Immunological and morphological characterisation of nucleated cells other than sperm in semen of oligospermic donors

Increased exfoliation of immature germ cells detected in semen analysis routine and its clinical significance

To the Editor, Currently, semen analysis is the unique test to evaluate men's fertility potential. Semen analysis provides valuable information on sperm production and quality. In addition to the conventional assessment of the sperm characteristics in a basic semen analysis routine, performing a differential diagnosis of leukocytes and sperm precursors immature germ cells (IGC) is also pivotal, due to adding valuable and clinically suitable information to the semen report [...].

Heat shock factor 5 is essential for spermatogenesis in mice: Detected by a new monoclonal antibody

OBJECTIVES

Here, we examined the function of our produced monoclonal antibody (mAb10C3) to recognize one of the most important members of the HEAT shock factor family, Hsf5, in embryonic development and in spermatogenic cells of adult mouse testis.

MATERIALS AND METHODS

The targeting effects of mAb10C3 were investigated by immunohistochemistry analysis in the different phases of the embryo and in the adult testis tissue sections.

RESULTS

The results of immunohistochemistry staining on the mouse embryos by the supernatant of hybridoma clone that produced mAb10C3, in the early and late phases (E7.5 and E14.5) of embryonic development, indicated that mAb10C3 could only detect Hsf5 in E7.5 and it did not have any targeting activity in the late phase of development. Therefore, we showed that the hsf5 gene has expressed in early mouse embryonic development. On the other hand, mAb10C3 could detect Hsf5 in spermatogonia and spermatocytes of adult testis in comparison with a known anti-Hsf5 antibody (ab98939) and an anti-PCNA antibody as a marker of spermatogonia cells.

CONCLUSION

Taken together, these data indicated that generated anti-testis mAb10C3 was generated against anti-testis proteins, specifically to target Hsf5, and can be useful as a scientific tool to investigate the critical genes in the development and spermatogenesis.

Immature germ cells in semen - correlation with total sperm count and sperm motility

Background:

Current data regarding infertility suggests that male factor contributes up to 30% of the total cases of infertility. Semen analysis reveals the presence of spermatozoa as well as a number of non-sperm cells, presently being mentioned in routine semen report as “round cells” without further differentiating them into leucocytes or immature germ cells.

Aim:

The aim of this work was to study a simple, cost-effective, and convenient method for differentiating the round cells in semen into immature germ cells and leucocytes and correlating them with total sperm counts and motility.

Materials and Methods:

Semen samples from 120 males, who had come for investigation for infertility, were collected, semen parameters recorded, and stained smears studied for different round cells. Statistical analysis of the data was done to correlate total sperm counts and sperm motility with the occurrence of immature germ cells and leucocytes. The average shedding of immature germ cells in different groups with normal and low sperm counts was compared. The clinical significance of “round cells” in semen and their differentiation into leucocytes and immature germ cells are discussed.

Conclusions:

Round cells in semen can be differentiated into immature germ cells and leucocytes using simple staining methods. The differential counts mentioned in a semen report give valuable and clinically relevant information. In this study, we observed a negative correlation between total count and immature germ cells, as well as sperm motility and shedding of immature germ cells. The latter was statistically significant with a P value 0.000.

Germ cell-specific localization of immunoreactive riboflavin carrier protein in the male golden hamster: appearance during spermatogenesis and role in sperm function

Riboflavin carrier protein (RCP) is a phosphoglycoprotein (37 kDa) that is well studied in chicken. An immunologically cross-reacting protein was identified in mammals and active immunization of male rats and bonnet monkeys with chicken RCP lead to an approximately 80% reduction in fertility. However, the physiological mechanism responsible for inhibition of male fertility has not been investigated. Moreover, information on the cell type-specific localization and the origin of immunoreactive RCP during spermatogenesis is extremely limited. Hence, studies were carried out to determine the pattern of expression of immunoreactive RCP during spermatogenesis and its role in sperm function in the golden hamster. Immunoreactive RCP was germ cell-specific, found to be associated with the acrosome-organizing region of early spermatids and showed interesting patterns of immunolocalization during late stages of spermiogenesis. Mature spermatozoa exhibited acrosome-specific localization, mainly in the peri-acrosomal membrane. The immunoreactive protein was undetectable in (non)gonadal somatic cells tested. The protein had a molecular mass of 45-55 kDa and was biosynthesized by round spermatids. The acrosome-specific localization of immunoreactive RCP was unchanged during capacitation, but it was substantially lost during acrosome reaction. Functional studies indicated that treatment of spermatozoa with anti-RCP antibodies did not have any effect on either capacitation or acrosome reaction, but markedly reduced the rate of sperm penetration into zona-free hamster oocytes. These results show the existence of male germ cell-specific immunoreactive RCP, having a potential role in sperm-egg interaction in hamsters. Also the pattern of immunoreactive-RCP localization makes it an ideal marker to monitor development of acrosome in mammalian spermatozoa.

