Estrogen promotes B cell activation in vitro through down-regulating CD80 molecule expression

Mendelian randomization study identifying immune cell phenotypes associated with breast cancer risk

BACKGROUND

Globally, breast cancer is among the most frequent cancers, and tumor progression is greatly impacted by the immune system. Studies have revealed a correlation between the phenotypes of immune cells and the incidence of breast cancer; nevertheless, the causal relationship has yet to be fully elucidated. Hence, we sought to ascertain the causal relationship between immune cell subtypes and breast cancer through the implementation of Mendelian randomization (MR).

METHODS

MR analysis utilized freely available genetic data to explore the causation link between 731 immune cell phenotypes and the susceptibility to breast cancer, distinguishing between estrogen receptor-positive (ER+) and negative (ER-) subtypes. ER+ patients are sensitive to endocrine drugs, and one more way to treat with endocrine drugs than ER- patients. Inverse variance weighting (IVW), MR-Egger regression, and weighted median methods were employed to evaluate MR. The IVW analysis was used as the primary research methodology.

RESULTS

Among 731 immune phenotypes, we found that breast cancer was causally related to eight immune phenotypes, six of which were protective against breast cancer, while two were risk factors. After grouping breast cancers based on the ER expression, ER+ breast cancer patients were significantly causally related to seven immune phenotypes, among which three were protective against ER+ breast cancers, and four were risk factors. Furthermore, ER-breast cancer patients were significantly causally related to 10 immune phenotypes, with four being protective against ER-breast cancers and six being risk factors.

CONCLUSIONS

This MR Study proved that there is a certain genetic relationship between immune cell phenotype and breast cancer, and the related genes may have certain significance for the treatment and drug development of breast cancer.

The intestinal flora: The key to unraveling heterogeneity in immune thrombocytopenia?

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by enhanced platelet destruction and impaired platelet production, due to a loss of immune tolerance that leads to targeting of platelets and megakaryocytes by glycoprotein-autoantibodies and/or cytotoxic T cells. There is a high degree of heterogeneity in ITP patients signified by unpredictable disease trajectories and treatment responses. Initial studies in humans have identified intestinal microbiota perturbance in ITP. Recently, gut microbial perturbance has been linked to other autoimmune diseases. Based on these findings, we hypothesize that intestinal microbiota may influence ITP pathophysiology through several mechanisms, including induction of platelet-autoantibody production, increasing complement-dependent platelet cytotoxicity, disturbing T cell homeostasis, impairing megakaryocyte function, and increasing platelet-desialylation and -clearance. The pathophysiological heterogeneity of ITP may, at least in part, be attributed to a perturbed intestinal microbiota. Therefore, a better understanding of intestinal microbiota in ITP may result in a more personalized therapeutic approach.

Contraceptives or Hormone Replacement Therapy and Associations with Autoimmune Conditions: Exploring Effects of Estrogen Analog Supplementation

OBJECTIVE

The aim of this study was to investigate the impact of estrogen and progesterone analog supplementation on the development of autoimmune conditions.

METHODS

This retrospective observational study used data from the TriNetX network, which comprised over 100 million patients from 89 health care organizations. We compared patients exposed to estrogen and progesterone analogs to those exposed to progesterone-only therapy, using 1:1 propensity score matching based on age, ethnicity, and additional criteria. The primary outcomes were incidences of various autoimmune conditions.

RESULTS

We included 3,338,925 patients in the group who received estrogen and progesterone and 2,090,758 patients in the group who received progesterone only. Prematching, the group who received combined therapy showed increased risks for Sjögren disease (risk ratio [RR] 1.46), rheumatoid arthritis (RR 1.1), and other autoimmune conditions. Postmatching, significant associations persisted for most conditions, with increased risks for systemic sclerosis, systemic lupus erythematosus, giant cell arteritis, Behcet disease, psoriatic arthritis, reactive arthritis, and ankylosing spondylitis. The group who received combination therapy appeared to have lower risks of developing antiphospholipid syndrome (RR 0.7).

