Estrogen administration activates extrathymic T cell differentiation in the liver

Prevalence and predictors of hepatitis C infection among antenatal attendees in a tertiary hospital in Southern Nigeria

Background

Hepatitis C virus infection as it specifically relates to pregnancy has been a neglected condition, thus its recognition and treatment in pregnancy is relevant because of the risks of the long-term complications of the infection in the mother, potential effects of the infection on the pregnancy and risk of vertical transmission to the newborn.

Objectives

To determine the proportion of pregnant women with serologic markers of hepatitis C infection, identify risk factors as well as factors that predict the occurrence of the infection in them.

Methodology

Over a 3-week period, blood samples from 456 pregnant women were assessed for antibodies to hepatitis C virus, while a pre-tested questionnaire was used to obtain socio-demographic data and the presence of risk factors in the University of Uyo Teaching Hospital, Nigeria.

Results

The prevalence of HCV infection in pregnancy was 4.6%. No known risk factors for HCV infection in pregnancy were identified. Only increasing gestational age was a predictor of HCV infection in pregnancy in the study.

Conclusion

The prevalence of hepatitis virus infection among the study population was high. Second trimester and increasing gravidity were protective of the infection in pregnancy. There is therefore need for introduction of general routine screening of all pregnant women presenting for antenatal care.

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.

Estrogens as regulator of hematopoietic stem cell, immune cells and bone biology

Hematopoietic stem cells provide continuous supply of all the immune cells, through proliferation and differentiation decisions. These decisions are controlled by local bone marrow environment as well as by long-range signals for example endocrine system. Sex dependent differential immunological responses have been described under homeostasis and disease conditions. Females show higher longevity than male counterpart that seems to depend on major female sex hormone, estrogen. There are four estrogens - Estrone (E1), estradiol (E2), Estriol (E3) and Estetrol (E4) that spatially and temporarily present during different female reproductive phases. In this review, we discussed recent updates describing the effects of estrogen on HSC, immune cells and in bone biology. Estradiol (E2) being a major/abundant estrogen is extensively investigated, while effects of other estrogens E1, E3 and E4 are started to unravel recently. Furthermore, clinical effect of estrogen as hormone therapy is discussed in HSC and immune cells perspectives. The data presented in this review is compiled by searches of PubMed, database of American Cancer Society (ACS). We have included article from September 1994 to March 2020 as covering all article in chronological order is not fissile so we included relevant article with substantial information in this specific area of research by using the search term (alone or in combination) estrogen, hematopoietic stem cell, immune cells, gender difference, estrone, estriol, estetrol, therapeutic application, pregnancy, effect on bone.

Perinatal transmission of hepatitis C virus: an update

Infection with hepatitis C virus (HCV) is a major health problem worldwide. A large proportion of perinatal HCV infections are silent and may present later in adulthood with long-term complications. HCV has no effective immune prophylaxis and hence appropriate follow-up of all infants born to HCV-infected mothers is necessary. Universal antenatal screening for HCV is largely debatable. Intrauterine and partum transmission of HCV are both possible and higher rates are associated with a high maternal serum viral load (> 10⁶ copies per milliliter), concomitant HIV infection, prolonged or difficult delivery, and invasive fetal monitoring during delivery. Infection during pregnancy and infancy needs to be investigated more in order to design management strategies for perinatal transmission of HCV most effectively. The recently approved new-generation, oral, direct-acting antiviral drugs may open a new era in HCV therapy for pregnant women and infected infants if proved to be safe during conception and infancy.

Beneficial and Deleterious Effects of Female Sex Hormones, Oral Contraceptives, and Phytoestrogens by Immunomodulation on the Liver

The liver is considered the laboratory of the human body because of its many metabolic processes. It accomplishes diverse activities as a mixed gland and is in continuous cross-talk with the endocrine system. Not only do hormones from the gastrointestinal tract that participate in digestion regulate the liver functions, but the sex hormones also exert a strong influence on this sexually dimorphic organ, via their receptors expressed in liver, in both health and disease. Besides, the liver modifies the actions of sex hormones through their metabolism and transport proteins. Given the anatomical position and physiological importance of liver, this organ is evidenced as an immune vigilante that mediates the systemic immune response, and, in turn, the immune system regulates the hepatic functions. Such feedback is performed by cytokines. Pro-inflammatory and anti-inflammatory cytokines are strongly involved in hepatic homeostasis and in pathological states; indeed, female sex hormones, oral contraceptives, and phytoestrogens have immunomodulatory effects in the liver and the whole organism. To analyze the complex and interesting beneficial or deleterious effects of these drugs by their immunomodulatory actions in the liver can provide the basis for either their pharmacological use in therapeutic treatments or to avoid their intake in some diseases.

Sex Hormones in Acquired Immunity and Autoimmune Disease

Women have stronger immune responses to infections and vaccination than men. Paradoxically, the stronger immune response comes at a steep price, which is the high incidence of autoimmune diseases in women. The reasons why women have stronger immunity and higher incidence of autoimmunity are not clear. Besides gender, sex hormones contribute to the development and activity of the immune system, accounting for differences in gender-related immune responses. Both innate and adaptive immune systems bear receptors for sex hormones and respond to hormonal cues. This review focuses on the role of sex hormones particularly estrogen, in the adaptive immune response, in health, and autoimmune disease with an emphasis on systemic lupus erythematosus.

Activated natural killer T cells in mice induce acute kidney injury with hematuria through possibly common mechanisms shared by human CD56+ T cells

Although activation of mouse natural killer T (NKT) cells by α-galactosylceramide (α-GalCer) causes failure of multiple organs, including the kidneys, the precise mechanisms underlying kidney injury remain unclear. Here, we showed that α-GalCer-activated mouse NKT cells injured both kidney vascular endothelial cells and tubular epithelial cells in vitro, causing acute kidney injury (AKI) with hematuria in middle-aged mice. The perforin-mediated pathway was mainly involved in glomerular endothelial cell injury, whereas the TNF-α/Fas ligand pathway played an important role in the injury of tubular epithelial cells. Kidney injury in young mice was mild but could be significantly exacerbated if NKT cells were strongly activated by NK cell depletion alone or in combination with IL-12 pretreatment. When stimulated by a combination of IL-2 and IL-12, human CD56⁺ T cells, a functional counterpart of mouse NKT cells, also damaged both glomerular endothelial cells and tubular epithelial cells, with the former being affected in a perforin-dependent manner. These data suggest that both mouse NKT cells and human CD56⁺ T cells are integral to the processes that mediate AKI. Targeting CD56⁺ T cells may, therefore, be a promising approach to treat AKI.

