Gonadotropin-releasing hormone increases CD4 T-lymphocyte numbers in an animal model of immunodeficiency

Effect of GnRH immunocastration on immune function in male rats

The present study aimed to reveal the effects of immunocastration on the development of the immune system in rats. Seventy rats were randomly assigned into two groups: Control (n = 35) and immunized (n = 35). Twenty-day-old rats were immunized with gonadotropin-releasing hormone (GnRH) and booster immunization was administered every two weeks (three immunizations in total). From 20-day-old rats, we collected samples every two weeks, including five immunized rats and five control rats (seven collections in total). We collected blood samples, testicles, thymuses, and spleens. The results showed that GnRH immunization increased the GnRH antibody titers and reduced the testosterone concentration (both P < 0.05). Compared with the control group, the number of CD4+CD8- cells, CD4-CD8+ cells, and CD4+CD8+ cells increased (P < 0.05) whereas the number of CD4-CD8- cells and CD4+CD25+ cells reduced in the immunized group (P < 0.05) over time. GnRH immunization also increased the relative weights of thymus and spleen (P < 0.05), serum concentrations of interleukin (IL)-2, IL-4, IL-6, IL-10, IL-17 and Interferon-γ (IFN-γ) over time (P < 0.05), and changed the mRNA levels of IL-2, IL-4, IL-6. IL-10, IL-17, IFN-γ, CD4, D8, CD19 GnRH, and GnRH receptor (GnRH-R) in thymus and spleen. Thus, GnRH immunization enhanced the immune markers in thymus, spleen, and blood immune cytokines in rats.

Association between GnRH analogue use and atopic diseases in patients with prostate cancer: A population-based retrospective cohort study

Purpose

Gonadotropin-releasing hormone (GnRH) analogues reduce testosterone levels to castration levels in patients with prostate cancer. However, the role of testosterone in atopic diseases has remained undefined. We aimed to investigate this role.

Materials and methods

This retrospective cohort study was conducted using the National Health Insurance Research Database (NHIRD). Patients with prostate cancer were categorized into two groups according to whether they received GnRH analogue treatment (study group I) or not (study group II), and men without prostate cancer and with no GnRH analogue use were defined to comprise the comparison group after their ages and index years were matched with group II. Cox proportional hazard models were used to assess the hazard ratio (HR) of atopic diseases.

Results

Group I, group II, and the comparison group comprised 663, 2,172, and 8,688 individuals, respectively. Group I had a significantly lower risk of atopic diseases (adjusted HR: 0.66, 95% CI, 0.49–0.89, p < 0.01) than did group II. A reduced risk of atopic diseases was found when GnRH analogues were prescribed for 2 months (adjusted HR 0.53, 95% CI, 0.29–0.97, p = 0.04) and 2–14 months (adjusted HR 0.66, 95% CI, 0.49–0.89, p = 0.007). No significant difference in the risk of atopic diseases between group II and the comparison group was observed.

Conclusions

A decreased risk of atopic diseases was observed in patients with prostate cancer treated with GnRH analogues. Further studies are warranted to verify the association between testosterone levels and atopic diseases.

Mechanisms of Reciprocal Regulation of Gonadotropin-Releasing Hormone (GnRH)-Producing and Immune Systems: The Role of GnRH, Cytokines and Their Receptors in Early Ontogenesis in Normal and Pathological Conditions

Different aspects of the reciprocal regulatory influence on the development of gonadotropin-releasing hormone (GnRH)-producing- and immune systems in the perinatal ontogenesis and their functioning in adults in normal and pathological conditions are discussed. The influence of GnRH on the development of the immune system, on the one hand, and the influence of proinflammatory cytokines on the development of the hypothalamic-pituitary-gonadal system, on the other hand, and their functioning in adult offspring are analyzed. We have focused on the effects of GnRH on the formation and functional activity of the thymus, as the central organ of the immune system, in the perinatal period. The main mechanisms of reciprocal regulation of these systems are discussed. The reproductive health of an individual is programmed by the establishment and development of physiological systems during critical periods. Regulatory epigenetic mechanisms of development are not strictly genetically controlled. These processes are characterized by a high sensitivity to various regulatory factors, which provides possible corrections for disorders.

