B Cell Subset Analysis and Gene Expression Characterization in Mid-Luteal Endometrium

B Cell Lineage in the Human Endometrium: Physiological and Pathological Implications

Immunocompetent cells of B lineage function in the humoral immunity system in the adaptive immune responses. B cells differentiate into plasmacytes upon antigen-induced activation and produce different subclasses of immunoglobulins/antibodies. Secreted immunoglobulins not only interact with pathogens to inactivate and neutralize them, but also involve the complement system to exert antibacterial activities and trigger opsonization. Endometrium is a mucosal tissue that lines the mammalian uterus and is indispensable for the establishment of a successful pregnancy. The lymphocytes of B cell lineage are a minority in the human cycling endometrium. Human endometrial B cells have therefore been understudied so far. However, the disorders of the female reproductive tract, including chronic endometritis and endometriosis, have highlighted the importance of further research on the endometrial B cell lineage. This review aims to revisit lymphopoiesis, maturation, commitment, and survival of B cells, shedding light on their physiological and pathological implications in the human endometrium.

Minimal residual disease assessment following CD19-targeted therapy in B-cell precursor acute lymphoblastic leukemia using standardized 12-color flow cytometry: A EuroFlow study

Detection of minimal/measurable residual disease (MRD) is a critical prognostic marker in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). The EuroFlow Consortium previously developed an 8-color flow cytometric MRD protocol, effective for >98% of BCP-ALL patients treated with chemotherapy. This study aimed to enhance MRD detection, particularly for patients treated with CD19-targeted therapies, by expanding the EuroFlow protocol to a 12-color panel. This new panel incorporates additional B-cell markers and exclusion T/NK-cell markers (CD3 and CD7). Through an evaluation of 237 diagnostic BCP-ALL samples, CD22, CD24, and HLA-DR were selected as additional B-cell gating markers. Two 12-color tubes were technically optimized and clinically validated across 101 patient follow-up samples, demonstrating excellent concordance with molecular MRD levels (R 2 = 0.88). The 12-color BCP-ALL MRD tubes were compatible with the previously developed 8-color automated gating and identification (AGI) tool and demonstrated good reproducibility. Our findings indicate that the 12-color panel performs comparably to the 8-color BCP-ALL MRD panel, including both CD19-positive and CD19-negative cases. However, it offers an improved definition of the B-cell lineage, particularly for expert-guided manual data analysis, and provides additional information on the expression of the targetable marker CD22.

A transcriptomic analysis of the interplay of ferroptosis and immune filtration in endometriosis and identification of novel therapeutic targets

Endometriosis is an inflammatory disease, involving immune cell infiltration and production of inflammatory mediators. Ferroptosis has recently been recognized as a mode of controlled cell death and the iron overload and peroxidative environment prevailing in the ectopic endometrium facilitates the occurrence of ferroptosis. In the current investigation, gene expression data was obtained from the dataset GSE7305.The variation in infiltration of immune cells amongst the samples with endometriosis and normal tissue was analysed using the CIBERSORTx tool which revealed higher infiltration of T cells gamma delta, macrophages M2, B cells naïve, T cells CD4 memory resting cells, plasma cells, T cells CD8 and mast cells activated in the tissue samples with endometriosis. An overlap of the differentially expressed genes (DEGs) and ferroptosis related genes revealed 32 ferroptosis related DEGs (FR-DEGs). GO and KEGG pathway analysis showed the FR-DEGs to be enriched in ferroptosis. The PPI network of the FR-DEGs was constructed and TP53, HMOX1, CAV1, CDKN1A, CD44, EPAS1, SLC2A1, MAP3K5, GCLC and FANCD2 were identified as the hub genes. Pearson correlation revealed significant correlation between the hub genes and infiltrating immune cells in endometriosis, thereby suggesting existence of a regulatory crosstalk between immune responses and ferroptosis in endometriosis. Hub gene- miRNA network analysis revealed that 7 of the 10 hub genes were targets of 3 miRNAs -hsa-miR-20a-5p, hsa-miR-16-5p and hsa-miR-17-5p, thereby providing further insight into the regulatory mechanisms underlying disease progression. Predictive analysis and cross validation studies revealed TP53 and CDKN1A as common targets of hsa-miR-16-5p, hsa-miR-17-5p, and hsa-miR-20a-5p, thereby revealing their regulatory roles in ferroptosis and immune modulatory pathways relevant to endometriosis. The present study indicates an important role of both immune dysregulation and ferroptosis in the pathogenesis of endometriosis and identifies ferroptosis related hub genes and their miRNA regulators as favourable novel targets for further studies and therapeutic interventions.