CONCLUSION

Combined estrogen and progesterone therapy is associated with an increased risk of several autoimmune conditions. The role of estrogen, despite its protective effects against some conditions, underscores the complex interplay of sex hormones in autoimmunity. Further prospective studies are needed to elucidate underlying mechanisms and evaluate causality.

Regulation of Stromal Cells by Sex Steroid Hormones in the Breast Cancer Microenvironment

Breast cancer is a prevalent hormone-dependent malignancy, and estrogens/estrogen receptor (ER) signaling are pivotal therapeutic targets in ER-positive breast cancers, where endocrine therapy has significantly improved treatment efficacy. However, the emergence of both de novo and acquired resistance to these therapies continues to pose challenges. Additionally, androgens are produced locally in breast carcinoma tissues by androgen-producing enzymes, and the androgen receptor (AR) is commonly expressed in breast cancer cells. Intratumoral androgens play a significant role in breast cancer progression and are closely linked to resistance to endocrine treatments. The tumor microenvironment, consisting of tumor cells, immune cells, fibroblasts, extracellular matrix, and blood vessels, is crucial for tumor progression. Stromal cells influence tumor progression through direct interactions with cancer cells, the secretion of soluble factors, and modulation of tumor immunity. Estrogen and androgen signaling in breast cancer cells affects the tumor microenvironment, and the expression of hormone receptors correlates with the diversity of the stromal cell profile. Notably, various stromal cells also express ER or AR, which impacts breast cancer development. This review describes how sex steroid hormones, particularly estrogens and androgens, affect stromal cells in the breast cancer microenvironment. We summarize recent findings focusing on the effects of ER/AR signaling in breast cancer cells on stromal cells, as well as the direct effects of ER/AR signaling in stromal cells.

B cells: roles in physiology and pathology of pregnancy

B cells constitute a diverse and adaptable immune cell population with functions that can vary according to the environment and circumstances. The involvement of B cells in pregnancy, as well as the associated molecular pathways, has yet to be investigated. This review consolidates current knowledge on B cell activities and regulation during pregnancy, with a particular focus on the roles of various B cell subsets and the effects of B cell-derived factors on pregnancy outcomes. Moreover, the review examines the significance of B cell-associated autoantibodies, cytokines, and signaling pathways in relation to pregnancy complications such as pregnancy loss, preeclampsia, and preterm birth.

Tissue-specific sex differences in pediatric and adult immune cell composition and function

Sex-based differences in immune cell composition and function can contribute to distinct adaptive immune responses. Prior work has quantified these differences in peripheral blood, but little is known about sex differences within human lymphoid tissues. Here, we characterized the composition and phenotypes of adaptive immune cells from male and female ex vivo tonsils and evaluated their responses to influenza antigens using an immune organoid approach. In a pediatric cohort, female tonsils had more memory B cells compared to male tonsils direct ex vivo and after stimulation with live-attenuated but not inactivated vaccine, produced higher influenza-specific antibody responses. Sex biases were also observed in adult tonsils but were different from those measured in children. Analysis of peripheral blood immune cells from in vivo vaccinated adults also showed higher frequencies of tissue homing CD4 T cells in female participants. Together, our data demonstrate that distinct memory B and T cell profiles are present in male vs. female lymphoid tissues and peripheral blood respectively and suggest that these differences may in part explain sex biases in response to vaccines and viruses.

Hormones and B-cell development in health and autoimmunity

The development of B cells into antibody-secreting plasma cells is central to the adaptive immune system as they induce protective and specific antibody responses against invading pathogens. Various studies have shown that, during this process, hormones can play important roles in the lymphopoiesis, activation, proliferation, and differentiation of B cells, and depending on the signal given by the receptor of each hormone, they can have a positive or negative effect. In autoimmune diseases, hormonal deregulation has been reported to be related to the survival, activation and/or differentiation of autoreactive clones of B cells, thus promoting the development of autoimmunity. Clinical manifestations of autoimmune diseases have been associated with estrogens, prolactin (PRL), and growth hormone (GH) levels. However, androgens, such as testosterone and progesterone (P4), could have a protective effect. The objective of this review is to highlight the links between different hormones and the immune response mediated by B cells in the etiopathogenesis of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS). The data collected provide insights into the role of hormones in the cellular, molecular and/or epigenetic mechanisms that modulate the B-cell response in health and disease.

