Dendritic cells in semen of infertile men: association with sperm quality and inflammatory status of the epididymis

Integrative bioinformatics analysis to identify ferroptosis-related genes in non-obstructive azoospermia

PURPOSE

The objective of this study was to discern ferroptosis-related genes (FRGs) linked to non-obstructive azoospermia and investigate the associated molecular mechanisms.

METHOD

A dataset related to azoospermia was retrieved from the Gene Expression Omnibus database, and FRGs were sourced from GeneCards. Ferroptosis-related differentially expressed genes (FRDEGs) were discerned. Subsequently, these genes underwent analyses encompassing Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, as well as protein-protein interaction (PPI) networks and assessments of functional similarity. Following the identification of hub genes, an exploration of immune infiltration, single-cell expression, diagnostic utility, and interactions involving hub genes, RNA-binding proteins (RBPs), transcription factors (TFs), microRNAs (miRNAs), and drugs was conducted.

RESULTS

A total of 35 differentially expressed FRGs were discerned. These genes demonstrated enrichment in functions and pathways associated with ferroptosis. From the PPI network, eight hub genes were selected. Functional similarity analysis highlighted the potential pivotal roles of HMOX1 and GPX4 in azoospermia. Analysis of immune cell infiltration indicated a significant decrease in activated dendritic cells in the azoospermia group, with notable correlations between hub genes, particularly SAT1 and HMGCR, and immune cell infiltration. Unique expression patterns of hub genes across various cell types in the human testis were observed, with GPX4 prominently enriched in spermatid/sperm. Eight hub genes exhibited robust diagnostic value (AUC > 0.75). Lastly, a comprehensive hub gene-miRNA-TF-RBP-drug network was constructed.

CONCLUSION

In summary, our investigation unveiled eight FRDEGs associated with azoospermia, which hold potential as biomarkers for the diagnosis and treatment of azoospermia.

The enigmatic interplay of immune cells and abnormal spermatozoa through Mendelian randomization

PURPOSE

Abnormal spermatozoa significantly impact reproductive health, affecting fertility rates, potentially prolonging conception time, and increasing the risk of miscarriages. This study employs Mendelian randomization to explore their potential link with immune cells, aiming to reveal their potential causal association and wider implications for reproductive health.

METHODS

We conducted forward and reverse Mendelian randomization analyses to explore the potential causal connection between 731 immune cell signatures and abnormal spermatozoa. Using publicly available genetic data, we investigated various immune signatures such as median fluorescence intensities (MFI), relative cell (RC), absolute cell (AC), and morphological parameters (MP). Robustness was ensured through comprehensive sensitivity analyses assessing consistency, heterogeneity, and potential horizontal pleiotropy. The MR study produced a statistically significant p-value of .0000684, Bonferroni-corrected for the 731 exposures.

RESULTS

The Mendelian randomization analysis revealed strong indications of a reciprocal relationship between immune cell pathways and sperm integrity. When examining immune cell exposure, a potential causal link with abnormal sperm was observed in 35 different types of immune cells. Conversely, the reverse Mendelian randomization results indicated that abnormal sperm might causally affect 39 types of immune cells. These outcomes suggest a potential mutual influence between alterations in immune cell functionality and the quality of spermatozoa.

CONCLUSION

This study highlights the close link between immune responses and sperm development, suggesting implications for reproductive health and immune therapies. Further research may offer crucial insights into male fertility and immune disorders.

Disturbed Follicular Microenvironment in Polycystic Ovary Syndrome: Relationship to Oocyte Quality and Infertility

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with infertility and poor reproductive outcomes. The follicular fluid (FF) microenvironment plays a crucial role in oocyte development. This review summarizes evidence elucidating the alterations in FF composition in PCOS. Various studies demonstrated a pronounced proinflammatory milieu in PCOS FF, characterized by increased levels of cytokines, including but not limited to interleukin-6 (IL-6), tumor necrosis factor α, C-reactive protein, and IL-1β, concomitant with a reduction in anti-inflammatory IL-10. T lymphocytes and antigen-presenting cells are dysregulated in PCOS FF. PCOS FF exhibit heightened reactive oxygen species production and the accumulation of lipid peroxidation byproducts, and impaired antioxidant defenses. Multiple microRNAs are dysregulated in PCOS FF, disrupting signaling critical to granulosa cell function. Proteomic analysis reveals changes in pathways related to immune responses, metabolic perturbations, angiogenesis, and hormone regulation. Metabolomics identify disturbances in glucose metabolism, amino acids, lipid profiles, and steroid levels with PCOS FF. Collectively, these pathological alterations may adversely affect oocyte quality, embryo development, and fertility outcomes. Further research on larger cohorts is needed to validate these findings and to forge the development of prognostic biomarkers of oocyte developmental competence within FF. Characterizing the follicular environment in PCOS is key to elucidating the mechanisms underlying subfertility in this challenging disorder.