Shedding of immature germ cells

The immature germ cells (IGC) constitute the highest percentage (90%) of nonsperm cells (NSpC) in ejaculates from fertile or infertile men. The objective of this study was to evaluate IGC concentration and the IGC/(IGC + Sp) ratio, in normozoospermia and dispermia. Normozoospermia from men with proven fertility (NPF). nonproven fertility (NNPF). dispermia (D) and semen samples with excessive shedding of immature germ cells (GI 1.7 x 10(6) to 5 x 10(6) IGC/mL and GII > 5.0 x 10(6) IGC/mL) were used in this study. The mean value +2 SD for the NNPF (1.7 x 10(6)/mL) and the value proposed by WHO (5 x 10(6)/mL) were employed to define GI and GII groups. IGC concentration is statistically different in the studied groups. The IGC/Sp ratio showed a significant difference only between the NNPF and the D. When comparing semen parameters (Sp/ejaculate. grade (a) motility and morphology) there was a highly significant difference between NNPF and GI and GII: no difference was found between GI and GII. While studying 200 cases of dispermias 83% showed a high shedding of immature germ cells. The cytological study of nonsperm cells and the count and identification of the immature germ cells could be used to evaluate the dispermic disorders.

Heterogeneity in the presence of CD4-like molecules on human spermatozoa

The object of the present study was to study if there are differences in the presence of CD4-like molecules on human ejaculated spermatozoa in fertile donors and infertile patients (with globozoospermia). Indirect and absorption enzyme-linked immunosorbent assay and indirect immunofluorescence were applied. The enzyme-linked immunosorbent assay data showed that monoclonal anti-human CD4-antibody recognizes an epitope common to the human spermatozoa with normal morphology and round-headed spermatozoa. Localization of the antigenic determinants, identified by anti-human CD4-monoclonal antibody, in the acrosomal region, including equatorial segment, postnuclear cap and tail was determined in normozoospermic samples. A positive reaction was found on the sperm head both in the acrosomal and postacrosomal region of some round-headed spermatozoa in the samples with globozoospermia. The tails of the normozoospermic spermatozoa and of some round-headed spermatozoa were weakly immunopositive. The results of the experiments carried out are evidence of heterogeneity in the presence of CD4-like antigen determinants on human spermatozoa. These data increased the information about the CD4-antigen characteristic of the spermatozoa from fertile donors and infertile patients.

Nonsperm cells in human semen: with special reference to seminal leukocytes and their possible influence on fertility

Nonspermatozoal cells (NSC) in semen, including immature germ cells, leukocytes (WBC) and epithelial cells, are normally found in a concentration less than 15% of the sperm concentration. Cytological staining methods and immunoenzymatic assays for characterization of seminal WBC and methods for detection of various enzymes from WBC are evaluated. Criteria for abnormally high levels of WBC in semen, caused by exogenic factors (e.g., infection) and possibly by endogenic factors (e.g., abnormal sperm), are discussed. Leukocytospermia is associated with reduced in vitro fertilization rate, and experimentally-measured sperm functions (e.g., motility) are inhibited by high concentrations of certain WBC products (e.g., reactive oxygen species and interferon-gamma). At the present stage, the following procedures could be used to evaluate WBC in ejaculates from infertile patients: (1) count the number of NSC using a hemocytometer. (2) Determine the number of WBC in percentage of NSC in smears using the Papanicolaou staining technique, or an immuno-enzymatic assay using monoclonal antibodies to the different kinds of WBC. (3) If, abnormally high levels of WBC (according to the WHO criteria or based on a percentile determined from examination of normal, fertile men) is detected, a second ejaculate should be examined 3 months later. (4) Persistent leukocytospermia should indicate physical and microbiological examinations, after which antibiotic treatment may be indicated.

