Sperm immobilization test and quantitative sperm immobilization test using frozen-thawed sperm preparation applied with computer-aided sperm analysis

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.