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Clinical associations and mechanisms of action of antisperm antibodies
FERTILITY AND STERILITY威 VOL. 83, NO. 3, SEPTEMBER 2004 Copyright ©2004 American Society for Reproductive Medicine Published by Elsevier Inc. Printed on acid-free paper in U.S.A.
MODERN TRENDS Edward E. Wallach, M.D. Associate Editor
Clinical associations and mechanisms of action of antisperm antibodies Will W.-C. Chiu, M.D., and Lawrence W. Chamley, Ph.D. Department of Obstetrics and Gynecology, University of Auckland, Auckland, New Zealand
Objective: To review and critique the current English literature describing the effects of antisperm antibodies (ASA) on mammalian fertility. Design: A comprehensive English language literature was searched using Medline and by hand-searching. Emphasis was placed on clinically relevant articles. Result(s): Results from the studies were extrapolated and the effects of ASA on fertility described. Conclusion(s): Antisperm antibodies may interfere with fertility. Not all ASA cause infertility. Current tests cannot differentiate the infertility-related ASA from those that do not interfere with infertility, because the antigenic specificities of these ASA are not known. The antigens which the infertility-related ASA must be characterized to allow an accurate detection and proper treatment for couples with ASA. (Fertil Steril威 2004; 83:529 –35. ©2004 by American Society for Reproductive Medicine.) Key Words: Assisted reproductive technology, fertilization, gamete biology, immunology, sperm
Infertility, the inability to conceive within 1 year of unprotected intercourse, is estimated to affect up to one in six couples of reproductive age and poses a significant health problem (1). Antisperm antibodies (ASA) are found in up to 9%–12.8% of infertile couples (2, 3). However, these antibodies are present also in approximately 1%–2.5% of fertile men (4, 5) and in 4% of fertile women (6). The presence of ASA in the fertile population indicates that not all ASA cause sterility.
Received June 30, 2003; revised and accepted September 29, 2003. Reprint requests: Larry Chamley, Ph.D., Department of Obstetrics and Gynecology, University of Auckland, Auckland 3, New Zealand (FAX: 64-96309858; E-mail: [email protected]). 0015-0282/04/$30.00 doi:10.1016/j.fertnstert.2003. 09.084
The confusion over the role of ASA in infertility, to some extent, reflects the inadequacies of the current diagnostic techniques. The methods of ASA detection can be categorized into the following: direct tests to detect the presence of ASA on sperm, such as the mixed agglutination assay and immunobead test; agglutination tests using donor sperm such as gelatin agglutination test, and tray agglutination test (7). These tests only detect the gross binding of antibodies to various locations on sperm and do not examine the antigenic specificities of the ASA. Moreover, each type of ASA, from both the man and woman, may be targeted against different antigens involved in various steps of human fertilization, such as acrosome reaction, capacitation, migration in the fallopian tube, and motility. Therefore,
each type of ASA may be interfering directly or indirectly with the different steps leading to fertilization. This review examines and critiques the current understanding of how ASA affect human fertility in a clinical and laboratory setting.
ASA AND FERTILIZATION A large body of retrospective and prospective analysis of data from programs performing IVF has provided a great amount of evidence regarding the effects of ASA in serum, semen, and follicular fluid (FF) as a possible cause of infertility (Table 1). These studies generally indicate that couples with ASA have lower pregnancy rates (PR) than couples without ASA. Of the 20 trials examining the effect of ASA on fertilization, 14 showed a decrease in the fertilization rate, 4 showed no effect, and 2 showed an equivocal effect (Table 1). One such study described infertile couples treated by IVF, in which the men had sperm ASA (8). The presence of ASA reduced the fertilization rate from 45.8% to 34.2% per cycle (8). Vazquez-Levin et al. (9) also found a reduced clinical PR when the male partner has sperm ASA compared with men who do not have ASA (11% vs. 44%). Tian et al. (10) 529
TABLE 1 Summary of IVF trials of the effects of antisperm antibodies on fertilization. ASA and method of detection (source of ASA)
Method of fertilization
End points/outcomes (ASA isotype/region of binding on sperm)
i-IBT (semen) i-IBT (FF)
IVF-ET IVF-ET
i-IBT
IVF-ET
IBT MAR
IVF-ET IVF-ET GIFT
IBT (sperm, female serum)
IVF-ET
IBT TAT (female serum) i-IBT (female serum as culture media)
IVF-ET
FR 2 (IgG ⫹ IgA) FR 2 (female serum-head; FF-head) CR 2 FR 2 (IgG ⫹ IgA) FR 3 (IgG or IgA) FR 2 (IgG ⫹ IgA) FR 2 PR 2 CR 3 EQ 2 FR 2 (sperm IgG) PR 2 (IgA-female serum) EQ 2 FR 2
32
IVF-ET
FR 2
13
IVF-ET
PR 2 EQ 2 FR 2
33
MAR IBT (IgG or IgA) TAT MAR TAT IBT i-IBT (female serum) IBT IBT IBT MAR FCM MAR IBT i-IBT (seminal plasma) MAR
IBT
IVF-ET IVF-ET IVF-ET GIFT IVF-ET IVF-ET ICSI ICSI IVF-ET IVF-ET
ICSI
FR 2 (MAR⬎90%) FR 3 (TAT) FR 3 PR 3 FR 2 PR 2 FR, CR, PR 3 FR 2 (IgA⬎68%, head) FR, CR 2 EQ 2 FR, PR 3 EQ 3 FR 2 FR 2 PR 2 EQ 2 IR 2 FR, PR 3 EQ 3
Reference 21 30 18 14 8
20
24 34 11 31 15 35 36 16 9
37
Note: GIFT ⫽ gamete intrafallopian transfer; IBT ⫽ direct immunobead test; i-IBT ⫽ indirect immunobead test; ICSI ⫽ intracytoplasmic sperm injection; IVF-ET ⫽ in vitro fertilization– embryo transfer; MAR ⫽ mixed agglutination test; FR ⫽ fertilization rate; CR ⫽ embryo cleavage rate; EQ ⫽ embryo quality; IR ⫽ embryo implantation rate: PR ⫽ pregnancy rate; FF ⫽ follicular fluid; 1 ⫽ increased; 2 ⫽ decreased; 3 ⫽ no change. Chiu. Significance of antisperm antibodies. Fertil Steril 2004.
observed that the presence of maternal serum ASA resulted in a reduction in PR from 31.8% to 20.8%. Acosta et al. (11) indicated that presence of sperm ASA reduced the PR from 62.1% to 21.1% per cycle and from 41.9% to 23.5% per embryo transfer. In vitro fertilization often entails the addition of maternal serum to the embryo culture medium and the fertilization rate was reported to be improved for women with serum ASA when their serum was replaced with either ASA-free serum or bovine serum albumin (BSA) (12, 13). 530
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These studies suggest that ASA decrease IVF and clinical PR. The proportion of sperm bound with ASA has been shown to be related to the fertilizing capacity of sperm. Several studies have shown an inverse relation between the proportion of sperm bound by ASA and the fertilizing capability of sperm. One such study showed that only 14% of oocytes were fertilized if 70% or more of sperm were bound Vol. 83, No. 3, September 2004
by both IgG and IgA antibodies; whereas, a higher fertilization rate (60%) was observed when less than 70% of sperm was bound with ASA (14). This effect was further illustrated by the decrease in fertilization rate when IgA ASA showed very high levels of binding (⬎68%) (15). In conclusion, the level of bound ASA can reduce fertilization. Studies have shown a decrease in fertilization rate when the titer of unbound ASA in seminal plasma and serum is high (12, 16). In addition, the combination of IgA present on all sperm together with a high serum ASA titer can reduce the PR to zero (12). However, studies using indirect assays for ASA may not reflect the presence of ASA on sperm and therefore should be regarded with caution (17).
