An improved indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antisperm antibodies

Defects in the regulatory clearance mechanisms favor the breakdown of self-tolerance during spontaneous autoimmune orchitis

We identified aberrations leading to spontaneous autoimmune orchitis (AIO) in mink, a seasonal breeder and natural model for autoimmunity. This study provides evidence favoring the view that a malfunction of the clearance mechanisms for apoptotic cell debris arising from imbalances in phagocyte receptors or cytokines acting on Sertoli cells constitutes a major factor leading to breakdown of self-tolerance during spontaneous AIO. Serum anti-sperm antibody titers measured by ELISA reflected spermatogenic activity without causing immune inflammatory responses. Orchitic mink showed excess antibody production accompanied by spermatogenic arrest, testicular leukocyte infiltration, and infertility. AIO serum labeled the postacrosomal region, the mid and end piece of mink sperm, whereas normal mink serum did not. Normal serum labeled plasma membranes, whereas AIO serum reacted with germ cell nuclei. Western blot analyses revealed that AIO serum reacted specifically to a 23- and 50-kDa protein. The number of apostain-labeled apoptotic cells was significantly higher in orchitic compared with normal tubules. However, apoptosis levels measured by ELISA in seminiferous tubular fractions (STf) were not significantly different in normal and orchitic tubules. The levels of CD36, TNF-alpha, TNF-alpha RI, IL-6, and Fas but not Fas-ligand (L), and ATP-binding cassette transporter ABCA1 were changed in AIO STf. TNF-alpha and IL-6 serum levels were increased during AIO. Fas localized to germ cells, Sertoli cells, and the lamina propria of the tubules and Fas-L, to germ cells. Fas colocalized with Fas-L in residual bodies in normal testis and in giant cells and infiltrating leukocytes in orchitic tubules.

The predominance of one of the SR-BI isoforms is associated with increased esterified cholesterol levels not apoptosis in mink testis

Scavenger receptor class B type I (SR-BI) contributes to HDL-mediated cellular cholesterol efflux and is a phagocytosis-inducing phospholipid phosphatidylserine receptor in rat Sertoli cells, whereas the spliced variant of the SR-B gene, SR-BII, is implicated in the efflux of free cholesterol in macrophages. This study aimed to assess whether spontaneous autoimmune orchitis (AIO), which causes impaired clearance of apoptotic germ cells and spermatogenic arrest, involves SR-BI, SR-BII, and/or cholesterol. The levels measured during development and the annual reproductive cycle in normal mink were compared with those in mink with spontaneous AIO. Time periods with lowest tubular esterified cholesterol (EC) levels showed maximal SR-BI and SR-BII levels, and the periods when one or the other SR-BI isoform predominated showed increased EC levels and spermatogenic arrest in normal mink seminiferous tubules. In tubules with AIO, the predominance of only one or the other SR-BI isoform was the reverse of that measured in normal tubules, and it was associated with an increase in EC levels but not with apoptosis levels. SR-BI and SR-BII levels were not correlated with serum testosterone levels. SR-BI mainly localized to the Leydig cell, germ cell, and Sertoli cell surface, where its distribution was stage-specific. SR-BII was principally intracellular. Tubules from testes with AIO showed a deregulation of cholesterol homeostasis and SR-BI expression but relatively unchanged apoptosis levels. These results suggest that the expression of both SR-BI isoforms is required for the maintenance of low EC levels and that the predominance of only one isoform is associated with the accumulation of EC but not with apoptosis in the tubules.

