| Abstract: | Sperm surface antigens may induce an immune response in mammals. In humans, the presence of antisperm antibodies has been noted in the blood, seminal plasma, cervical mucus, and follicular liquid. Because they provoke immobilization and/or agglutination of sperm and a diminution of the rate of fertilization in vitro, these antibodies are believed to be a factor in some unexplained infertility, as for example after surgical reversal of vasectomy. These observations have led to research oriented toward development of a nonhormonal contraceptive method based on the immunological capacities of some sperm antigens. Possible secondary effects and the modes of action remain poorly understood. Antisperm immunoglobulins in the male should be induced by epitopes that are specific to sperm excluding the proteins of the sperm membrane, so that they will be without effect on functions other than fertilization. The epitopes should be located on the sperm surface and should be of post-testicular origin because of the risk of orchitis posed by testicular antigens. The antisperm immunoglobulins should also be present in the area surrounding he sperm in the male genital tract because of the limited permeability of the tract to immunoglobulins and other large molecules. The antisperm immunoglobulins should not be inhibited in the male by the immunosuppressive activities of the seminal plasma or in the female by capacitation. In vivo and in vitro observations indicate that various functions may be altered by antisperm antibodies. The antibodies may immobilize the sperm, block interaction with the oocyte at the level of the zona pellucida, block adherence to the vitelline membrane, or cause anomalies in embryonic development. In rats, isoimmunization against epididymal cofactor of the sperm zona pellucida receptor results in reduced sperm mobility and reduced fertility. The same study was conducted in 12 rams selected for homogeneity of sperm characteristics. Isoimmunization of rams induced transient asthenospermia. Most sperm antigens involved in fertilization are poorly understood. Observations in the ram suggest that embryonic mortality following isoimmunization should be studied. |