Glucocorticoids, Sex Hormones, and Immunity

Glucocorticoid hormones regulate essential body functions in mammals, control cell metabolism, growth, differentiation, and apoptosis. Importantly, they are potent suppressors of inflammation, and multiple immune-modulatory mechanisms involving leukocyte apoptosis, differentiation, and cytokine production have been described. Due to their potent anti-inflammatory and immune-suppressive activity, synthetic glucocorticoids (GCs) are the most prescribed drugs used for treatment of autoimmune and inflammatory diseases. It is long been noted that males and females exhibit differences in the prevalence in several autoimmune diseases (AD). This can be due to the role of sexual hormones in regulation of the immune responses, acting through their endogenous nuclear receptors to mediate gene expression and generate unique gender-specific cellular environments. Given the fact that GCs are the primary physiological anti-inflammatory hormones, and that sex hormones may also exert immune-modulatory functions, the link between GCs and sex hormones may exist. Understanding the nature of this possible crosstalk is important to unravel the reason of sexual disparity in AD and to carefully prescribe these drugs for the treatment of inflammatory diseases. In this review, we discuss similarities and differences between the effects of sex hormones and GCs on the immune system, to highlight possible axes of functional interaction.

Lymphocyte Subpopulations in Patients with Advanced Breast Cancer Submitted to Neoadjuvant Chemotherapy

Aims and background

There is an enhanced immune response in patients with breast cancer after the use of chemotherapy. The objective of this study was therefore to investigate alterations in the number of peripheral lymphocytes in patients with breast cancer after neoadjuvant chemotherapy (NC) and the relationship with prognosis.

Methods

Thirty women were analyzed. Their UICC staging was IIb (only T3N0 included) and III (N3 not included). Sample analysis was performed using flow cytometry before the first cycle and 18 to 21 days after the last cycle of NC. The lymphocyte subsets studied were: T (CD3, CD4, CD8), B (CD19, CD23), natural killer (NK) (CD56, CD16), and interleukin-2 (CD25). CD3, CD56, CD8, and CD16 lymphocytes were analyzed with double marking. After x = 3.8 ± 1.3 cycles of 5-fluorouracil, epirubicin and cyclophosphamide (FEC), 16 patients showed a complete or partial response (group 1). After three cycles 14 showed no response or tumor progression (group 2). A control group of healthy women was used for pretreatment analysis.

Results

Before NC there was a significant increase in B lymphocytes and NK cells in comparison to the control group. After NC there was a significant percentage increase in CD3, CD4, CD8, CD25 and CD3+CD56+ cells and a decrease in CD19, CD23, CD56, CD16 and CD16+CD8+ cells. There was a significant fall in the absolute number of CD4, CD19, CD23, CD56, CD16 and CD16+CD8+ lymphocytes and an increase in GD3+CD56+ lymphocytes. Before NC the ratio CD4/CD8 in group 1 was 2.25 ± 0.5 and in group 2 it was 1.79 ± 0.5 (P <0.05).

Conclusions

Patients with advanced breast cancer showed increases in B and NK lymphocytes. Neoadjuvant chemotherapy (FEC) caused an increase in CD3+CD56+ and a decrease in B lymphocytes. Patients with an increased CD4/CD8 ratio have a better chance of responding to neoadjuvant chemotherapy.

The production of alpha/beta and gamma/delta double negative (DN) T-cells and their role in the maintenance of pregnancy

The ability of the thymus gland to convert bone marrow-derived progenitor cells into single positive (SP) T-cells is well known. In this review we present evidence that the thymus, in addition to producing SP T-cells, also has a pathway for the production of double negative (DN) T-cells. The existence of this pathway was noted during our examination of relevant literature to determine the cause of sex steroid-induced thymocyte loss. In conducting this search our objective was to answer the question of whether thymocyte loss is the end product of a typical interaction between the reproductive and immune systems, or evidence that the two systems are incompatible. We can now report that "thymocyte loss" is a normal process that occurs during the production of DN T-cells. The DN T-cell pathway is unique in that it is mediated by thymic mast cells, and becomes functional following puberty. Sex steroids initiate the development of the pathway by binding to an estrogen receptor alpha located in the outer membrane of the mast cells, causing their activation. This results in their uptake of extracellular calcium, and the production and subsequent release of histamine and serotonin. Lymphatic vessels, located in the subcapsular region of the thymus, respond to the two vasodilators by undergoing a substantial and preferential uptake of gamma/delta and alpha/beta DN T- cells. These T- cells exit the thymus via efferent lymphatic vessels and enter the lymphatic system.The DN pathway is responsible for the production of three subsets of gamma/delta DN T-cells and one subset of alpha/beta DN T-cells. In postpubertal animals approximately 35 % of total thymocytes exit the thymus as DN T-cells, regardless of sex. In pregnant females, their levels undergo a dramatic increase. Gamma/delta DN T-cells produce cytokines that are essential for the maintenance of pregnancy.

Sex, the aging immune system, and chronic disease

The immune systems of men and women differ in significant ways, especially after puberty. In particular, females are generally more prone to autoimmunity, but experience lower rates of infections and chronic inflammatory disease. Sex hormones, genes encoded on the sex chromosomes, and gender-specific behaviors likely contribute to these differences. The aging process is associated with changes in the composition and function of the immune system and these changes may occur at an accelerated rate in men as compared to women. Moreover, after the age of menopause, the incidence of chronic inflammatory disease in women approaches or exceeds that observed in males. At the same time, the incidence of autoimmunity in post-menopausal women is decreased or equivalent to the rates observed in similarly-aged men. Additional studies addressing the influence of sex on the pathogenesis of chronic and autoimmune diseases in the aged are warranted.

Pathogenesis of hepatitis C during pregnancy and childhood

The worldwide prevalence of HCV infection is between 1% and 8% in pregnant women and between 0.05% and 5% in children. Yet the pathogenesis of hepatitis C during pregnancy and in the neonatal period remains poorly understood. Mother-to-child transmission (MTCT), a leading cause of pediatric HCV infection, takes place at a rate of <10%. Factors that increase the risk of MTCT include high maternal HCV viral load and coinfection with HIV-1 but, intriguingly, not breastfeeding and mode of delivery. Pharmacological prevention of MTCT is not possible at the present time because both pegylated interferon alfa and ribavirin are contraindicated for use in pregnancy and during the neonatal period. However, this may change with the recent introduction of direct acting antiviral agents. This review summarizes what is currently known about HCV infection during pregnancy and childhood. Particular emphasis is placed on how pregnancy-associated immune modulation may influence the progression of HCV disease and impact MTCT, and on the differential evolution of perinatally acquired HCV infection in children. Taken together, these developments provide insights into the pathogenesis of hepatitis C and may inform strategies to prevent the transmission of HCV from mother to child.

