Effect of sex hormones on experimental autoimmune uveoretinitis (EAU)

Progesterone attenuates Th17-cell pathogenicity in autoimmune uveitis via Id2/Pim1 axis

BACKGROUND

Autoimmune uveitis (AU) is the most common ophthalmic autoimmune disease (AD) and is characterized by a complex etiology, high morbidity, and high rate of blindness. AU remission has been observed in pregnant female patients. However, the effects of progesterone (PRG), a critical hormone for reproduction, on the treatment of AU and the regulatory mechanisms remain unclear.

METHODS

To this end, we established experimental autoimmune uveitis (EAU) animal models and constructed a high-dimensional immune atlas of EAU-model mice undergoing PRG treatment to explore the underlying therapeutic mechanisms of PRG using single-cell RNA sequencing.

RESULTS

We found that PRG ameliorated retinal lesions and inflammatory infiltration in EAU-model mice. Further single-cell analysis indicated that PRG reversed the EAU-induced expression of inflammatory genes (AP-1 family, S100a family, and Cxcr4) and pathological processes related to inflammatory cell migration, activation, and differentiation. Notably, PRG was found to regulate the Th17/Treg imbalance by increasing the reduced regulatory functional mediators of Tregs and diminishing the overactivation of pathological Th17 cells. Moreover, the Id2/Pim1 axis, IL-23/Th17/GM-CSF signaling, and enhanced Th17 pathogenicity during EAU were reversed by PRG treatment, resulting in the alleviation of EAU inflammation and treatment of AD.

CONCLUSIONS

Our study provides a comprehensive single-cell map of the immunomodulatory effects of PRG therapy on EAU and elaborates on the possible therapeutic mechanisms, providing novel insights into its application for treating autoimmune diseases.

Presence of Choroidal Caverns in Patients with Posterior and Panuveitis

Choroidal caverns (CCs) have been described in association with age-related macular degeneration and pachychoroid disease. However, it is unknown if caverns are found in patients with chronic non-infectious uveitis (NIU). Herein, we evaluated patients with NIU who had optical coherence tomography and indocyanine green angiography for CCs. Clinical and demographic characteristics were extracted from the chart review. Univariate and multivariate mixed-effects logistical models were used to assess the association between clinical and demographic factors and the presence of CCs. One hundred thirty-five patients (251 eyes) met the inclusion criteria: 1 eye had anterior uveitis, 5 had intermediate uveitis, 194 had posterior uveitis, and 51 had panuveitis. The prevalence of CCs was 10%. CCs were only observed in patients with posterior and panuveitis, with a prevalence of 10.8% and 7.8%, respectively. Multifocal choroiditis (MFC) was the type of uveitis where CCs were most frequently observed, with 40% of eyes with MFC having CCs. In addition, male sex (p = 0.024) was associated with CCs. There was no significant difference in the degree of intraocular inflammation or mean subfoveal choroidal thickness between CC+ and CC- eyes. This is the first study to describe CCs in uveitis. Overall, these findings suggest that caverns may be a sequela of structural and/or vascular perturbations in the choroid from uveitis.

Salivary Proteomic Profiling Identifies Role of Neutrophil Extracellular Traps Formation in Pregnancy Gingivitis

Pregnancy gingivitis peaks during mid-pregnancy and resolves transiently towards the postpartum period. However, the role of maternal immune response in orchestrating gingival inflammation has not yet been fully understood. Hence, in this study, we examined the salivary protein profile during the three trimesters of pregnancy, in context to pregnancy gingivitis, employing iTRAQ-based quantitative proteomics. Unstimulated saliva was collected from 10 subjects in each trimester of pregnancy and postpartum period. Samples were analysed using iTRAQ analysis and ELISA and SEM was performed to validate results. Neutrophil mediated immune response was overrepresented in all three trimesters of pregnancy, despite the decrease in phagocytic responses during the second and third trimesters. ELISA showed a significantly higher Neutrophil Extracellular Traps (NETs) formation in the third trimester of pregnancy coinciding with the resolution of pregnancy gingivitis. The NETs-associated proteins (neutrophil elastase and myeloperoxidase) showed a positive correlation with estrogen hormones, which was also highest during the third trimester. Sex hormone-driven NETs formation could be the mainstay of defence that contributes to the remission of pregnancy gingivitis. This study has provided a new insight into the role of immune-modulation in pregnancy gingivitis, which will aid development of new therapeutics for managing pregnancy gingivitis in future.