Gonadotropin-Releasing Hormone in Regulation of Thymic Development in Rats: Profile of Thymic Cytokines

An increasing body of recent experimental data confirms the impact of neurohormones on fetal development and function of different body systems. The synthesis of many neurohormones starts in fetal tissues before the hypothalamic–pituitary–adrenal and hypothalamic–pituitary–gonadal systems are formed, and their high levels are detected in the bloodstream. Here, we studied the role of gonadotropin-releasing hormone (GnRH) in rat thymus development and tried to reveal possible mechanisms underlying the GnRH effects in early development. Western blotting and reverse transcription-polymerase chain reaction allowed us to identify receptor for GnRH in the fetal thymus with peak expression on embryonic days 17–18 (ED17–18). Blocking the receptors in utero on ED17 by a GnRH antagonist suppressed the concanavalin A-induced proliferative response of T cells in adults. GnRH (10⁻⁷ M) increased mRNA expression of interleukin (IL)-4, IL-10, IL-1β, interferon γ (IFNγ), and tumor necrosis factor α (TNFα) in the thymus of 18-day fetuses after an ex vivo culture for 24 h. The increased mRNA levels of the cytokines in the thymus were accompanied by increased numbers of CD4+ T helpers. Overall, the data obtained confirm the regulatory or morphogenetic effect of GnRH on fetal thymus development mediated by synthesis of thymic cytokines.

Gender Difference in the Role of Posterodorsal Amygdala on the Regulation of Food Intake, Adiposity and Immunological Responses in Albino Wistar Rats

Lesion of posterodorsal amygdala (PDA) has been known to produce hyperphagia and obesity in animal models. However, the influence of gender on food intake (FI), body weight (BW) and immunological parameters following PDA lesion is not yet known. The present work was carried out to study the effect of gender on the regulation of FI, BW and immunological parameters following lesions of PDA in albino Wistar rats. Twenty-four albino Wistar rats were divided equally into 2 groups - PDA group and control group - with 6 male and 6 female rats in each. In the experimental group, bilateral electrolytic lesion of the respective nuclei was performed by stereotaxy and post-lesion parameters were recorded. In the control group, sham lesion was made. Male-female difference in each parameter was determined. Following PDA lesion, FI increased significantly in both male (p < 0.001) and female rats (p < 0.01) but the percentage increase in FI was significantly more in female rats (p < 0.001). BW also increased in both the sexes but the increase in BW was significant only in male rats (p < 0.05). Both male and female rats showed increase in the concentration of cluster of differentiation 4 (CD4), but the significant increase in CD4 concentration (p < 0.01) was seen only in male rats. CD8 concentration increased significantly in male rats (p < 0.05). The liver weight-BW ratio was significantly greater in female rats (p < 0.001) following PDA lesions. Lesion of PDA results in accentuation of FI and BW gain and activation of immunity. There is a gender difference in the inhibitory control of PDA on FI, BW and immunity.

Neuroendocrine immunoregulation in multiple sclerosis

Currently, it is generally accepted that multiple sclerosis (MS) is a complex multifactorial disease involving genetic and environmental factors affecting the autoreactive immune responses that lead to damage of myelin. In this respect, intrinsic or extrinsic factors such as emotional, psychological, traumatic, or inflammatory stress as well as a variety of other lifestyle interventions can influence the neuroendocrine system. On its turn, it has been demonstrated that the neuroendocrine system has immunomodulatory potential. Moreover, the neuroendocrine and immune systems communicate bidirectionally via shared receptors and shared messenger molecules, variously called hormones, neurotransmitters, or cytokines. Discrepancies at any level can therefore lead to changes in susceptibility and to severity of several autoimmune and inflammatory diseases. Here we provide an overview of the complex system of crosstalk between the neuroendocrine and immune system as well as reported dysfunctions involved in the pathogenesis of autoimmunity, including MS. Finally, possible strategies to intervene with the neuroendocrine-immune system for MS patient management will be discussed. Ultimately, a better understanding of the interactions between the neuroendocrine system and the immune system can open up new therapeutic approaches for the treatment of MS as well as other autoimmune diseases.

Short-term treatment with a gonadotropin-releasing hormone antagonist, cetrorelix, in rheumatoid arthritis (AGRA): a randomized, double-blind, placebo-controlled study

Objectives

Gonadotropin-releasing hormone (GnRH) stimulates immune responses; therefore, antagonizing GnRH with cetrorelix may have anti-inflammatory effects. The aim of this study was to assess short-term cetrorelix therapy in rheumatoid arthritis (RA) patients.

