Immunity in sperm and in vitro fertilization

Diagnosis and treatment of immunologically infertile males with antisperm antibodies

The presence of antisperm antibodies (ASA) can reduce fecundity in both males and females. The present review describes a strategy, established by investigations of the diverse inhibitory effects of ASA on fertility, for the appropriate diagnosis and treatment of infertile males with ASA. For infertile males with ASA, diagnosis using the direct-immunobead test (D-IBT), the postcoital test (PCT) and the hemizona assay (HZA) should be carried out as the basis for decision-making. If the patient with ASA has an abnormal hemizona index, it seems reasonable to advise selecting intracytoplasmic sperm injection-embryo transfer (ICSI-ET) as a primary treatment. However, it has been shown that some immunologically infertile males with normal fertilizing ability established pregnancy by timed intercourse (TI) or intrauterine insemination (IUI). In such patients with ASA having normal hemizona index, TI or IUI can be selected based on the PCT result. Therefore, the treatment strategy for males with ASA is similar to that for infertile males with oligozoospermia or asthenozoospermia. In conclusion, it should be emphasized that a diversity of ASA exists and their effects on fertility in infertile males. Although there is an argument that routine testing for ASA in males is not always necessary, one should be aware that in some cases of failed IUI or IVF, ICSI is selected afterward because of the diagnosis of ASA. (Reprod Med Biol 2005; 4: 133-141).

Cloning and characterization of a novel sperm-associated isoantigen (E-3) with defensin- and lectin-like motifs expressed in rat epididymis

In the present study we report the identification of a novel epididymis-specific secretory glycoprotein, E-3, which is a sperm-associated isoantigen containing defensin- and lectin-like motifs. E-3 was detected in rat epididymal fluid and in sperm extracts by two-dimensional (2-D) Western blotting using rat hyperimmune sera raised against rat sperm. The immunoreactive spot of approximately 28 kDa with an isoelectric point (pI) of 3.5 was cored from silver-stained gels. Microsequencing by tandem mass spectrometry and database searches revealed several peptides to be novel sequences. Degenerate deoxyinosine-containing primers corresponding to the novel peptides were used in rapid amplification of cDNA ends and polymerase chain reaction to clone E-3 from a rat epididymal cDNA library. A 449-base pair nucleotide sequence was subsequently obtained consisting of a complete open reading frame (ORF) of 111 amino acids, which showed similarity to the defensin and lectin families. The first 21 amino acids constituted a putative signal peptide, suggesting that E-3 is a secretory protein. Mature E-3 protein corresponding to amino acids 22-111 was expressed in E. coli, and chickens were immunized with recombinant E-3 (rE-3). The resulting anti-rE-3 antisera recognized the recombinant immunogen as well as a "native" protein of 28 kDa, pI 2.5-3.5 in both epididymal fluid and in sperm extracts on 2-D Western blots. Northern hybridization indicated that E-3 mRNA was present in the epididymis but not in testis or other tissues, and that E-3 mRNA was predominantly expressed in the corpus and cauda of the epididymis, but not in the initial segment or caput. Similarly, Western blots detected the E-3 protein only in the epididymal fluid and sperm from the corpus and caudal regions. Finally, indirect immunofluorescence localized E-3 on the entire tail, and with less intensity on the head of the sperm. These observations indicate that E-3 is a secreted epididymal protein that becomes associated with the sperm as it transits through the corpus and cauda. The presence of a defensin-like motif suggests that E-3 may play a role in protecting the sperm from microbial infections in the epididymis and in the female reproductive tract.

Normal fertilization in men with high antibody sperm binding by the addition of sufficient unbound sperm in vitro

A high incidence of fertilization failure has been reported in men with over 70% of their sperm bound with isoantibodies. In three men with greater than 80% antisperm antibody binding with IgG and IgA immunoglobulins, a normal rate of fertilization (29/46 oocytes; 63%) was achieved by adding a sufficient number of motile sperm to provide at least 50,000 unbound sperm per oocyte. This method appears to be simpler and more effective than attempting to separate unbound sperm in vitro.