Genes and Pathways Underpinning Klinefelter Syndrome at Bulk and Single-Cell Levels

Klinefelter syndrome (KS) is the most frequent genetic anomaly in infertile men. Given its unclear mechanism, we aim to investigate critical genes and pathways in the pathogenesis of KS based on three bulk and one single-cell transcriptome data sets from Gene Expression Omnibus. We merged two data sets (GSE42331 and GSE47584) with human KS whole blood samples. When comparing the control and KS samples, five hub genes, including defensin alpha 4 (DEFA4), bactericidal permeability increasing protein (BPI), myeloperoxidase (MPO), intelectin 1 (ITLN1), and Xg Glycoprotein (XG), were identified. Besides, infiltrated degree of certain immune cells such as CD56bright NK cell were positively associated with the expression of ITLN1 and XG. Kyoto Encyclopedia of Genes and Genomes analysis identified upregulated phosphatidylinositol 3-kinase (PI3K)/AKT pathway in KS. Gene set enrichment analysis followed by gene set variation analysis confirmed the upregulation of G2M checkpoint and heme metabolism in KS. Thereafter, the GSE200680 data set was used for external validation of the expression variation of hub genes from healthy to KS testicular samples, and each hub gene yielded excellent discriminatory capability for KS without exception. At the single-cell level, the GSE136353 data set was utilized to evaluate intercellular communication between different cell types in KS patient, and strong correlations were detected between macrophages/ dendritic cells/ NK cells and the other cell types. Collectively, we provided hub genes, pathways, immune cell infiltration degree, and cell-cell communication in KS, warranting novel insights into the pathogenesis of this disease.

Germline cell de novo mutations and potential effects of inflammation on germline cell genome stability

Uncontrolled pathogenic genome mutations in germline cells might impair adult fertility, lead to birth defects or even affect the adaptability of a species. Understanding the sources of DNA damage, as well as the features of damage response in germline cells are the overarching tasks to reduce the mutations in germline cells. With the accumulation of human genome data and genetic reports, genome variants formed in germline cells are being extensively explored. However, the sources of DNA damage, the damage repair mechanisms, and the effects of DNA damage or mutations on the development of germline cells are still unclear. Besides exogenous triggers of DNA damage such as irradiation and genotoxic chemicals, endogenous exposure to inflammation may also contribute to the genome instability of germline cells. In this review, we summarized the features of de novo mutations and the specific DNA damage responses in germline cells and explored the possible roles of inflammation on the genome stability of germline cells.

Immune regulatory cytokines in seminal plasma of healthy men: A scoping review and analysis of variance

OBJECTIVE

Seminal plasma cytokines are associated with fertility and reproductive health, but progressing their clinical utility is hampered by absence of reference data on concentration ranges of relevant cytokines in healthy men. We employed a systematic approach to assemble current evidence on the concentrations of immune regulatory cytokines present in seminal plasma (SP) of normozoospermic and/or fertile men and evaluated the impact of different platform methodologies for cytokine quantification.

EVIDENCE REVIEW

A systematic literature search was performed utilising PubMed, Web of Science and Scopus. Databases were searched from inception until 30th June 2022 inclusive, using combinations of keywords pertaining to seminal fluid and cytokines, and was restricted to human participants. Original data with values reported as concentration of specific cytokines in SP of men clearly defined as fertile or normozoospermic were extracted from studies written in English.

RESULTS

A total of 3769 publications were initially identified, of which 118 fulfilled the eligibility criteria for inclusion. A total of 51 individual cytokines are detectable in SP of healthy men. The number of studies reporting on each cytokine range from 1 to >20. The reported concentrations for many cytokines linked with fertility status, including IL6, CXCL8/IL8, and TNFA, are highly variable between published studies. This is associated with the different immunoassay methodologies utilised and may be exacerbated by a lack of validation of assays to ensure suitability for SP assessment. Due to the large variation between studies, accurate reference ranges for healthy men cannot be determined from the published data.

