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

Prevention of monkey sperm penetration of zona-free hamster ova by sperm antibody obtained from vasectomized cynomolgus monkeys

Incubation of antisperm sera from vasectomized cynomolgus monkeys (Macaca fascicularis) with monkey sperm caused a fourfold reduction of sperm attachment to and penetration of zona-free Golden hamster ova. The attachment of sperm to hamster ova was reduced from 64% to 11%, and the penetration of ova was reduced from 20% to 5%. Sperm antibodies block sperm attachment to the vitelline membrane, thus preventing ovum penetration. This blockage may be one of the reasons for low fertility rates observed following reanastomosis of the vas deferens in those vasectomized males that show high levels of circulating antisperm antibody.

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.

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.

Sperm-specific isoantibodies and autoantibodies inhibit the binding of human sperm to the human zona pellucida

Heterologous antisperm antibodies induced by immunization with Freund's adjuvants are known to inhibit sperm-zona binding. We have tested whether spontaneously occurring sperm-directed isoantibodies and autoantibodies inhibit the binding of human sperm to the human zona pellucida. Zonae pellucidae were obtained from the ovaries of a woman of reproductive age undergoing surgery for uterine malignancy. Couples at risk for immunity to spermatozoa were screened for humoral antisperm antibodies by immunobead binding. Sera containing head-directed antibodies of IgA and/or IgG classes were selected for passive antibody transfer. Populations of spermatozoa exhibiting differing proportions of antibody-bound sperm were obtained by exposure of antibody-negative sperm of a fertile donor to untreated sera or sera depleted of head-directed antisperm antibodies by prior absorption. Each zona pellucida was challenged sequentially with two populations of sperm. an inverse relationship was found between the number of spermatozoa adherent to the zona and the proportion of sperm exhibiting binding of IgA or IgG immunoglobulins over the head, indicating that the presence of these antibodies in the acrosomal region of the sperm head inhibited their ability to attach to the zona pellucida.