The biologic significance of white blood cells in semen

OBJECTIVE

To analyze the data available on the biologic significance of white blood cells (WBC) in semen of infertility patients.

DATA RESOURCES

The relevant literature was reviewed.

RESULTS

It is not possible to identify reliably WBC by conventional sperm staining techniques. The peroxidase method is sufficient for quantification of granulocytes, but immunocytology is the gold standard for the detection of all WBC populations in semen. Granulocytes are the most prevalent WBC type in semen (50% to 60%), followed by macrophages (20% to 30%) and T-lymphocytes (2% to 5%). The prevalence of leukocytospermia (> 10(6) WBC/mL semen) among male infertility patients is approximately 10% to 20%. There is controversy on the significance of WBC in semen. Whereas some authors did not observe sperm damage in the presence of leukocytospermia, others have found evidence that WBC are significant cofactors of male infertility: [1] seminal WBC numbers were higher in infertility patients than among fertile men; [2] leukocytospermia was associated with decreased sperm numbers and impaired sperm motility; [3] WBC damaged sperm function and hamster ovum penetration in vitro and were important prognostic factors for IVF-ET failure. Because of absence of clinical symptoms, the origin of WBC is difficult to determine. Normally, most WBC appear to originate from the epididymis because vasectomized men show very few WBC in semen. On the other hand, leukocytospermic samples show low citric acid levels, pointing to asymptomatic prostatitis as a source of WBC in semen. Surprisingly, approximately 80% of leukocytospermic samples are microbiologically negative. In some cases Chlamydia trachomatis might have triggered a persistent inflammatory reaction leading to leukocytospermia. Sperm damage by WBC can be mediated by reactive oxygen species, proteases and cytokines. Furthermore, genital tract inflammation facilitates the formation of sperm antibodies. As seminal plasma has strong anti-inflammatory properties and because there is only short contact between sperm and WBC in prostatitis and seminal vesiculitis, inflammations of the epididymis and testis are likely to have the largest impact on sperm.

CONCLUSIONS

There is ample evidence that WBC can affect sperm function. Further studies are needed to define cofactors that increase or decrease the risk of sperm damage by WBC.

A quantitative study of sperm head ultrastructure in subfertile males with excess sperm precursors

OBJECTIVE

To make an objective comparison between sperm head ultrastructure in fertile subjects and a subfertile cohort with an excess of immature germinal elements in the ejaculate.

DESIGN

A quantitative analysis of ultrastructural features of the sperm head using transmission electron microscopy in the defined groups.

PATIENTS

Ten men of proven fertility as controls and 10 subfertile subjects with a persistent excess of sperm precursors in the ejaculate were investigated.

SETTING

The Infertility Clinic at Queen Charlotte's and Chelsea Hospital, London.

MAIN OUTCOME MEASURES

Each individual in the study achieved a score for a range of previously defined features of sperm head ultrastructure. These scores provided the basis for comparison between fertile and subfertile subjects.

RESULTS

Subfertile individuals were found to have motile sperm with significantly more hypoplastic, detached, and abnormally shaped acrosomes than fertile controls. Sperm nuclei in these subjects also contained significantly more intranuclear vacuoles and immature chromatin and were associated more commonly with cytoplasmic droplets than fertile controls.

CONCLUSION

Men with an excess of sperm precursors in the ejaculate have motile sperm with a range of abnormalities involving the nucleus and acrosome to account for reduced functional competence.

Antigenic determinants of human sperm tail fibrous sheath proteins

Mouse anti-fibrous sheath antisera (MAFA) produced by immunizing mice with purified preparations of human sperm tail fibrous sheath (FS) reacted with the principal piece of less than 10% of freshly isolated spermatozoa which were immotile and probably dead. Following their demembranation by detergents or repeated freezing and thawing, all spermatozoa were stained. This was also demonstrated on spermatozoa dried onto slides, but the undiluted xenoantisera showed additional reactivity with the acrosomal zone (AZ). Using immunogold electron microscopy, the target antigens were ultrastructurally localized to the FS, and a few spermatozoa showed some reaction at the AZ subacrosomal perinuclear theca. Following titration of the antibodies, the anti-AZ-reaction became undetectable at a dilution of 1:20 while their reactivity with the principal piece continued to a 1:400-dilution. These results indicated that the xenoantisera probably contained an additional unrelated antibody component which reacted with the AZ. Western blotting and staining of purified FS with MAFA detected seven major protein bands with MW ranging between 25 kDa and 97.4 kDa. In human testes, the 1:50 diluted MAFA reacted with sperm tails only, indicating the late expression of the antigenic determinants during spermatogenesis. MAFA did not react with oesophagus, stomach, duodenum, ileum, nasal lining tissues, uterus, pericardium, pancreas, thyroid gland, or cultured fibroblasts. The xenoantisera did, however stain the skin epidermis and cultured keratinocytes which exhibited filamentous cytoplasmic staining although their target antigens could not be biochemically identified. These results indicate that the FS proteins express antigenic determinants which are not shared with other cytoskeletal elements within the sperm flagellum or a variety of somatic tissues.