EFFECT OF ASA ISOTYPE ON FERTILIZATION Antisperm antibodies of isotypes IgG, IgA, and IgM are all capable of binding to sperm (14, 18). Witkin and David (19) found that IgG and IgA ASA were present in up to 21.1% of infertile men. Another study showed that IgG ASA on sperm correlated with a reduction in fertilization rate, whereas only IgM ASA in female serum correlated with a decrease in fertilization rate (20). However, the presence of IgA ASA in female sera was associated with a decrease in PR (20). In another study, the fertilization of mature oocytes was reduced more markedly when mixed with sperm coated with IgG ASA than sperm coated with IgA ASA (14). Some researchers have reported that the combination of IgG and IgA ASA has a synergistic negative effect on fertilization (21). A study involving men with seminal plasma ASA revealed that fertilization of human oocytes was significantly reduced only if both IgA and IgG ASA were present (18). This synergistic effect of IgG and IgA ASA was also reported by Meinertz et al. (22). In this study of 216 vasovasostomized men with sperm ASA, these workers observed a PR of 85.7% among the men with sperm IgG ASA and 42.9% among men with both IgG and IgA sperm ASA (22). In contrast, other workers did not observe an impact on PR when sperm with ASA were used to fertilize oocytes (23, 24). These lines of evidence imply that different ASA isotypes have different effects on fertilization and some ASA can act synergistically to reduce fertility.
EFFECT, ON FERTILIZATION, OF THE LOCATION OF ASA BINDING ON SPERM A correlation has been observed between localization of ASA on sperm and the fertilizing capability of sperm. For example, a significant reduction in fertilization was reported when IgA ASA were present on the head of sperm compared to when none were present (15). Likewise, a decrease in the rate of fertilization was observed when IgM ASA directed to the head or tail tip of sperm were found (15). In addition, FERTILITY & STERILITY威
Clarke et al. (25) found a reduction in the fertilization rate (27%) when more than 80% of sperm had head-directed IgA and IgG compared to when less than 80% of sperm were coated with head directed IgA ASA (72%). Bronson et al. (26) reported an inverse relationship between the number of sperm with head binding IgG or IgA ASA and number of sperm binding to human zona pellucida (ZP). Similarly, Mahony et al. (27) reported that 7 of 10 sperm samples in their study with head-directed IgG and IgA ASA reduced the percentage of zona binding by half (27). Bronson et al. (28), using sperm complement-mediated immobilization tests, indicated that a high degree of immobilization was found only when IgG ASA were bound to the distal two-fifth of the principal piece of the tail or when IgM bound to the end piece of the tail. Carson et al. (29) assayed sera from 214 infertile patients and found a preferential binding of IgG and IgA to head and tail, and of IgM ASA to the tail tip. In contrast, other researchers did not observe a correlation between the localization of ASA and fertility or a distinction in the localization of IgG or IgA ASA (16, 30, 31). Collectively, these lines of evidence suggest that there is no consensus as to the value of localization of ASA binding on sperm on the prediction of the fertilizing capacity of ASA bound sperm.
MECHANISMS OF ACTION OF ASA IN REDUCING FERTILITY Effect of ASA on Sperm Transport The mucus of the uterine cervix can function as a filter to sperm attempting to travel into the upper reproductive tract. The ability of ASA to inhibit sperm penetration into cervical mucus is well described (38, 39). First, in several studies, the proportion of motile sperm with ASA correlated with the inhibition of sperm penetration in cervical mucus (38, 40 – 42). Second, ASA were detected in the cervical mucus from up to 29.6% of infertile women (42– 44). These cervical mucus ASA immobilized sperm and prevented passage through the cervical mucus (42, 44). Third, a study examining migration of sperm through cervical mucus indicated that ASA (mainly IgA) directed against the sperm head, along with IgA and IgG ASA directed against the sperm principal piece, severely impaired the ability of sperm to penetrate the cervical mucus (45). In contrast, the binding of IgG and IgA to the tail tip of sperm did not appear to affect the ability of sperm to penetrate the cervical mucus (46). Hence, it has been suggested that cervical mucus aids in the selection of the most fertile sperm of an ejaculate by acting as an immunological filter, preventing the passage of sperm coated with ASA (47). Antisperm antibodies of IgG and IgA isotypes have been found in cervical mucus and can cause sperm to become immobilized (44). The mechanisms by which ASA interfere with the movement of sperm in cervical mucus have been 531
extensively studied. Kremer and Jager (48) suggested that the secretory component of sperm IgA ASA binding to the glycoproteins of cervical mucus caused the shaking of sperm in cervical mucus. Jager et al. (49) reported that IgG can also induce a shaking phenomenon but suggested that Fc region of the IgG molecule may be impairing the motility of antibody-bound sperm in cervical mucus. The ability of IgA1 protease, which cleaves the Fc region from the IgA molecule, to improve the ability of IgA-coated sperm to penetrate cervical mucus supports the involvement of the Fc fragment in ASA/cervical mucus interactions (50, 51). It has been suggested that ASA on sperm bind to Fc receptors, as a 15-kD protein with an amino terminus identical to that of secretory leukocyte protease inhibitor is found in human cervical mucus, and this inhibits sperm transport (52).
ASA and Complement Complement is a cascade of proteins that can bind to antibody/antigen complexes on a cell surface and cause lysis of the cell. The IgG isotype antibodies are efficient at stimulating complement, whereas IgA is a relatively poor activator of complement. D’Cruz et al. (53) have shown that incubating complement-activating ASA with normal sperm caused a significant reduction (87%– 43%) in mobility and also observed alterations in sperm morphology with subsequent sperm lysis in vitro. D’Cruz et al. (54) have also demonstrated that sperm-bound ASA obtained from the ejaculates of men with ASA are capable of activating complement. However, whether complement exists in the female reproductive tract at physiologically relevant concentrations is questionable. Price et al. (55), using a hemolysis assay, have shown that complement is present in the cervical mucus but at approximately one-tenth of the levels found in the blood. This level of complement appeared to induce immobilization of 70% of ASA-coated sperm after 3 hours. In contrast to the low levels of complement in cervical mucus, FF has been shown to contain levels of complement approximately onehalf of that found in serum (56). However, although FF may contain adequate levels of complement to cause sperm damage in vitro, the dilution of FF after ovulation makes it unlikely that complement from FF causes sperm damage in vivo.