Tertiary lymphoid structures in endometriosis

OBJECTIVE

To determine whether tertiary lymphoid structures (TLSs), which reflect organized immune cell aggregates present in non-lymphoid tissues, are consistent features of endometriosis lesions.

DESIGN

Detailed histopathological analysis of endometrial and lesion tissue from patients with endometriosis and controls was performed. Multiplex immunofluorescence on select samples was then conducted to identify canonical cell populations present within TLSs: CD3+ and CD8+ T-cells, CD79a+ B-cells, CD208+ dendritic cells, CD21+ follicular dendritic cells, and PNAd+ high endothelial venules.

PATIENT(S)

Patients with histologically confirmed endometriosis (N = 113; 44.3 ± 6.0) and control individuals (N = 110; 44.6 ± 7.1).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE(S)

Detection of TLSs as characterized by the presence of all canonical cell types that constitute TLS and structure morphology.

RESULT(S)

Of the selected samples (N = 18; 6 ectopic/eutopic/control), mature TLSs were identified in 3 ectopic tissue samples present on the ovary and fallopian tube, with immature TLSs (lacking follicular dendritic cell networks and high endothelial venules) present throughout eutopic and control endometrial samples.

CONCLUSION

These findings demonstrate the presence of TLSs across various endometriosis phenotypes, prompting further research into their significance within disease pathophysiology and the prognostic implications for patients.

Pregnancy-related factors induce immune tolerance through regulation of sCD83 release

A well-balanced maternal immune system is crucial to maintain fetal tolerance in case of infections during pregnancy. Immune adaptations include an increased secretion of soluble mediators to protect the semi-allogeneic fetus from excessive pro-inflammatory response. B lymphocytes acquire a higher capacity to express CD83 and secrete soluble CD83 (sCD83) upon exposure to bacteria-derived components such as LPS. CD83 possesses immune modulatory functions and shows a promising therapeutic potential against inflammatory conditions. The administration of sCD83 to pregnant mice reduces LPS-induced abortion rates. The increased CD83 expression by endometrial B cells as compared to peripheral blood B cells suggests its modulatory role in the fetal tolerance, especially in the context of infection. We postulate that in pregnancy, CD83 expression and release is controlled by pregnancy-related hormones. The intra- and extracellular expression of CD83 in leukocytes from peripheral blood or decidua basalis and parietalis at term were analyzed by flow cytometry. After treatment with pregnancy-related hormones and LPS, ELISA and qPCR were performed to study sCD83 release and CD83 gene expression, respectively. Cleavage prediction analysis was used to find potential proteases targeting CD83. Expression of selected proteases was analyzed by ELISA. Higher levels of CD83 were found in CD11c+ dendritic cells, CD3+ T cells and CD19+ B cells from decidua basalis and decidua parietalis after LPS-stimulation in vitro. An increase of intracellular expression of CD83 was also detected in CD19+ B cells from both compartments. Stimulated B cells displayed significantly higher percentages of CD83+ cells than dendritic cells and T cells from decidua basalis and peripheral blood. Treatment of B lymphocytes with pregnancy-related molecules (E2, P4, TGF-β1 and hCG) enhanced the LPS-mediated increase of CD83 expression, while dexamethasone led to a reduction. Similarly, the release of sCD83 was increased under TGF-β1 treatment but decreased upon dexamethasone stimulation. Finally, we found that the hormonal regulation of CD83 expression is likely a result from a balance between gene transcription from CD83 and the modulation of the metalloproteinase MMP-7. Thus, data supports and complements our previous murine studies on hormonal regulation of CD83 expression, reinforcing its immunomodulatory relevance in anti-bacterial responses during pregnancy.

Innate and adaptive immune dysregulation in women with recurrent implantation failure

Recurrent implantation failure (RIF) is a condition where a woman fails to obtain pregnancy after multiple embryo transfer cycles, even with superior-quality blastocysts. There are various factors that can contribute to RIF, including immunologic disturbances. The immune system is extremely important during pregnancy. Immune cells such as T cells, B cells, natural killer (NK) cells, and macrophages (MQ) are present in the female reproductive tract and are accountable for regulating the immune response to invading pathogens and maintaining tissue homeostasis. Dysregulation of these immune cells can lead to inflammation, which can impair fertility. One of the most common immunological disturbances observed in RIF is an altered Th1/Th2 ratio, along with changes in NK cell and macrophage numbers. In addition, the presence of some antibodies, such as anti-ovarian antibodies, can also contribute to RIF. Interleukins have been implicated in the development of an inflammatory response that can interfere with successful embryo implantation. As a result, a comprehensive understanding of immunological compartments in RIF women could assist us in determining the immunological origins of this disease. We will discuss immunological factors that might contribute to RIF etiology, including cellular and molecular components.

