Role and regulation of EGFR in actin remodeling in sperm capacitation and the acrosome reaction

To bind and fertilize the egg, the spermatozoon should undergo few biochemical and motility changes in the female reproductive tract collectively called capacitation. The capacitated spermatozoon binds to the egg zona pellucida, and then undergoes the acrosome reaction (AR), which allows its penetration into the egg. The mechanisms regulating sperm capacitation and the AR are not completely understood. In the present review, we summarize some data regarding the role and regulation of the epidermal growth factor receptor (EGFR) in these processes. In the capacitation process, the EGFR is partially activated by protein kinase A (PKA), resulting in phospholipase D (PLD) activation and actin polymerization. Protein kinase C alpha (PKCα), which is already activated at the beginning of the capacitation, also participates in PLD activation. Further activation of the EGFR at the end of the capacitation enhances intracellular Ca(2+) concentration leading to F-actin breakdown and allows the AR to take place. Under in vivo conditions, the EGFR can be directly activated by its known ligand epidermal growth factor (EGF), and indirectly by activating PKA or by transactivation mediated by G protein-coupled receptors (GPCRs) activation or by ouabain. Under physiological conditions, sperm PKA is activated mainly by bicarbonate, which activates the soluble adenylyl cyclase to produce cyclic adenosine monophosphate (cAMP), the activator of PKA. The GPCR activators angiotensin II or lysophosphatidic acid, as well as ouabain and EGF are physiological components present in the female reproductive tract.     

Synchronous assay for human sperm capacitation and the acrosome reaction

A synchronous acrosome reaction system was established for human spermatozoa. Seminal plasma is removed from the spermatozoa by centrifugation and the washed spermatozoa are capacitated in a modified BWW medium (without exogenous substrates) containing 35 mg/ml human serum albumin for 3 h at 37 C. Subsequently, 10 microM ionophore A23187 (final concentration) is added, the mixture incubated for 15 min at 37 C and the percent acrosome reaction determined by a modified triple stain technique (trypan blue stain omitted). Since no significant decrease in sperm motility occurs during incubation or after ionophore treatment, a vital stain does not need to be employed, allowing the use of any acrosome detection technique. The average percentage of acrosome-rejected spermatozoa after ionophore treatment (40 +/- 10%) was about 2- to 3-fold higher than that seen without ionophore treatment. Ionophore treatment for 15 min failed to stimulate the acrosome reaction in spermatozoa incubated for less than 3 h. Additionally, the presence of substrates in the BWW medium, higher sperm numbers, increased ionophore concentrations or longer incubation periods did not enhance the induction of the acrosome reaction. Ionomycin, a more specific calcium ionophore than A23187, produced essentially the same results as A23187 but tended to decrease sperm motility. This synchronous acrosome reaction system for human spermatozoa is relatively simple and can be used to study the effect of modulators on capacitation and/or the acrosome reaction.     

Mechanism of sperm capacitation and the acrosome reaction: role of protein kinases

Mammalian sperm must undergo a series of biochemical and physiological modifications, collectively called capacitation, in the female reproductive tract prior to the acrosome reaction (AR). The mechanisms of these modifications are not well characterized though protein kinases were shown to be involved in the regulation of intracellular Ca²⁺ during both capacitation and the AR. In the present review, we summarize some of the signaling events that are involved in capacitation. During the capacitation process, phosphatidyl-inositol-3-kinase (PI3K) is phosphorylated/activated via a protein kinase A (PKA)-dependent cascade, and downregulated by protein kinase C α (PKCα). PKCα is active at the beginning of capacitation, resulting in PI3K inactivation. During capacitation, PKCα as well as PP1γ2 is degraded by a PKA-dependent mechanism, allowing the activation of PI3K. The activation of PKA during capacitation depends mainly on cyclic adenosine monophosphate (cAMP) produced by the bicarbonate-dependent soluble adenylyl cyclase. This activation of PKA leads to an increase in actin polymerization, an essential process for the development of hyperactivated motility, which is necessary for successful fertilization. Actin polymerization is mediated by PIP₂ in two ways: first, PIP₂ acts as a cofactor for phospholipase D (PLD) activation, and second, as a molecule that binds and inhibits actin-severing proteins such as gelsolin. Tyrosine phosphorylation of gelsolin during capacitation by Src family kinase (SFK) is also important for its inactivation. Prior to the AR, gelsolin is released from PIP₂ and undergoes dephosphorylation/activation, resulting in fast F-actin depolymerization, leading to the AR.     

