Application of a sperm micro-immobilization test to cervical mucus in the investigation of immunologic infertility

Sex difference in anti-sperm antibodies

Background

Some diseases have sex differences. There have been no reports on the relationship between anti‐sperm antibodies (ASA) and sex differences.

Methods

ASA are detected by sperm‐immobilization test using patients' sera in women. In men, the ASA testing is generally performed by direct‐immunobead test.

Main findings

Sperm‐immobilizing antibodies in women inhibit sperm migration in their genital tract and exert inhibitory effects on fertilization. ASA bound to sperm surface in men also show inhibitory effect on sperm passage through cervical mucus. The fertilization rate of IVF significantly decreased when sperm were coated with higher numbers of ASA. For women with the antibodies, it is important to assess individual patients' SI₅₀ titers. In patients with continuously high SI₅₀ titers, pregnancy can be obtained only by IVF. For men with abnormal fertilizing ability by ASA, it is necessary to select intracytoplasmic sperm injection. Production of sperm‐immobilizing antibodies is likely to occur in women with particular HLA after exposure to sperm. The risk factors for ASA production in men are still controversial.

Conclusion

Attention to sex differences in specimens, test methods and the diagnosis of ASA should be paid. For patients with ASA, treatment strategies have been established by considering sex difference for each.

Relationship between level of serum sperm immobilizing antibody and its inhibitory effect on sperm migration through cervical mucus in immunologically infertile women

PROBLEM

Sperm immobilizing antibodies often interfere with the penetration of sperm through the cervical mucus. However, the relationship between sperm immobilizing antibody titer and the result of the post-coital test (PCT) has not yet been clarified. The aim of this study was to investigate whether the 50% sperm immobilization unit (SI50) titer, a quantitative measure of sperm immobilizing antibody, in patients' sera was correlated with the result of PCT.

METHOD OF STUDY

The sperm immobilization test (SIT) was performed for 2834 infertile women in two university hospitals. The SI50 titers were evaluated by quantitative SIT. In some cases with sperm immobilizing antibody, PCT was carried out before ovulation and assessed according to the criteria of World Health Organization (1992). Infertile couples with abnormal semen characteristics were excluded.

RESULTS

Seventy-four of 2834 women had sperm immobilizing antibodies in their sera, giving a positive rate of 2.6%. Twenty-four (77.4%) of 31 women with sperm immobilizing antibodies and 28 (20.4%) of 137 women without the antibody had abnormal PCT results. There was a significant difference between the two groups (P<0.0001). When patients with sperm immobilizing antibodies were divided into two groups according to the SI50 titers, the abnormal result of PCT was obtained in all 10 patients with high (>10) SI50 titers, while that was 14 (66.7%) in 21 patients with low (10) SI50 titers. There was a significant difference between the two groups (P=0.04).

CONCLUSION

The SI50 titer in the serum can predict inhibitory effects on sperm migration through cervical mucus in immunologically infertile women. Evaluation of the SI50 titers in patients' sera seems to be useful for decision-making in infertile women with sperm immobilizing antibodies regarding whether they have the possibility of conceiving by timed intercourse.

Antisperm antibodies in women undergoing intrauterine insemination

Intrauterine insemination is widely used for the treatment of infertility as a result of cervical or male factors or empirically before in vitro fertilization or gamete intrafallopian transfer. This study was designed to confirm or refute the theoretical concern that intrauterine insemination may induce antisperm antibodies in such women. Serum and cervical mucus were obtained at the first, fourth, and sixth intrauterine inseminations. The serum was screened by the Immunobead test for IgG and IgA. If screening results were positive (greater than 10% binding), antisperm antibodies were titered by the microimmobilization and microagglutination tests. The Immunobead test was performed on the cervical mucus after liquefication with bromelin. Ninety-three patients were followed up prospectively. Of these, 40 completed six intrauterine insemination cycles and the remaining 53 completed four cycles. Low transient antisperm antibody levels were detected in 10.8% of the patients and would not be expected to affect the prognosis for fertility. It is concluded that intrauterine insemination does not induce significant antisperm antibody production in women.