A single mid-gestation exposure to TCDD yields a postnatal autoimmune signature, differing by sex, in early geriatric C57BL/6 mice

We recently observed an autoimmune profile in 24-week-old C57BL/6 mice that received a 2.5 or 5.0μg/kg mid-gestation dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (Mustafa et al., 2008). The clinical signs were consistent with a lupus-like syndrome and included: increased autoantibody levels, renal IgG and C3 immune complex deposition with associated inflammation, and increased peripheral Vβ(+) T cells. No studies currently exist following the progression of such disease into middle or advanced ages, when human autoimmune diseases may manifest. Therefore in the present study, littermates of mice from the previous 24 week prenatal TCDD study were allowed to age to 48 weeks, considered early geriatric in mice. Similarities and differences in the disease profile based on age and sex were observed. Peripheral autoreactive Vβ(+) T cells were increased in both sexes at 48 weeks, in contrast to males only at 24 weeks. Activated T cells from 48-week-old prenatal TCDD females over-produced the pro-inflammatory cytokine IFN-γ while males over-produced IL-10, effects again not seen at 24 weeks. Splenic transitional-2 B cells (CD21(int)CD24(hi)) were increased in males while transitional-1 B cells (CD23(neg) CD1(neg)) were increased in females at 48 weeks. Autoantibodies to cardiolipin and CD138(+) spleen plasma cells were significantly increased in the aged males but not females. Anti-IgG and anti-C3 immune complex renal deposition were also significantly increased in the prenatal TCDD males but not females. These selective changes in the aged male mice may be noteworthy, in that the prevalence of SLE in humans shifts dramatically toward males with aging. The collective findings in aged mice suggest that prenatal TCDD permanently biases the postnatal immune response in C57BL/6 mice toward autoimmunity, and support a significant B cell component to the induced renal autoimmune disease.

Hepatitis C virus infection during pregnancy and the newborn period--are they opportunities for treatment?

The worldwide prevalence of hepatitis C virus (HCV) infection in pregnant women is estimated to be between 1 and 8% and in children between 0.05% and 5%. While parenteral transmission is still common in children living in developing countries, perinatal transmission is now the leading cause of HCV transmission in developed countries. The absence of an HCV vaccine or approved therapy during pregnancy means that prevention of vertical transmission is still not possible. However, a low vertical transmission rate of 3-5%, a high rate of spontaneous clearance (25-50%) and delayed morbidity have resulted in HCV being overlooked in pregnant women and their infants. Yet a study of the natural history in mothers and children demonstrates that the prognosis of HCV can vary greatly and should be taken seriously. Factors known to increase the risk of perinatal transmission include HIV coinfection and higher maternal viral loads, while elective C-section and withholding breastfeeding have not been demonstrated to reduce vertical transmission. Current guidelines for the diagnosis of persistent perinatal infection require a positive anti-HCV test in infants born to infected mothers after 12 months or two positive HCV RNA tests at least 6 months apart. Current HCV treatment options using pegylated interferon and ribavirin are both unsuitable for use in pregnancy and infancy. However, new agents currently in preclinical phases of development, along with the recently identified association between single-nucleotide polymorphisms within the IL28 gene and treatment response, may serve to create a therapeutic window for these patients.

Salivary glands - "an unisex organ'?

Usually no distinction is made between female and male salivary glands although cyclic changes of and ⁄ or differences in serum and salivary sex steroid concentrations characterize women and men. Moreover, sexual dimorphism is well recognized in salivary glands of rodents.Salivary glands contain estrogen and androgen receptors and are, according to modern high throughput technologies,subjected to gender differences not explainable by gene dose effects by the X chromosome alone. Because sex steroids are lipophilic, it is often thought that approximately 10% of them passively diffuse from plasma to saliva. Indeed, saliva can find use as sample material in sports medicine, pediatrics, veterinary medicine and behavioral sciences. Last but not least, humans and other primates are unique in that they have a reticular zone in their adrenal cortex, which produces dehydroepiandrosterone and androstendione pro-hormones. These are processed in peripheral tissues, not only in female breast and uterus and male prostate, but also in salivary glands by an intracrine enzymatic machinery to active 17b-estradiol,dihydrotestosterone and others, to satisfy and buffer against a constantly changing needs caused by circadian,menstrual, pregnancy and chronobiological hormonal changes in the systemic circulation. Female dominance of Sjögren's syndrome and certain forms of salivary gland cancer probably reflect these gender-based differences.

Developmental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin alters postnatal T cell phenotypes and T cell function and exacerbates autoimmune lupus in 24-week-old SNF1 mice

BACKGROUND

Untreated, more than 95% of female SWR x NZB: F(1) (SNF(1)) mice spontaneously develop a fatal lupus-like glomerulonephritis by 8 months-of-age, while disease onset in males is much slower.

METHODS

: Timed-pregnant SNF(1) mice (10 per treatment) were exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on gestational day (GD) 12 by oral maternal gavage with 0, 40, or 80 microg/kg TCDD.

RESULTS

Offspring of the TCDD-exposed dams showed numerous alterations in T lineage cells at 24 weeks-of-age. Females but not males showed decreased CD4(+)8(+) and increased CD4(-)8(-) thymocytes. Females also showed increased autoreactive CD4(+)Vbeta17(a+) axillary and inguinal lymph node T cells. Concanavalin A-stimulated splenocytes from prenatal TCDD-treated mice produced decreased interleukin 17 (IL-17) in the females while males showed increased IL-2 and IFN-gamma, and diminished IL-4. Mitogen-stimulated pan-lymphoproliferative responses were significantly increased across sex by TCDD. Anti-IgG and anti-C3 immune complex deposition in kidneys was present in the males after TCDD, and visibly worsened in females.

CONCLUSIONS

Developmental TCDD exposure can permanently alter T lymphopoiesis in autoimmune-prone SNF1 mice. The alteration profile is beyond the classic immune suppression response, to also include exacerbation and induction of a lupuslike autoimmune disease.

Role of ovarian hormones in age-associated thymic involution revisited

A commonly held view that ovarian hormones are causally involved in age-associated thymic involution has been recently challenged. In particular, their relevance in the progression of thymic involution has been disputed. To reassess this issue 10-month-old rats with well advanced thymic involutive changes were ovariectomized (Ovx), and after 1 month thymic cellularity, thymocyte development and levels of recent thymic emigrants (RTEs) were examined in peripheral blood and spleen. In addition, the distribution of major conventional and regulatory T-cell subsets was analyzed in the same peripheral lymphocyte compartments. Ovariectomy increased thymic weight and cellularity above the levels in both 10-month-old and age-matched controls indicating that ovarian hormone ablation not only prevented further progression of thymic involution, but also reversed it. The increased thymic cellularity was accompanied by altered thymocyte differentiation/maturation culminating in increased thymic output of naïve T cells as indicated by elevated levels of both CD4+ and CD8+ RTEs in peripheral blood and spleen. The changes in T-cell development produced: (i) a disproportional increase in cellularity across thymocyte subsets, so that relative proportions of cells at all maturational stages preceding the CD4+CD8+ T cell receptor (TCR)alphabeta(low) stage were reduced; the relative numbers of CD4+CD8+ TCRalphabeta(low) cells entering positive selection and their immediate CD4+CD8+ TCRalphabeta(high) descendents were increased, while those of the most mature CD4+CD8- and CD4-CD8+ TCRalphabeta(high) cells remained unaltered; (ii) enhanced cell proliferation across all thymocyte subsets and (iii) reduced apoptosis of cells within the CD4+CD8+ thymocyte subset. The augmented thymic output of naïve T cells in Ovx rats most likely reflected an early disinhibition of thymocyte development followed by increased positive/reduced negative selection, at least partly, due to raised thymocyte surface Thy-1 expression. The greater number of CD4+CD25+Foxp3+ cells in both thymus and peripheral blood suggested augmented thymic production of these cells. In addition, an increased CD4+/CD8+ cell ratio was found in the spleen of Ovx rats. Thus, ovarian hormone ablation led not only to increased diversity of the T-cell repertoire, but also to a new balance among distinct T-cell subsets in the periphery.