[Gender medicine in ophthalmology : The "small difference" between women and men]

Gender-specific or sex-specific medicine is part of "personalized" medicine. After differences in heart diseases between women and men were first identified and increasingly published in the field of cardiology since the 1980s, differences between the sexes have also become the focus of interest in other disciplines. Immunological and hormonal aspects indicate significant differences, e.g. in the severity of the disease or the response to treatment. Even in ophthalmology epidemiological differences in some diseases are known but so far these do not lead to a different approach in the practical treatment of patients. This CME article aims to raise awareness of gender medicine also in the field of ophthalmology and at the same time to promote understanding of these differences by presenting the fundamental differences between the sexes.

Eye diseases in women

Although eye diseases are considered to be relatively less affected by patient sex, it is noteworthy that the presence of hormone receptors have been confirmed in various ocular tissues, which were considered to have few sex-based differences. Female hormone levels are known to change because of menstruation, pregnancy, and menopause. When female hormone levels markedly fluctuate in such situations, the disease state may change.The fluctuations in the levels of sex hormones affect the corneal thickness conditions of uveitis.Estrogen may be a possible therapeutic option for glaucoma because it protects the eyes from damage caused by glaucoma and reduces intraocular pressure;it is particularly promising in the treatment of postmenopausal women with glaucoma.Estrogen is considered to have a prophylactic effect against eye diseases. However, there is a report that female sex is an independent risk factor for the progression of diabetic retinopathy, so it may not always exert a prophylactic effect. Thus, caution should be exercised.Based on recent progression of studies on this field, the importance of treatment according to gender has been recognized in the treatment of eye diseases.

Modulation of immune cells and Th1/Th2 cytokines in insulin-treated type 2 diabetes mellitus

BACKGROUND

The role of the immune system in insulin resistance associated with type 2 diabetes has been suggested.

OBJECTIVES

We assessed the profile of Th1/Th2 cytokines along with the frequencies of immune cells in insulin-treated type 2 diabetic patients (T2DP).

METHODS

45 T2D patients and 43 age-matched healthy subjects were selected. Serum concentrations of T-helper type 1 (Th1) and Th2 cytokines and the frequencies of innate and adaptive immunity cells were assessed.

RESULTS

T2DP were hyperglycemic and showed high level of insulin, normal levels of triglycerides and total-cholesterol and without any change in HDL-cholesterol.Compared to healthy subjects, T2DP exhibited significant decreased frequencies of neutrophils, without any change in monocytes, eosinophils and natural killer cells. The percentages of total lymphocytes (CD3+) and CD8+-T-cells decreased whereas those of regulatory T-cells increased without any change in CD4+ T-cells in T2DP. Interestingly, the frequencies of effector CD4+-T and B-cells increased in T2DP. Serum concentrations of IL-2, IFN-γ and IL-4 decreased while IL-10 significantly enhanced in T2DP, suggesting a differentiation of CD4+T helper cells towards IL-10-producing-Teff-cells in these patients.

CONCLUSION

Insulin-treated type 2 diabetes is associated with anti-inflammatory profile consistent with differentiation of CD4+-Th-cells towards IL-10-producing-Teff-cells, concomitant with increased frequencies of Treg and B-cells, and this may probably offer prevention against certain infections or autoimmune/inflammatory diseases.

The role of sex in uveitis and ocular inflammation

Uveitides can be due to non-infectious and infectious etiologies. It has been observed that there is a gender difference with a greater preponderance of non-infectious uveitis in women than in men. This review will describe both non-infectious and infectious uveitides and describes some of the current autoimmune mechanisms thought to be underlying the gender difference. It will specifically look at non-infectious uveitides with systemic involvement including juvenile idiopathic arthritis, spondyloarthopathies, sarcoidosis, Behçet’s disease, and Vogt-Koyanagi-Harada disease and at uveitides without systemic involvement including sympathetic ophthalmia, birdshot chorioretinitis, and the white dot syndromes. Infectious uveitides like acute retinal necrosis, progressive outer retinal necrosis, and cytomegalovirus mediated uveitis will be mentioned. Different uveitides with female- or male- predominance are presented and discussed.