Effect of ASA on Capacitation and Acrosome Reaction Antisperm antibodies on sperm can be affected by or affect the changes in the sperm membrane associated with capacitation and acrosome reaction. Fusi and Bronson (57) suggested that the change in sperm membrane induced by capacitation and acrosome reaction can affect the binding of ASA. These investigators incubated ASA-containing sera with capacitated, acrosome-reacted sperm and found 48% of ASA-positive and 20% of ASA-negative sera demonstrated a different pattern of indirect ImmunoBead test binding with capacitated sperm (57). Evidence has also emerged that ASA 532
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might prevent membrane fluidity changes needed for capacitation before fertilization (58). In addition, sperm incubated with serum containing immobilizing ASA were found to have lower rates of spontaneous and induced acrosome reactions than sperm that were not incubated with the serum (59, 60). Furthermore, ASA can inhibit the ability of sperm to undergo spontaneous capacitation as an antibody raised against a human sperm protein, BS-17, prevented capacitation of human sperm (61). The effects of ASA on acrosome reaction have been contradictory. For instance, Romano et al. (62) found that the proportion of acrosome-reacted sperm was higher in ASAcoated sperm. Lansford et al. (63) found that IgG ASA from different individuals could inhibit the acrosome reaction, whereas other ASA initiated or had no effect on the acrosome reaction. In addition, Saragueta et al. (64) found heavy and light chains of human IgG in FF that were capable of inducing the acrosome reaction. Taken together, these lines of evidence suggest that ASA have a variable effect on the acrosome reaction and capacitation. Some ASA can adversely alter the ability of sperm to undergo capacitation or acrosome reaction, whereas other ASA do not (63, 65).
Effect of ASA on Sperm–Oocyte Binding Several lines of evidence indicate that ASA might interfere with recognition of sperm binding sites on ZP. Bronson et al. (26) reported binding of head-directed IgG or IgA ASA to sperm reduced sperm binding to human ZP. Another study showed that donor sperm, when incubated with ASA containing serum, was unable to fertilize human oocytes or bind to ZP (66). When the serum ASA were preabsorbed by normal sperm, the serum no longer showed this negative effect on sperm–zona binding (66). Additional evidence that ASA can affect sperm binding to ZP was provided by Mahony et al. (27). Using the hemizona assay they demonstrated that 7 of the 10 ASA-containing sera tested reduced zona binding. In addition, Rajah et al. (33) found that ASA could affect fertilization but not the clinical PRs once fertilization had occurred. In contrast, other investigators found that ASA did not affect sperm– oocyte binding (67, 68). Further adding to the complicated pool of data, other researchers found that ASA were capable of both stimulating and suppressing sperm– oocyte fusion (69, 70). These conflicting lines of evidence suggest that not all ASA affect sperm– oocyte binding/fusion and it is likely, as would be expected, that the antigenic specificity of ASA is important in their effects on fertilization. The effect of ASA on sperm– oocyte fusion can be studied by observing the ability of ASA-coated sperm to adhere and penetrate zona-free hamster oocytes. This assay uses hamster oocytes stripped of the cumulus oophorus and ZP to test the penetrating ability of acrosome-reacted human sperm (71). Numerous investigators have shown that human ASA can inhibit the penetration of hamster oocytes by human sperm Vol. 83, No. 3, September 2004
(72–76). In addition, antibodies raised against specific sperm proteins are capable of inhibiting sperm hamster oocyte penetration (75, 77, 78). For example, rabbit antibodies raised against sperm proteins of 36 and 18 kD reduced the binding and penetration of hamster zona-free egg by human sperm (78) and monoclonal antibodies reactive with sperm proteins inhibited sperm fusion with zona-free rodent eggs (75, 77). In contrast, some serum ASA have been found to promote the penetration and adhesion of human sperm to hamster oocytes (70, 79). Mixed results were also reported by Aitken et al. (69), who found that ASA could promote, inhibit, or be neutral in their influence on sperm penetration of oocytes. These lines of conflicting data outline the importance of knowing the specificities of the ASA involved; some of the ASA do not affect fertilization and some do.
Effect of ASA on Embryo Development, Implantation, and Spontaneous Abortions Retrospective studies carried out to determine the effect of sperm-bound ASA on embryonic development and implantation indicated that ASA significantly inhibited early embryonic cleavage, thereby reducing the number of highquality embryos (9, 13). In a study of 150 IVF-embryo transfer cycles, oocytes from women with serum ASA had a lower embryo cleavage rate (64.2%) than oocytes from women without ASA (84.8%) (10). Moreover, the presence of ASA in FF was also correlated with reduced embryo cleavage rate (91%– 67%) (30). In another study, oocytes fertilized with ASA-bound sperm demonstrated abnormal cleavage of the embryos (80). These investigators found that the relevant ASA recognized human and murine sperm proteins of low molecular weights: 14, 18, and 22 kD (80). The relationship between ASA and pregnancy loss has been demonstrated by several IVF-embryo transfer studies. One study examined 109 infertile couples during an 18month period (19). During this period, pregnancy occurred in 30.3% of the couples; half of these women subsequently suffered a miscarriage during the first trimester (81). Serum ASA were present in 11.8% of the women with successful pregnancies, but were found in 43.8% of the women who miscarried and in 38.2% of women who did not conceive. Both IgG and IgA ASA were present in 37.5% of those women who miscarried (81). In a separate study, the isotype and regional specificity of serum ASA of women with recurrent spontaneous abortions were examined (82). It was found that there was a statistically significant correlation between the presence of IgG tail-directed ASA and a history of spontaneous abortion. However, no correlation could be seen with sperm head-directed IgG or IgA ASA (82). Further evidence that ASA influence the rate of miscarriage can be seen in IVF settings where intracytoplasmic sperm injection (ICSI) technique was used. In a study of couples undergoing ICSI, Lahteenmaki et al. (35) found that FERTILITY & STERILITY威
spontaneous abortion occurred in 38.5% of the pregnancies that resulted from fertilization using sperm with ASA. In contrast, none of the pregnancies that resulted from sperm without ASA ended in spontaneous abortion. In a separate study, Check et al. (83) injected oocytes with sperm of varying percentage of surface ASA and found that pregnancies that resulted from using sperm with lower percentage of binding (⬍50%) resulted in fewer spontaneous abortions (14% vs. 25%) than those pregnancies that resulted from using sperm with a high percentage ASA binding (⬎80%). These data suggest that injecting sperm with ASA still resulted in a higher spontaneous abortion rate than using sperm without ASA and that ASA may, therefore, affect the processes of fertilization and implantation.