Local Effects of Steroid Hormones within the Bone Microenvironment

Steroid hormone production via the adrenal cortex, gonads, and placenta (so-called glandular steroidogenesis) is responsible for the endocrine control of the body's homeostasis and is organized by a feedback regulatory mechanism based on the hypothalamus-pituitary-steroidogenic gland axis. On the other hand, recently discovered extraglandular steroidogenesis occurring locally in different tissues is instead linked to paracrine or autocrine signaling, and it is independent of the control by the hypothalamus and pituitary glands. Bone cells, such as bone-forming osteoblasts, osteoblast-derived osteocytes, and bone-resorbing osteoclasts, respond to steroid hormones produced by both glandular and extraglandular steroidogenesis. Recently, new techniques to identify steroid hormones, as well as synthetic steroids and steroidogenesis inhibitors, have been introduced, which greatly empowered steroid hormone research. Based on recent literature and new advances in the field, here we review the local role of steroid hormones in regulating bone homeostasis and skeletal lesion formation. The novel idea of extraglandular steroidogenesis occurring within the skeletal system raises the possibility of the development of new therapies for the treatment of bone diseases.

Sex hormone signaling and regulation of immune function

Immune responses to antigens, including innocuous, self, tumor, microbial, and vaccine antigens, differ between males and females. The quest to uncover the mechanisms for biological sex differences in the immune system has intensified, with considerable literature pointing toward sex hormonal influences on immune cell function. Sex steroids, including estrogens, androgens, and progestins, have profound effects on immune function. As such, drastic changes in sex steroid concentrations that occur with aging (e.g., after puberty or during the menopause transition) or pregnancy impact immune responses and the pathogenesis of immune-related diseases. The effect of sex steroids on immunity involves both the concentration of the ligand and the density and distribution of genomic and nongenomic receptors that serve as transcriptional regulators of immune cellular responses to affect autoimmunity, allergy, infectious diseases, cancers, and responses to vaccines. The next frontier will be harnessing these effects of sex steroids to improve therapeutic outcomes.

Immunomodulatory role of estrogen in ischemic stroke: neuroinflammation and effect of sex

Although estrogen is predominantly related to the maintenance of reproductive functioning in females, it mediates various physiological effects in nearly all tissues, especially the central nervous system. Clinical trials have revealed that estrogen, especially 17β-estradiol, can attenuate cerebral damage caused by an ischemic stroke. One mechanism underlying this effect of 17β-estradiol is by modulating the responses of immune cells, indicating its utility as a novel therapeutic strategy for ischemic stroke. The present review summarizes the effect of sex on ischemic stroke progression, the role of estrogen as an immunomodulator in immune reactions, and the potential clinical value of estrogen replacement therapy. The data presented here will help better understand the immunomodulatory function of estrogen and may provide a basis for its novel therapeutic use in ischemic stroke.

Characterization of Estrogen Receptors in Pancreatic Adenocarcinoma with Tertiary Lymphoid Structures

The role of estrogen signaling in antitumor immunology remains unknown for non-traditional sex-biased cancer types such as pancreatic adenocarcinoma (PAAD). Tertiary lymphoid structures (TLS) are active zones composed of multiple types of immune cells, whose presence indicates anti-tumor immune responses. In this study, we employed a 12-chemokine signature to characterize potential gene categories associated with TLS development and identified seventeen major gene categories including estrogen receptors (ERs). Immunohistochemistry staining revealed the expression patterns of three ERs (ERα, ERβ, and GPER) in 174 PAAD samples, and their correlation with clinicopathological characteristics, immune cell infiltration levels, and intratumoral TLS presence was analyzed. The results indicated that ERα (+) and ERβ (+) were correlated with high tumor grade, and ERβ (+) and GPER (+) were correlated with lower TNM stage, and both ERα (+) and GPER (+) displayed a beneficial effect on prognosis in this cohort. Interestingly, positive staining of all three ERs was significantly correlated with the presence of intratumoral TLSs and infiltration of more active immune cells into the microenvironment. Moreover, the chemotaxis of CD8+T-cells to PAAD cells was significantly increased in vitro with upregulated expression of ERα or ERβ on PAAD cells. To conclude, our study showed a novel correlation between ER expression and TLS development, suggesting that ERs may play a protective role by enhancing anti-tumor immune responses in PAAD.

