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

The Expression of Non B Cell-Derived Immunoglobulins

Although V(D)J recombination and immunoglobulin (Ig) production are traditionally recognised to occur only in B lymphocytes and plasma cells, the expression of Igs in non-lymphoid cells, which we call non B cell-derived Igs (non B Igs), has been documented by growing studies. It has been demonstrated that non B-Igs can be widely expressed in most cell types, including, but not limited to, epithelial cells, cardiomyocytes, hematopoietic stem/progenitor cells, myeloid cells, and cells from immune-privileged sites, such as neurons and spermatogenic cells. In particular, malignant tumour cells express high level of IgG. Moreover, different from B-Igs that mainly localised on the B cell membrane and in the serum and perform immune defence function mainly, non B-Igs have been found to distribute more widely and play critical roles in immune defence, maintaining cell proliferation and survival, and promoting progression. The findings of non B-Igs may provide a wealthier breakthrough point for more therapeutic strategies for a wide range of immune-related diseases.

Immunoglobulin G Expression in Human Sperm and Possible Functional Significance

Immunoglobulin G (IgG), the major molecule of the immune system, which was traditionally thought to be produced by differentiated B-lymphocytes, had recently been found in non-immune cells including spermatozoa of rabbit testis. To study if human sperms could produce IgG that might play a role in fertilization, we employed immunofluorescent staining, Western blot, in situ hybridization, RT-PCR (reverse transcription polymerase chain reaction) and immunoelectron microscope and found that human sperms were capable of synthesizing IgG. IgG protein and mRNA were detected in the cytoplasm, mainly the neck region of the sperm and IgG immunoreactivity was found to cover the entire sperm cell. The essential enzymes necessary for IgG synthesis and class switching, RAG1 (recombination activating gene 1), RAG2 (recombination activating gene 2) and AID (activation-induced cytidine deaminase), were also detected in the sperm cells. Furthermore, we found that anti-IgG antibody could inhibit sperm from penetrating Zona-free hamster egg with statistical significance. These discoveries suggested that immunoglobulin G could be produced by human sperms and it might play a role during fertilization.

Expression of immunoglobulin gene with classical V-(D)-J rearrangement in mouse testis and epididymis

Immunoglobulin (Ig) molecules have thus far been found only to be produced by differentiated B lymphocytes. As we know, immune privilege in the normal adult mouse testis exists to make these privileged sites generally free of patrolling immune cells and Igs. However, in this study, the expression of Ig in normal adult mouse testis and epididymis was detected. First, by IHC, a strong pattern of Ig expression was detected in the spermatogenic cells of adult mouse testis at different development stages. Second, by Western blot analysis, different strong bands of Igs in mouse testicular spermatogenic cells and epididymal epithelial cell extract were recognized using specific antibodies against IgG. More importantly, by ISH and cell sorting-related RT-PCR, rearranged Ig gamma chain and kappa chain transcripts were expressed in testicular spermatogenic cells and epididymal epithelial cells. These results suggested that Ig in testis and epididymis was mainly produced by adult mouse testicular spermatogenic cells and epididymal epithelial cells.

Do autoantibodies to sperm reduce fecundity? A mini-review in historical perspective

PROBLEM

The paradox that early studies of antisperm antibodies in men showed a strong correlation between titers of circulating antibodies (essentially immunoglobulin [Ig] G) and reduction in conception rates, whereas more recent studies have indicated that the antifertility effect is mainly (or exclusively?) associated with IgA antibodies, impairing sperm migration through cervical mucus, was studied.

METHOD OF STUDY

Relevant literature focusing on antibodies on ejaculated sperm was analyzed.

RESULTS

Direct mixed antiglobulin reaction (MAR) and immunobead-binding tests are excellent and sensitive techniques for demonstrating antibodies of the IgG and IgA classes on sperm, and they have revealed that IgA antibodies are, with very rare exceptions, found only when IgG antibodies are also present. However, these tests tell little about the amounts of antibodies present, and attempts to measure quantitatively the amounts of Ig on sperm have indicated higher levels of IgA than IgG (despite the strongest MAR reactivities for IgG).

CONCLUSIONS

The patients with high levels of IgA to their sperm are mainly men with strong immune responses and, therefore, also high antibody titers in serum. Apparently, the locally produced IgA antibodies reach the sperm and occupy the binding sites before the main bulk of IgG reaches the seminal compartment with the prostatic fluid.

A chimeric sperm peptide induces antibodies and strain-specific reversible infertility in mice

The development of a contraceptive vaccine based on a gamete-specific antigen requires knowledge of the ability of the antigen to elicit an immune response that inhibits fertilization. A well-defined immune response, as elicited by a synthetic peptide comprising a dominant B-cell epitope coupled to a common promiscuous T-cell epitope, might be preferable. In this study, the immunodominant B-cell epitope of sperm antigen Sp17 has been identified and synthesized as a chimeric peptide with the promiscuous T-cell epitope bovine RNase[94-104] at the N terminal. Immunization of female BALB/c mice with this peptide induced a dose-dependent reduction in fertility. Although antibodies to recombinant and native Sp17 were elicited in these mice, there was no strict correlation between the level of these antibodies and the reduction in fertility. Moreover, the induction of infertility was strain-specific since no effect on fertility could be induced in B6AF1 mice. To understand the mechanism behind this apparent strain-specific infertility induction, a more extended study on both the humoral and the cellular immune response to the chimeric peptide was performed. The antigen-specific T-cell response and the levels of antigen-specific cytokines are the major factors that affect fertility outcome.

Seminal plasma immunoglobulin concentrations in autoimmune male subfertility

The presence of anti-sperm antibodies (ASAs) in seminal plasma is associated with infertility. They have been shown to reduce sperm motility, interfere with cervical mucus penetration and gamete interaction, and have been shown to reduce spontaneous fertilization and pregnancy rates. Although some causes can be determined, in the majority of cases the initial event causing the immune sensitisation and the reasons for the continuing antibody secretion remains unknown. Quantitative determination of total IgG, IgA and IgM within seminal plasma had not been previously reported in patients with and without specific ASAs. Semen samples from 512 men presenting with infertility were analyzed. One hundred and forty-six men (28.5%) had seminal fluid ASAs as determined by the MAR or TAT tests. The total seminal plasma IgG and IgA concentrations were significantly elevated in the ASA-positive groups compared with ASA-negative groups (IgG: 8.83 mg/100 ml vs. 7.15, P = 0.0008; and IgA: 2.88 mg/100 ml vs. 1.64, P = 0.0001). Only 19 samples showed seminal fluid IgM, and there was no difference between the ASA positive or ASA negative samples. The significance of these findings is discussed.