A model of insulin resistance in mice, born to diabetic pregnancy, is associated with alterations of transcription-related genes in pancreas and epididymal adipose tissue

Objective. This study is conducted on a model of insulin-resistant (IR) mice born to dams which were rendered diabetic by the administration of streptozotocin. Methods. Adult IR and control offspring were selected and we determined the mRNA expression of transcription factors known to modulate pancreatic and adipose tissue activities and inflammation. Results. We observed that serum insulin increased, and the mRNA of insulin gene transcription factors, Pdx-1, Nkx6.1 and Maf-A, were upregulated in IR mice pancreas. Besides, their pancreatic functional capacity seemed to be exhausted as evidenced by low expression of pancreatic Glut2 and glucokinase mRNA. Though IR offspring exhibited reduced epididymal adipose tissue, their adipocytes seemed to be differentiated into macrophage-like cells, as they exhibited upregulated CD14 and CD68 antigens, generally expressed by macrophages. However, there was no peripheral macrophages infiltration into epididymal adipose tissue, as the expression of F4/80, a true macrophage marker, was undetectable. Furthermore, the expression of IL-6, TNF-α and TLR-2, key players of insulin resistance, was upregulated in the adipose tissue of IR offspring. Conclusion. Insulin resistant state in mice, born to diabetic pregnancy, alters the expression of function-related genes in pancreas and epididymal adipose tissue and these offspring are prone to develop metabolic syndrome.

Influence of genes, sex, age and environment on the onset of autoimmune hepatitis

The pathogenesis of autoimmune hepatitis (AIH) is complex. However, it is believed that a susceptible individual, owing to his genetic background, sex and age, can develop the disease following exposure to an environmental trigger. Autoimmune hepatitis does not follow a Mendelian pattern of inheritance; hence no single causative genetic locus has been identified. However, several genes, inside and outside the HLA locus, have been linked to an increased susceptibility to AIH. Epidemiological evidence also suggests that the sex and age of the patient plays a role in AIH pathogenesis as the disease onset occurs mainly in the two first decades of life and a higher disease incidence is observed in females. No environmental trigger has been identified, but several have been proposed, mainly viruses and xenobiotics. This article aims at reviewing the current knowledge on susceptibility factors leading to AIH and putative triggers, emphasizing fundamental mechanisms responsible for the break of liver immunological tolerance.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Retinal ganglion cell protection by 17-beta-estradiol in a mouse model of inherited glaucoma

Glaucoma is the second leading cause of blindness in the world. The ultimate cause of vision loss due to glaucoma is thought to be retinal ganglion cell (RGC) apoptosis. Neuroprotection of RGC is becoming an important approach of glaucoma therapy. Several lines of evidence suggest that estrogen has neurotrophic and neuroprotective properties. In this study, we examine the role of estrogen in preventing RGC loss in DBA/2J mouse, an in vivo model of an inherited (pigmentary) glaucoma. Two-month-old female DBA/2J mice were anesthetized and ovariectomized with or without subcutaneous 17beta-estradiol (betaE2) pellet implantation. RGC survival was evaluated from flat-mounted whole retinas by counting retrograde-labeled cells. The loss of nerve fibers and RGC were also evaluated in paraffin-fixed retinal cross sections. Biochemical alterations in the retinas of DBA/2J mice in response to systemic injection of betaE2 were also examined. We have made several important observations showing that: (1) betaE2 treatment reduced the loss of RGC and neurofibers through inhibition of ganglion cell apoptosis, (2) betaE2 activated Akt and cAMP-responsive-element-binding-protein (CREB), (3) betaE2 up-regulated thioredoxin-1 (Trx-1) expression, (4) betaE2 reduced the increased activations of mitogen-activated protein kinases (MAPK) and NF-kappaB, (5) betaE2 inhibited the increased interleukin-18 (IL-18) expression, and (6) treatment with tamoxifen, an estrogen receptor antagonist, blocked betaE2-mediated activation of Akt and inhibition of MAPK phosphorylation in the retinas of DBA/2J mice. These findings suggest the possible involvement of multiple biochemical events, including estrogen receptor/Akt/CREB/thioredoxin-1, and estrogen receptor/MAPK/NF-kappaB, in estrogen-mediated retinal ganglion cell protection.