Activation of protein kinase A during human sperm capacitation and acrosome reaction

Spermatozoa undergo a variety of changes during their life that are prerequisites to their maturation and ability to fertilize eggs. Mammalian sperm capacitation and acrosome reaction are regulated by signal transduction systems involving cyclic adenosine monophosphate (cAMP) as a second messenger. This second messenger acts through the activation of protein kinase A (PKA) and indirectly regulates protein tyrosine phosphorylation. cAMP levels are controlled by a balance of phosphodiesterases (PDEs) and adenylyl cyclase (AC) enzymatic activities, which are responsible for its degradation and production, respectively. The aim of this study was to evaluate the possible relationship between the intracellular levels of cAMP and PDE and PKA activities during human sperm capacitation induced by fetal cord serum ultrafiltrate (FCSu) and acrosome reaction induced by calcium ionophore A23187. We report that PKA activity was higher in capacitating than in noncapacitating spermatozoa and that intracellular levels of cAMP decreased but that PDE activity remained constant during capacitation. The acrosome reaction induced by A23187 was associated with increases in cAMP and PKA activity but not in PDE activity. These results strongly suggest that net cAMP concentration is under the control of AC, since PDE activity is constant during sperm capacitation and the acrosome reaction. Moreover, the results suggest that low levels of cAMP are sufficient for capacitation and PKA activation and/or that the cAMP concentration measured in whole spermatozoa does not reflect the effective intracellular cAMP levels present in specific compartments of these cells.     

酸性磷酸酶检测评价人精子获能和顶体反应

目的 探讨酸性磷酸酶(ACP)检测评价人精子获能和顶体反应(AR)的可行性。方法 32名健康生育男性的精子悬液，于37℃下孵育lh获能，用孕酮在有无苯甲基磺酰氟(PMSF)下诱导AR15、30、45、60min，分别检测获能前后及AR各时间点的精子悬液上清中ACP活性，同时用CASA分析精子运动参数证实精子发生获能和AR。结果 精子获能前后的ACP活性无显著性差异；AR(有PMSF)各时间点的ACP活性显著高于获能前后及不加PMSF时的ACP活性；CASA分析证实，精子运动参数的改变与其发生获能和AR的运动特性一致。结论 ACP分析为一种简便易行、耗时少、能反映精子群体AR状态的较为客观的方法，但蛋白酶的潜在影响不容忽视。     

Human sperm chromatin undergoes physiological remodeling during in vitro capacitation and acrosome reaction

Capacitation (CAP) and acrosome reaction (AR) are sequential processes of sperm activation. Beside the known ionic, membrane, and transduction events and final release of proteolytic enzymes that help sperm movement toward the egg, chromatin changes, such as a physiological remodeling, are also possible. Our aims were to ascertain that CAP and AR do not induce DNA damage and to evaluate changes occurring in the human sperm head during these physiological processes using cytochemical stains. Percollpurified spermatozoa from normal donors were incubated in Biggers, Whitten, and Whittingham medium ± fetal cord serum ultrafiltrate (CAP inducer) and then with lysophosphatidylcholine (AR inducer). CAP and AR were associated with increases in aniline blue (AB, for histones; ～70%) and toluidine blue (TB, for chromatin compaction; ～40%) staining but had no influence on that of chromomycin A3 (for protamines). The increase (～40%) in iodoacetamide-fluorescein (IAF, for sulfhydryl groups) staining observed during CAP was absent after AR. CAP and AR did not damage DNA (percentage of DNA fragmentation index remained low) nor affect histone content. CAP, and even more AR, primed sperm heads to decondense (～80% and ～140% increases, respectively) when challenged with sodium dodecyl sulfate + dithiothreitol. Interestingly, induced decondensation correlated with all other tests (CAP, AB, TB, and IAF). Therefore, the data strongly support a physiological remodeling of nondamaged human sperm chromatin during CAP and AR, and modifications are probably interlinked and help prepare chromatin for postfertilization events.     

