Rajesh K. Naz

Antisperm antibodies : origin, regulation, and sperm reactivity in human infertility

OBJECTIVEnTo follow-up and expand discussion on the action mechanisms of antisperm antibodies in human infertility, the etiology and control of antisperm antibody induction, sperm antigens involved in immunoinfertility, and strategies for therapy.nnnDESIGNnA review of the recent literature with an emphasis on female immunoinfertility.nnnRESULTSnThe role of antisperm antibodies in clinical infertility continues to be defined. Through assisted reproductive technologies, antisperm antibodies were shown to exert detrimental effects on different prefertilization and possibly postfertilization events. The female reproductive tract is part of the common mucosal immune system and is able to mount effective immune responses against infectious agents, foreign antigens, and, occasionally, sperm cells. Sperm membranes and constituents contain numerous antigenic components foreign to the human body, and yet antisperm antibodies become problematic in few women exposed to semen. Semen and sperm cells contain immunosuppressive factors capable of inhibiting different immune cells. Fertile women apparently produce antisperm antibodies but also possess neutralizing serum anti-idiotypic antibodies that are lacking in virgin and immunoinfertile women.nnnCONCLUSIONSnAntisperm antibodies can affect adversely human fertility but normally may be controlled by anti-idiotypic antibodies, which along with immunosuppressor factors in semen prevent their induction to a significant degree. This balance between detrimental and beneficial immune response to sperm may be shifted toward an antisperm antibody response by stimulatory factors such as infection. Therapies may be devised to stimulate the anti-idiotypic antibody system, to induce immune tolerance to sperm antigens, and to use antigens to adsorb antisperm antibodies from spermatozoa.

INFERTILITY DUE TO ANTISPERM ANTIBODIES

Immunoinfertility is an important problem, involving a significant number of infertile couples. Although the presence of antibodies on sperm has better prognostic value than those in serum or seminal plasma, it may not be the sole authentic evidence of immunoinfertility. Infertility from antisperm antibodies is likely only when they bind to a relevant sperm antigen involved in a specific fertility function. The variance in functional deficits seen in immunologic infertility is most likely related to antibodies directed at different sperm antigens or different class, subclass, or isotypes. Antibodies to FA-1 seem to be of significant importance in human immunoinfertility. In approaching couples with infertility, a high index of suspicion for antibodies is necessary to avoid misdiagnosis. In the optimal situation, all semen analyses should be screened for sperm-bound antibodies, but if this is impractical, testing should be performed on high-risk individuals (Table I). In couples in which the man has sperm-bound antibodies, and in whom there is no identifiable female factor, treatment should be instituted. Most treatments for immunoinfertility have been disappointing because of poor results, adverse effects, or high cost. Corticosteroid therapy has shown some promise in published reports (mostly poorly designed studies), but increase in pregnancy rate is modest and adverse effects may be significant. In our opinion, informed consent should be documented prior to institution of corticosteroid therapy, and subjects should be closely monitored. Advanced reproductive technologies offer a higher safety profile, and, with increasing technology, higher pregnancy rates. We recommend progressing from low-tech procedures, such as IUI and reserving the higher level procedures, such as IVF and ICSI, for those couples in whom pregnancy does not occur. The highest level reproductive technologies give the best current prospects for pregnancy in patients with this difficult problem but also are invasive and costly. It is hoped that further work in the laboratory will give rise to newer, safer, and less expensive effective treatments in the very near future.

Immunoglobulin (Ig) G, IgA, and IgA subclass antibodies against fertilization antigen-1 in cervical secretions and sera of women of infertile couples