CONCLUSIONS

The concentrations of cytokines and chemokines detected in SP is inconsistent and highly variable between studies and cohorts, limiting current capacity to define reference ranges for cytokine concentrations in fertile men. The lack of standardisation in methods used to process and store SP, and variation in platforms used to evaluate cytokine abundance, are factors contributing to the observed heterogeneity. To progress the clinical utility of SP cytokine analysis will require standardisation and validation of methodologies so that reference ranges for healthy fertile men can be defined.

Remodeling of Gut Microbiota by Probiotics Alleviated Heat Stroke-Induced Necroptosis in Male Germ Cells

SCOPE

Systemic heat stress (or heatstroke; HS) induces germ cell death and spermatogenesis disorders in men and male mammals. Also, it affects the immune environment of the circulatory system promoting gut inflammation and intestinal permeability, leading to pathogenic infection. In this study, the crosstalk between the gut and testis (gut-testis axis) under HS is explored, by examining the effects of intestinal immune status on the health of the male reproductive system in mice.

METHODS AND RESULTS

A mouse model of systemic heat stress is established to investigate the effect of probiotics on testis health. The results reveal that pro-inflammatory factor receptor activation pathway and pathogen infection response pathway are significantly upregulated in HS testes, leading to necroptosis, while pro-inflammatory factor and endotoxin are detected locally in the intestine and then entered the blood. The study then uses probiotics to intervene in gut microbiota, which results in milder gut microbial changes, lower inflammatory responses in the HS gut, and less necroptosis in the HS testes.

CONCLUSION

Probiotics-based remodeling of gut microbiota (GM) reduces the proliferation of abnormal bacteria and decreases the spread of gut-derived inflammatory mediators into the blood circulation under long-term systemic heat stress, which relieves inflammation on germ cells.

Integrative bioinformatics analysis to identify novel biomarkers associated with non-obstructive azoospermia

Aim

This study aimed to identify autophagy-related genes (ARGs) associated with non-obstructive azoospermia and explore the underlying molecular mechanisms.

Methods

Two datasets associated with azoospermia were downloaded from the Gene Expression Omnibus database, and ARGs were obtained from the Human Autophagy-dedicated Database. Autophagy-related differentially expressed genes were identified in the azoospermia and control groups. These genes were subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, protein–protein interaction (PPI) network, and functional similarity analyses. After identifying the hub genes, immune infiltration and hub gene–RNA-binding protein (RBP)–transcription factor (TF)–miRNA–drug interactions were analyzed.

Results

A total 46 differentially expressed ARGs were identified between the azoospermia and control groups. These genes were enriched in autophagy-associated functions and pathways. Eight hub genes were selected from the PPI network. Functional similarity analysis revealed that HSPA5 may play a key role in azoospermia. Immune cell infiltration analysis revealed that activated dendritic cells were significantly decreased in the azoospermia group compared to those in the control groups. Hub genes, especially ATG3, KIAA0652, MAPK1, and EGFR were strongly correlated with immune cell infiltration. Finally, a hub gene–miRNA–TF–RBP–drug network was constructed.

Conclusion

The eight hub genes, including EGFR, HSPA5, ATG3, KIAA0652, and MAPK1, may serve as biomarkers for the diagnosis and treatment of azoospermia. The study findings suggest potential targets and mechanisms for the occurrence and development of this disease.

Case Report: Dendritic Cells and Macrophages Capture Sperm in Chronically Inflamed Human Epididymis

Chronic inflammation of the male genital tract is thought to be a primary etiological factor of male infertility. The abundance and activation of macrophages and dendritic cells in patients with chronic inflammation of genital tract were closely associated with oligozoospermia and asthenospermia. Chronic epididymitis appears to be more important than seminal vesiculitis or prostatitis due to the direct interaction between spermatozoa and epididymal inflammatory cells. In this study, we present a case report of a 41-year-old male with oligoasthenospermia and chronic epididymitis. Hematoxylin-eosin staining and immunofluorescence analyses showed that antigen presenting cells including macrophages and dendritic cells were found capturing spermatozoa in the lumen of cauda epididymis. To our knowledge, this is the first case report that directly observed dendritic cells capturing spermatozoa in the lumen of an inflamed epididymis. This finding directly explains chronic epididymitis as the possible cause of oligospermia in patients.