Single-fiber electromyography during menstrual exacerbation and ovulatory suppression in MuSK antibody–positive myasthenia gravis

We report a patient with muscle-specific tyrosine kinase (MuSK) antibody-positive myasthenia gravis who experienced worsening of myasthenic weakness associated with alterations in estrogen and progesterone levels during the administration of oral contraceptive therapy. Single-fiber electromyography was performed to document changes in neuromuscular transmission associated with the clinical exacerbation and subsequent resolution of the menstrual exacerbation and clinical improvement experienced with continuous monophasic oral contraceptive therapy. The potential long-term benefit of ovulatory suppression in MuSK antibody-positive myasthenia gravis is discussed.

Peroxisome proliferator-activated receptor alpha deficiency increases the risk of maternal abortion and neonatal mortality in murine pregnancy with or without diabetes mellitus: Modulation of T cell differentiation

We assessed the implication of peroxisome proliferator-activated receptor (PPAR) alpha deficiency in pregnancy outcome and neonatal survival and in the modulation of T cell differentiation in murine diabetic pregnancy and their offspring. Pregnant wild-type (WT) and PPAR alpha-null mice of C57BL/6J genetic background were rendered diabetic by five low doses of streptozotocin. We observed that, in the absence of diabetes, PPAR alpha deficiency resulted in an increase in abortion rate, i.e. 0% in WT mice vs. 20% in PPAR alpha-null mice [odds ratio (OR) = 14.33; P = 0.013]. Under diabetic conditions, the abortion rate was enhanced, i.e. 8.3% in WT mice vs. 50% in PPAR alpha-null mice (OR = 4.28; P = 0.011). In the pups born to diabetic dams, the offspring mortality, due to the absence of PPAR alpha, was enhanced, i.e. 27.7% in WT mice vs. 78.9% in PPAR alpha-null animals (OR = 11.48; P < 0.001). Moreover, we observed that T helper (Th) 1/Th2 balance was shifted to a pregnancy protecting Th2 phenotype in WT diabetic dams and to a noxious Th1 phenotype in PPAR alpha-null mice with diabetic pregnancy. Furthermore, offspring born to diabetic WT dams were hyperinsulinemic and hyperglycemic, and they exhibited up-regulated profile of Th2 cytokines, whereas those born to diabetic PPAR alpha-null dams were hypoinsulinemic and hyperglycemic, and they showed down-regulated profile of Th2 cytokines. However, IFN-gamma, a Th1 cytokine, was up-regulated in the offspring of both diabetic WT and PPAR alpha-null dams. Altogether, our results suggest that PPAR alpha deficiency in mice may be implicated in the increase in maternal abortion, neonatal mortality, and T cell differentiation.

Estrogen has a neuroprotective effect on axotomized RGCs through ERK signal transduction pathway

The neuroprotective effects of estrogen on neuronal cells in central nervous system have been described previously, however, the mechanisms of neuroprotective effect of estrogen against retinal ganglion cell (RGC) death has not been well identified. To examine the role of endogenous sex steroids produced in ovary, retina samples were prepared from female rats with or without ovariectomy and the density of RGC was calculated. Ovariectomy alone had no effect on the density of fluorogold (FG)-labeled RGC without injury, while the density of surviving RGC after optic nerve axotomy with ovariectomy was significantly decreased compared to that without ovariectomy. To examine the role of exogenous sex steroids, 17beta-estradiol was injected into the vitreous cavity in ovariectomized rats and showed neuroprotective effect on axotomy-induced RGC death while exogenous progesterone showed no effect. Immunoblot and immunohistochemical analysis demonstrated that ERK-c-Fos signal transduction pathway was activated by exogenous 17beta-estradiol in ganglion cell layer. U0126, an ERK inhibitor, inhibited the neuroprotective effect of estrogen on axotomized RGC death. These data suggest that estrogen has neuroprotective effect through activation of ERK-c-Fos signaling pathway on axotomy-induced RGC death. The neuroprotective effect of estrogen may have therapeutic benefits in retinal diseases associated with RGC death such as glaucoma.