Monoclonal antibodies to canine intra-acrosomal sperm proteins recognizing acrosomal status during capacitation and acrosome reaction

Summary.  Monoclonal antibodies Ds-1 and Ds-2 specifically labelling dog sperm acrosome were prepared by immunization of mice with acetic acid extracts of dog spermatozoa. Electron microscopy and indirect immunofluorescence localized the site of Ds-1 and Ds-2 proteins inside the acrosomal vesicle. Ds-1 antibody detected 55, 76, 115, 120 and 190kDa proteins under non-reducing conditions, and 73 kDa and 54 kDa proteins after reduction (p73/Ds-1 and p54/Ds-1). 92 kDa and 40 kDa proteins recognized by Ds-2 (p92/Ds-2 and p40/Ds-2) migrated at > 200 kDa in the absence of reducing agent. In vivo , p73/Ds-1 and p54/Ds-1 are therefore likely to be present both in free and complexed form, while all of p92/Ds-2 and p40/Ds-2 form disulfide-bonded complexes. Decrease in the rate of acrosomes stained with Ds-1 and Ds-2 was correlated with the progress of capacitation resulting in the increased rate of spontaneous acrosome reactions, as suggested by a dramatic effect of A23187. Monoclonal antibody to boar acrosin (ACR-2) recognized dog sperm acrosin homologue. A higher rate of ACR-2-negative spermatozoa was observed after capacitation and A23187 treatment compared to Ds-1 and Ds-2, indicating that proteins recognized by Ds-1 and Ds-2 are localized in a specific compartment of acrosome, distinct from acrosin and possibly representing fraction of acrosomal matrix.     

Stimulation of capacitation and the acrosome reaction in ejaculated buffalo (Bubalus bubalis) sperm and the effects of a sperm motility factor

The conditions for stimulation of in vitro capacitation and the acrosome reaction of ejaculated buffalo sperm has been determined. Washed ejaculated sperm were successfully capacitated in BWW medium supplemented with bovine serum albumin (BSA) and a sperm motility factor(s) (SMF(s) isolated from the adrenal glands of rats. The acrosome reaction was induced in capacitated sperm by introducing Ca++ ions (final concentration 5 mM) into the medium. Supplementation of BWW medium with SMF(s) in the presence of BSA significantly increased the percentage of sperm showing capacitation and the acrosome reaction. SMF(s) also significantly increased the percentage motility, the percentage forward motility and maintained a higher percentage of live sperm in BWW medium under the conditions used in this study. The significance of the present findings is discussed.     

Fluorometric study of rabbit sperm head membrane phospholipid asymmetry during capacitation and acrosome reaction using Annexin-V FITC

This study was conducted to evaluate phosphatidylserine translocation in head plasma membrane of Percoll-gradient purified of rabbit cauda epididymal sperm during capacitation and acrosome reaction (AR) using Annexin-V. Propidium iodide was used as control to reject dead or dying cells. The presence and distribution of Annexin-V binding sites were analyzed using flow fluorocytometry and confocal microscopy. After 6 h of incubation of sperm in capacitation medium, the number of cells positively stained with Annexin-V showed a small but significant increment. The Annexin-V binding sites produced during capacitation were found mainly in the post-acrosomal region of the sperm head plasma membrane. After AR induction with progesterone, the localization of phosphatidylserine was changed and the Annexin-V binding sites were found almost only in the acrosomal region, but with higher number of binding sites in the equatorial area. On the contrary, after AR induction with A23187, phosphatidylserine translocation, although predominant over the acrosomal region, was also observed in the post-acrosomal region. Plasma membrane destabilization during capacitation and AR may be important for sperm-oocyte fusion.     

Antibodies to human sperm YLP12 peptide that is involved in egg binding inhibit human sperm capacitation/acrosome reaction

Recently, the authors reported a novel dodecamer peptide sequence, designated as YLP12 on human sperm, that is involved in binding to zona pellucida (ZP) of human oocyte [10]. This unique sequence is present on the acrosomal region of the human sperm cell and is expressed only in human testis/ sperm. The aim of the present study was to examine whether YLP12 sequence is involved in capacitation/acrosome reaction. Swim-up sperm were capacitated with anti-YLP12 Fab' antibodies or control Fab's (40 and 85 microg/mL) and then the acrosome reaction was induced with calcium ionophore. An average of 64-73% sperm underwent acrosome reaction when they were capacitated in the presence of 40-85 microg/mL of bovine serum albumin or control Fab's. A significant (p < .01 to < .001) reduction (58-75%) in the percentage of acrosome-reacted sperm was observed when the sperm were capacitated in the presence of YLP12 Fab's. These data indicate that the YLP12 peptide sequence is involved in sperm capacitation / acrosome reaction, and may find clinical applications in the diagnosis and treatment of male infertility and immunocontraception.     