The importance of semen leukocytes in HIV-1 transmission and the development of prevention strategies

HIV-1 sexual transmission occurs mostly through contaminated semen, which is a complex mixture of soluble factors with immunoregulatory functions and cells. It is well established that semen cells from HIV-1-infected men are able to produce the virus and that are harnessed to efficiently interact with mucosal barriers exposed during sexual intercourse. Several cofactors contribute to semen infectivity and may enhance the risk of HIV-1 transmission to a partner by increasing local HIV-1 replication in the male genital tract, thereby increasing the number of HIV-1-infected cells and the local HIV-1 shedding in semen. The introduction of combination antiretroviral therapy has improved the life expectancy of HIV-1 infected individuals; however, there is evidence that systemic viral suppression does not always reflect full viral suppression in the seminal compartment. This review focus on the role semen leukocytes play in HIV-1 transmission and discusses implications of the increased resistance of cell-mediated transmission to immune-based prevention strategies.

Soluble Fibrinogen-like protein 2 plays a role in varicocele induced male infertility

Varicocele is the most common cause of male infertility. Several theories have been proposed to explain how varicocele induces infertility. The role of epididymis in male infertility is not fully well established. Fibrinogen-like protein 2 is one of serine proteases and is a potent coagulant in membranous form and immune-modulator in soluble form (sFGL-2) and expressed in the epididymis. There are no previous reports about its possible role in varicocele. This case-controlled study aimed to evaluate the seminal level of sFGL-2 in infertile men with varicocele and in men with idiopathic infertility. This study included 85 participants divided into three groups; 25 normal fertile men, 30 infertile men with varicocele and 30 infertile men of idiopathic cause. Clinical examination, Doppler ultrasound, semen analysis and measurement of seminal level of sFGL-2 were done to all participants. Seminal level of sFGL-2 was significantly elevated in infertile than normal fertile men. Seminal level of sFGL-2 showed negative correlations with sperm concentration, motility and normal morphology. Seminal level of sFGL-2 had a positive correlation with seminal liquefaction time. This study concluded that seminal level of sFGL-2 is increased in infertile men with idiopathic cause and with varicocele induced infertility and affects seminal liquefaction.

NCOA5 Haplo-insufficiency Results in Male Mouse Infertility through Increased IL-6 Expression in the Epididymis

Male infertility might be caused by genetic and/or environmental factors that impair spermatogenesis and epididymal sperm maturation. Here we report that heterozygous deletion of the nuclear receptor coactivator-5 (Ncoa5) gene resulted in decreased motility and progression of spermatozoa in the cauda epididymis, leading to infertility in male mice. Light microscopic and ultrastructural analysis revealed morphological defects in the spermatozoa collected from the cauda epididymis of Ncoa5^+/− mice. Immunohistochemistry showed that interleukin-6 (IL-6) expression in epithelial cells of Ncoa5^+/− epididymis was higher than wild type counterparts. Furthermore, heterozygous deletion of Il-6 gene in Ncoa5^+/− male mice partially improved spermatozoa motility and moderately rescued infertility phenotype. Our results uncover a previously unknown physiological role of NCOA5 in the regulation of epididymal sperm maturation and suggest that NCOA5 deficiency could cause male infertility through increased IL-6 expression in epididymis.

The association of seminal leucocytes, interleukin-6 and interleukin-8 with sperm DNA fragmentation: A prospective study

The effect of seminal leucocytes on sperm DNA integrity has been discussed controversially in literatures. Moreover, the studies investigating the in vivo effect of pro-inflammatory cytokines interleukin-6 and interleukin-8 on sperm DNA fragmentation are scarce and inconsistent. The association of standard sperm parameters with sperm DNA fragmentation is also a matter of ongoing discussion. Hence, the aims of this study were, first, to evaluate the effect of seminal leucocytes, interleukin-6 and interleukin-8 on sperm DNA integrity and, second, to examine whether standard semen parameters are associated with sperm DNA fragmentation. Seminal leucocytes, interleukin-6, interleukin-8 and standard semen parameters, including total sperm number, sperm concentration, progressive motility, nonprogressive motility, immotility and normal morphology, were determined in 134 consecutive men. The concentrations of seminal leucocytes, interleukin-6 and interleukin-8, did not correlate with sperm DNA fragmentation. In contrast, total sperm number, sperm concentration, progressive motility, nonprogressive motility and normal morphology exhibited significant inverse correlations with sperm DNA fragmentation. Immotile spermatozoa were directly correlated with sperm DNA fragmentation. In conclusion, seminal leucocytes, interleukin-6 and interleukin-8, are not associated with sperm DNA fragmentation. Poor standard semen parameters are significantly related to the high levels of sperm DNA fragmentation.