Techniques for sperm immobilization test

Several semiquantitative, quantitative, and microassay techniques had been developed to detect antibodies bound to human spermatozoa: sperm agglutination test (SAT), sperm immobilization test (SIT), immunofluorescence test, radioantiglobulin test, enzyme-linked immunosorbent assay (ELISA), mixed erythrocyte-spermatozoa antiglobulin reaction (MAR), "Panning" test, and immunobead test (IBT). Clinical application of these techniques include (a) detection of sperm immobilizing antibodies in sera of sterile women, (b) follow-up study of sperm immobilizing antibodies, and (c) detection of sperm immobilizing antibodies in cervical mucus and other secretions. The chemical structure of antigen epitope corresponding to Mab H6-3C4 may recognize the internally located repetitive unbranched N-acetyllactosamine structure, regardless of terminal substitution at Gal (i.e., sialyl-i as well as i structure). The majority of sperm-immobilization (SI) positive women's sera were absorbed with carbohydrate components on ejaculated sperm, but only one serum competed with Mab H6-3C4 on binding to sperm except a serum from whom lymphocytes were donated to make Mab H6-3C4. The SI agglutinating antibodies (Abs) in women's sera were raised to the carbohydrate epitopes of glycoprotein in HSP, but epitopes might have several different conformational structures. Studies are in progress to find whether or not SI-Abs could be generated to peptide epitope of human seminal plasma (HSP) or sperm.

Interaction between human cervical mucus and sperm surface antibodies

The immunobead test was used to study the immunoglobulin class of antibodies on sperm before and after penetration through a microcolumn of cervical mucus. Sixteen men with positive sperm antibodies (positive sperm immobilization test) and sperm that penetrated cervical mucus in prior tests were selected for study. However, at the time of study, sperm from seven subjects could not be recovered from the microcolumn. The nine subjects from whom motile sperm were obtained after passage through the column had better sperm mucus penetration tests, lower proportions of sperm binding to anti-IgA immunobeads, and higher proportions of sperm with tail-tip-only binding. Sperm recovered after penetration through the mucus microcolumn displayed a greatly reduced binding to anti-IgA immunobeads in all nine subjects, whereas similar reductions in anti-IgG binding occurred only in four subjects. These results confirm that IgA and sperm-head-directed antibodies are more important than IgG and sperm tail-tip-directed antibodies in impairing sperm penetration of cervical mucus.

Detection of antispermatozoal antibodies of IgG, IgA, and IgM immunoglobulin classes in cervical mucus

The immunobead test (IBT) was applied to bromelin-treated cervical mucus (CM) samples from 78 infertile women. Seven (8.9%) of the patients were positive for IgG and/or IgA class antibodies, whilst none (0/35) were found positive for IgM class antibodies. We found that 57% of the positive samples contained IgG and IgA classes, whilst the remaining samples contained IgA alone. The implications of these results were discussed.

Detection of antispermatozoal antibodies of IgA class in cervical mucus

A simple procedure for detection of antisperm antibodies of IgA class in human cervical mucus is described and the results of its application to samples from 102 patients are presented. The results suggest that the IgA immunobead test (IgA-IBT) is a specific and clinically useful test for sperm antibodies. There was a strong correlation between the IgA-IBT and the presence of complement-dependent sperm immobilization in serum (Spearman's, r = 0.92, p less than 0.001). Positive IgA-IBT results occurred only in mucus samples that showed poor penetration by normal sperm. An added advantage of the IgA-IBT is that both the immunoglobulin class and the site of binding to the sperm surface can be determined simultaneously.

Are sperm immobilizing antibodies in cervical mucus an explanation for a poor postcoital test?

Previous authors reported high incidences of complement dependent sperm immobilizing antibodies in cervical mucus (CM) and found a correlation with poor postcoital tests. In all those investigations the CM samples were tested after dilution with a salt solution. In the present study we investigated 50 CM samples from infertile couples who had during the routine fertility investigation poor postcoital tests. All CM samples were tested after dilution with an equal volume of normal human serum; only one sample was found positive. On the other hand, if the CM samples were diluted with an equal volume of a buffered salt solution, many positive results were obtained. With some guinea pig serum batches, however, all tests with buffer-diluted CM samples were negative, despite good reaction of the positive control serum. We concluded that the positive results with buffer-diluted CM samples were due to a factor in the animal serum used as complement preparation and that complement-dependent sperm immobilizing antibodies in CM are an unlikely cause of a poor postcoital test.

Monoclonal antibody inducing human sperm agglutination

A mouse fused splenic cell line producing antibody that induces agglutination of human sperm was cultivated. The antibody was localized to the midpiece and tail of human spermatozoa by an indirect immunofluorescence method. The interacting antigen was identified in a sperm membrane protein preparation by SDS gel/protein blot immunofluorescence method. The molecular weight of the antigen was in the vicinity of 84 Kdaltons.