CONCLUSION In the light of these lines of evidence, we can conclude ASA have multiple effects on various facets of fertilization, such as acrosome reaction, capacitation, fertilization, and implantation. However, the evidence for each of these effects of ASA remains controversial. During the past decade, our knowledge of the role of ASA in infertility has progressed relatively little. It is likely that little progress will continue to be made in understanding the clinical significance of ASA until current diagnostic tests, which detect antibody binding to sperm but do not examine the antigenic specificities of the ASA, are replaced by antigen-specific assays that allow for the study of the effects of ASA on individual sperm proteins. References 1. Mosher WD, Pratt WF. Fecundity and infertility in the United States: incidence and trends. Fertil Steril 1991;56:192–3. 2. Ayvaliotis B, Bronson R, Rosenfeld D, Cooper G. Conception rates in couples where autoimmunity to sperm is detected. Fertil Steril 1985; 43:739 – 42. 3. Collins JA, Burrows EA, Yeo J, Young Lai EV. Frequency and predictive value of antisperm antibodies among infertile couples. Hum Reprod 1993;8:592– 8. 4. Sinisi AA, Di Finizio B, Pasquali D, Scurini C, D’Apuzzo A, Bellastella A. Prevalence of antisperm antibodies by SpermMARtest in subjects undergoing a routine sperm analysis for infertility. Int J Androl 1993;16:311– 4. 5. Heidenreich A, Bonfig R, Wilbert DM, Strohmaier WL, Engelmann UH. Risk factors for antisperm antibodies in infertile men. Am J Reprod Immunol 1994;31:69 –76. 6. Omu AE, Makhseed M, Mohammed AT, Munim RA. Characteristics of men and women with circulating antisperm antibodies in a combined infertility clinic in Kuwait. Arch Androl 1997;39:55– 64. 7. Helmerhorst FM, Finken MJ, Erwich JJ. Antisperm antibodies: detection assays for antisperm antibodies: what do they test? Hum Reprod 1999;14:1669 –71. 8. Palermo G, Devroey P, Camus M, Khan I, Wisanto A, Van Steirteghem AC. Assisted procreation in the presence of a positive direct mixed antiglobulin reaction test. Fertil Steril 1989;52:645–9. 9. Vazquez-Levin MH, Notrica JA, Polak de Fried E. Male immunologic infertility: sperm performance on in vitro fertilization. Fertil Steril 1997;68:675– 81. 10. Tian X, Zhang L, Wu Y, Yang C, Liu P. Relationship between serum antisperm antibodies and anticardiolipin antibodies and clinical pregnancy outcome in an in vitro fertilization and embryo transfer program. Chin Med J (Engl) 1999;112:34 – 6. 11. Acosta AA, van der Merwe JP, Doncel G, Kruger TF, Sayilgan A, Franken DR, et al. Fertilization efficiency of morphologically abnormal spermatozoa in assisted reproduction is further impaired by antisperm antibodies on the male partner’s sperm. Fertil Steril 1994;62:826 –33.
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37. Clarke GN, Bourne H, Baker HW. Intracytoplasmic sperm injection for treating infertility associated with sperm autoimmunity. Fertil Steril 1997;68:112–7. 38. Jager S, Kremer J, van Slochteren-Draaisma T. A simple method of screening for antisperm antibodies in the human male. Detection of spermatozoal surface IgG with the direct mixed antiglobulin reaction carried out on untreated fresh human semen. Int J Fertil 1978;23:12–21. 39. Haas GG Jr, Schreiber AD, Blasco L. The incidence of sperm-associated immunoglobulin and C3, the third component of complement, in infertile men. Fertil Steril 1983;39:542–7. 40. De Almeida M, Soumah A, Jouannet P. Incidence of sperm-associated immunoglobulins in infertile men with suspected autoimmunity to sperm. Int J Androl 1986;9:321–30. 41. Busacca M, Fusi F, Brigante C, Doldi N, Smid M, Vigano P. Evaluation of antisperm antibodies in infertile couples with immunobead test: prevalence and prognostic value. Acta Eur Fertil 1989;20:77– 82. 42. Menge AC, Beitner O. Interrelationships among semen characteristics, antisperm antibodies, and cervical mucus penetration assays in infertile human couples. Fertil Steril 1989;51:486 –92. 43. Moghissi KS, Sacco AG, Borin K. Immunologic infertility. I. Cervical mucus antibodies and postcoital test. Am J Obstet Gynecol 1980;136: 941–50. 44. Menge AC, Medley NE, Mangione CM, Dietrich JW. The incidence and influence of antisperm antibodies in infertile human couples on sperm– cervical mucus interactions and subsequent fertility. Fertil Steril 1982;38:439 – 46. 45. Witkin SS, Viti D, David SS, Stangel J, Rosenwaks Z. Relation between antisperm antibodies and the rate of fertilization of human oocytes in vitro. J Assist Reprod Genet 1992;9:9 –13. 46. Wang C, Baker HW, Jennings MG, Burger HG, Lutjen P. Interaction between human cervical mucus and sperm surface antibodies. Fertil Steril 1985;44:484 – 8. 47. Mortimer D, Pandya IJ, Sawers RS. Relationship between human sperm motility characteristics and sperm penetration into human cervical mucus in vitro. J Reprod Fertil 1986;78:93–102. 48. Kremer J, Jager S. Characteristics of anti-spermatozoal antibodies responsible for the shaking phenomenon with special regard to immunoglobulin class and antigen-reactive sites. Int J Androl 1980;3:143–52. 49. Jager S, Kremer J, Kuiken J, van Slochteren-Draaisma T, Mulder I, de Wilde-Janssen IW. Induction of the shaking phenomenon by pretreatment of spermatozoa with sera containing antispermatozoal antibodies. Fertil Steril 1981;36:784 –91. 50. Jager S, Kremer J, Kuiken J, Mulder I. The significance of the Fc part of antispermatozoal antibodies for the shaking phenomenon in the sperm-cervical mucus contact test. Fertil Steril 1981;36:792–7. 51. Bronson RA, Cooper GW, Rosenfeld DL, Gilbert JV, Plaut AG. The effect of an IgA1 protease on immunoglobulins bound to the sperm surface and sperm cervical mucus penetrating ability. Fertil Steril 1987;47:985–91. 52. Hirano M, Kamada M, Maegawa M, Gima H, Aono T. Binding of human secretory leukocyte protease inhibitor in uterine cervical mucus to immunoglobulins: pathophysiology in immunologic infertility and local immune defense. Fertil Steril 1999;71:1108 –14. 53. D’Cruz OJ, Haas GG Jr, Wang BL, DeBault LE. Activation of human complement by IgG antisperm antibody and the demonstration of C3 and C5b-9-mediated immune injury to human sperm. J Immunol 1991; 146:611–20. 54. D’Cruz OJ, Wang BL, Haas GG Jr. Phagocytosis of immunoglobulin G and C3-bound human sperm by human polymorphonuclear leukocytes is not associated with the release of oxidative radicals. Biol Reprod 1992;46:721–32. 55. Price RJ, Boettcher B. The presence of complement in human cervical mucus and its possible relevance to infertility in women with complement-dependent sperm-immobilizing antibodies. Fertil Steril 1979;32: 61– 6. 56. D’Cruz OJ, Haas GG Jr, Lambert H. Evaluation of antisperm complement-dependent immune mediators in human ovarian follicular fluid. J Immunol 1990;144:3841– 8. 57. Fusi F, Bronson RA. Effects of incubation time in serum and capacitation on spermatozoal reactivity with antisperm antibodies. Fertil Steril 1990;54:887–93. 58. Benoff S, Cooper GW, Hurley I, Mandel FS, Rosenfeld DL. Antisperm antibody binding to human sperm inhibits capacitation induced changes in the levels of plasma membrane sterols. Am J Reprod Immunol 1993;30:113–30. 59. Tasdemir I, Tasdemir M, Fukuda J, Kodama H, Matsui T, Tanaka T. Sperm immobilization antibodies in infertile male sera decrease the acrosome reaction: a possible mechanism for immunologic infertility. J Assist Reprod Genet 1996;13:413– 6. 60. Myogo K, Yamano S, Nakagawa K, Kamada M, Maegawa M, Irahara M, et al. Sperm-immobilizing antibodies block capacitation in human spermatozoa. Arch Androl 2001;47:135– 42.