Soluble Human Leukocyte Antigen class I antigen and interleukin-12 in hepatectomized patients

BACKGROUND

Interleukin-12 (IL-12) has been shown to enhance the cytotoxic activity of NK cells and CTL. IL-12 also acts as a growth factor for activated NK, T and NKT cells. The soluble HLA class I (sHLA-I) has been reported to bind a killer-cell inhibitory receptor, which is expressed on the NK cell, and its signals inhibit NK cell-mediated cytotoxicity. Effects of fresh frozen plasma (FFP) on post-operative immune status have not yet been completely examined.

METHODS

Thirty consecutive patients taking a hepatectomy were enrolled. The levels of IL-12 and sHLA-I were examined by enzyme-linked immunosorbent assay.

RESULTS

The rate of complication after hepatectomy in the FFP-administered patients was higher than that in patients without FFP administration (P = 0.0358). Decreased IL-12 levels after surgery in patients without FFP administration recovered to the preoperative state earlier than those in patients with FFP administration (P < 0.05). The levels of sHLA-I in the FFP-administered patients were higher than those in the patients without FFP administration (P < 0.05).

CONCLUSIONS

Administration of FFP, which contains sHLA-I, affected the levels of sHLA-I after hepatectomy. Both high levels of sHLA-I and low levels of IL-12 could attenuate NK activities after hepatectomy, especially when FFP would be administered.

Perinatal TCDD exposure and the adult onset of autoimmune disease

Modulation of the developing immune system can occur following perinatal exposure to a number of immunotoxic compounds, including polyhalogenated hydrocarbons like 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD; dioxin), the most toxic of the congeners. Studies in rodents have shown immunologic effects from perinatal TCDD exposure are more severe and persistent than following exposure in the adult, and include what appears to be life-long immunosuppression. Whether prenatal TCDD exposure may predispose an individual to postnatal autoimmune disease remains largely unknown. TCDD crosses the placenta and alters normal prenatal thymocyte maturation, T-cell receptor expression and expression of thymic major histocompatability complex Class II molecules. During the juvenile stage, mice exposed to TCDD prenatally show increased peripheral T-cells possessing "autoreactive" variable-beta receptors. These data suggest that gestational exposure to TCDD may interfere with normal development of central tolerance in the thymus. In possible support of this theory, when autoimmune disease-prone mice were treated with TCDD during gestation, postnatal autoimmunity had an accelerated onset and was exacerbated. This review provides an overview of the currently available information, which appears to support a hypothesis for increased risk of postnatal autoimmune responses as a result of TCDD exposure during the sensitive time of immune system establishment.

The estrogen-injected female mouse: new insight into the etiology of PCOS

BACKGROUND

Female mice and rats injected with estrogen perinatally become anovulatory and develop follicular cysts. The current consensus is that this adverse response to estrogen involves the hypothalamus and occurs because of an estrogen-induced alteration in the GnRH delivery system. Whether or not this is true has yet to be firmly established. The present study examined an alternate possibility in which anovulation and cyst development occurs through an estrogen-induced disruption in the immune system, achieved through the intermediation of the thymus gland.

METHODS, RESULTS AND CONCLUSION

A putative role for the thymus in estrogen-induced anovulation and follicular cyst formation (a model of PCOS) was examined in female mice by removing the gland prior to estrogen injection. Whereas all intact, female mice injected with 20 microg estrogen at 5-7 days of age had ovaries with follicular cysts, no cysts were observed in animals in which thymectomy at 3 days of age preceded estrogen injection. In fact, after restoring immune function by thymocyte replacement, the majority of thymectomized, estrogen-injected mice had ovaries with corpora lutea. Thus, when estrogen is unable to act on the thymus, ovulation occurs and follicular cysts do not develop. This implicates the thymus in the cysts' genesis and discounts the role of the hypothalamus. Subsequent research established that the disease is transferable by lymphocyte infusion. Transfer took place between 100-day-old estrogen-injected and 15-day-old naïve mice only when recipients were thymectomized at 3 days of age. Thus, a prerequisite for cyst formation is the absence of regulatory T cells. Their absence in donor mice was judged to be the result of an estrogen-induced increase in the thymus' vascular permeability, causing de facto circumvention of the final stages of regulatory T cell development. The human thymus has a similar vulnerability to steroid action during the fetal stage. We propose that in utero exposure to excessive levels of steroids such as estrogen has a long-term effect on the ability of the thymus to produce regulatory T cells. In female offspring this can lead to PCOS.

Gender and sex hormones in multiple sclerosis pathology and therapy

Several lines of evidence indicate that gender affects the susceptibility and course of multiple sclerosis (MS) with a higher disease prevalence and overall better prognosis in women than men. This sex dimorphism may be explained by sex chromosome effects and effects of sex steroid hormones on the immune system, blood brain barrier or parenchymal central nervous system (CNS) cells. The well known improvement in disease during late pregnancy has also been linked to hormonal changes and has stimulated recent clinical studies to determine the efficacy of and tolerance to sex steroid therapeutic approaches. Both clinical and experimental studies indicate that sex steroid supplementation may be beneficial for MS. This could be related to anti-inflammatory actions on the immune system or CNS and to direct neuroprotective properties. Here, clinical and experimental data are reviewed with respect to the effects of sex hormones or gender in the pathology or therapy of MS or its rodent disease models. The different cellular targets as well as some molecular mechanisms likely involved are discussed.