Microsurgical Epididymal Cystectomy does not Impact Upon Sperm Count, Motility or Morphology and is a Safe and Effective Treatment for Epididymal Cystic Lesions (ECLs) in Young Men With Fertility Requirements

OBJECTIVE

To assess the therapeutic efficacy and safety of microsurgical epididymal cystectomy for the treatment of epididymal cystic lesions in young men with fertility requirements and the impact of this surgery upon sperm quality and epididymal function.

MATERIALS AND METHODS

We prospectively evaluated the therapeutic outcomes, complications, safety and efficacy of microsurgical epididymal cystectomy and the impact of microsurgery upon sperm parameters. All patients were followed-up 3, 6 and 12 months after surgery to investigate sperm count, motility, morphology, neutral α-glucosidase, improvement of symptoms, recurrence, and complications.

RESULTS

Palpated cyst pain was evident in 32 out of 51 patients. Pathologists identified 29 spermatoceles and 22 epididymal cysts. Mean operation time was 39.27 ± 5.98 minutes, and the mean length of postoperative hospital stay was 2.02 ± 0.35 days. After surgery, scrotal pain disappeared in 80.4% of patients (41/51). A significantly higher rate of pain disappearance was observed in patients with palpated pain than those without palpated pain. Insignificant difference was seen in terms of sperm count, motility, sperm morphology or neutral α-glucosidase between preoperation and postoperation at 1-year follow-up. Sperm count and NGA in patients with an epididymal cystic lesions > 2.5 cm were significantly increased after surgery. The rate of complications was 7.3%. No cyst recurrence was observed during follow-up.

CONCLUSION

Microsurgical epididymal cystectomy does not impact upon sperm count, motility, morphology, or epididymal function and is a safe and effective surgical modality for young men with fertility requirements. Local palpated pain on the epididymal cyst is recommended as an optional surgical indication.

Detection of dendritic cells and related cytokines in follicular fluid of patients with polycystic ovary syndrome

PROBLEM

The presence of dendritic cells (DCs) and associated cytokines in follicular fluid (FF) from patients with polycystic ovary syndrome (PCOS) remains unknown.

METHODS OF STUDY

FF was collected from PCOS patients and patients with severe male factor infertility (control) at the day of transvaginal oocyte retrieval. Phenotypes of DC were detected by flow cytometry, and TNF-α, IL-6, IL-10, and IL-23 were assessed by ELISA.

RESULTS

A significant decrease in the percentage of DC was found in patients with PCOS (16.22±5.5%) compared with control (21.27±5.5%, P<.01). E₂ on the day of hCG administration was correlated positively with the mean fluorescence intensity of HLA-DR (r=.75, P<.01) and reversely correlated with the concentration of TNF-α in FF (r=-.69, P<.01). The level of TNF-α, IL-6, and IL-10 increased significantly but IL-23 decreased in FF from patients with PCOS.

CONCLUSION

The decrease of DC and disturbance of associated cytokines in FF from PCOS patients indicates a disorder of immunological microenvironment of the ovarian follicle, which might be involved in the dysfunction of folliculogenesis.

Shedding Light on the Nature of Seminal Round Cells

INTRODUCTION

In this investigation we assess the incidence of round cells (RCs) in semen samples in our infertile patient population and their significance on intracytoplasmic sperm injection (ICSI) cycle outcomes. We also evaluate the usefulness of RCs as indicators of bacterial infection and highlight the origin of this cell-type, as well as its role in the human ejaculate.

PATIENTS AND METHODS

In a prospective fashion, a total of 4,810 ejaculated samples were included in the study during a period of 24 months. RCs were characterized for white blood cell (WBC) components versus exfoliated germ cells by testing for multiple markers of ploidy as well as protamine assays. Cases displaying ≥ 2 x 106/ml RCs were screened for bacteria. Raw specimens containing RC were processed by peroxidase and other leukocyte assays, specific stains for protamines were used to identify spermiogenic stage, aneuploidy (FISH) assessment was carried out, and the presence of various Sertoli-cell cytoplasmic remnants was analyzed to identify and characterize immature germ cells. The effect of RC on clinical outcome was assessed in specimens used for ICSI.