The cyclic GMP-specific phosphodiesterase inhibitor, sildenafil, stimulates human sperm motility and capacitation but not acrosome reaction

Capacitation is the series of transformations that spermatozoa undergo in the female genital tract in order to bind to the zona pellucida, initiate the acrosome reaction, and fertilize an egg. Cyclic adenosine monophosphate (cAMP) plays an important role in this process and its levels are regulated by 2 key enzymes, adenylyl cyclase and cyclic nucleotide phosphodiesterase (PDE), the latter being involved in cAMP degradation. Evidence was provided for the involvement of PDE in sperm motility and capacitation. Of the 10 gene families of PDE that exist in mammalian tissues, the calcium-calmodulin-dependent (type 1) and the cAMP-specific (type 4) have been found in human spermatozoa. Using sildenafil, we investigated a highly potent cyclic guanosine monophosphate (cGMP)-specific PDE (type 5) inhibitor and whether this PDE is present in human spermatozoa and is involved in sperm functions. Sildenafil inhibited PDE activity of Percoll-washed spermatozoa with an IC50 of 97+/-3 and 33+/-3 microM when cAMP and cGMP, respectively, were used as substrates. Because the IC50 of sildenafil obtained for PDE type 5 is much lower (2 to 6 nM) than that obtained with sperm PDE, the data suggest that PDE type 5 represents only a small fraction of the whole PDE activity of spermatozoa. Sildenafil causes dose-dependent increases in sperm cAMP levels and capacitation, which are associated with an increase in the levels of tyrosine phosphorylation of 2 fibrous sheath proteins (p105/81). Sperm velocity, amplitude of lateral head displacement, and hyperactivation were increased at 30-180 minutes. Sildenafil did not trigger the acrosome reaction in capacitated spermatozoa. These results suggest that under our experimental conditions, sildenafil triggers human sperm motility and capacitation, probably via its inhibitory action on PDE activity other than type 5 with a resultant rise in cAMP levels.     

Zona pellucida mediated acrosome reaction and sperm morphology

Summary. Sperm samples from 29 men randomly selected from the andrology laboratory, were used to evaluate acrosome reaction response to solubilized human zona pellucida. Capacitated sperm samples were exposed to a solution containing 2 zona pellucidae (ZP) per μl for 60 min, after which acrosomal status were recorded using a PSA-FITC technique. Controls included samples supplied by fertile sperm donors. After completion of acrosome reaction studies, patient samples were divided according to the percentage of morphologically normal spermatozoa. Three basic groups were identified, namely, fertile donors, teratozoo-spermic (normal sperm morphology 5–14%; n = 25) and severely teratozoospermic (normal sperm morphology <4%; n = 4) groups. The mean percent normal sperm were 15.8 ± 0.9, 10.4 ± 0.7 and 2.7 ± 0.7, respectively, for normozoospermic donors, teratozoospermic and severely teratozoospermic men. The mean percentage (± SE) ZP mediated acrosome reacted sperm among teratozoospermic and severely teratozoospermic cases was 25.8% ± 0.9 and 19.0% ± 0.9 (P = 0.001), compared to 36.8% ± 0.9 for the donor controls. Results were analysed and expressed as correlations between sperm morphology and acrosomal response to human solubilized zona pellucida, spontaneous and calcium ionophore induced acrosome reaction. Predictive values for acrosome responsiveness were depicted with ROC curve analyses. Sperm morphology evaluated by strict criteria correlated positively and highly significantly with the responsiveness of the acrosome reaction (r = 0.91, P = 0.0001). At a morphology cut-off value of 4%, the ROC curve analysis showed sperm morphology to be highly predictive of zona pellucida induced acrosome responsiveness with a sensitivity of 100% and negative predictive value of 100%. Spontaneous and calcium ionophore induced acrosome reactions revealed no correlation with sperm morphology. It was concluded that (i) morphological features of human spermatozoa are indicative of specific functional characteristics; (ii) zona pellucida induction of the acrosome reaction is superior, as a predictor of sperm morphology, compared to calcium ionophore induced and spontaneous acrosome reactions.     