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61. Wei SG, Wang LF, Miao SY, Zong SD, Koide SS. Fertility studies with antisperm antibodies. Arch Androl 1994;32:251– 62. 62. Romano R, Santucci R, Marrone V, Francavilla F. Effect of ionophore challenge on hamster egg penetration and acrosome reaction of antibody-coated human sperm. Am J Reprod Immunol 1993;29:56 – 61. 63. Lansford B, Haas GG Jr, DeBault LE, Wolf DP. Effect of spermassociated antibodies on the acrosomal status of human sperm. J Androl 1990;11:532– 8. 64. Saragueta P, Lanuza G, Miranda PV, Tezon JG, Baranao JL. Immunoglobulins from human follicular fluid induce the acrosome reaction in human sperm. Mol Reprod Dev 1994;39:280 – 8. 65. Bohring C, Skrzypek J, Krause W. Influence of antisperm antibodies on the acrosome reaction as determined by flow cytometry. Fertil Steril 2001;76:275– 80. 66. Tsukui S, Noda Y, Yano J, Fukuda A, Mori T. Inhibition of sperm penetration through human zona pellucida by antisperm antibodies. Fertil Steril 1986;46:92– 6. 67. Liu DY, Clarke GN, Baker HW. Inhibition of human sperm–zona pellucida and sperm– oolemma binding by antisperm antibodies. Fertil Steril 1991;55:440 –2. 68. Coddington CC, Demochowski R, Oehninger S, Auman JR, Hodgen GD. Hemizona assay: evaluation of fertility potential in patients with vasectomy reversal. Arch Androl 1997;38:143–50. 69. Aitken RJ, Parslow JM, Hargreave TB, Hendry WF. Influence of antisperm antibodies on human sperm function. Br J Urol 1988;62:367– 73. 70. Bronson RA, Fusi F, Cooper GW, Phillips DM. Antisperm antibodies induce polyspermy by promoting adherence of human sperm to zonafree hamster eggs. Hum Reprod 1990;5:690 – 6. 71. Yanagimachi R, Yanagimachi H, Rogers BJ. The use of zona-free animal ova as a test-system for the assessment of the fertilizing capacity of human spermatozoa. Biol Reprod 1976;15:471– 6. 72. Haas GG Jr, Ausmanus M, Culp L, Tureck RW, Blasco L. The effect of immunoglobulin occurring on human sperm in vivo on the human sperm/hamster ova penetration assay. Am J Reprod Immunol Microbiol 1985;7:109 –12.
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73. Kamada M, Daitoh T, Hasebe H, Irahara M, Yamano S, Mori T. Blocking of human fertilization in vitro by sera with sperm-immobilizing antibodies. Am J Obstet Gynecol 1985;153:328 –31. 74. Abdel-Latif A, Mathur S, Rust PF, Fredericks CM, Abdel-Aal H, Williamson HO. Cytotoxic sperm antibodies inhibit sperm penetration of zona-free hamster eggs. Fertil Steril 1986;45:542–9. 75. Shibahara H, Shigeta M, Inoue M, Hasegawa A, Koyama K, Alexander NJ, et al. Diversity of the blocking effects of antisperm antibodies on fertilization in human and mouse. Hum Reprod 1996;11:2595–9. 76. Francavilla F, Romano R, Santucci R, Marrone V, Properzi G, Ruvolo G. Occurrence of the interference of sperm-associated antibodies on sperm fertilizing ability as evaluated by the sperm–zona pellucida binding test and by the TEST-yolk buffer enhanced sperm penetration assay. Am J Reprod Immunol 1997;37:267–74. 77. Primakoff P, Hyatt H. An antisperm monoclonal antibody inhibits sperm fusion with zona-free hamster eggs but not homologous eggs. Fertil Steril 1986;46:489 –93. 78. Auer J, Senechal H, Desvaux FX, Albert M, De Almeida M. Isolation and characterisation of two sperm membrane proteins recognised by sperm-associated antibodies in infertile men. Mol Reprod Dev 2000; 57:393– 405. 79. Bronson RA, Fleit HB, Fusi F. Identification of an oolemmal IgG Fc receptor: its role in promoting binding of antibody-labelled human sperm to zona-free hamster eggs. Am J Reprod Immunol 1990;23:87– 92. 80. Naz RK. Effects of antisperm antibodies on early cleavage of fertilized ova. Biol Reprod 1992;46:130 –9. 81. Witkin SS, Chaudhry A. Relationship between circulating antisperm antibodies in women and autoantibodies on the ejaculated sperm of their partners. Am J Obstet Gynecol 1989;161:900 –3. 82. Witkin SS, Chaudhry A. Association between recurrent spontaneous abortions and circulating IgG antibodies to sperm tails in women. J Reprod Immunol 1989;15:151– 8. 83. Check ML, Check JH, Katsoff D, Summers-Chase D. ICSI as an effective therapy for male factor with antisperm antibodies. Arch Androl 2000;45:125–30.
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MODERN TRENDS Edward E. Wallach, M.D. Associate Editor
Clinical associations and mechanisms of action of antisperm antibodies Will W.-C. Chiu, M.D., and Lawrence W. Chamley, Ph.D. Department of Obstetrics and Gynecology, University of Auckland, Auckland, New Zealand
Objective: To review and critique the current English literature describing the effects of antisperm antibodies (ASA) on mammalian fertility. Design: A comprehensive English language literature was searched using Medline and by hand-searching. Emphasis was placed on clinically relevant articles. Result(s): Results from the studies were extrapolated and the effects of ASA on fertility described. Conclusion(s): Antisperm antibodies may interfere with fertility. Not all ASA cause infertility. Current tests cannot differentiate the infertility-related ASA from those that do not interfere with infertility, because the antigenic specificities of these ASA are not known. The antigens which the infertility-related ASA must be characterized to allow an accurate detection and proper treatment for couples with ASA. (Fertil Steril威 2004; 83:529 –35. ©2004 by American Society for Reproductive Medicine.) Key Words: Assisted reproductive technology, fertilization, gamete biology, immunology, sperm
Infertility, the inability to conceive within 1 year of unprotected intercourse, is estimated to affect up to one in six couples of reproductive age and poses a significant health problem (1). Antisperm antibodies (ASA) are found in up to 9%–12.8% of infertile couples (2, 3). However, these antibodies are present also in approximately 1%–2.5% of fertile men (4, 5) and in 4% of fertile women (6). The presence of ASA in the fertile population indicates that not all ASA cause sterility.