Quantitative determination of IgG and IgA on sperm from infertile patients with and without antisperm antibodies

Immunoglobulins on patients sperm were determined by an ELISA technique, modified from the RIA described by Haas and D'Cruz (Am J Reprod Immunol, 1989; 20:37-43), i.e., suspensions of washed sperm (40, 20, 10, and 5 mill/ml) were added to a dilution of peroxydase-labelled anti-IgG or anti IgA, and after incubation the supernatants were transferred to cups in microtrays, coated with IgG or IgA, respectively. After incubation and washing ELISA reaction was carried out. Known amounts of IgG and IgA were processed in the same way to obtain a standard curve, allowing the Ig on the sperm to be expressed in ng/mill sperm. Ejaculates with increased viscosity revealed high values, irrespective of MAR-results and in some cases the same was true for samples with large numbers of non-spermatozoal cells (NSC). However, among 48 samples from men from infertile couples with negative MAR, > 20 mill sperm/ml, normal viscosity, and a ratio between sperm and NSC > 5, the median for IgG was 0.2 ng/mill sperm, 90% had < or = 0.8 ng/mill sperm, and the highest value recorded was 1.9 ng/mill sperm. For IgA the median was 0.5 ng, 90% of the 47 samples contained < or = 1.9 ng, and the highest value was 3.1 ng/mill sperm. The values for sperm from patients with a positive MAR, but without free antibodies in seminal plasma, were generally within the normal range. In contrast, increased values were recorded for most of the patients with free antibodies in seminal plasma, up to 4.2 ng/mill sperm for IgG and up to 12.5 ng/mill sperm for IgA.

The use of ELISA to evaluate human antibody binding to epididymal sperm from different species

PROBLEM

The impact of antibodies to epididymal sperm antigens in human infertility has been poorly understood. Cross-reactivity of human antibodies with animal epididymal sperm has been previously observed, however, only by means of qualitative methods. Moreover, it has been always compared to reactivity against human ejaculated rather than human epididymal sperm.

METHOD

Following a screening study of 940 infertility patients, sperm agglutinating and immobilizing sera as well as sperm antibody negative controls were used to standardize an ELISA employing human ejaculated sperm. Nine sera positive in ELISA were further tested against epididymal human, guinea pig, rat, and hamster sperm. Differences among groups were evaluated by factorial analysis of variance (ANOVA).

RESULTS

The specificity and sensitivity of ELISA were shown to be 85.1% and 61.18%, respectively. Eight out of nine antisperm antibody-positive sera from infertile subjects reacted relatively stronger with epididymal than with ejaculated human sperm. All tested infertility sera showed strong although variable cross-reactivity with sperm from guinea pig, hamster, and rat.

CONCLUSION

ELISA has definite potential in sperm antibody research, allowing quantitative assessment of the results and immotile sperm employment. The suggested predominant role of epididymal sperm antigens in immune responses related to fertility needs further investigation. Some of these antigens are obviously phylogenetically preserved, and possibly in a quantitative aspect present differently on epididymal spermatozoa from various mammalian species.

Enzyme-linked immunosorbent assay (ELISA) for detecting antisperm antibodies in mice with testicular autoimmunity

We developed an ELISA for measuring antisperm antibodies in the mouse by using serum samples obtained from mice immunized with murine testicular antigens in complete Freund's adjuvant (CFA) as well as from mice rendered vasectomized. Sperm antigens used were syngeneic epididymal spermatozoa and two types of soluble, murine testicular antigens prepared in our laboratory. This study deals with a) the sequential changes of antisperm antibody levels following immunization; b) determination of immunoglobulin classes of these antibodies; c) a correlation between the absorbance values and the endpoint titers of antisperm antibodies; and d) comparison of endpoint titers of antisperm antibodies detected by ELISA with those by immunoperoxidase staining method in immune and nonimmune sera. It is suggested that serum dilution as high as 1/800 or more is required for detecting antibody titers of immune sera, because nonimmune mouse sera reveal a definite, although low, level of absorbance value at a serum dilution of 1/400 or less.