Estrogen Receptor Signaling in the Immune System

The immune system functions in a sexually dimorphic manner, with females exhibiting more robust immune responses than males. However, how female sex hormones affect immune function in normal homeostasis and in autoimmunity is poorly understood. In this review, we discuss how estrogens affect innate and adaptive immune cell activity and how dysregulation of estrogen signaling underlies the pathobiology of some autoimmune diseases and cancers. The potential roles of the major circulating estrogens, and each of the 3 estrogen receptors (ERα, ERβ, and G-protein coupled receptor) in the regulation of the activity of different immune cells are considered. This provides the framework for a discussion of the impact of ER modulators (aromatase inhibitors, selective estrogen receptor modulators, and selective estrogen receptor downregulators) on immunity. Synthesis of this information is timely given the considerable interest of late in defining the mechanistic basis of sex-biased responses/outcomes in patients with different cancers treated with immune checkpoint blockade. It will also be instructive with respect to the further development of ER modulators that modulate immunity in a therapeutically useful manner.

Immune regulation based on sex differences in ischemic stroke pathology

Ischemic stroke is one of the world's leading causes of death and disability. It has been established that gender differences in stroke outcomes prevail, and the immune response after stroke is an important factor affecting patient outcomes. However, gender disparities lead to different immune metabolic tendencies closely related to immune regulation after stroke. The present review provides a comprehensive overview of the role and mechanism of immune regulation based on sex differences in ischemic stroke pathology.

A cutting-edge immunomodulatory interlinkage between HOTAIR and MALAT1 in tumor-associated macrophages in breast cancer: A personalized immunotherapeutic approach

Breast cancer (BC) is one of the most common cancers, accounting for 2.3 million cases worldwide. BC can be molecularly subclassified into luminal A, luminal B HER2-, luminal B HER2+, HER2+, and triple-negative breast cancer (TNBC). These molecular subtypes differ in their prognosis and treatment strategies; thus, understanding the tumor microenvironment (TME) of BC could lead to new potential treatment strategies. The TME hosts a population of cells that act as antitumorigenic such as tumor-associated eosinophils or pro-tumorigenic such as cancer-associated fibroblasts (CAFs), tumor-associated neutrophils (TANs), monocytic-derived populations such as MDSCs, or most importantly "tumor-associated macrophages (TAMs)," which are derived from CD14+ monocytes. TAMs are reported to have the pro-inflammatory phenotype M1, which is found only in the very early stages of tumor and is not correlated with progression; however, the M2 phenotype is anti-inflammatory that is correlated with tumor progression and metastasis. The current study focused on controlling the anti-inflammatory activity in TAMs of hormonal, HER2+, and TNBC by epigenetic fine-tuning of two immunomodulatory proteins, namely, CD80 and mesothelin (MSLN), which are known to be overexpressed in BC with pro-tumorigenic activity. Long non-coding RNAs are crucial key players in tumor progression whether acting as oncogenic or tumor suppressors. We focused on the regulatory role of MALAT1 and HOTAIR lncRNAs and their role in controlling the tumorigenic activity of TAMs. This study observed the impact of manipulation of MALAT1 and HOTAIR on the expression of both CD80 and MSLN in TAMs of BC. Moreover, we analyzed the interlinkage between HOTAIR and MALAT1 as regulators to one another in TAMs of BC. The current study reported an upstream regulatory effect of HOTAIR on MALAT1. Moreover, our results showed a promising use of MALAT1 and HOTAIR in regulating oncogenic immune-modulatory proteins MSLN and CD80 in TAMs of HER2+ and TNBC. The downregulation of MALAT1 and HOTAIR resulted in the upregulation of CD80 and MSLN, which indicates that they might have a cell-specific activity in TAMs. These data shed light on novel key players affecting the anti-inflammatory activity of TAMs as a possible therapeutic target in HER2+ and TNBC.