RESULTS

The average age of the men involved was 39.2 ± 7 years. Semen samples had a mean concentration of 40.7 ± 31 x 106/ml, motility of 42.6 ± 35%, and morphology of 2.3 ± 2%. RCs were identified in 261 specimens, representing a proportion of 5.4%. Men with RCs had comparable age but lower sperm concentration and morphology than the control group (P<0.001). The aneuploidy rate of 4.3% in RCs group was remarkably higher than the control group (2.3%; P<0.001). Sperm aneuploidy rate positively correlated with the number of RCs (P<0.001). Of 44 men, 17 of them in 18 cycles had up to 1.9 x 106/ml RCs without affecting fertilization and clinical pregnancy rates when compared to controls (n = 365 cycles). In 27 men undergoing 33 ICSI cycles with ≥ 2 x 106/ml RCs, the fertilization rate trended lower and the miscarriage rate was significantly increased (P = 0.05). There was lack of correlation between RC and bacteriological growth. Specific markers indicated that seminal RCs are mostly immature germ cells encased in the remnants of Sertoli cell cytoplasm. Moreover, their modest protamine content and their haploid status confirm that they are post-meiotic. Sequential observation in the same man showed that RC episodes were followed by an amelioration of semen parameters, and interestingly, the episodic occurrence of RCs often coincides with flu season peaks.

CONCLUSIONS

Seminal RCs are not a marker of infectiousness but rather a transient indicator of spermatogenic insult that possibly occurs in most men following a mild and transient ailment such as the flu.

Characteristics and quantities of HIV host cells in human genital tract secretions

Human immunodeficiency virus (HIV)-infected leukocytes have been detected in genital secretions from HIV-infected men and women and may play an important role in the sexual transmission of HIV. However, they have been largely overlooked in studies on mechanisms of HIV transmission and in the design and testing of HIV vaccine and microbicide candidates. This article describes the characteristics and quantities of leukocytes in male and female genital secretions under various conditions and also reviews evidence for the involvement of HIV-infected cells in both horizontal and vertical cell-associated HIV transmission. Additional research is needed in this area to better target HIV prevention strategies.

CD169-dependent cell-associated HIV-1 transmission: a driver of virus dissemination

Sexual transmission of human immunodeficiency virus type 1 (HIV-1) occurs across mucosal surfaces of the genital and gastrointestinal tracts and accounts for the vast majority of newly acquired infections worldwide. In the absence of an effective vaccine, interventional strategies such as microbicides that target viral attachment and entry into mucosa-resident target cells are particularly attractive and might have the greatest impact on reducing the HIV-1 pandemic. Rational development of microbicides would be greatly aided with a better understanding of several key questions of mucosal HIV-1 transmission, including the molecular mechanism(s) of how HIV-1 traverses mucosal barriers, the type of cells that it initially infects to gain a foothold in the naive host, and how it is disseminated from local sites of infection to draining lymph nodes. In this review, we discuss the role of myeloid dendritic cells (DCs) in cell-associated HIV-1 transmission and in facilitating systemic HIV-1 dissemination. We will evaluate the role of CD169 as a DC-associated HIV-1 attachment factor, investigate the molecular mechanisms by which HIV-1 particles are transferred from DCs to CD4(+) T cells across virological synapses, and provide arguments for inclusion of molecules in microbicides that can effectively target HIV-1 attachment to DCs and DC-mediated virus transfer.

The blood-epididymis barrier and inflammation

The blood-epididymis barrier (BEB) is a critical structure for male fertility. It enables the development of a specific luminal environment that allows spermatozoa to acquire both the ability to swim and fertilize an ovum. The presence of tight junctions and specific cellular transporters can regulate the composition of the epididymal lumen to favor proper sperm maturation. The BEB is also at the interface between the immune system and sperm. Not only does the BEB protect maturing spermatozoa from the immune system, it is also influenced by cytokines released during inflammation, which can result in the loss of barrier function. Such a loss is associated with an immune response, decreased sperm functions, and appears to be a contributing factor to post-testicular male infertility. Alterations in the BEB may be responsible for the formation of inflammatory conditions such as sperm granulomas. The present review summarizes current knowledge on the morphological, physiological and pathological components associated with the BEB, the role of immune function on the regulation of the BEB, and how disturbance of these factors can result in inflammatory lesions of the epididymis.