Immunological infertility Immunological infertility refers to infertility due to immunological factors. Immunologic infertility accounts for 10-30% of all infertility cases, including anti-sperm antibodies, closed antibodies, anti-ovarian antibodies and other types of immunologic infertility. The most common clinical condition is immune infertility caused by anti-sperm antibodies. Semen consists of sperm and seminal plasma, of which more than 30 types of antigens have been identified. Under normal conditions, sperm and seminal plasma are isolated from the autoimmune system by the blood-testis barrier and do not produce antibodies. However, under pathological conditions, seminal fluid can act as an antigen, causing the body itself to produce antibodies and an antigen-antibody reaction. Anti-sperm antibodies (AsAb) are a complex pathological product that can affect both men and women, and their exact cause is not fully understood. The sperm and seminal plasma of men are specific antigens for women, and when they come into contact with the blood, both men and women can have an immune response, producing antibodies that prevent the sperm from binding to the egg, resulting in infertility. The autoimmune reaction in men can be caused by the following reasons: ① Injury, infection or obstruction of testes, epididymis or secondary gonads, the blood-testis barrier is damaged and semen as an antigen is exposed to the autoimmune system; ② Low level of male immunosuppressive substances in semen reduces the protection against sperm antigens; ③ Mutation of immunologically active cells to the extent that they react to autoantigens. The result of autoimmune reaction in men is, on the one hand, cellular immunity leading to testicular inflammation, causing azoospermia or oligospermia; on the other hand, the production of sperm agglutination and sperm braking antibodies, which are distributed in the plasma and seminal plasma, reducing sperm survival and motility, largely reducing the quality of semen, inhibiting sperm attachment and penetration of the zona pellucida of the egg, and preventing sperm-egg union. In addition, anti-sperm antibodies can act on the embryo to cause its resorption or abortion, and interfere with the fertilization process in many ways to cause infertility. When anti-sperm antibodies are present in the female cervical mucus, they prevent the sperm from passing through the mucus by agglutinating them, damaging the sperm, enhancing the function of macrophages in phagocytosis of sperm, and preventing the sperm from entering the fallopian tubes, leading to infertility. This is caused by an alloimmune reaction caused by semen entering the woman’s body through the damaged reproductive organs during sexual intercourse.