Method

In this proof-of-concept, randomized, double-blind study involving 99 patients with active, long-standing RA, 48 patients received subcutaneous cetrorelix (5 mg/day on days 1 and 2; 3 mg/day on days 3–5) and 51 received placebo. The primary end-point was the change in the 28-joint Disease Activity Score based on C-reactive protein (DAS28-CRP) by day 5, when the greatest GnRH suppression was anticipated. Secondary end-points included the change in tumour necrosis factor (TNF)-α, and achievement of American College of Rheumatology (ACR) responses and DAS28-CRP < 2.6 by day 5. Patients were followed up on days 10 and 15.

Results

By day 5, DAS28-CRP was non-significantly reduced by 0.82 in the cetrorelix group compared to a 0.57 reduction in the placebo group (p = 0.091), TNF-α (log pg/mL) was significantly reduced in the cetrorelix group compared with the placebo group [0.55, 95% confidence interval (CI) 0.08–1.01, p = 0.023], and more patients on cetrorelix achieved ACR20 responses (40% vs. 18%, p = 0.015) and DAS28-CRP < 2.6 (13% vs. 0%, p = 0.009). Inflammatory markers increased towards baseline levels after withdrawal of treatment. Rates of adverse events were similar in both groups.

Conclusions

Although there was no significant difference in the primary end-point between groups, antagonizing GnRH led to significant improvements in key secondary end-points. Thus, GnRH antagonists may have rapid anti-inflammatory effects in RA, already occurring within 5 days. The data suggest a novel mode of action for TNF-α inhibition in RA, and potentially in other autoimmune diseases.

Modulation of immune responses in stress by Yoga

Stress is a constant factor in today's fastpaced life that can jeopardize our health if left unchecked. It is only in the last half century that the role of stress in every ailment from the common cold to AIDS has been emphasized, and the mechanisms involved in this process have been studied. Stress influences the immune response presumably through the activation of the hypothalamic-pituitary adrenal axis, hypothalamic pituitary-gonadal axis, and the sympathetic-adrenal-medullary system. Various neurotransmitters, neuropeptides, hormones, and cytokines mediate these complex bidirectional interactions between the central nervous system (CNS) and the immune system. The effects of stress on the immune responses result in alterations in the number of immune cells and cytokine dysregulation. Various stress management strategies such as meditation, yoga, hypnosis, and muscle relaxation have been shown to reduce the psychological and physiological effects of stress in cancers and HIV infection. This review aims to discuss the effect of stress on the immune system and examine how relaxation techniques such as Yoga and meditation could regulate the cytokine levels and hence, the immune responses during stress.

Thymus hormones as prospective anti-inflammatory agents

IMPORTANCE OF THE FIELD

Inflammatory diseases are characterized by severe immune imbalances, leading to excessive or inappropriate release of mediators, which, in turn, result in massive damage to organs and systems. Effective means to control inappropriate immune reactions are often life-critical needs. Available data on the role of thymus-derived hormones in inflammation show their great potential.

AREAS COVERED IN THIS REVIEW

The review aims to systematize information for the last two decades on immune system regulation by thymic peptide hormones, with a primary focus on the role of these hormones in the systemic inflammatory response and inflammatory diseases. Anti-inflammatory potential of three thymic hormones - thymulin, thymosin-alpha, and thymopoietin - is discussed, reviewing recently published clinical and experimental studies.

WHAT THE READER WILL GAIN

Our analysis revealed the regulation of inflammatory processes via thymic hormones that could be prospective for therapeutic application. This regulation may be mediated through thymic hormone effects on peripheral immune cell activities and bidirectional coupling between thymic hormones and the hypothalamic-pituitary-adrenal axis.

TAKE-HOME MESSAGE

In view of the role of thymic hormones in immune and neuroendocrine systems, they could be suitable as therapeutic agents for inflammation.

Report of an HIV and HHV-8 negative case of primary effusion lymphoma with idiopathic T4 lymphocytopenia

Although primary effusion lymphoma (PEL) is usually associated with human herpes virus-8/Kaposi sarcoma herpes virus (HHV-8/KSHV) and human immunodeficiency virus (HIV), there are several reports of HHV-8/KSHV and HIV negative cases, mainly in the setting of immunodeficiency. Here, we report the second case of PEL associated with idiopathic T4 lymphocytopenia (ICL), which was HHV-8/KSHV negative, HIV negative and Epstein-Barr virus positive, while no other causative agents for immunodeficiency were documented. Flow cytometry revealed a hyperdiploid and highly mitotic large B-cell population, CD30, EMA, CD66, CD38 and CD71 positive. The malignant lymphoma cells showed atypia with prominent nuclei and basophilic vacuolated cytoplasm, while cytogenetic analysis with fluorescent in situ hybridization showed trisomy 18. The patient was administered R-COP chemotherapy, but no remission was achieved, up to 3 months from diagnosis.