Received June 30, 2003; revised and accepted September 29, 2003. Reprint requests: Larry Chamley, Ph.D., Department of Obstetrics and Gynecology, University of Auckland, Auckland 3, New Zealand (FAX: 64-96309858; E-mail: [email protected]). 0015-0282/04/$30.00 doi:10.1016/j.fertnstert.2003. 09.084
The confusion over the role of ASA in infertility, to some extent, reflects the inadequacies of the current diagnostic techniques. The methods of ASA detection can be categorized into the following: direct tests to detect the presence of ASA on sperm, such as the mixed agglutination assay and immunobead test; agglutination tests using donor sperm such as gelatin agglutination test, and tray agglutination test (7). These tests only detect the gross binding of antibodies to various locations on sperm and do not examine the antigenic specificities of the ASA. Moreover, each type of ASA, from both the man and woman, may be targeted against different antigens involved in various steps of human fertilization, such as acrosome reaction, capacitation, migration in the fallopian tube, and motility. Therefore,
each type of ASA may be interfering directly or indirectly with the different steps leading to fertilization. This review examines and critiques the current understanding of how ASA affect human fertility in a clinical and laboratory setting.
ASA AND FERTILIZATION A large body of retrospective and prospective analysis of data from programs performing IVF has provided a great amount of evidence regarding the effects of ASA in serum, semen, and follicular fluid (FF) as a possible cause of infertility (Table 1). These studies generally indicate that couples with ASA have lower pregnancy rates (PR) than couples without ASA. Of the 20 trials examining the effect of ASA on fertilization, 14 showed a decrease in the fertilization rate, 4 showed no effect, and 2 showed an equivocal effect (Table 1). One such study described infertile couples treated by IVF, in which the men had sperm ASA (8). The presence of ASA reduced the fertilization rate from 45.8% to 34.2% per cycle (8). Vazquez-Levin et al. (9) also found a reduced clinical PR when the male partner has sperm ASA compared with men who do not have ASA (11% vs. 44%). Tian et al. (10) 529
TABLE 1 Summary of IVF trials of the effects of antisperm antibodies on fertilization. ASA and method of detection (source of ASA)
Method of fertilization
End points/outcomes (ASA isotype/region of binding on sperm)
i-IBT (semen) i-IBT (FF)
IVF-ET IVF-ET
i-IBT
IVF-ET
IBT MAR
IVF-ET IVF-ET GIFT
IBT (sperm, female serum)
IVF-ET
IBT TAT (female serum) i-IBT (female serum as culture media)
IVF-ET
FR 2 (IgG ⫹ IgA) FR 2 (female serum-head; FF-head) CR 2 FR 2 (IgG ⫹ IgA) FR 3 (IgG or IgA) FR 2 (IgG ⫹ IgA) FR 2 PR 2 CR 3 EQ 2 FR 2 (sperm IgG) PR 2 (IgA-female serum) EQ 2 FR 2
32
IVF-ET
FR 2
13
IVF-ET
PR 2 EQ 2 FR 2
33
MAR IBT (IgG or IgA) TAT MAR TAT IBT i-IBT (female serum) IBT IBT IBT MAR FCM MAR IBT i-IBT (seminal plasma) MAR
IBT
IVF-ET IVF-ET IVF-ET GIFT IVF-ET IVF-ET ICSI ICSI IVF-ET IVF-ET
ICSI
FR 2 (MAR⬎90%) FR 3 (TAT) FR 3 PR 3 FR 2 PR 2 FR, CR, PR 3 FR 2 (IgA⬎68%, head) FR, CR 2 EQ 2 FR, PR 3 EQ 3 FR 2 FR 2 PR 2 EQ 2 IR 2 FR, PR 3 EQ 3
Reference 21 30 18 14 8
20
24 34 11 31 15 35 36 16 9
37
Note: GIFT ⫽ gamete intrafallopian transfer; IBT ⫽ direct immunobead test; i-IBT ⫽ indirect immunobead test; ICSI ⫽ intracytoplasmic sperm injection; IVF-ET ⫽ in vitro fertilization– embryo transfer; MAR ⫽ mixed agglutination test; FR ⫽ fertilization rate; CR ⫽ embryo cleavage rate; EQ ⫽ embryo quality; IR ⫽ embryo implantation rate: PR ⫽ pregnancy rate; FF ⫽ follicular fluid; 1 ⫽ increased; 2 ⫽ decreased; 3 ⫽ no change. Chiu. Significance of antisperm antibodies. Fertil Steril 2004.
observed that the presence of maternal serum ASA resulted in a reduction in PR from 31.8% to 20.8%. Acosta et al. (11) indicated that presence of sperm ASA reduced the PR from 62.1% to 21.1% per cycle and from 41.9% to 23.5% per embryo transfer. In vitro fertilization often entails the addition of maternal serum to the embryo culture medium and the fertilization rate was reported to be improved for women with serum ASA when their serum was replaced with either ASA-free serum or bovine serum albumin (BSA) (12, 13). 530
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These studies suggest that ASA decrease IVF and clinical PR. The proportion of sperm bound with ASA has been shown to be related to the fertilizing capacity of sperm. Several studies have shown an inverse relation between the proportion of sperm bound by ASA and the fertilizing capability of sperm. One such study showed that only 14% of oocytes were fertilized if 70% or more of sperm were bound Vol. 83, No. 3, September 2004
by both IgG and IgA antibodies; whereas, a higher fertilization rate (60%) was observed when less than 70% of sperm was bound with ASA (14). This effect was further illustrated by the decrease in fertilization rate when IgA ASA showed very high levels of binding (⬎68%) (15). In conclusion, the level of bound ASA can reduce fertilization. Studies have shown a decrease in fertilization rate when the titer of unbound ASA in seminal plasma and serum is high (12, 16). In addition, the combination of IgA present on all sperm together with a high serum ASA titer can reduce the PR to zero (12). However, studies using indirect assays for ASA may not reflect the presence of ASA on sperm and therefore should be regarded with caution (17).
EFFECT OF ASA ISOTYPE ON FERTILIZATION Antisperm antibodies of isotypes IgG, IgA, and IgM are all capable of binding to sperm (14, 18). Witkin and David (19) found that IgG and IgA ASA were present in up to 21.1% of infertile men. Another study showed that IgG ASA on sperm correlated with a reduction in fertilization rate, whereas only IgM ASA in female serum correlated with a decrease in fertilization rate (20). However, the presence of IgA ASA in female sera was associated with a decrease in PR (20). In another study, the fertilization of mature oocytes was reduced more markedly when mixed with sperm coated with IgG ASA than sperm coated with IgA ASA (14). Some researchers have reported that the combination of IgG and IgA ASA has a synergistic negative effect on fertilization (21). A study involving men with seminal plasma ASA revealed that fertilization of human oocytes was significantly reduced only if both IgA and IgG ASA were present (18). This synergistic effect of IgG and IgA ASA was also reported by Meinertz et al. (22). In this study of 216 vasovasostomized men with sperm ASA, these workers observed a PR of 85.7% among the men with sperm IgG ASA and 42.9% among men with both IgG and IgA sperm ASA (22). In contrast, other workers did not observe an impact on PR when sperm with ASA were used to fertilize oocytes (23, 24). These lines of evidence imply that different ASA isotypes have different effects on fertilization and some ASA can act synergistically to reduce fertility.