Influence of Gestational Hormones on the Bacteria-Induced Cytokine Response in Periodontitis

Periodontitis is an inflammatory disease that affects the supporting structures of teeth. The presence of a bacterial biofilm initiates a destructive inflammatory process orchestrated by various inflammatory mediators, most notably proinflammatory cytokines, which are upregulated in the gingival crevicular fluid, leading to the formation of periodontal pockets. This represents a well-characterized microbial change during the transition from periodontal health to periodontitis; interestingly, the gestational condition increases the risk and severity of periodontal disease. Although the influence of periodontitis on pregnancy has been extensively reviewed, the relationship between pregnancy and the development/evolution of periodontitis has been little studied compared to the effect of periodontitis on adverse pregnancy outcomes. This review is aimed at summarizing the findings on the pregnancy-proinflammatory cytokine relationship and discussing its possible involvement in the development of periodontitis. We address (1) an overview of periodontal disease, (2) the immune response and possible involvement of proinflammatory cytokines in the development of periodontitis, (3) how bone tissue remodelling takes place with an emphasis on the involvement of the inflammatory response and metalloproteinases during periodontitis, and (4) the influence of hormonal profile during pregnancy on the development of periodontitis. Finally, we believe this review may be helpful for designing immunotherapies based on the stage of pregnancy to control the severity and pathology of periodontal disease.

Revisiting steroidogenesis and its role in immune regulation with the advanced tools and technologies

Historically tools and technologies facilitated scientific discoveries. Steroid hormone research is not an exception. Unfortunately, the dramatic advancement of the field faded this research area and flagged it as a solved topic. However, it should have been the opposite. The area should glitter with its strong foundation and attract next-generation scientists. Over the past century, a myriad of new facts on biochemistry, molecular biology, cell biology, physiology and pathology of the steroid hormones was discovered. Several innovations were made and translated into life-saving treatment strategies such as synthetic steroids, and inhibitors of steroidogenesis and steroid signaling. Steroid molecules exhibit their diverse effects on cell metabolism, salt and water balance, development and function of the reproductive system, pregnancy, and immune-cell function. Despite vigorous research, the molecular basis of the immunomodulatory effect of steroids is still mysterious. The recent excitement on local extra-glandular steroidogenesis in regulating inflammation and immunity is revitalizing the topic with a new perspective. Therefore, here we review the role of steroidogenesis in regulating inflammation and immunity, discuss the unresolved questions, and how this area can bring another golden age of steroid hormone research with the development of new tools and technologies and advancement of the scientific methods.

Sex Hormones and Lung Inflammation

Inflammation is a characteristic marker in numerous lung disorders. Several immune cells, such as macrophages, dendritic cells, eosinophils, as well as T and B lymphocytes, synthetize and release cytokines involved in the inflammatory process. Gender differences in the incidence and severity of inflammatory lung ailments including asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), lung cancer (LC), and infectious related illnesses have been reported. Moreover, the effects of sex hormones on both androgens and estrogens, such as testosterone (TES) and 17β-estradiol (E2), driving characteristic inflammatory patterns in those lung inflammatory diseases have been investigated. In general, androgens seem to display anti-inflammatory actions, whereas estrogens produce pro-inflammatory effects. For instance, androgens regulate negatively inflammation in asthma by targeting type 2 innate lymphoid cells (ILC2s) and T-helper (Th)-2 cells to attenuate interleukin (IL)-17A-mediated responses and leukotriene (LT) biosynthesis pathway. Estrogens may promote neutrophilic inflammation in subjects with asthma and COPD. Moreover, the activation of estrogen receptors might induce tumorigenesis. In this chapter, we summarize the most recent advances in the functional roles and associated signaling pathways of inflammatory cellular responses in asthma, COPD, PF, LC, and newly occurring COVID-19 disease. We also meticulously deliberate the influence of sex steroids on the development and progress of these common and severe lung diseases.