Pneumocystis pneumonia in a patient with type 2 diabetes mellitus

A 76-year-old man, who was in the hospital for the treatment of type 2 diabetes mellitus and was receiving gonadotropin-releasing hormone (GnRH) agonist treatment for prostate cancer, developed fever and hypoxemia. Imaging revealed diffuse interstitial shadows, and PCR of the bronchoalveolar lavage fluid was positive for Pneumocystis jirovecii. The patient's absolute CD4-positive lymphocyte count dropped to 145/microl, but the HIV antibody was negative. After trimethoprim-sulfamethoxazole (TMP/SXT) treatment, the absolute CD4 positive lymphocyte count returned to normal. This patient with type 2 diabetes mellitus developed Pneumocystis pneumonia and developed a transient decrease in CD4-positive lymphocytes.

GnRH-I and GnRH-II have differential modulatory effects on human peripheral blood mononuclear cell proliferation and interleukin-2 receptor gamma-chain mRNA expression in healthy males

GnRH-I and its receptor (GnRHR-I) have previously been demonstrated and shown to be biologically active in the immune system, notably within peripheral lymphocytes. Recently however, a second form of GnRH (GnRH-II) has been described in the human. The functions of both these neuropeptides in PMBCs have not been understood yet. The present study was therefore designed to investigate the effects of GnRH-I and/or GnRH-II on human PMBC proliferation in males. Secondly, the effects of GnRH-I and GnRH-II on IL-2 dependent lymphocyte proliferation were examined. Finally, we analysed the role of GnRH-I and GnRH-II in IL-2R gamma-chain expression. Peripheral venous blood samples were obtained from six male healthy volunteers (Mean age 27.75 +/- 1.5). Non-radioactive cell proliferation assay was used for proliferation studies and we used quantitative real-time RT-PCR to examine the role of GnRH-I and GnRH-II on IL-2R gamma-chain expression in PMBCs. Treatment of PMBCs with GnRH-I (10(-9) M and 10(-5) M) and with interleukin-2 (IL-2) (50 U/ml) resulted in a significant increase in cell proliferation compared with the untreated control. PMBCs cotreated with IL-2 and GnRH-I demonstrated higher proliferative responses than IL-2 treatment alone, the enhancement of GnRH-I on IL-2 response being significant only at GnRH-I concentration of 10(-5) M. Co-incubation of IL-2+ GnRH 10(-5) M with a GnRH antagonist (Cetrorelix; 10(-6) M) significantly decreased the proliferation. GnRH-II did not affect the proliferation of PMBCs alone, and did not alter the proliferative response to IL-2. The proliferative responses to GnRH-I (alone and with IL-2) were significantly attenuated by GnRH-II coincubation (each in equal molar concentrations; 10(-9) M to 10(-5) M). It was found that GnRH-I increased the expression of IL-2Rgamma mRNA in a dose dependent manner, with a significant increase of percentage 162.3 +/- 14 of control at 10(-5) M. In contrast, IL-2Rgamma expression was significantly decreased in all concentrations of GnRH-II (10(-9) M to10(-5) M), and the maximum decrease was detected at 10(-5) M, with percentage 37.7 +/- 6.6 of control. All these findings strongly suggest that regulation of IL-2R expression may therefore be an important target for GnRH-I and GnRH-II in PMBCs in males. In summary, present study clearly demonstrates the differential effects of GnRH-I and GnRH-II on PMBC proliferation, IL-2 proliferative response, and IL-2Rgamma expression in PMBCs in males. To our knowledge, our observations provide the first evidence for the interactions of these local neuropeptides at lymphocyte level. Further experimental data in human are warranted to explore the clinical implications of these data.

Autoimmune thyroiditis during leuprolide acetate treatment

Autoimmune thyroiditis developed in a 9-year-old girl with precocious puberty approximately 8 months after initiation of Leuprolide acetate therapy. In addition, gonadotropin concentrations as measured by radioimmunoassay appeared high. Treatment with levothyroxine, in addition to continued Leuprolide acetate treatment, resolved gonadotropin elevation and hypothyroidism.