An enhanced postnatal autoimmune profile in 24 week-old C57BL/6 mice developmentally exposed to TCDD

Developmental exposure of mice to the environmental contaminant and AhR agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), causes persistent postnatal suppression of T cell-mediated immune responses. The extent to which prenatal TCDD may induce or exacerbate postnatal autoimmune disease remains unknown. In the present study, time-pregnant high affinity AhR C57BL/6 mice received a single oral administration of 0, 2.5, or 5 microg/kg TCDD on gestation day (gd) 12. Offspring of these mice (n=5/gender/treatment) were evaluated at 24 weeks-of-age and showed considerable immune dysregulation that was often gender-specific. Decreased thymic weight and percentages of CD4(+)CD8(+) thymocytes, and increased CD4(+)CD8(-) thymocytes, were present in the female but not male offspring. Males but not females showed decreased CD4(-)CD8(+) T cells, and increased Vbeta3(+) and Vbeta17a(+) T cells, in the spleen. Males but not females also showed increased percentages of bone marrow CD24(-)B220(+) B cell progenitors. Antibody titers to dsDNA, ssDNA and cardiolipin displayed increasing trends in both male and female mice, reaching significance for anti-dsDNA in both genders and for ssDNA in males at 5 microg/kg TCDD. Immunofluorescent staining of IgG and C3 deposition in kidney glomeruli increased in both genders of prenatal TCDD-exposed mice, suggestive of early stages of autoimmune glomerulonephritis. Collectively, these results show that exposure to TCDD during immune system development causes persistent humoral immune dysregulation as well as altered cell-mediated responses, and induces an adult profile of changes suggestive of increased risk for autoimmune disease.

The role of sex steroids and gonadectomy in the control of thymic involution

A major underlying cause for aging of the immune system is the structural and functional atrophy of the thymus, and associated decline in T cell genesis. This loss of naïve T cells reduces adaptive immunity to new stimuli and precipitates a peripheral bias to memory cells against prior antigens. Whilst multiple mechanisms may contribute to this process, the temporal alliance of thymic decline with puberty has implicated a causative role for sex steroids. Accordingly ablation of sex steroids induces profound thymic rejuvenation. Although the thymus retains some, albeit highly limited, function in healthy adults, this is insufficient for resurrecting the T cell pool following cytoablative treatments such as chemo- and radiation-therapy and AIDS. Increased risk of opportunistic infections and cancer relapse or appearance, are a direct consequence. Temporary sex steroid ablation may thus provide a clinically effective means to regenerate the thymus and immune system in immunodeficiency states.

Extrathymic rearrangement of alphabetaT-lymphocyte antigen receptor genes during pregnancy

The existence of alphabetaT-lymphocyte differentiation processes have been demonstrated in mouse peripheral lymphoid organs during pregnancy. Study of pregnant Swiss mice has shown that the development of the second half of gestation is accompanied by expression of RAG-1 recombinase mRNA and unrearranged TCR alpha-chain (pre-TCRalpha) preferentially in T-lymphocytes of lymph nodes involved in uterine drainage (para-aortal lymph nodes), and to a lesser extent in other lymph nodes (mainly from axillary lymph nodes). The data suggest that during pregnancy the differentiation of alphabetaT lymphocytes may occur not only in central (thymus) but also in peripheral lymphoid organs.

Estrogen and CD4+ T cells

PURPOSE OF REVIEW

Many autoimmune rheumatic autoimmune disorders predominantly affect women. Sex hormones, in particular estrogen, can influence CD4 T-helper development and function. We highlight recent studies that begin to provide insights into the mechanisms by which estrogen modulates CD4 T-cell development and function, and thus potentially contribute to disease pathogenesis.

RECENT FINDINGS

High levels of estrogen can lead to thymic atrophy. Recent studies showed that this phenomenon results from effects of estrogen at multiple stages in early T-cell development. Estrogen is also known to affect mature CD4 T-cell function, and, in particular, their ability to produce selected cytokine profiles. The mechanisms by which estrogen can exert these effects were also recently explored and shown to include effects on expression of critical molecules known to be involved in these processes.

SUMMARY

Dissecting the molecular pathways employed by estrogen to modulate CD4 T cells will be critical in elucidating the manner by which estrogen exerts its effects on this compartment. Given that cell type specific differences underlie the ability of many hormonal therapies to exert tissue-specific estrogenic or antiestrogenic activities, this knowledge will be crucial to further exploitation of hormonal therapies in rheumatic autoimmune diseases.

Estrogen-induced generation of reactive oxygen and nitrogen species, gene damage, and estrogen-dependent cancers

In addition to the direct effect of estrogen on mitochondria and the redox cycling of catechol estrogen, estrogen-induced proinflammatory cytokines, such as interleukin-1 beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha), also generate reactive oxygen and nitrogen species (RO/NS). Different cellular signaling pathways may operate in response to varying levels of estrogen-induced RO/NS, leading to genotoxic damage, cell apoptosis, or cell growth. At high levels of RO/NS, cells receiving genotoxic insults, if not repaired, may engage the apoptotic pathways. There is increasing evidence supporting that estrogen-induced alterations in the genome of cells is produced by oxidative attack. Furthermore, ROS generated by estrogen exposure and/or active metabolites of estrogen in combination with receptor-mediated proliferation of genetically damaged cells may be involved in tumor development. This view is supported by the findings of DNA modifications produced in vitro or in vivo by natural and synthetic estrogens in the target organs of cancer both in experimental models and in humans. Interaction of estrogen-induced oxidants and estrogen metabolites with DNA was shown to generate mutations in genes. Cotreatment with an inhibitor of IL-1beta and TNF-alpha synthesis, pentoxifylline, decreased stilbene estrogen-induced levels of myeloperoxidase (MPO), 8-hydroxydeoxyguanosine formation, and gene mutations, and prevented stilbene estrogen-induced lesions. Stable MCF-7 clones overexpressing IL-1beta resulted in a high level of IL-1beta peptide secretion undergoing cell apoptosis, and an elevated level of p53 protein in response to high oxidative stress when compared to nontransfected cells, whereas MCF-7 clones overexpressing IL-1beta that resulted in a moderate level of IL-1beta secretion stimulated the clonal expansion of MCF-7 and TM3 cells. Estrogen-induced MCF-7 cell growth and cyclin D1 expression were suppressed by antioxidants and mitochondrial blockers. These studies support that in addition to ovarian estrogen-mediated ER signaling, mitogenic signals may also come from estrogen-induced RO/NS. Further validation of this concept that the concentration of the RO/NS within the cellular microenvironment determines its stimulatory or inhibitory growth signals as well as its genotoxic effects regulating the growth of estrogen-dependent tumors may result in novel preventive strategies.

Estrogen Induces Thymic Atrophy by Eliminating Early Thymic Progenitors and Inhibiting Proliferation of β-Selected Thymocytes

Although it has been established that high levels of estrogen can induce thymic involution, the mechanism by which this happens is not known. We have found that daily i.p. injections of the synthetic estrogen 17-beta-estradiol reduce thymus cellularity by 80% over a period of 4-6 days. Although the atrophy is most strikingly observed in the CD4/CD8 double-positive (DP) thymic subset, the loss of thymocytes is not accompanied by a significant increase in thymocyte apoptosis, suggesting that direct killing of cells may not be the dominant means by which estrogens induce thymic atrophy. Instead, we find that estradiol drastically reduces the lineage-negative, Flt3(+)Sca-1(+)c-Kit(+) population in the bone marrow, a population that contains thymic homing progenitors. Within the thymus, we observe that estradiol treatment results in a preferential depletion of early thymic progenitors. In addition, we find that estradiol leads to a significant reduction in the proliferation of thymocytes responding to pre-TCR signals. Reduced proliferation of DN3 and DN4 cell subsets is likely the major contributor to the reduction in DP thymocytes that is observed. The reduction in early thymic progenitors is also likely to contribute to thymic atrophy, as we show that estradiol treatment can reduce the size of Rag1-deficient thymuses, which lack pre-TCR signals and DP thymocytes.