Sex Differences in Immunity: Implications for the Development of Novel Vaccines Against Emerging Pathogens

Vaccines are one of the greatest public health achievements and have saved millions of lives. They represent a key countermeasure to limit epidemics caused by emerging infectious diseases. The Ebola virus disease crisis in West Africa dramatically revealed the need for a rapid and strategic development of vaccines to effectively control outbreaks. Seven years later, in light of the SARS-CoV-2 pandemic, this need has never been as urgent as it is today. Vaccine development and implementation of clinical trials have been greatly accelerated, but still lack strategic design and evaluation. Responses to vaccination can vary widely across individuals based on factors like age, microbiome, co-morbidities and sex. The latter aspect has received more and more attention in recent years and a growing body of data provide evidence that sex-specific effects may lead to different outcomes of vaccine safety and efficacy. As these differences might have a significant impact on the resulting optimal vaccine regimen, sex-based differences should already be considered and investigated in pre-clinical and clinical trials. In this Review, we will highlight the clinical observations of sex-specific differences in response to vaccination, delineate sex differences in immune mechanisms, and will discuss the possible resulting implications for development of vaccine candidates against emerging infections. As multiple vaccine candidates against COVID-19 that target the same antigen are tested, vaccine development may undergo a decisive change, since we now have the opportunity to better understand mechanisms that influence vaccine-induced reactogenicity and effectiveness of different vaccines.

Human pregnancy levels of estrogen and progesterone contribute to humoral immunity by activating TFH /B cell axis

Circulating T_FH (cT_FH ) cells express CXCR5, PD-1, and, when activated, ICOS, and release IL-21. According to the production of IFN-γ, IL-4, and IL-17 and expression of FoxP3, these cells are also classified as cT_FH 1, cT_FH 2, cT_FH 17, and cT_FR cells, respectively. This CD4⁺ T-cell subset is pivotal to efficient humoral immunity, and pregnancy appears to favor IgG production. Here, not only pregnancy amplified the in vivo production of anti-HBsAg IgG in HBV immunized women, but the frequency of cT_FH cells was directly correlated with estradiol levels. In vitro, pregnancy-related dose of 17-β-estradiol (E2) directly increased the percentage of different cT_FH subsets. While E2 and progesterone (P4) increased the proportion of differentiated T_FH cells derived from naïve CD4⁺ T-cells, only E2 amplified the release of IL-21 in those cell cultures. In addition, E2 and P4 increased the proportion of memory B cells and plasma cells, respectively. In SEB-activated B/T_FH cell co-cultures, E2, in the presence of P4, increased the production of total IgG. Finally, among the hormones, P4 was stronger in upregulating the percentage of IL-10⁺ T_FR cells. Collectively, our findings suggested that E2 and P4 cooperate in the humoral immune response by favoring the expansion of different cT_FH and B cell subsets.

Pregnancy favors circulating IL-21-secreting TFH -like cell recovery in ARV-treated HIV-1-infected women

PROBLEM

Pregnancy appears to favor maternal antibody production. In contrast, by damaging follicular helper T cells (T_FH ), HIV-1 infection compromises protective humoural immune response. Therefore, we aimed to investigate the frequency of different T_FH -like cells in HIV-infected pregnant women (PW) before and after antiretroviral (ARV) therapy.

METHOD OF STUDY

Peripheral blood mononuclear cells, CD4⁺ T and B cells, were obtained from asymptomatic HIV-1-infected non-PW and PW just before and after ARV therapy. In some experiments, healthy HIV-1-negative PW were also tested. The frequency of different T_FH -like cell subsets was determined by flow cytometry. The plasma titers of IgG anti-tetanus toxoid (TT), anti-HBsAg, and anti-gp41 were determined by ELISA. The in vitro production of total IgG, IL-21, and hormones (estrogen and progesterone) was quantified also by ELISA.