Bioinformatic Analysis of the Significance of the KIR2DL4 Gene in Recurrent Implantation Failure

Related studies have pointed out that Killer immunoglobulin-like receptor 2DL4 (KIR2DL4) was associated with vascular remodeling in early pregnancy, and it might play an important role in immunity. In this study, recurrent implantation failure (RIF)-related GSE58144 dataset was extracted from the Gene Expression Omnibus (GEO) database. Firstly, the immune micro-environment analyses were conducted to analyze the pathogenesis of KIR2DL4 in RIF. Then, the gene set enrichment analysis (GSEA) was performed to investigate the function of KIR2DL4. Moreover, the TF-mRNA-miRNA and the co-expression networks were constructed to reveal the potential regulation of KIR2DL4. Furthermore, the genes that were associated with KIR2DL4 and differentially expressed in RIF were obtained and defined as key genes, and the functions of these genes were further explored. KIR2DL4 could be used for clinical diagnosis of RIF, and it was correlated with the changes in the immune micro-environment in RIF. From the perspective of function, KIR2DL4 was associated with complement and coagulation cascades, natural killer cell-mediated cytotoxicity, etc. Moreover, the TF-mRNA-miRNA regulatory network was constructed with KIR2DL4, 9 TFs, and 29 miRNAs. Furthermore, KIR2DL4, ACSM1, IL2RB, and PTPN11 were screened as key genes, which were associated with immune-related functions. This study deeply analyzed the function of KIR2DL4 and its role in RIF, and we found that STAT1 might up-regulate KIR2DL4 by INF-γ/JAK2/STAT1 signaling pathway. Besides, over-expressed KIR2DL4 in the mid-luteal endometrium might influence embryo implantation by affecting the embryo implantation microenvironment, which might help deepen the understanding of the molecular mechanism of RIF.

Predicting Response to Immunotargeted Therapy in Endometrial Cancer via Tumor Immune Microenvironment: A Multicenter, Observational Study

Only one-third of patients with advanced MSS/pMMR endometrial cancer exhibit a lasting response to the combination treatment of Pembrolizumab and Lenvatinib. The combined administration of these two drugs is based on Lenvatinib's ability to modulate the tumor microenvironment, enabling Pembrolizumab to exert its effect. These findings underscore the importance of exploring tumor microenvironment parameters to identify markers that can accurately select candidates for this type of therapy. An open non-randomized observational association study was conducted at six clinical centers, involving a total of 28 patients with advanced MSS/pMMR endometrial cancer who received Pembrolizumab and Lenvatinib therapy. Using TSA-associated multiplex immunofluorescence, we analyzed the proportion of CD8+ T lymphocytes, CD20+ B lymphocytes, FoxP3+ T regulatory lymphocytes, and CD163+ macrophages in tumor samples prior to immunotargeted therapy. The percentage of CD20+ B lymphocytes and the CD8-to-CD20 lymphocytes ratio was significantly higher in patients who responded to treatment compared to non-responders (responders vs. non-responders: 0.24 (0.1-1.24)% vs. 0.08 (0.00-0.15)%, p = 0.0114; 1.44 (0.58-2.70) arb. unit vs. 19.00 (3.80-34.78) arb. unit, p = 0.0031). The sensitivity and specificity of these biomarkers were 85.71% and 70.59%, and 85.71% and 85.71%, respectively. The proportion of CD20+ B lymphocytes and the CD8-to-CD20 lymphocytes ratio in the stroma of endometrial cancer serves as both a prognostic marker of response to immunotargeted therapy and a prognostic factor for progression-free survival in patients.

Follicular helper T lymphocytes in the endometria of patients with reproductive failure: Association with pregnancy outcomes and inflammatory status of the endometria

PROBLEM

The phenotypes and functions of B and CD4⁺ T-helper cell subsets during chronic inflammation of the endometria remain largely unexplored. This study aimed to investigate the characteristics and functions of follicular helper T (Tfh) cells to understand the pathological mechanisms of chronic endometritis (CE).