EFFECT, ON FERTILIZATION, OF THE LOCATION OF ASA BINDING ON SPERM A correlation has been observed between localization of ASA on sperm and the fertilizing capability of sperm. For example, a significant reduction in fertilization was reported when IgA ASA were present on the head of sperm compared to when none were present (15). Likewise, a decrease in the rate of fertilization was observed when IgM ASA directed to the head or tail tip of sperm were found (15). In addition, FERTILITY & STERILITY威
Clarke et al. (25) found a reduction in the fertilization rate (27%) when more than 80% of sperm had head-directed IgA and IgG compared to when less than 80% of sperm were coated with head directed IgA ASA (72%). Bronson et al. (26) reported an inverse relationship between the number of sperm with head binding IgG or IgA ASA and number of sperm binding to human zona pellucida (ZP). Similarly, Mahony et al. (27) reported that 7 of 10 sperm samples in their study with head-directed IgG and IgA ASA reduced the percentage of zona binding by half (27). Bronson et al. (28), using sperm complement-mediated immobilization tests, indicated that a high degree of immobilization was found only when IgG ASA were bound to the distal two-fifth of the principal piece of the tail or when IgM bound to the end piece of the tail. Carson et al. (29) assayed sera from 214 infertile patients and found a preferential binding of IgG and IgA to head and tail, and of IgM ASA to the tail tip. In contrast, other researchers did not observe a correlation between the localization of ASA and fertility or a distinction in the localization of IgG or IgA ASA (16, 30, 31). Collectively, these lines of evidence suggest that there is no consensus as to the value of localization of ASA binding on sperm on the prediction of the fertilizing capacity of ASA bound sperm.
MECHANISMS OF ACTION OF ASA IN REDUCING FERTILITY Effect of ASA on Sperm Transport The mucus of the uterine cervix can function as a filter to sperm attempting to travel into the upper reproductive tract. The ability of ASA to inhibit sperm penetration into cervical mucus is well described (38, 39). First, in several studies, the proportion of motile sperm with ASA correlated with the inhibition of sperm penetration in cervical mucus (38, 40 – 42). Second, ASA were detected in the cervical mucus from up to 29.6% of infertile women (42– 44). These cervical mucus ASA immobilized sperm and prevented passage through the cervical mucus (42, 44). Third, a study examining migration of sperm through cervical mucus indicated that ASA (mainly IgA) directed against the sperm head, along with IgA and IgG ASA directed against the sperm principal piece, severely impaired the ability of sperm to penetrate the cervical mucus (45). In contrast, the binding of IgG and IgA to the tail tip of sperm did not appear to affect the ability of sperm to penetrate the cervical mucus (46). Hence, it has been suggested that cervical mucus aids in the selection of the most fertile sperm of an ejaculate by acting as an immunological filter, preventing the passage of sperm coated with ASA (47). Antisperm antibodies of IgG and IgA isotypes have been found in cervical mucus and can cause sperm to become immobilized (44). The mechanisms by which ASA interfere with the movement of sperm in cervical mucus have been 531
extensively studied. Kremer and Jager (48) suggested that the secretory component of sperm IgA ASA binding to the glycoproteins of cervical mucus caused the shaking of sperm in cervical mucus. Jager et al. (49) reported that IgG can also induce a shaking phenomenon but suggested that Fc region of the IgG molecule may be impairing the motility of antibody-bound sperm in cervical mucus. The ability of IgA1 protease, which cleaves the Fc region from the IgA molecule, to improve the ability of IgA-coated sperm to penetrate cervical mucus supports the involvement of the Fc fragment in ASA/cervical mucus interactions (50, 51). It has been suggested that ASA on sperm bind to Fc receptors, as a 15-kD protein with an amino terminus identical to that of secretory leukocyte protease inhibitor is found in human cervical mucus, and this inhibits sperm transport (52).
ASA and Complement Complement is a cascade of proteins that can bind to antibody/antigen complexes on a cell surface and cause lysis of the cell. The IgG isotype antibodies are efficient at stimulating complement, whereas IgA is a relatively poor activator of complement. D’Cruz et al. (53) have shown that incubating complement-activating ASA with normal sperm caused a significant reduction (87%– 43%) in mobility and also observed alterations in sperm morphology with subsequent sperm lysis in vitro. D’Cruz et al. (54) have also demonstrated that sperm-bound ASA obtained from the ejaculates of men with ASA are capable of activating complement. However, whether complement exists in the female reproductive tract at physiologically relevant concentrations is questionable. Price et al. (55), using a hemolysis assay, have shown that complement is present in the cervical mucus but at approximately one-tenth of the levels found in the blood. This level of complement appeared to induce immobilization of 70% of ASA-coated sperm after 3 hours. In contrast to the low levels of complement in cervical mucus, FF has been shown to contain levels of complement approximately onehalf of that found in serum (56). However, although FF may contain adequate levels of complement to cause sperm damage in vitro, the dilution of FF after ovulation makes it unlikely that complement from FF causes sperm damage in vivo.
Effect of ASA on Capacitation and Acrosome Reaction Antisperm antibodies on sperm can be affected by or affect the changes in the sperm membrane associated with capacitation and acrosome reaction. Fusi and Bronson (57) suggested that the change in sperm membrane induced by capacitation and acrosome reaction can affect the binding of ASA. These investigators incubated ASA-containing sera with capacitated, acrosome-reacted sperm and found 48% of ASA-positive and 20% of ASA-negative sera demonstrated a different pattern of indirect ImmunoBead test binding with capacitated sperm (57). Evidence has also emerged that ASA 532
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might prevent membrane fluidity changes needed for capacitation before fertilization (58). In addition, sperm incubated with serum containing immobilizing ASA were found to have lower rates of spontaneous and induced acrosome reactions than sperm that were not incubated with the serum (59, 60). Furthermore, ASA can inhibit the ability of sperm to undergo spontaneous capacitation as an antibody raised against a human sperm protein, BS-17, prevented capacitation of human sperm (61). The effects of ASA on acrosome reaction have been contradictory. For instance, Romano et al. (62) found that the proportion of acrosome-reacted sperm was higher in ASAcoated sperm. Lansford et al. (63) found that IgG ASA from different individuals could inhibit the acrosome reaction, whereas other ASA initiated or had no effect on the acrosome reaction. In addition, Saragueta et al. (64) found heavy and light chains of human IgG in FF that were capable of inducing the acrosome reaction. Taken together, these lines of evidence suggest that ASA have a variable effect on the acrosome reaction and capacitation. Some ASA can adversely alter the ability of sperm to undergo capacitation or acrosome reaction, whereas other ASA do not (63, 65).