Immunomodulatory actions of gonadal steroids may be mediated by gonadotropin-releasing hormone

Estrogens are considered to be immunostimulatory, whereas androgens are considered to be immunosuppressive. We hypothesized that the divergent actions of gonadal steroids on the immune system may be mediated indirectly, via their potent divergent feedback effects on the hypothalamic hormone GnRH, which is itself immunostimulatory. We used the GnRH-deficient HPG/Bm mouse in an effort to disentangle the effects of gonadal steroids from the effects of GnRH. We randomized GnRH-deficient mice and their GnRH-sufficient littermates to receive androgens, estrogens, or GnRH. We subsequently measured B and T cell proliferative responses to mitogen and serum IgG levels. We demonstrate that estrogens exert stimulatory effects on B cell proliferation and serum IgG levels in the presence of GnRH but not in the absence of GnRH. Testosterone exerts suppressive effects on B cell function in the presence of GnRH but not in its absence. Androgens and estrogens exerted divergent actions on T cell function irrespective of the presence and absence of GnRH, although responses were markedly attenuated in GnRH-deficient mice. Our data suggest that the immunostimulatory effects of estrogen and the immunosuppressive effects of androgens on B cell function may be mediated indirectly via GnRH.

Gonadotropin-releasing hormone alters the T helper cytokine balance in the pregnant rat

The interactions between immune-endocrine and reproductive systems are heightened during pregnancy as an adaptive mechanism, and are regulated by a complex array of hormones and cytokines that control the survival of a semiallogeneic conceptus. GnRH can exert direct effects on the immune system via its receptor (GnRH-R) on lymphoid cells. In the present study, we employed in vitro, ex vivo, and in vivo approaches to investigate the role of GnRH in the modulation of T helper cytokines in pregnant rats undergoing termination of pregnancy. Day 8 pregnant rats were infused with a GnRH agonist (GnRH-Ag) for 24 h using an osmotic minipump. Sham control rats were infused with the vehicle, saline. Lymphocytes were isolated from sham and treated rats and polyclonally stimulated with immobilized anti-CD3 antibody. The levels of the signature T helper 1 (Th-1) cytokines (interferon-gamma [IFN-gamma] and interleukin-2 [IL-2]) and Th-2 cytokines (IL-4 and IL-10) were measured in culture supernatants. Using immunoflourescence confocal microscopy, we demonstrated for the first time the spatial localization of GnRH-R protein on the surface of lymphocytes. We observed a marked increase in IFN-gamma and inhibition of IL-4 production from lymphocytes of pregnant rats treated in vitro with different doses of GnRH-Ag. Further, the responsiveness of lymphocytes to produce IFN-gamma was markedly increased in cells cultured ex vivo from GnRH-Ag infused rats, whereas the capacity of lymphocytes to produce IL-4 was significantly inhibited. In addition, GnRH-Ag infusion in pregnant rats induced a shift toward Th-1 cytokines in the serum. We did not observe any significant difference in IL-2 and IL-10 production in response to GnRH-Ag. Our results suggest an additional function for GnRH as a Th-1 inducer and Th-2 inhibitor. GnRH can thus skew the cytokine balance to predominantly Th-1 type in pregnancy, leading to the termination of pregnancy in rats.

Gonadotropin-releasing hormone attenuates pregnancy-associated thymic involution and modulates the expression of antiproliferative gene product prohibitin

Thymic involution during pregnancy is believed to be a critical adaptive mechanism for regulation and control of the maternal immune system. These regulatory feedback mechanisms are important for the survival of the semiallogeneic fetus. In the present study, we examined the effects of GnRH on pregnancy-induced thymic involution by characterizing the expression patterns of prohibitin (PHB), an antiproliferative gene product, GnRH, and GnRH receptor (GnRH-R) proteins in the rat thymus and in mature splenic lymphocytes. GnRH agonist infusions in pregnant rats markedly attenuated pregnancy-induced thymic involution resulting in significant increases in thymic weight and thymocyte numbers. In addition, histological examination of the thymus revealed increase in cortical cellularity. Western blot analyses revealed a significant increase of total PHB protein content in thymi during pregnancy. Furthermore, distinct changes in PHB isoform expression were observed in the pregnant involuting thymi with greater expression of the basic PHB isoform. Basic isoform expression decreased in pregnant rats and was comparable with nonpregnant rat thymi upon GnRH agonist treatment. PHB is mainly expressed in mature cells of the thymic medulla, where it strongly colocalized with GnRH. We have observed GnRH-R immunoreactivity mainly in thymic medulla. Furthermore, as assessed by immunofluorescence double labeling with proliferating cell nuclear antigen, PHB was preferentially expressed in nonproliferating thymocytes. In this study, we demonstrated that GnRH, GnRH-R, and PHB show characteristic polarized expression in thymocytes. In addition, GnRH and PHB were coexpressed in mature splenic T cells. Our results suggest that PHB and GnRH are involved in thymic growth and may be important for maturation of T lymphocytes.