Albumin is required for the guinea pig sperm capacitation but is not essential for acrosome reaction and fusion with eggs.

The importance of serum albumin in supporting guinea pig sperm capacitation, acrosome reaction, and fusion with eggs in vitro was studied by incubating the spermatozoa in albumin-free medium containing different synthetic polymers. Serum albumin was found to be an obligatory component in the incubating medium for the capacitation of guinea pig spermatozoa. Albumin in the medium is not essential for the acrosome reaction and fusion with the eggs, but these phenomena take place most efficiently in presence of albumin.     

Role of ions and ion channels in capacitation and acrosome reaction of spermatozoa

Capacitation and acrosome reaction are important prerequisites of the fertilization process. Capacitation is a highlycomplex phenomenon occurring in the female genital tract, rendering the spermatozoa capable of binding and fusionwith the oocyte. During capacitation various biochemical and biophysical changes occur in the spermatozoa and thespermatozoal membranes. Ions and ion channels also play important roles in governing the process of capacitation bychanging the fluxes of different ions which in turn controls various characteristics of capacitated spermatozoa. Alongwith the mobilization of ions the generation of free radicals and efflux of cholesterol also plays an impo~.nt role in thecapacitation state of the spermatozoa. The generation of free radical and efflux of cholesterol change the mechano-dynamic properties of the membrane by oxidation of the polyunsaturated lipids and by generating the cholesterol freepatches. The process of capacitation renders the spermatozoa responsive to the inducers of the acrosome reaction. Theglycoprotein zona pellucida 3 (ZP3) of the egg coat zona pellucida is the potent physiological stimulator of the acro-some reaction; progesterone, a major component of the follicular fluid, is also an inducer of the acrosome reaction.The inducers of the acrosome reaction cause the activation of the various ion-channels leading to high influxes of calci-um, sodium and bicarbonate. The efflux of cholesterol during the process of capacitation alters the permeability of themembrane to the ions and generate areas which are prone to fusion and ve.siculation process during the acrosome reactioa. this review focuses mainly on effects of the ion and ion-channels, free radicals, and membrane fluidity changesduring the process of capacitation and acrosome reaction.     

Effect of freezing–thawing on the expression of mannose-ligand receptors on human spermatozoa: the impact on sperm capacitation and acrosome reaction

The aim of this study was to evaluate the change in the expression of mannose-ligand receptors following a freezing-thawing procedure, in order to assess its impact on sperm capacitation and acrosome reaction. Twenty semen samples were obtained from fertile donors. Sperm samples were divided into two equal volumes. One aliquot was cryopreserved and the other aliquot was incubated at 32 degrees C. After 2 h the frozen sample was thawed and both samples were further incubated at 32 degrees C to allow capacitation. Mannose receptors were examined following 4 and 22 h of incubation using a mannosylated-BSA-FITC probe. The expression of mannose-ligand receptors on the sperm plasma membrane was determined according to the fluorescence pattern: pattern I represents pre-capacitation, pattern II represents capacitated spermatozoa and pattern III represents acrosome-reacted spermatozoa. After 4 h incubation in capacitating medium, the percentages of patterns I, II and III were 90, 7 and 3% for fresh spermatozoa and 89, 8 and 3% for frozen-thawed spermatozoa, respectively (P > 0.05). Following 22 h of incubation, the percentages of patterns I, II and III were 84, 11 and 5 for fresh spermatozoa and 83, 11 and 6% for frozen-thawed spermatozoa, respectively (not significant at P > 0.05). The percentages of patterns II and III in fresh and frozen-thawed spermatozoa were increased by the same magnitude with longer incubation in the capacitating conditions. It was concluded that the freezing-thawing procedure for human spermatozoa does not affect the expression of mannose-ligand receptors and the dynamics of sperm pre-fertilization processes.     

