Richard A. Bronson

Ability of antibody-bound human sperm to penetrate zona-free hamster ova in vitro.

Sera from men and women at risk for immunologic causes of infertility were screened for sperm-specific antibodies by a new test devised to assess directly the presence of immunoglobulins bound to the sperm plasma membrane. Passive antibody transfers to antibody-negative sperm of a fertile donor were performed with the use of sera that possessed iso- or auto-antibodies directed against the sperm head, including the acrosome and postacrosomal regions. The ability of these antibody-bound sperm to penetrate the zona-free hamster egg in vitro, a prerequisite for fertilization, was enhanced, as compared with the penetrating ability of antibody-free sperm of the same donor. These results indicate that the sperm-specific antibodies studied in these experiments, although bound to the sperm head, do not cause infertility by interfering with the acrosome reaction or gamete membrane fusion.

Conception rates in couples where autoimmunity to sperm is detected

In men with autoimmunity to sperm, a varying proportion of spermatozoa in the ejaculate are found to have surface-bound immunoglobulins. We asked whether the extent of autoimmunity, as judged by this criterion, would have predictive value in determining the chance of conception. Infertile couples where husbands were found to have antisperm antibodies were treated for other factors leading to impaired reproduction, but no specific treatment was offered for reduction of these antibodies. The chance of pregnancy for those couples where autoimmunity to sperm was the sole definable factor leading to infertility was 15.3% when most spermatozoa were antibody-bound. A significantly greater number of wives whose husbands had P

Correlation Between Regional Specificity of Antisperm Antibodies to the Spermatozoan Surface and Complement-Mediated Sperm Immobilization

ABSTRACT: Sera from men at risk for immunity to spermatozoa were screened for antisperm antibodies by immunobead binding following passive antibody transfer to antibody‐free sperm of fertile donors. The percent motile sperm after incubation in diluted antibody positive serum in the presence of complement was compared with the regional distribution of immunoglobulins bound to the sperm surface. The extent of complement‐mediated sperm immobilization varied with immunoglobulin class and with the location of antibody bound to the sperm surface. Tests utilizing complement‐mediated immobilization of sperm are insensitive to the presence of antibodies of IgG and IgA classes that are directed against the head, the distal one‐fifth of the sperm tail principal piece, or the tail end piece. A high degree of immobilization was found only when IgG binding occurred on the distal two‐fifths to three‐fifths of the principal piece of the tail or when IgM bound to the sperm tail end piece.

Autoimmunity to spermatozoa: effect on sperm penetration of cervical mucus as reflected by postcoital testing

In couples with abnormal postcoital tests, where husbands exhibited autoimmunity to spermatozoa, the degree of impairment of sperm penetration into cervical mucus correlated with the proportion of sperm in ejaculates exhibiting surface-bound immunoglobulins. Residual sperm-directed antibodies detected within seminal fluid were not representative of the cell-bound immunoglobulins present on the sperm surfaces. When all sperm were antibody-bound, spermatozoa were rarely seen in cervical mucus. Conversely, the number of motile sperm seen at postcoital testing was normal, that is, no different from that of antibody-negative couples, when less than 50% of sperm were antibody-bound in the ejaculate. In this group, other causes of infertility should be explored. The extent of autoimmunity to spermatozoa as reflected in the proportion of sperm exhibiting immunobead binding, then, provides guidelines for treatment of these men.

The effect of an IgA1 protease on immunoglobulins bound to the sperm surface and sperm cervical mucus penetrating ability.

A major site of impaired fertility in men with autoimmunity to sperm rests at the level of restricted sperm entry and motion within cervical mucus. We studied the effects of a protease derived from Neisseria gonorrhoeae, whose substrate specificity is limited to human IgA1, on the ability of antibody-bound sperm to penetrate human cervical mucus in vitro. IgA on the sperm surface, but not IgG, was degraded by IgA1 protease. A correlation was seen between the levels of IgA bound relative to IgG and the improvement in sperm cervical mucus penetrating ability after IgA1 protease exposure. These results provide evidence that antisperm autoantibodies of both IgA and IgG classes impair the ability of spermatozoa to populate the female reproductive tract. They implicate the Fc region of the immunoglobulin molecule in mediating this effect and offer the potential to restore male fertility by treating antibody-bound sperm in vitro with immunoglobulin-directed bacterial proteases, before insemination.