Gene Expression Profiling of 17β-Estradiol and Genistein Effects on Mouse Thymus

Estrogen regulates thymic development and involution and modulates immune function. Despite its critical role in thymus, as well as in autoimmune disorders, the mechanism by which estrogen affects the thymus is not well understood. We previously reported that the estrogenic soy isoflavone genistein, as well as 17beta-estradiol (E2), could induce thymic involution, but genistein effects were only partially mediated through estrogen receptors. To provide insights into mechanisms of estrogenic effects in the thymus, we investigated thymic gene expression changes induced by E2 (125 ng/day) and genistein (1500 ppm in feed) in weanling mice using high-density DNA arrays. We identified several E2-responsive genes involved in thymic development and thymocyte signaling during selection and maturation. Functional characterization indicated effects on genes involved in transcription, apoptosis, and the cell cycle. This study also identified changes in several E2-regulated transcripts essential to maintain immune self-tolerance. E2 upregulated more genes than genistein, while genistein downregulated more genes than E2. Though each treatment regulated several genes not altered by the other, there was considerable overlap in the genes regulated by E2 and genistein. Changes in transcription factors and cell cycle factors were consistent with decreases in cell proliferation induced by both genistein and E2. As indicated by the regulation of non-E2-responsive genes, genistein also induced unique effects through non-estrogenic mechanisms. The specific downregulation of the CD4 coreceptor transcript by genistein was consistent with the decline of CD4+ thymocytes in genistein-treated mice in our previous study. This is the first study identifying E2 and genistein target genes in the thymus. These findings provide new mechanistic insights toward explaining estrogen action on thymocyte development, selection, and maturation, as well as the effects of genistein on prenatal and neonatal thymic development and function.

Liver immunobiology

Tle liver has a number of important functions in innate and adaptive immunity. Contributions to the innate (nonspecific) immune system include production of acute phase proteins, nonspecific phagocytosis of particles, nonspecific pinocytosis of molecules, and nonspecific cell killing. Hepatic involvement in innate immunity contributes to the systemic response to local inflammation, clearance of particles and soluble molecules from the circulation, and killing of invading cells such as neoplastic cells. Liver involvement in the adaptive (specific) immune system includes deletion of activated T cells, induction of tolerance to ingested and self-antigens, extrathymic proliferation of T cells, and deletion of many of the signaling and effector molecules. Hepatic involvement in adaptive immunity allows clearance of activated T cells and signaling molecules following inflammatory reactions, and promotes immunologic tolerance toward potentially antigenic proteins that are absorbed from the intestinal tract. The liver is a major site of extrathymic T cell development, which assumes increasing significance with aging in mammals. Perturbations in hepatic structure or function can result in significant ramifications in both the innate and adaptive immune systems.

Endocrine-Immune Interactions in Human Endometrium

The immune system is a complex entity designed to eliminate foreign intruding antigens and is influenced by and, in turn, influences the function of the reproductive system. Despite the widespread associations between immunology and reproductive medicine, the study of system interactions remains in its infancy. Many diverse facts are accumulating, and pieces of the puzzle are becoming available to provide a clearer picture. In this review article, we focus on the interactions between endocrine and immune systems in the human endometrium. Understanding the molecular pathways in endocrine-immune interactions in the human endometrium is crucial to understand events such as menstrual bleeding, tissue repair and regeneration, inflammation, angiogenesis, blastocyst implantation, and progression of pregnancy. These events require a balanced regulation of endometrial differentiation, proliferation, cell survival, leukocyte recruitment, apoptosis, and angiogenesis by sex steroids. In this review, we first outline the role of survival factors such as phosphoinositol 3-kinase/protein kinase B, PTEN, NFkappaB, and apoptotic molecules (Fas-FasL, Bcl-2). We then discuss their regulation by estrogen and progesterone in the endometrium. We present evidence for direct and/or indirect roles of steroid hormones on the expression of chemotactic cytokines (interleukin-8 and monocyte chemotactic protein-1) and on the survival versus apoptosis of resident endometrial cells (stromal, epithelial, and endothelial cells) and nonresident cells (leukocytes).

Thymectomy impairs but does not uniformly abrogate long-term acceptance of semi-identical liver allograft in inbred miniature Swine temporarily treated with FK506

BACKGROUND

Long-term acceptance of semi-identical orthotopic liver transplants (OLTs) in inbred swine is induced by a 12-day course of FK506. To study whether acceptance is attributable to central or peripheral immune mechanisms, the effect of complete thymectomy was determined.

METHODS

Total thymectomy was performed in 15 swine 3 to 4 weeks before OLT. Twelve of these animals received a 12-day course of FK506 after OLT, and three animals did not receive immunosuppression. Five additional nonthymectomized pigs received OLT and a FK506 regimen. Graft survival, liver function, histology, and cellular and humoral responses were assessed.

RESULTS

Nonthymectomized, FK506-treated animals uniformly showed long-term acceptance of OLT and developed stable donor unresponsiveness. Of the 12 thymectomized, FK506-treated pigs, seven died of non-immunologic causes within 3 postoperative months, and five maintained their OLT for more than 6 months (range 180-450 days). Among these survivors, two developed a complete anti-donor response (mixed lymphocyte reaction [MLR], cell-mediated lymphocytotoxicity [CML], and immunoglobulin [IgG] antibodies) and eventually rejected their OLT at postoperative day 180. The three remaining pigs kept their liver allografts up to 450 days and developed a donor-specific unresponsiveness (a transient anti-donor MLR was observed during the follow-up but never an anti-donor CML or IgG antibodies). All three thymectomized, untreated animals rejected their allografts acutely and displayed a complete anti-donor response (MLR, CML, and IgG antibodies).

CONCLUSIONS

Complete thymectomy before OLT impaired but did not uniformly abrogate long-term acceptance of semi-identical OLT, suggesting that peripheral immune mechanisms may be sufficient to induce long-term acceptance of liver allografts in some recipients.

Estradiol and Progestins Differentially Modulate Leukocyte Infiltration After Vascular Injury

Background— Inflammation plays an important role in the response to endoluminal vascular injury. Estrogen (17β-estradiol, E 2 ) inhibits neointima formation in animal models, and the progestin medroxyprogesterone acetate (MPA) blocks this effect. This study tested the hypothesis that E 2 inhibits the migration of inflammatory cells, particularly granulocytes, into the rat carotid arteries after acute endoluminal injury and that MPA blocks this effect.