N-3 Fatty acids modulate antioxidant status in diabetic rats and their macrosomic offspring

OBJECTIVE

We investigated the role of dietary n-3 polyunsaturated fatty acids (n-3 PUFA) in the modulation of total antioxidant status in streptozotocin (STZ)-induced diabetic rats and their macrosomic offspring.

DESIGN

Female wistar rats, fed on control diet or n-3 PUFA diet, were rendered diabetic by administration of five mild doses of STZ on day 5 and were killed on days 12 and 21 of gestation. The macrosomic (MAC) pups were killed at the age of 60 and 90 days.

MEASUREMENTS

Lipid peroxidation was measured as the concentrations of plasma thiobarbituric acid reactive substances (TBARS), and the total antioxidant status was determined by measuring (i) plasma oxygen radical absorbance capacity (ORAC), (ii) plasma vitamin A, E and C concentrations, and (iii) antioxidant enzymes activities in erythrocytes. The plasma lipid concentrations and fatty acid composition were also determined.

RESULTS

Diabetes increased plasma triglyceride and cholesterol concentrations, whereas macrosomia was associated with enhanced plasma cholesterol and triglyceride levels, which diminished by feeding n-3 PUFA diet. N-3 PUFA diet also reduced increased plasma TBARS and corrected the decreased ORAC values in diabetic rats and their macrosomic offspring. EPAX diet increased the diminished vitamin A levels in diabetic mothers and vitamin C concentrations in macrosomic pups. Also, this diet improved the decreased erythrocyte superoxide dismutase and glutathione peroxidase activities in diabetic and macrosomic animals.

CONCLUSION

Diabetes and macrosomia were associated with altered lipid metabolism, antioxidant enzyme activities and vitamin concentrations. N-3 PUFA diet improved hyperlipidemia and restored antioxidant status in diabetic dams and MAC offspring.

Autonomic dysfunction may be an under-recognized cause of female fertility disorders

Female conditions of impaired fertility comprise a heterogeneous group of disorders that are attributed to various anatomic, hormonal and immunologic disturbances. We hypothesize that autonomic dysfunction may be a previously unrecognized factor in female fertility disorders. Emerging physiologic and molecular evidence suggests that autonomic balance varies during normal menstrual cycles with a shift to sympathetic bias during the luteal phase. Furthermore, many diseases associated with autonomic dysfunction show catamenial variations in patterns consistent with a shift to sympathetic bias occurs during the second half of normal menstrual cycles. The shift to sympathetic bias during the normal luteal phase may be an evolutionary adaptation to address the immunologic and physiologic demands for successful implantation and gestation. Through direct modulation of the lymphoid system and activation of the cortisol pathway, sympathetic bias promotes a shift to relative T helper (Th)-2 biased immunity which may favor maternal tolerance of the embryo by attenuating Th-1 mediated interference of implantation. Indeed, a growing body of evidence has implicated abnormal Th balance in fertility disorders, but the link has been attributed to factors other than autonomic function, such as hormonal factors. After implantation, maternal sympathetic bias may further support gestation through physiologic changes necessary to maintain placental perfusion pressure. We propose that insufficient shift to sympathetic bias during the luteal phase, which manifests in inadequate shift towards Th-2 bias and down-regulation of Th-1 function, may be the mechanism of impaired fertility in certain patients. Our hypothesis portends new potential methods to treat fertility disorders by modulating autonomic balance.

Short day lengths enhance skin immune responses in gonadectomised Siberian hamsters

In Siberian hamsters and other photoperiodic rodents, exposure to short photoperiods simultaneously inhibits gonadal hormone secretion and enhances some measures of immune function. The present study tested whether gonadal hormones mediate the effects of short days on skin immune function (delayed-type hypersensitivity reactions) in male Siberian hamsters. The magnitude of delayed-type hypersensitivity reactions was greater in hamsters exposed to short days relative to those in long days. Comparable effects of photoperiod were obtained in castrated hamsters bearing empty or testosterone-filled implants. The data suggest that contemporary gonadal hormone secretion is neither necessary, nor sufficient to mediate the effects of short photoperiods on skin immune function.