Use of specific monoclonal antibodies to secretory IgA for the detection of spermatozoal antibodies in serum and seminal plasma by enzyme-linked immunosorbent assay

The role of anti-sperm secretory IgA has recently received attention since some workers feel it plays an important role in the prognosis of the immunologically infertile couple. Current methods used in our laboratory cannot separately detect anti-sperm secretory IgA. An enzyme-linked immunosorbent assay (ELISA) utilizing specific monoclonal antibodies to secretory IgA was used to detect anti-sperm secretory IgA as well as anti-sperm monomeric IgA and IgG in serum and seminal plasma of a sperm-antibody-positive (ASA+) and sperm-antibody-negative (ASA-) group of men. Results showed significantly raised serum levels in the ASA+ group when compared to the ASA- group for anti-sperm secretory IgA (P less than .001), anti-sperm monomeric IgA (P less than .001), and anti-sperm IgG (P less than .01). Seminal plasma levels were also raised in the ASA+ group, but only significantly so for monomeric IgA (P less than .02). The performed ELISA has definite potential in research, especially with the use of monoclonal antibodies for the detection of anti-sperm secretory IgA, but cannot as yet be used as a prognostic predictor of fertility in the individual antibody-positive patient. Infertility specific antigens will have to be identified and isolated and subsequently used in the ELISA.

Antisperm antibody tests: traditional methods compared to ELISA

Enzyme-linked immunosorbent assays (ELISAs) to detect sperm antibodies can be a useful addition to other tests. ELISAs allow more quantitative and detailed information than some other tests, but results should be compared to those of other tests. This study was conducted to correlate results of an ELISA that used a sperm membrane extract as antigen with those of other tests. Semen, seminal plasma, and serum of 34 sperm-antibody-positive and 36 sperm-antibody-negative men were tested. There was poor correlation between the ELISA results and those of the other tests. Only the results of a direct immunobead test done on semen correlated fairly well with results from ELISAs done on serum. Further studies are needed on fertility-specific antigens that can be identified and isolated and then studied by means of ELISAs.

Clinical evaluation of the enzyme-linked immunosorbent assay (ELISA) kit for antisperm antibodies

A commercially available enzyme-linked immunosorbent assay (ELISA) kit for the detection of antisperm antibodies in serum was compared with standard sperm immobilization test (SIT) with the use of sera from 83 infertile women and 29 control individuals. For the ELISA, 24% of the infertile patients and 10% of the controls showed positive results, whereas 15% of the patients and none of the control were positive in the SIT. Parallel tests carried out on the same sera indicated that these methods detect a different, though often overlapping, spectrum of antibody activity. The presence and number of motile sperm in cervical mucus during postcoital tests were found to be related to the results of the SIT. On the other hand, the ELISA did not appear to be related to the quality of postcoital tests. These data indicate that care must be employed to interpret the results of this ELISA kit for the detection of antisperm antibodies.

An enzyme-linked immunosorbent assay for measuring antisperm autoantibodies following vasectomy in Lewis rats

An indirect enzyme-linked immunosorbent assay (ELISA) was devised to measure antisperm auto-antibodies in the Lewis rat following vasectomy. The assay system was validated by employing prevasectomy sera and postvasectomy antisera, previously demonstrated to contain antisperm antibodies by indirect immunofluorescence. A standardized ELISA protocol was developed employing 10(5) sperm per microtiter plate well and sucrose-polyvinylpyrrolidone as a postcoat stabilizer solution. The ELISA was shown to yield significant detectable antibody at dilutions of 1/512 or greater in the most reactive sera. A standard for scoring positive titers was adopted: 1.96 standard deviations above the mean of the preimmune value. Using the criterion, 88% of 7-week postvasectomy samples could be discriminated from preimmune samples at a 1:16 dilution, which was adopted for subsequent assays. The ELISA demonstrated 73% and 91% reproducibility for an intraassay analysis of single prevasectomy and postvasectomy serum samples (7 weeks postvasectomy) tested in 160 determinations on a standard sperm pool. When this single antigen pool was employed in 35 determinations at 0, 1, and 4 weeks in an interassay study, 56% and 70% reproducibility was found for pre- and postvasectomy sera respectively. A correlation (r = 0.75) was made between a single absorbance value and the endpoint titer of the same sera, which indicated that single absorbance values could be used to predict serum titer and single dilutions could be used for general screening of a large number of samples. The ELISA described provides a rapid, sensitive, and reliable method that discriminated between samples taken before and after vasectomy.