Methods and Results— Ovariectomized rats were randomly divided into subgroups and treated with E 2 , MPA, E 2 +MPA, or vehicle and subjected to balloon injury of the right carotid artery. After 1, 3, or 7 days, rats were euthanized, and carotid arteries (injured and control) were analyzed for inflammatory cells by flow cytometry. At 1 day, granulocytes (HIS48 + and CD45 + ), monocyte/macrophages (Mar1 + and CD45 + ), and T lymphocytes (CD3 + and CD45 + ) were increased 26-fold, 12-fold, and 3-fold, respectively, in injured compared with contralateral control arteries of vehicle-treated rats. Granulocytes and monocyte/macrophages decreased markedly by 3 days. E 2 reduced the granulocyte and monocyte/macrophage populations of injured vessels by ≈50% and increased T lymphocytes. MPA had no independent effect on inflammatory cells but completely blocked the effect of E 2 . Immunohistochemical examination verified these findings and localized inflammatory cells to the adventitial and periadventitial domains of injured vessels.

Conclusions— E 2 may limit the neointimal response to endoluminal vascular injury, at least in part, by limiting leukocyte entry from adventitial/periadventitial tissues into injured vessels early in the injury response.

Regulation of innate and adaptive immunity by the female sex hormones oestradiol and progesterone

Women mount more vigorous antibody- and cell-mediated immune responses following either infection or vaccination than men. The incidence of most autoimmune diseases is also higher in women than in men; however, during pregnancy many autoimmune diseases go into remission, only to flare again in the early post-partum period. Successful pregnancy requires that the female immune system tolerate the presence of a semi-allogeneic graft for 9 months. Oral contraceptive use can increase susceptibility to certain genital tract infections and sexually transmitted diseases in women. Moreover, treatment of mice and rats with female sex hormones is required to establish animal models of genital tract Chlamydia, Neisseria and Mycoplasma infection. This review describes what is currently known about the effects of the female sex hormones oestradiol and progesterone on innate and adaptive immune responses in order to provide a framework for understanding these sex differences. Data from both human and animal studies will be reviewed.

Influence of stage of the reproductive cycle and estradiol on thymus cell antigen presentation

The objective of this study was to determine whether thymus cells present antigen and if endocrine balance influences antigen presentation. We report here that antigen presenting cells (APC) from the thymus glands of male and female rats, when incubated with ovalbumin (OVA)-specific T cells and OVA, are functionally able to present antigen via MHC class II. To determine whether antigen presentation in the thymus is under hormonal control, tissues from female rats at different stages of the estrous cycle were analyzed. Antigen presentation was higher at estrus and proestrus than that seen at diestrus when estradiol levels are low. Estradiol given to ovariectomized animals for 3 days stimulated antigen presentation by adherent thymus cells compared to saline controls. Flow cytometry studies indicated that the adherent thymus cell preparations consisted of DC, T cells, B cells and cells of the myeloid lineage all of which expressed MHC class II, as did a small population of non-leukocytes. Antibody neutralization studies indicated that thymus cell antigen presentation involves the expression of transmembrane proteins B7.1 and B7.2. These studies demonstrate that sex hormones play a central role in regulating antigen presentation in the thymus.

The administration of cortisone to female B6A mice during their immune adaptive period causes anovulation and the formation of ovarian cysts

PROBLEM

Female mice that are injected with estradiol-17beta (E2) and testosterone during the 7-day immune adaptive period are infertile at adulthood. To determine whether the resultant infertility can be caused by steroids other than estrogens/ androgens, this study examined the effect of injecting cortisone, alone, and in combination with E2 and testosterone, on reproductive function.

METHOD OF STUDY

Neonatal (C57BL/6J x A/J)F1 B6A female mice were injected from 3 to 6 days of age with sesame oil:ethanol (9:1; v:v), alone, or containing 20 microgg cortisone acetate, 20 microg E2, or 20 microg testosterone. Two additional groups were given 20 microg cortisone acetate in combination with 20 microg E2 or 20 microg testosterone. At adulthood the animals were killed, the stage of vaginal estrus determined, the ovaries examined for the presence of corpora lutea and follicular cysts, and circulating levels of progesterone, E2, and testosterone were measured by radioimmunoassay (RIA).

RESULTS

It was found that injections of cortisone seriously compromise reproductive development. For example, 11% of cortisone-injected animals had ovaries that lacked corpora lutea. In addition, 39% of cortisone-injected females had ovaries with follicular cysts. Cortisone-injected females also had low levels of circulating progesterone (18 ng/mL versus 30 ng/mL for the sesame oil-injected females).

CONCLUSION

It is concluded that the deleterious effect of steroids on reproductive function, when administered during the immune adaptive period, is not restricted to estrogens and androgens. It is proposed that injections of cortisone alter T-lymphocyte subsets, which contributes to anovulation and the production of follicular cysts.

Estrogen receptor gene polymorphism and multiple sclerosis in Japanese patients: interaction with HLA-DRB1*1501 and disease modulation

We investigated PvuII and XbaI polymorphism in the estrogen receptor gene (ERG) and HLA-DRB1*1501 positivity in 116 conventional multiple sclerosis (MS) patients and 101 healthy controls in a Japanese population. Logistic analysis revealed independent associations of [P] allele in the profiles for PvuII (p=0.0005, adjusted odds ratio (aOR)=3.17) and DRB1*1501 (p=0.0089, aOR=2.61) with conventional MS. Synergistic elevated risk of MS due to interaction between the [P] allele and HLA-DRB1*1501 allele was found among female patients (odds ratio=16.0; 95% CI=3.99-63.8, p<0.0001). The [P] allele-positive patients with disease duration of more than 5 years had a significantly higher progression index (PI) of disability (p=0.0230) and a worse ranked MS severity score (p=0.0152) than their non-[P] counterparts.

Having it all? Stem cells, haematopoiesis and lymphopoiesis in adult human liver

Because of its location and function, the liver is continuously exposed to large antigenic loads that include pathogens, toxins and tumour cells, as well as harmless dietary and commensal proteins and peptides. Therefore, the liver must be actively immunocompetent and, at the same time, control inappropriate inflammatory responses to dietary and other harmless antigens encountered in the portal circulation. In addition to conventional CD4+ and CD8+ T lymphocytes from the circulation, several specialized lymphoid populations are found in the liver to meet these diverse immunological challenges. These populations display the functional and phenotypic properties of innate cells as well as conventional CD4+ or CD8+ helper and cytotoxic T lymphocytes and B cells. The innate lymphoid cells include gammadeltaTCR+ T cells, B1-B cells and NKT cells as well as large numbers of NK cells. The origin of these cells is unknown, but their murine counterparts have been shown to be capable of differentiation in situ in adult liver. Because haematopoietic stem cells have been found in adult human liver as well as molecular evidence of T-cell maturation, we hypothesize that some resident human hepatic lymphoid cells, particularly those expressing innate phenotypes, also differentiate locally. In particular, it is likely that the adult human liver is an important site of NK cell maturation. In this review, we explore the evidence for an active lymphopoietic role for the normal adult human liver.