RESULTS

Our results demonstrate that antiretroviral (ARV) therapy was more efficient in elevating the percentage of circulating IL-21-secreting T_FH cells in HIV-1-infected pregnant women (PW) than in non-pregnant patients (nPW). Moreover, in co-culture systems, CD4⁺ T cells from ART-treated PW were more efficient in assisting B cells to produce IgG production. The in vivo anti-HBsAg IgG titers after ARV therapy were also significantly higher in PW, and their levels were directly associated with both IL-21⁺ T_FH frequency and plasma concentration of estrogen.

CONCLUSION

In summary, our results suggest that pregnancy favors the recovery of T_FH -like cells after ARV therapy in HIV-1-infected women, which could help these mothers to protect their newborns from infectious diseases by transferring IgG across the placenta.

Estrogen and estrogen receptor signaling promotes allergic immune responses: Effects on immune cells, cytokines, and inflammatory factors involved in allergy

Hypersensitivity occurs when the body is stimulated by an antigen, resulting in an immune response, and leads to a physiological disorder or abnormal tissue trauma. Various immune cells, cytokines, and inflammatory mediators are involved in the immune responses related to allergic diseases, which are the core of anaphylaxis. Estrogen receptors are widely distributed in immune cells, which combine with estrogen and participate in allergic responses by affecting immune cells, cytokines, and inflammatory factors. We aimed to summarize the association between estrogen and allergic reactions to provide a scientific basis for understanding and studying the mechanisms of allergic diseases.

Pregnancy favors the expansion of circulating functional follicular helper T Cells

Pregnancy favors antibody production, and some evidence has suggested a direct effect of estrogen on B cells. The impact of pregnancy on circulating follicular helper T (T_FH) cells, typically identified by the expression of CD45RO and CXCR5, has not been previously investigated. Here, the percentage of T_FH cells, co-expressing or not PD-1, ICOS, or CXCR3 markers was significantly higher in pregnant women (PW) as compared with non-pregnant ones (nPW). Furthermore, the percentage of CXCR3⁺ T_FH cells able to produce IL-6, IL-21, and IL-10 was significantly higher in PW than nPW. Interestingly, anti-CMV and anti-HBs antibody titers were significantly higher in the plasma of PW and were directly correlated with IL-21-producing CXCR3⁺ T_FH cells. Finally, peripheral estrogen levels, but not progesterone, were positively related to either PD-1⁺ CXCR3⁺ T_FH cells or plasma anti-CMV and anti-HBs IgG antibodies. In summary, our data suggests a positive effect of pregnancy on the proportion of CD4⁺ T cell subset specialized in helping B cells. This phenomenon, which could be related to the high estrogen levels produced during pregnancy, may help to explain why pregnancy favor humoral immunity.

Mammary gland involution as an immunotherapeutic target for postpartum breast cancer

Postpartum mammary gland involution has been identified as tumor-promotional and is proposed to contribute to the increased rates of metastasis and poor survival observed in postpartum breast cancer patients. In rodent models, the involuting mammary gland microenvironment is sufficient to induce enhanced tumor cell growth, local invasion, and metastasis. Postpartum involution shares many attributes with wound healing, including upregulation of genes involved in immune responsiveness and infiltration of tissue by immune cells. In rodent models, treatment with non-steroidal anti-inflammatory drugs (NSAIDs) ameliorates the tumor-promotional effects of involution, consistent with the immune milieu of the involuting gland contributing to tumor promotion. Currently, immunotherapy is being investigated as a means of breast cancer treatment with the purpose of identifying ways to enhance anti-tumor immune responses. Here we review evidence for postpartum mammary gland involution being a uniquely defined 'hot-spot' of pro-tumorigenic immune cell infiltration, and propose that immunotherapy should be explored for prevention and treatment of breast cancers that arise in this environment.