electrochemical impedance spectroscopy biosensors with small device-to-device variations. Furthermore, it was found that the PPE allows ultrasensitive detection, that is, the sensor exhibited a linear range from 1 × 10-13 to 1 × 10-7 mol/L with a detection limit of 1 × 10-14 mol/L, which is a record sensitivity at low concentrations for EIS-based IgG sensors.

Impact of Lateral SnO2 Nanofilm Channel Geometry on a 1024 Crossbar Chemical Sensor Array.

We propose a rational strategy to fabricate thermally robust, highly integrated molecular and gas sensors utilizing a lateral SnO2 nanofilm channel geometry on a 1024 crossbar sensor array. The proposed lateral channel geometry substantially suppresses the detrimental effects of parasitic interconnect wire resistances compared with those of a conventional vertical sandwich-type crossbar array because of its excellent resistance controllability. A conductive oxide top-contact electrode on the lateral SnO2 nanofilm channel enhances the thermal stability at temperatures of up to 500 °C in ambient air. Integrating this lateral SnO2 nanofilm geometry with analog circuits enables the operation of a 1024 crossbar sensor array without selector devices to avoid sneak currents. The developed 1024 crossbar sensor array system detects the local spatial distribution of the molecular gas concentration. The spatial data of molecular concentrations include molecule-specific data to distinguish various volatile molecules based on their vapor pressures. Thus, this integrated crossbar sensor array system using lateral nanofilm geometry offers a platform for robust, reliable, highly integrated molecular and gas sensors.