OBJECTIVESnTo assess the occurrence of immunoglobulin (Ig) G, IgA, and IgA subclass antibodies against human sperm fertilization antigen-1 (FA-1) in cervical mucus (CM) and serum of women of infertile couples.nnnDESIGNnEnzyme-linked immunosorbent assay methodology was used to detect anti-FA-1 antibodies. Antisperm antibodies were detected by agglutinating, immobilizing, and indirect immunobead (IB) methods. Control samples for the ELISA were from 10 women negative in the antisperm antibody assays.nnnPARTICIPANTSnSamples were from women of 32 infertile couples undergoing antisperm antibody analysis.nnnRESULTSnOne of 10 control CM samples was slightly positive for IgG anti-FA-1 and none for IgA. Of the 22 CM samples from antisperm antibody-positive women, 9 were positive for IgG antibodies, 9 for IgA, 7 for IgA1, and 6 for IgA2. Cervical mucus samples from eight women were positive for both IgA and IgG antibodies. Assay of 19 serum samples, including 8 controls, by ELISA, indicated 9 of 11 from antisperm antibody-positive women and none from controls were positive for IgA and IgG (7 of 9 identical women). In addition, of the nine IgA-positive sera, seven were of the A1 subclass and five were of the A2 subclass. Positive IB assays occurred more frequently in CM and serum samples positive for anti-FA-1 antibodies than in negative samples.nnnCONCLUSIONnThe results suggest that cervical secretions and sera of antisperm antibody-positive women contain IgA and IgG antibodies against sperm antigen FA-1 that may be involved in antifertility effects.

Reduction of fertility in female rabbits and mice actively immunized with a germ cell antigen (GA-1) from the rabbit

Female rabbits and mice were actively immunized against germ cell antigen (GA-1) of 63 kDa molecular mass isolated from rabbit sperm and testis. There was a significant (P less than 0.05) reduction of fertility in rabbits actively immunized with GA-1 as compared to controls, as seen by the percentage of 9-day implants/corpora lutea ratio (GA-1, 36.3%; controls, 85.7%). In mice, there was again a significant (P less than 0.01) reduction in fertility as seen by mean 7-9 day implants +/- S.D. per mated mouse actively immunized with GA-1 whether through the intraperitoneal route (GA-1, 1.2 +/- 1.6; controls, 8.0 +/- 3.4) or through the subcutaneous/intramuscular route (GA-1, 3.8 +/- 3.4; controls, 10.1 +/- 3.9). The antisera from these actively immunized animals were negative for sperm agglutinating and immobilizing antibodies. In the Western blot enzyme-immunobinding procedure, the antisera showed specific binding to a single protein of 63 kDa. The incidence of fertilization of eggs recovered from rabbits inseminated with anti-GA-1 antibodies-treated sperm was not significantly different from control rabbits. The percentage of fertilized eggs obtained from rabbits inseminated with anti-GA-1 antibodies-treated sperm that reached the blastocyst stage upon in vitro incubation, however, was significantly less than that for embryos obtained from rabbits inseminated with control serum-treated sperm. Incubation of normal fertilized eggs in vitro with the antibodies did not affect development. Neither antiserum nor immune uterine fluid reacted with 4-day blastocysts in the indirect immunofluorescence technique. It is concluded that active immunization with GA-1 results in post-fertilization reduction of fertility in rabbits and mice by inhibiting early embryonic development.

The fertilization antigen-1 does not have proteolytic/acrosin activity, but its monoclonal antibody inhibits sperm capacitation and acrosome reaction**Supported in part by grant HD 24425 from the National Institutes of Health (to R.K.N.), Bethesda, Maryland.

OBJECTIVEnTo determine if human sperm surface fertilization antigen exhibits proteolytic or acrosin activity and to investigate the mechanism(s) whereby monoclonal antibody (mAb) to fertilization antigen inhibits human sperm penetration of zona-free hamster ova.nnnDESIGNnProteolytic and acrosin activities of human fertilization antigen were determined. Acrosomal status, acrosin activity, and motion characteristics were evaluated after incubation of human sperm with immunoaffinity-purified mAb to fertilization antigen.nnnSETTINGnAcademic research environment.nnnPARTICIPANTSnFertile donors used as controls for infertile patients for fertility evaluation.nnnINTERVENTIONSnHuman spermatozoa were treated with mAb to fertilization antigen and induced to undergo acrosome reaction using calcium ionophore A23187.nnnMAIN OUTCOME MEASURESnProteolytic and acrosin activities of fertilization antigen. Sperm penetration assay, acrosomal status, and motion parameters.nnnRESULTSnFertilization antigen does not exhibit proteolytic or acrosin activity; however, its mAb completely blocks human sperm penetration of zona-free hamster ova. The mAb to fertilization antigen inhibits ionophore-induced acrosome reaction and blocks development of the hyperactivated state of human sperm cells.nnnCONCLUSIONSnMonoclonal antibody to fertilization antigen blocks fertilization by inhibiting capacitation and acrosome reaction.