AJ-p90: a novel protein of the perinuclear theca in human sperm subacrosome

A perinuclear theca protein of the human sperm subacrosome was detected using LH43 monoclonal antibody which was originally raised against human keratinocytes. Using indirect immunofluorescence, the antibody stained the acrosomal zone (AZ) of dried ejaculated spermatozoa but did not react with viable cells, thus suggesting that the antigen was intracellular. This was confirmed by immunogold electron microscopy which also revealed the ultrastructural localisation of the antigen to the subacrosomal fibrils. Throughout spermatogenesis the antigen was only detected on the AZ of developed testicular spermatozoa and its expression was continued during their epididymal passage. Biochemically, the protein was insoluble in Triton, and dithiothreitol (DTT) was required for its solubilisation. In Western blotting of sperm and keratinocyte lysates, the antibody detected similar 90-kDa protein doublets (AJ-p90). These biochemical features exclude the identity of AJ-p90 with various cyto- and karyo-skeletal antigens, including the intermediate filaments and microfilaments. AJ-p90 therefore represents a novel product of the subacrosomal perinuclear theca. The significance of these data is discussed together with the importance of the antibody for probing the perinuclear theca in normal and abnormal germ cells, including multinucleated spermatids which also showed reactivity with the antibody.

Differentiation of round cells in semen by means of monoclonal antibodies and relationship with male fertility

OBJECTIVE

To differentiate round cells in semen samples of subfertile men and evaluate the clinical significance during infertility investigation.

PATIENTS

One hundred and eight randomly chosen couples with a median duration of infertility of 4 (range, 1 to 20) years presenting at the outpatient infertility clinic of the University of Heidelberg, Germany.

MAIN OUTCOME MEASURES

Differentiation of round cells in semen by means of monoclonal antibodies (mABs) and a streptavidin-biotin system for staining. Correlation of results with medical history, outcome of clinical examination, sperm analysis, microbial screening of both partners, evaluation of sperm functional capacity in vivo by means of the postcoital test (PCT) and in vitro with the standardized crossed sperm-cervical mucus penetration test (SCMPT) and the subsequent fertility in a prospective study.

RESULTS

The method used for differentiation of round cells proved to be practical and suitable for routine use. The percentage of leukocytes ranged from 0% to 58% with a median of 3%. Number of round cells and percentage of leukocytes did not differ markedly with regard to andrologic history, clinical findings, for example, varicocele, results of standard sperm analysis, and microbial colonization of semen samples. However, high rates of leukocytes of the round cells correlated with reduced sperm count and morphology and results of PCT. Leukocyte-positive (> 15% leukocytes) specimens were also significantly more frequent in case of inadequate SCMPT and reduced sperm penetration ability in vitro.

CONCLUSIONS

In asymptomatic patients (in terms of genital tract infection), the majority of round cells consist of immature germ cells and < 5% are white blood cells. The streptavidin-biotin system and the mABs used in this study proved to be useful to identify patients with elevated rates of leukocytes in semen possibly reflecting subclinical genital tract infection with influence on sperm functional capacity and subsequent fertility. Thus the procedure can be recommended to be included in a comprehensive evaluation of male fertility.