METHOD OF STUDY

Eighty patients who underwent hysteroscopic and histopathological examinations for CE were divided into three groups-those with positive results for hysteroscopy and CD138 staining (DP), negative results for hysteroscopy but positive CD138 staining (SP), and negative results for hysteroscopy and CD138 staining (DN). The phenotypes of B cells and CD4⁺ T-cell subsets were analyzed using flow cytometry.

RESULTS

CD38⁺ and CD138⁺ cells were mainly expressed in the non-leukocyte population of the endometria, and the endometrial CD19⁺ CD138⁺ B cells were fewer than the CD3⁺ CD138⁺ T cells. The percentage of Tfh cells increased with chronic inflammation in the endometria. Additionally, the elevated percentage of Tfh cells correlated with the number of miscarriages.

CONCLUSIONS

CD4⁺ T cells, particularly Tfh cells, may be critical in chronic endometrial inflammation and affect its microenvironment, thereby regulating endometrial receptivity, compared to B cells.

Immune alterations in recurrent implantation failure

A failure to achieve pregnancy after three or more embryo transfer cycles with high-quality blastocysts is referred to as recurrent implantation failure (RIF). RIF can be due to altered uterine factors or male factors or embryo factors. Disrupted endometrial receptivity, altered expression of genes in several pathways, immunologic disturbances in the peripheral blood and/or the endometrium, and epigenetic alterations are associated with RIF. Amongst the immunologic disturbances, altered Th1/Th2 ratio, altered NK cell and macrophage numbers are observed in women with RIF. However, not all women with RIF have the same kind of immune dysfunction suggesting that RIF is a heterogeneous condition associated with varied immune responses and one size may not fit all. Thus, personalized therapies based on the immune status of the patient are being tested in women with RIF. In general, women with a high Th1/Th2 ratio are offered Tacrolimus, while intravenous IgG is recommended in women with high NK cell numbers/HLA mismatch. Women with hyperactivated immune status in the uterus are offered progesterone support, prednisolone, vitamin E, and intralipid treatment to suppress inflammation and oxidative stress, while endometrial scratching and intrauterine hCG administration are offered to women with hypo-active immune status. There is a need for standardized tests for evaluation of immune status in patients and sufficiently powered randomized controlled trials for personalized therapies to determine which of these will be beneficial in women with RIF. Till then, the ART community should limit the use of such add-on interventions in women with RIF.

Importance of the endometrial immune environment in endometrial cancer and associated therapies

Endometrial cancer is rising in prevalence. The standard treatment modality of hysterectomy is becoming increasingly inadequate due primarily to the direct link between endometrial cancer and high BMI which increases surgical risks. This is an immunogenic cancer, with unique molecular subtypes associated with differential immune infiltration. Despite the immunogenicity of endometrial cancer, there is limited pre-clinical and clinical evidence of the function of immune cells in both the normal and cancerous endometrium. Immune checkpoint inhibitors for endometrial cancer are the most well studied type of immune therapy but these are not currently used as standard-of-care and importantly, they represent only one method of immune manipulation. There is limited evidence regarding the use of other immunotherapies as surgical adjuvants or alternatives. Levonorgestrel-loaded intra-uterine systems can also be effective for early-stage disease, but with varying success. There is currently no known reason as to what predisposes some patients to respond while others do not. As hormones can directly influence immune cell function, it is worth investigating the immune compartment in this context. This review assesses the immunological components of the endometrium and describes how the immune microenvironment changes with hormones, obesity, and in progression to malignancy. It also describes the importance of investigating novel pathways for immunotherapy.

BCL6, a key oncogene, in the placenta, pre-eclampsia and endometriosis

BACKGROUND

The key oncogene B-cell lymphoma 6 (BCL6) drives malignant progression by promoting proliferation, overriding DNA damage checkpoints and blocking cell terminal differentiation. However, its functions in the placenta and the endometrium remain to be defined.

OBJECTIVE AND RATIONALE

Recent studies provide evidence that BCL6 may play various roles in the human placenta and the endometrium. Deregulated BCL6 might be related to the pathogenesis of pre-eclampsia (PE) as well as endometriosis. In this narrative review, we aimed to summarize the current knowledge regarding the pathophysiological role of BCL6 in these two reproductive organs, discuss related molecular mechanisms, and underline associated research perspectives.

SEARCH METHODS

We conducted a comprehensive literature search using PubMed for human, animal and cellular studies published until October 2021 in the following areas: BCL6 in the placenta, in PE and in endometriosis, in combination with its functions in proliferation, fusion, migration, invasion, differentiation, stem/progenitor cell maintenance and lineage commitment.