Neuroendocrine-immune (NEI) circuitry from neuron-glial interactions to function: Focus on gender and HPA-HPG interactions on early programming of the NEI system

Bidirectional communication between the neuroendocrine and immune systems during ontogeny plays a pivotal role in programming the development of neuroendocrine and immune responses in adult life. Signals generated by the hypothalamic-pituitary-gonadal axis (i.e. luteinizing hormone-releasing hormone, LHRH, and sex steroids), and by the hypothalamic-pituitary-adrenocortical axis (glucocorticoids (GC)), are major players coordinating the development of immune system function. Conversely, products generated by immune system activation exert a powerful and long-lasting regulation on neuroendocrine axes activity. The neuroendocrine-immune system is very sensitive to preperinatal experiences, including hormonal manipulations and immune challenges, which may influence the future predisposition to several disease entities. We review our work on the ongoing mutual regulation of neuroendocrine and immune cell activities, both at a cellular and molecular level. In the central nervous system, one chief compartment is represented by the astroglial cell and its mediators. Hence, neuron-glial signalling cascades dictate major changes in response to hormonal manipulations and pro-inflammatory triggers. The interplay between LHRH, sex steroids, GC and pro-inflammatory mediators in some physiological and pathological states, together with the potential clinical implications of these findings, are summarized. The overall study highlights the plasticity of this intersystem cross-talk for pharmacological targeting with drugs acting at the neuroendocrine-immune interface.

Gender, neuroendocrine-immune interactions and neuron-glial plasticity. Role of luteinizing hormone-releasing hormone (LHRH)

Signals generated by the hypothalamic-pitutary-gonadal (HPG) axis powerfully modulate immune system function. This article summarizes some aspects of the impact of gender in neuroendocrine immunomodulation. Emphasis is given to the astroglial cell compartment, defined as a key actor in neuroendocrine immune communications. In the brain, the principal hormones of the HPG axis directly interact with astroglial cells. Thus, luteinizing hormone releasing hormone, LHRH, influences hypothalamic astrocyte development and growth, and hypothalamic astrocytes direct LHRH neuron differentiation. Hormonally induced changes in neuron-glial plasticity may dictate major changes in CNS output, and thus actively participate in sex dimorphic immune responses. The impact of gender in neuroimmunomodulation is further underlined by the sex dimorphism in the expression of genes encoding for neuroendocrine hormones and their receptors within the thymus, and by the potent modulation exerted by circulating sex steroids during development and immunization. The central role of glucocorticoids in the interactive communication between neuroendocrine and immune systems, and the impact of gender on hypothalamic-pituitary-adrenocortical (HPA) axis modulation is underscored in transgenic mice expressing a glucocorticoid receptor antisense RNA.

Gonadotropin-releasing hormone and G proteins: potential roles in autoimmunity

The hypothalamic homone gonadotropin-releasing hormone (GnRH) displays gender-specific actions. Pituitary responsiveness to GnRH is generally increased by estrogens and decreased by androgens. GnRH is now known to be produced by the immune system and to exert potent immunologic actions. Our central hypothesis is that gender differences in responsiveness to GnRH in the immune system play a pivotal role in the gender differences in immunity and autoimmunity. Studies in lupus-prone mice demonstrate that GnRH exacerbates murine lupus in a gender-specific fashion. Subsequent studies from our laboratory suggest that the gender differences in immunologic responsiveness to GnRH may relate to differences in the expression of the signal transducers through which GnRH acts, namely, the G proteins, Gs, and Gq/11. We have further demonstrated gender differences in second messengers for GnRH, IP3, and cAMF in immune cells. We have also demonstrated that GnRH agonist increases the quantities and/or activity of G proteins in immune cells in a gender-specific fashion. We speculate that gender differences in GnRH production and action, and in G protein expression play a role in a variety of autoimmune diseases that affect females predominantly.