Subcellular distribution of phospholipase A2 and ATPases during capacitation and acrosome reaction in guinea pig spermatozoa

The presence, distribution, and levels of phospholipase A2 and ATPases activities in those structures of the guinea pig spermatozoa that participate in the acrosome reaction were studied, both before and after capacitation, as well as during the acrosome reaction induced in vitro. Spermatozoa were collected from the cauda epididymis and incubated in the absence and presence of 1.15 mmol/L calcium, with and without the addition of 1 mumol/L A23187. Membrane fractions were recovered by vortexing and discontinuous sucrose density gradient centrifugation. Most of the Na+, K(+)-ATPase was recovered in the acrosome-free spermatozoa, but a clear, distinct presence of this enzyme was observed in the plasma membrane (25 against 101 nmoles Pi released per milligram of protein, respectively). The activity of this enzyme in the periacrosomal plasma and in the outer acrosomal membrane increased during calcium incubation. Ca2(+)-dependent ATPase was found in both membrane fractions, being higher in the periacrosomal plasma membrane. The addition of calcium induced a significant inhibition of this acrosomal ATPase, whereas the activity in the acrosome-free spermatozoa increased. The activity of phospholipase A2, under all experimental conditions, was found to be restricted to the soluble fraction.     

Effect of leptin on motility, capacitation and acrosome reaction of human spermatozoa

Leptin is a polypeptide hormone with important roles in reproduction. It has been detected in human seminal plasma as well as on human ejaculated spermatozoa. This study aimed at studying the possible role of leptin in regulating human sperm functions. Immunofluorescent staining was used to study the expression of leptin and its receptor. The correlation between the concentration of leptin and soluble leptin receptor (ObRs) in seminal plasma as measured by enzyme-linked immunosorbant assay and sperm motility parameters measured by computer-assisted sperm analyais (CASA) was determined. The effects of recombinant leptin on human sperm motility, capacitation and acrosome reaction as measured by chlortetracycline staing were also studied. Leptin immunoreactivity was demonstrated at the equatorial and neck regions of human spermatozoa, whereas that of ObRs was shown up on the tail. After Percoll separation, spermatozoa with high density had more intense leptin immunoreactivity compared with those with low density. No significant correlation was found between seminal plasma concentration of leptin/ObRs and sperm motility parameters. After incubation with recombinant human leptin for either 3 h or overnight, there was no change in all the CASA motility parameters determined and percentages of capacitated and acrosome-reacted spermatozoa. We concluded that leptin does not have a significant effect on motility and capacitation/acrosome reaction in human ejaculated mature spermatozoa. Its role in male reproduction is yet to be determined.     

Effect of zinc on human sperm motility and the acrosome reaction

This study has assessed the effect of zinc on human sperm motility and the acrosome reaction in vitro. Progressively motile human sperm were selected by swim-up and by glass bead columns and then incubated in a medium in which capacitation happened in an asynchronous way. Different doses of zinc (1, 10, 100 and 1000 microM) were added for periods of 2, 4 or 6 h. Other samples were incubated with zinc (1000 microM), and after 1 h incubation, the zinc was removed. Aliquots of each culture were used to evaluate progressive motility and the acrosome reaction using a triple-stain technique. Sperm motility was reduced when the amount of zinc added was greater than or equal to 100 microM, and these doses also caused a significant reduction in the % of sperm undergoing the acrosome reaction. After removal of zinc and further incubation in zinc-free medium for 1 h, an increase in the percentage of motile and acrosome-reacted sperm was observed. However, the increase in acrosome reaction did not reach the values observed in controls. Results suggest that extracellular zinc acts as an inhibitor of human sperm motility and the acrosome reaction (and/or capacitation and the acrosome reaction). This inhibitory effect is reversible and occurs in a dose-dependent fashion. The probable mechanisms involved are discussed.     

IgA抗精子抗体对精子顶体反应的影响

目的 探讨精浆中IgA抗精子抗体对人精子顶体反应的影响。方法 利用免疫珠法（IBT）筛选出IgA抗精子抗体阳性精浆标本同正常人精子孵育，以孕酮诱发精子顶体反应；以特异性荧光标记物．络合异硫氰酸荧光素的花生凝集素（FITC-PNA）标记精子顶体，通过流式细胞仪检测精子顶体完整性。结果 与IgA抗精子抗体阳性精浆孵育的精子，其孕酮诱发的顶体反应发生率明显低于正常精浆及精子培养液组（P〈0．01），正常精浆组及精子培养液组间无显著性差异（P〉0．05）；IgA抗精子抗体阳性精浆组、正常精浆组、精子培养液组自发顶体反应的发生率无显著性差异（P〉0．05）。结论 免疫性不育患者精浆中的IgA抗精子抗体可以明显抑制孕酮诱发的顶体反应的发生，可能是导致不育的原因之一。