A correlation of pregnancy term, disease activity, serum female hormones, and cytokines in uveitis

BACKGROUND/AIMS

Pregnancy and the postpartum period are associated with the activity of autoimmune diseases including uveitis. Although the exact mechanism is unknown, hormones are reported to alter inflammatory cytokines and influence disease activity. The authors studied ocular inflammation, female hormones, and serum cytokine levels during and after pregnancy.

METHODS

A prospective, observational case study was conducted. Four pregnant women in their first trimester with chronic non-infectious uveitis were followed monthly until 6 months after delivery. Serum female hormones (oestrogen, progesterone, prolactin) and various cytokines (IL-2, IL-4, IL-5, IL-6, IL-10, IFN-gamma, and TGF-beta) were measured by ELISA.

RESULTS

The four patients had five full term pregnancies. Uveitis activity decreased after the first trimester but flared in the early postpartum period. Serum female hormones, highly elevated during pregnancy, drastically dropped post partum. Cytokine levels except TGF-beta were mostly undetectable.

CONCLUSION

Female hormones and TGF-beta may contribute to the activity of uveitis during pregnancy and the postpartum period.

Dendritic cells exposed to estrogen in vitro exhibit therapeutic effects in ongoing experimental allergic encephalomyelitis

Immunomodulatory effects of estrogen have been demonstrated by clinical and experimental observations, but the mechanisms by which estrogen exhibits the effects remain to be defined. One possible mechanism by which estrogen inhibits the development of experimental allergic encephalomyelitis (EAE), a commonly used model of multiple sclerosis (MS) in humans, is over the functions of dendritic cells (DC). Here, we describe that splenic DC from Lewis rats obtained on day 12 post-immunization (p.i.) with myelin basic protein (MBP) encephalitogenic peptide 68-86+Freund's complete adjuvant (FCA), after being exposed in vitro 17beta-estradiol, exhibited therapeutic effects on acute EAE when injected subcutaneously on day 5 p.i. Blood mononuclear cells (MNC) were isolated from thus treated rats on day 12 p.i. Administration of estrogen-exposed DC prevented the expansion of CD4+ T cells and increased proportions of regulatory T cells producing IL-10 and CD4+CD28- suppressor T cells, accompanied with increased IL-10 and IFN-gamma, and reduced TNF-alpha production. Infiltrates of CD68+ macrophages within the central nervous system and MBP 68-86-induced T cell proliferation were inhibited in rats injected with estrogen-exposed DC compared to rats injected with naive DC. Estrogen up-regulated the expression of indoleamine 2,3-dioxygenase, which promotes tolerogenic properties of DC. The results suggest that in vitro exposure of DC to estrogen modulates DC functions and results in a therapeutic effect of DC.

Menstrual variation of autonomic balance may be a factor in exacerbations of certain diseases during the menstrual cycle

Exacerbation of certain medical conditions during specific phases of the menstrual cycle has long been recognized. Mechanisms of the cyclic variations are poorly understood, but are often attributed to fluctuations in reproductive hormones. We hypothesize that normal variations in autonomic balance during the menstrual cycle, which likely evolved as adaptations for reproduction, may contribute to catamenial variations in diseases independent of hormonal variations. Emerging evidence suggests that autonomic balance shifts towards sympathetic bias during the second half of the menstrual cycle. This shift can be seen as an evolutionary adaptation to address the immunologic and physiologic demands for successful implantation and gestation. Through direct modulation of lymphoid system and activation of the cortisol pathway, sympathetic bias promotes a shift to relative T helper (Th)-2-biased immunity which may favor maternal tolerance of the embryo by attenuating Th-1-mediated interference of implantation. Immune variance during the menstrual cycle has been implicated in menstrual fluctuations of many diseases, but until now the immune variance has been attributed to female hormonal changes. We propose that shifts in autonomic balance independently contribute to fluctuations in diseases by modulating the immune system. Still further, we propose that many other diseases fluctuate due to the direct nervous system actions of shifts in autonomic balance. Our hypothesis portends new therapeutic paradigms based on cyclical modulation of autonomic balance to address catamenial variations of medical conditions.