OUTCOMES

The data demonstrate that BCL6 is important in cell proliferation, survival, differentiation, migration and invasion of trophoblastic cells. BCL6 may have critical roles in stem/progenitor cell survival and differentiation in the placenta and the endometrium. BCL6 is aberrantly upregulated in pre-eclamptic placentas and endometriotic lesions through various mechanisms, including changes in gene transcription and mRNA translation as well as post-transcriptional/translational modifications. Importantly, increased endometrial BCL6 is considered to be a non-invasive diagnostic marker for endometriosis and a predictor for poor outcomes of IVF. These data highlight that BCL6 is crucial for placental development and endometrium homeostasis, and its upregulation is associated with the pathogenesis of PE, endometriosis and infertility.

WIDER IMPLICATIONS

The lesson learned from studies of the key oncogene BCL6 reinforces the notion that numerous signaling pathways and regulators are shared by tumors and reproductive organs. Their alteration may promote the progression of malignancies as well as the development of gestational and reproductive disorders.

The role of endometrial B cells in normal endometrium and benign female reproductive pathologies: a systematic review

STUDY QUESTION

What are the similarities and differences in endometrial B cells in the normal human endometrium and benign reproductive pathologies?

SUMMARY ANSWER

Endometrial B cells typically constitute <5% of total endometrial CD45+ lymphocytes, and no more than 2% of total cells in the normal endometrium, and while their relative abundance and phenotypes vary in benign gynaecological conditions, current evidence is inconsistent.

WHAT IS KNOWN ALREADY

B cells are vitally important in the mucosal immune environment and have been extensively characterized in secondary lymphoid organs and tertiary lymphoid structures (TLSs), with the associated microenvironment germinal centre. However, in the endometrium, B cells are largely overlooked, despite the crucial link between autoimmunity and reproductive pathologies and the fact that B cells are present in normal endometrium and benign female reproductive pathologies, scattered or in the form of lymphoid aggregates (LAs). A comprehensive summary of current data investigating B cells will facilitate our understanding of endometrial B cells in the endometrial mucosal immune environment.

STUDY DESIGN SIZE DURATION

This systematic review retrieved relevant studies from four databases (MEDLINE, EMBASE, Web of Science Core Collection and CINAHL) from database inception until November 2021.

PARTICIPANTS/MATERIALS SETTING METHODS

The search strategy combined the use of subject headings and relevant text words related to 'endometrium', 'B cells' and B-cell derivatives, such as 'antibody' and 'immunoglobulin'. Non-benign diseases were excluded using cancer-related free-text terms, and searches were limited to the English language and human subjects. Only peer-reviewed research papers were included. Each paper was graded as 'Good', 'Fair' or 'Poor' quality based on the NEWCASTLE-OTTAWA quality assessment scale. Only 'Good' quality papers were included.

MAIN RESULTS AND THE ROLE OF CHANCE

Twenty-seven studies met the selection criteria and were included in this review: 10 cross-sectional studies investigated B cells in the normal endometrium; and 17 case-control studies compared the characteristics of endometrial B cells in control and benign female reproductive pathologies including endometritis, endometriosis, infertility, abnormal uterine bleeding, endometrial polyps and uterine fibroids. In all studies, B cells were present in the endometrium, scattered or in the form of LAs. CD20+ B cells were more abundant in patients with endometritis, but the data were inconsistent as to whether B-cell numbers were increased in endometriosis and patients with reproductive pathologies.

LIMITATIONS REASONS FOR CAUTION

Although only 'good' quality papers were included in this systematic review, there were variations in patients' age, diagnostic criteria for different diseases and sample collection time among included studies. Additionally, a large number of the included studies only used immunohistochemistry as the identification method for endometrial B cells, which may fail to provide an accurate representation of the numbers of endometrial B cells.

WIDER IMPLICATIONS OF THE FINDINGS

Histological studies found that endometrial B cells are either scattered or surrounded by T cells in LAs: the latter structure seems to be under hormonal control throughout the menstrual cycle and resembles TLSs that have been observed in other tissues. Further characterization of endometrial B cells and LAs could offer insights to endometrial B-cell function, particularly in the context of autoimmune-associated pathologies, such as endometriosis. Additionally, clinicians should be aware of the limited value of diagnosing plasma cell infiltration using only CD138.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by Finox Biotech. The authors have no conflicts of interest to declare.

PROSPERO REGISTRATION NUMBER

This systematic review was registered in PROSPERO in January 2020 (PROSPERO ID: CRD42020152915).