Complement-mediated effects of sperm head-directed human antibodies on the ability of human spermatozoa to penetrate zona-free hamster eggs

The ability of immunoglobulins of IgA, IgG, and IgM classes to mediate complement-dependent membrane damage varies. Sera containing antisperm antibodies of differing immunoglobulin classes were studied, in association with complement, for their ability to alter human sperm penetration of zona-free hamster eggs. Sera that contained immunoglobulins of IgG, IgA, or IgM classes directed primarily against the sperm head (as determined by immunobead binding) were selected from men and women judged to be at risk for immune causes of infertility. Spermatozoa were incubated in these sera in the presence and absence of complement. Following an additional incubation in a modified Biggers, Whitten and Whittingham medium, zona-free hamster eggs were inseminated with these spermatozoa. Antibodies known to fix complement (IgG and IgM) diminished the percentage of eggs penetrated and the number of penetrating sperm per egg without impairing the ability of sperm to contact the egg surface, as judged by comparable numbers of spermatozoa adherent to the oolemma. IgA, which cannot fix the first component of complement, did not alter the ability of sperm to penetrate eggs.

Seminal fluid antisperm antibodies do not reflect those present on the sperm surface

Given the increasing evidence that head-directed antibodies can impair fertilization in vitro, as well as play a role in the impaired entry of sperm into cervical mucus, our findings provide strong support for the direct analysis of immunoglobulins bound to the sperm surface, rather than by indirect analysis through the study of seminal fluid.

Luteal phase sera and progesterone enhance sperm penetration in the hamster egg assay

The hormonal factors responsible for variation in sperm penetration rates of zona-free hamster ova caused by the use of human sera were investigated. Sera obtained at different times in the menstrual cycle, 17-beta estradiol (E2), or progesterone (P) was added to Biggers Whitten and Whittingham (BWW) medium used for the sperm penetration assay. Luteal phase sera enhanced egg penetration significantly when compared with either follicular or preovulatory sera (48.8% versus 23% and 25%; P less than 0.01). E2 at concentrations of 2 pg/ml to 2 X 10(6) pg/ml had no effect on sperm motility or egg penetration. Addition of P to control media at final concentrations of 0.5 to 50 ng/ml caused a significant elevation of egg penetration (68% to 91% to 96%; P less than 0.01) without affecting sperm motility. Since P has been shown to have a direct effect on plasma membranes and to bind to spermatozoan plasma membrane, the authors propose that P could have a physiologic role during capacitation or sperm egg interaction in vivo.

Detection in human sera of antibodies directed against the hamster egg oolemma

Heteroantibodies were demonstrated by indirect immunofluorescence in human sera, which reacted with unfertilized and fertilized hamster eggs. Oolemmal antigens to which these antibodies were directed were distinct from antigen present on the surface of living human spermatozoa. Both species-specific and tissue-specific heteroantibodies were demonstrated by absorption with hamster liver and ovary. An increased degree of heteroantibody binding was noted following penetration of zona-free hamster eggs by human spermatozoa, indicating that an alteration in oolemmal antigen distribution had occurred. No evidence was found, however, that antisperm antibodies in these sera reacted with zona-free hamster eggs following their fertilization.

Immunity in sperm and in vitro fertilization.

Currently, neither are the causes of immunities to sperm known nor have treatments proven effectual. Against this background, in vitro fertilization (IVF) offers the best chance of conception of couples with d o c u m e n t e d immuni t ies to sperm. For women, it ensures the meeting of gametes in the absence of antisperm antibodies. When present in follicular fluid (1), these antibodies can be removed by washing, and any res idua that may remain within the cumulus masses do not appear to interfere with sperm penetration. Fertilization is successful at rates comparable to those in the absence of antisperm antibodies (2). Whether such antibodies present within the reproductive tract may