Detection of a novel basement membrane antigen by GDA-J/F3 anti-human sperm fibrous sheath monoclonal antibody

Basement membrane zones (BMZ) of human epithelia were stained with GDA-J/F3 monoclonal antibody, which was originally raised against sperm cells. Using indirect immunofluorescence and immunoperoxidase techniques, the antibody reacted with the BMZ of stratified squamous epithelia (skin and its appendages, tongue, lip, oesophagus and cervix). It also stained the BMZ of trachea, nasal ciliated mucosa, some mammary ducts of lactating and resting breast, amnion and ureter but failed to react with that of stomach, ileum, colon, rectum, kidney, liver, fallopian tube, lung or their blood vessels. In testes, the antibody did not react with the BMZ of the seminiferous tubules although the sperm tails were stained. Split-skin immunofluorescence and immunoelectron microscopy localized GDA-J/F3 antigen to the inferior border of the lamina densa of the BMZ. In human foetuses, the epidermally associated antigen was detected at an estimated gestational age of 9 weeks, and in the amnion at 15 weeks. The antibody reacted with tissues from monkey but not from mouse, rat, cow or pig suggesting the late appearance of the antigen during evolution. Although the GDA-J/F3 was difficult to characterize biochemically, its tissue distribution, ontogeny and ultrastructural localization suggests that this antigen may be a type VII collagen-associated protein, whose expression is altered in recessive dystrophic epidermolysis bullosa. This disease could represent abnormalities in type VII collagen structure, assembly, transport or interaction with associated proteins.

AJ-p97: a novel antigen of the human sperm tail fibrous sheath detected by a neurofilament monoclonal antibody

Using indirect immunofluorescence (IIF), the RT97 anti-neurofilament monoclonal antibody (MoAb) detected an intracellular antigen in the principal piece of human ejaculated sperm tails. Its localisation to the tail fibrous sheath (FS) was confirmed by immunoelectron microscopy (IEM), which showed the binding of the gold particles to the outer FS surface. During spermatogenesis the antigen was first expressed on the spermatid FS, and its expression was continued on ejaculated mature sperm. In Western blotting of sperm lysates, the RT97 reacted with a 97 kDa protein (AJ-p97) which lacked disulphide bonds. This antigen was not detected on mouse or rat sperm tail FS, suggesting a sequence divergence of the AJ-p97 during evolution. The significance of these results and the relationship of AJ-p97 to neurofilaments are discussed, together with the use of the antibody as a probe for the structural dissection of the FS and for analysing the molecular events that take place during spermiogenesis, especially those involved in sperm tail morphogenesis.

GDA-J/F7 monoclonal antibody: a new marker for sperm cell precursors in human semen

Germ cells isolated from semen of oligospermic human donors were found to react with GDA-J/F7 monoclonal antibody (MoAb). Their reactions with this antibody were demonstrated by using fluorescein activated cell sorter (FACS) analysis and indirect immunofluorescence (IIF) test. In the IIF test, the MoAb recognised an antigen on the surface of the sperm cell precursors (SpP) as well as on mature spermatozoa. The specificity of the antibody reaction with the SpP was further confirmed by immunoelectron microscopy. The MoAb did not react with peripheral blood lymphocytes or polymorphonuclear cells but did show cross-reactivity with monocytes. This antibody therefore provides the first marker for the SpP and could be used as a probe for their distinction from leucocytes. This could have clinical application in seminal analysis.

Differential diagnosis of immature germ cells in semen utilizing monoclonal antibody MHS-10 to the intra-acrosomal antigen SP-10

The monoclonal antibody (mAb) MHS-10 (IgG1) is a mouse antihuman sperm antibody which recognizes a polymorphic sperm protein, (SP-10), which has previously been localized within the acrosomal matrix and the acrosomal membranes. The SP-10 antigen has been shown to be sperm-specific and is not found in somatic tissues. It is stage specific, having been immunohistologically localized to Golgi phase spermatids and all subsequent phases of spermiogenesis. In the present study, acetone-dried smears from washed human semen containing significant numbers of round cells were probed with mAb MHS-10. Monoclonal antibody-labeled cells were visualized by a standard streptavidin-biotin immunoperoxidase method using a light microscope. The MHS-10 mAb immunoreacted with mature sperm and with a subset of round cells diagnosed as developing spermatids, which had been sloughed off from the testis at varying stages of acrosome formation. To rule out possible cross-reactivity of the mAb with leukocytes in semen, a leukocyte surface marker (anti-HLe-1) was used in conjunction with MHS-10. Round cell populations staining with MHS-10 did not stain with anti-HLe-1. The mAb MHS-10 is thus a promising probe for the identification and quantitation of immature germ cells in human semen.