Effect of ASA on Sperm–Oocyte Binding Several lines of evidence indicate that ASA might interfere with recognition of sperm binding sites on ZP. Bronson et al. (26) reported binding of head-directed IgG or IgA ASA to sperm reduced sperm binding to human ZP. Another study showed that donor sperm, when incubated with ASA containing serum, was unable to fertilize human oocytes or bind to ZP (66). When the serum ASA were preabsorbed by normal sperm, the serum no longer showed this negative effect on sperm–zona binding (66). Additional evidence that ASA can affect sperm binding to ZP was provided by Mahony et al. (27). Using the hemizona assay they demonstrated that 7 of the 10 ASA-containing sera tested reduced zona binding. In addition, Rajah et al. (33) found that ASA could affect fertilization but not the clinical PRs once fertilization had occurred. In contrast, other investigators found that ASA did not affect sperm– oocyte binding (67, 68). Further adding to the complicated pool of data, other researchers found that ASA were capable of both stimulating and suppressing sperm– oocyte fusion (69, 70). These conflicting lines of evidence suggest that not all ASA affect sperm– oocyte binding/fusion and it is likely, as would be expected, that the antigenic specificity of ASA is important in their effects on fertilization. The effect of ASA on sperm– oocyte fusion can be studied by observing the ability of ASA-coated sperm to adhere and penetrate zona-free hamster oocytes. This assay uses hamster oocytes stripped of the cumulus oophorus and ZP to test the penetrating ability of acrosome-reacted human sperm (71). Numerous investigators have shown that human ASA can inhibit the penetration of hamster oocytes by human sperm Vol. 83, No. 3, September 2004
(72–76). In addition, antibodies raised against specific sperm proteins are capable of inhibiting sperm hamster oocyte penetration (75, 77, 78). For example, rabbit antibodies raised against sperm proteins of 36 and 18 kD reduced the binding and penetration of hamster zona-free egg by human sperm (78) and monoclonal antibodies reactive with sperm proteins inhibited sperm fusion with zona-free rodent eggs (75, 77). In contrast, some serum ASA have been found to promote the penetration and adhesion of human sperm to hamster oocytes (70, 79). Mixed results were also reported by Aitken et al. (69), who found that ASA could promote, inhibit, or be neutral in their influence on sperm penetration of oocytes. These lines of conflicting data outline the importance of knowing the specificities of the ASA involved; some of the ASA do not affect fertilization and some do.
Effect of ASA on Embryo Development, Implantation, and Spontaneous Abortions Retrospective studies carried out to determine the effect of sperm-bound ASA on embryonic development and implantation indicated that ASA significantly inhibited early embryonic cleavage, thereby reducing the number of highquality embryos (9, 13). In a study of 150 IVF-embryo transfer cycles, oocytes from women with serum ASA had a lower embryo cleavage rate (64.2%) than oocytes from women without ASA (84.8%) (10). Moreover, the presence of ASA in FF was also correlated with reduced embryo cleavage rate (91%– 67%) (30). In another study, oocytes fertilized with ASA-bound sperm demonstrated abnormal cleavage of the embryos (80). These investigators found that the relevant ASA recognized human and murine sperm proteins of low molecular weights: 14, 18, and 22 kD (80). The relationship between ASA and pregnancy loss has been demonstrated by several IVF-embryo transfer studies. One study examined 109 infertile couples during an 18month period (19). During this period, pregnancy occurred in 30.3% of the couples; half of these women subsequently suffered a miscarriage during the first trimester (81). Serum ASA were present in 11.8% of the women with successful pregnancies, but were found in 43.8% of the women who miscarried and in 38.2% of women who did not conceive. Both IgG and IgA ASA were present in 37.5% of those women who miscarried (81). In a separate study, the isotype and regional specificity of serum ASA of women with recurrent spontaneous abortions were examined (82). It was found that there was a statistically significant correlation between the presence of IgG tail-directed ASA and a history of spontaneous abortion. However, no correlation could be seen with sperm head-directed IgG or IgA ASA (82). Further evidence that ASA influence the rate of miscarriage can be seen in IVF settings where intracytoplasmic sperm injection (ICSI) technique was used. In a study of couples undergoing ICSI, Lahteenmaki et al. (35) found that FERTILITY & STERILITY威
spontaneous abortion occurred in 38.5% of the pregnancies that resulted from fertilization using sperm with ASA. In contrast, none of the pregnancies that resulted from sperm without ASA ended in spontaneous abortion. In a separate study, Check et al. (83) injected oocytes with sperm of varying percentage of surface ASA and found that pregnancies that resulted from using sperm with lower percentage of binding (⬍50%) resulted in fewer spontaneous abortions (14% vs. 25%) than those pregnancies that resulted from using sperm with a high percentage ASA binding (⬎80%). These data suggest that injecting sperm with ASA still resulted in a higher spontaneous abortion rate than using sperm without ASA and that ASA may, therefore, affect the processes of fertilization and implantation.
CONCLUSION In the light of these lines of evidence, we can conclude ASA have multiple effects on various facets of fertilization, such as acrosome reaction, capacitation, fertilization, and implantation. However, the evidence for each of these effects of ASA remains controversial. During the past decade, our knowledge of the role of ASA in infertility has progressed relatively little. It is likely that little progress will continue to be made in understanding the clinical significance of ASA until current diagnostic tests, which detect antibody binding to sperm but do not examine the antigenic specificities of the ASA, are replaced by antigen-specific assays that allow for the study of the effects of ASA on individual sperm proteins. References 1. Mosher WD, Pratt WF. Fecundity and infertility in the United States: incidence and trends. Fertil Steril 1991;56:192–3. 2. Ayvaliotis B, Bronson R, Rosenfeld D, Cooper G. Conception rates in couples where autoimmunity to sperm is detected. Fertil Steril 1985; 43:739 – 42. 3. Collins JA, Burrows EA, Yeo J, Young Lai EV. Frequency and predictive value of antisperm antibodies among infertile couples. Hum Reprod 1993;8:592– 8. 4. Sinisi AA, Di Finizio B, Pasquali D, Scurini C, D’Apuzzo A, Bellastella A. Prevalence of antisperm antibodies by SpermMARtest in subjects undergoing a routine sperm analysis for infertility. Int J Androl 1993;16:311– 4. 5. Heidenreich A, Bonfig R, Wilbert DM, Strohmaier WL, Engelmann UH. Risk factors for antisperm antibodies in infertile men. Am J Reprod Immunol 1994;31:69 –76. 6. Omu AE, Makhseed M, Mohammed AT, Munim RA. Characteristics of men and women with circulating antisperm antibodies in a combined infertility clinic in Kuwait. Arch Androl 1997;39:55– 64. 7. Helmerhorst FM, Finken MJ, Erwich JJ. Antisperm antibodies: detection assays for antisperm antibodies: what do they test? Hum Reprod 1999;14:1669 –71. 8. Palermo G, Devroey P, Camus M, Khan I, Wisanto A, Van Steirteghem AC. Assisted procreation in the presence of a positive direct mixed antiglobulin reaction test. Fertil Steril 1989;52:645–9. 9. Vazquez-Levin MH, Notrica JA, Polak de Fried E. Male immunologic infertility: sperm performance on in vitro fertilization. Fertil Steril 1997;68:675– 81. 10. Tian X, Zhang L, Wu Y, Yang C, Liu P. Relationship between serum antisperm antibodies and anticardiolipin antibodies and clinical pregnancy outcome in an in vitro fertilization and embryo transfer program. Chin Med J (Engl) 1999;112:34 – 6. 11. Acosta AA, van der Merwe JP, Doncel G, Kruger TF, Sayilgan A, Franken DR, et al. Fertilization efficiency of morphologically abnormal spermatozoa in assisted reproduction is further impaired by antisperm antibodies on the male partner’s sperm. Fertil Steril 1994;62:826 –33.
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