Towards a unified model of neuroendocrine-immune interaction

Although the neuroendocrine system has immunomodulating potential, studies examining the relationship between stress, immunity and infection have, until recently, largely been the preserve of behavioural psychologists. Over the last decade, however, immunologists have begun to increasingly appreciate that neuroendocrine-immune interactions hold the key to understanding the complex behaviour of the immune system in vivo. The nervous, endocrine and immune systems communicate bidirectionally via shared messenger molecules variously called neurotransmitters, cytokines or hormones. Their classification as neurotransmitters, cytokines or hormones is more serendipity than a true reflection of their sphere of influence. Rather than these systems being discrete entities we would propose that they constitute, in reality, a single higher-order entity. This paper reviews current knowledge of neuroendocrine-immune interaction and uses the example of T-cell subset differentiation to show the previously under-appreciated importance of neuroendocrine influences in the regulation of immune function and, in particular, Th1/Th2 balance and diurnal variation there of.

Extrathymic pathways of T-cell differentiation and immunomodulation

It is well established that the thymus is an essential organ for the support of T-cell differentiation. However, some T cells, termed extrathymic T cells, have been found to differentiate without such support by the thymus. The major sites of these T cells are the intestine and liver. Subsequent studies have revealed that extrathymic T cells are also present in the uterus and exocrine glands (e.g., the salivary gland). Depending on the sites, extrathymic T cells have some distinct properties as well as some common properties. For example, all extrathymic T cells have a TCR-CD3 complex similar to thymus-derived T cells. Extrathymic T cells comprise both alpha beta T cells and gamma delta T cells. Although extrathymic T cells are very few in number at any extrathymic sites in youth, they increase in number as a function of age. This phenomenon seems to occur in parallel with thymic involution. Even in youth, extrathymic T cells are activated in number and function by stress, in autoimmune diseases, and during pregnancy. Acute thymic atrophy always accompanies this activation. Therefore, reciprocal regulation between extrathymic T cells and thymus-derived T cells might be present. We hypothesize that extrathymic T cells are intimately associated with innate immunity and that the mechanisms underlying autoimmune diseases and intracellular infection (e.g., malaria) cannot be properly understood without introducing the concept of extrathymic T cells.

Evidence for estradiol-induced apoptosis and dysregulated T cell maturation in the thymus

In an attempt to delineate the immunological alterations that may occur following treatment with estrogen, groups of C57BL/6 mice were treated with 75mg/kg body weight of beta-estradiol-17-valerate (E2) or the vehicle. The thymus from these mice were harvested on days 1, 4 and 7 following treatment. The thymocytes from E2-treated mice when cultured in vitro for 24h, showed increased levels of apoptosis when compared to controls. The apoptosis was demonstrable by both TUNEL assay and AnnexinV/propidium iodide (PI) staining. Also, thymic atrophy and increased apoptosis of thymocytes when cultured in vitro were seen when lower doses of E2 (5mg/kg) were administered. The thymus from E2-treated mice on days 4 and 7 also showed a decrease in the percentage of CD4(+)CD8(+) (DP) T cells and an increase in the percentage of CD4(-)CD8(-) (DN), CD4(+) and CD8(+) T cells. However, the total cellularity of all T cell subsets in the thymus was decreased following E2 treatment. Earlier studies from our laboratory and elsewhere have demonstrated that in thymocytes undergoing apoptosis, there is increased expression of surface markers including CD3, alphabetaTCR and CD44 with a simultaneous decrease in the expression of J11d. Similar changes were observed in thymocytes from mice on days 4 and 7 following E2 treatment. These data therefore confirmed that the thymocytes were indeed undergoing apoptosis following E2 treatment. Together, our studies suggest for the first time that estrogen may induce thymic atrophy by triggering apoptosis.

Estrogen, prolactin, and autoimmunity: actions and interactions

Estrogen and prolactin have a reciprocal endocrinologic relationship and both hormones have pleiotropic effects on the immune system. Despite the presence of a number of confounding variables, these hormones modulate autoimmunity; however, mechanisms by which this modulation occurs remain obscure. Estrogen appears to suppress cell-mediated and augment humoral-based immunity. Prolactin appears to stimulate both cell and humoral-based immunity. Both hormones have been shown to modulate IFN gamma secretion. Similar evidence in experimental models, human autoimmune disease, and during pregnancy in autoimmune disease patients suggests disparate effects of estrogen and prolactin on autoimmune responses and disease pathogenesis. In the NZB x NZW F1 mouse model of lupus, prolactin accelerates disease expression, whereas estrogen, devoid of its prolactin stimulating properties, is immunosuppressive and inhibits IL-2 production. Estrogen, because of its endocrinologic and immune effects, may directly or indirectly stimulate or inhibit immune responses. These dichotomous effects have limited its successful pharmacologic manipulation in human autoimmune disease with estrogen compounds, tamoxifen, oral contraceptives, antigonadotropic agents, or ovulation induction regimens. In contrast, reduction of immunostimulatory concentrations of prolactin with bromocriptine has successfully suppressed development or expression of murine and human autoimmune disease. Further investigation into actions and interactions of estrogen and prolactin with autoimmunity will provide a better understanding of the female preponderance of autoimmunity and facilitate a more rational approach to hormonal immunotherapy.

Postmenopausal oestrogen replacement therapy and atherosclerosis: can current compounds provide cardiovascular protection?

The natural oestrogen, 17 beta-oestradiol, has been implicated in protection from atherosclerosis, a chronic systemic vascular disease with an inflammatory component accounting for the majority of morbidity and mortality in Western countries. Despite the protective effects of 17 beta-oestradiol in premenopausal women and experimental evidence demonstrating inhibitory effects of oestrogen on atherosclerosis progression, it is currently unclear whether hormone replacement therapy can affect cardiovascular morbidity and mortality in postmenopausal women. The recent advances in understanding the mechanisms of oestrogen action demonstrated roles for different oestrogen receptors and oestrogen metabolites in the pathogenesis of vascular injury and endothelial cell dysfunction. However, their respective role in the process of atherogenesis remains yet to be elucidated. Moreover, the availability of novel drugs with tissue- and/or receptor-specific actions will help to understand the role of oestrogen in cardiovascular diseases. Several ongoing large-scale clinical trials using opposed or unopposed replacement therapy with natural or synthetic oestrogens, or selective oestrogen receptor modulators (SERMs) will resolve the question whether the drugs currently available have therapeutic potential to interfere with the progression of atherosclerosis and its complications.