Analysis of HLA antigens on germ cells in human semen

Nucleated cells other than sperm (NCOS) were isolated from human semen by centrifugation on a Ficoll density gradient. Using tissue-specific monoclonal antibodies (mAb) greater than 99% of the NCOS were found to be sperm cell precursors (SpP). These cells were tested for the expression of class I and II (DR, DP and DQ) HLA antigens by using specific mAb. The anti-HLA class I and II and anti-beta 2-microglobulin mAb reacted with less than 1% of the NCOS. This was demonstrated by indirect immunofluorescence microscopy and fluorescence-activated cell sorter analysis. These results were similar to those obtained from testing germ cells in frozen sections of normal adult testis using the same panel of mAb. In mixed lymphocyte-NCOS cultures, the SpP failed to stimulate allogeneic lymphocytes even when different concentrations of cells were used. These results indicate little or no expression of HLA class I and II including the HLA-D (T cell-defined) determinant on the SpP, a phenomenon which could be of biological importance.

Reduced levels of T suppressor/cytotoxic lymphocytes in semen from vasovasostomized men: relationship to sperm autoantibodies

The regulation of lymphocyte populations in semen and their function remains unknown. Using monoclonal antibodies and immunohistochemical techniques we compared the levels of mononuclear cells in ejaculates obtained from 14 men with intact vas deferens and 13 men who had undergone both a vasectomy and a microsurgical vasovasostomy. The presence of antisperm antibodies was also assessed by the immunobead binding assay. Semen from both groups contained about 10(3) T and B lymphocytes and monocytes. In men with intact vasa, T suppressor/cytotoxic cells predominated. In contrast, in vasovasostomized men the levels of T suppressor/cytotoxic cells were significantly reduced (P less than 0.005) and T helper/inducer cells predominated in their semen. Concentrations of seminal T helper/inducer lymphocytes, B lymphocytes and monocytes were similar in both groups. Antisperm antibodies were detected on sperm, in seminal fluid and/or in serum of all the vasovasovasostomy patients but in none of the controls, T suppressor/cytotoxic cells may limit the immune response to sperm within the male reproductive tract. Chronic obstruction resulting in damage to the integrity of the excurrent ducts may induce alterations in T cell regulation leading to a decrease in T suppressor/cytotoxic cells and create conditions permissive for the formation of autoantibodies to sperm-specific antigens.

Mechanisms of active suppression of the immune response to spermatozoa

The production of autoantibodies to spermatozoa in males and isoantibodies in females is inhibited both by the physical isolation of spermatozoa from the systemic immune system and by active immunosuppression mechanisms. Lymphoid cells present in the epithelial lining of the rete testis, epididymis, and vas deferens, as well as the human ejaculate, are predominantly T suppressor/cytotoxic cells. Mononuclear cells derived from semen inhibit the in vitro activation of peripheral blood lymphocytes. Soluble specific T suppressor/cytotoxic cell activators in semen or on the sperm surface may be responsible for the predominance of this T cell subset in the male reproductive tract. The activation of T suppressor/cytotoxic cells following coitus may also limit the immune response to spermatozoa in females. Spermatozoa can also initiate immunosuppression, either by selectively inducing T suppressor cells or through the generation of activated complement components that block antibody production. Antisperm antibodies in sera from females may be associated with either a deficiency in the ability of their T suppressor/cytotoxic cells to be induced by factors in semen or by the occurrence in their husbands' ejaculates of microorganisms, antibodies, or other factors that induce T helper lymphocytes. Activated T cells produce interferon gamma, which induces Ia antigen expression on macrophages and allows the female's T helper cells to recognize processed sperm antigens. Recognition of the role of cell-mediated immune functions in the male and female genital tract identifies possible new target sites for the development of contraceptive agents.

Molecular dissection of human testicular germ cell differentiation with monoclonal antibodies

Monoclonal antibodies (MoAbs) were raised by immunising mice with nucleated cells other than sperm (NCOS) obtained from semen of an oligospermic donor. These MoAbs recognised different germ cell differentiation antigens (GDA) which appear at various stages of spermatogenesis and/or spermiogenesis. The GDA were found to be differentially expressed on spermatocytes, spermatids and on the various sub-regions of human spermatozoe. Some of the MoAbs also recognised changes in the antigenic structure of the sperm during their post-testicular maturation. Using solubilised sperm products, MoAb GDA-J/F1 reacted with a 92 kDa band in Western immunoblotting. The importance of these antibodies in the study of germ cell differentiation together with their potential clinical uses in the investigation of infertility, autoimmunity and immunological contraception are discussed.