Reproductive immunology: a focus on the role of female sex hormones and other gender-related factors

Prolactin and autoimmunity: The hormone as an inflammatory cytokine

Nowadays, more than 80 autoimmune disorders are recognized, in which an aberrant immune response against different organs and tissues plays a crucial role. Hormonal homeostasis has great influence in achieving competent and healthy immune system function. Prolactin has a bioactive function acting as a hormone and a cytokine. It influences the immune system modulation, mainly inhibiting the negative selection of autoreactive B lymphocytes. Hyperprolactinemia has been detected in many patients with different autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, Sjögren syndrome, multiple sclerosis, autoimmune thyroid disease, systemic sclerosis, among others, and its believed to play a crucial role in disease pathogenesis. A direct correlation between prolactin levels and disease activity was not clear. Genetic factors may have a role in humans as in animal models. Dopamine agonists have proven to offer clinical benefits among autoimmune patients and represent a promising therapy to be explored. In this review, the authors attempt to provide a critical overview on the role of prolactin in the immune system, exploring its contribution to the development of autoimmune diseases.

Prevalence of autoimmune disease in patients with prolactinomas and non-functioning pituitary adenomas

PURPOSE

Prolactin can affect autoimmune response and evidence suggests that hyperprolactinemia can primarily precipitate autoimmunity. We postulate that patients with prolactinomas are more prone to autoimmune disease (AID).

METHODS

We conducted a retrospective case-control study comparing prevalence of AID in 100 prolactinoma patients (PRL-P, cases) and 100 age- and gender-matched non-functioning pituitary adenoma patients (NFPA-P, controls) assessed at the Neuroendocrine Clinics of the McGill University Health Centre between January 2005 and December 2014. Comparisons were done using a conditional logistic regression (CLR) analysis. Multiple imputation was used to account for missing data values.

RESULTS

Sixty-eight women and 32 men were in each group. Median age was 37 years for PRL-P and 46 years for NFPA-P. AID was diagnosed in 28/100 cases and 16/100 controls. Autoimmune thyroid disease was the most common AID reported in both groups, representing 70 and 61% of the AID diagnoses respectively. CLR analysis revealed a multiplicative interaction effect between AID prevalence and age (p 0.004). Odds ratios for AID in PRL-P compared to NFPA-P increase with age and become significant at age 43, reaching 4.17 (95% CI 1.26, 13.82) at age 45 and 8.09 (95% CI 1.96, 33.43) at age 50 (p 0.05).

CONCLUSION

Our data showed a higher prevalence of AID in both PRL-P and NFPA-P than in a reference population. In both groups, prevalence of AID increased with age, given a multiplicative interaction effect. A significant higher prevalence of autoimmunity in PRL-P compared with NFPA-P occurs after age 43. These associations may have significant implications for the management of prolactinoma patients.

Connective tissue diseases in primary biliary cirrhosis: A population-based cohort study

AIM: To establish the frequency and clinical features of connective tissue diseases (CTDs) in a cohort of Chinese patients with primary biliary cirrhosis (PBC).

METHODS: Three-hundred and twenty-two Chinese PBC patients were screened for the presence of CTD, and the systemic involvement was assessed. The differences in clinical features and laboratory findings between PBC patients with and without CTD were documented. The diversity of incidence of CTDs in PBC of different countries and areas was discussed. For the comparison of normally distributed data, Student’s t test was used, while non-parametric test (Wilcoxon test) for the non-normally distributed data and 2 × 2 χ² or Fisher’s exact tests for the ratio.

RESULTS: One-hundred and fifty (46.6%) PBC patients had one or more CTDs. The most common CTD was Sjögren’s syndrome (SS, 121 cases, 36.2%). There were nine cases of systemic sclerosis (SSc, 2.8%), 12 of systemic lupus erythematosus (SLE, 3.7%), nine of rheumatoid arthritis (RA, 2.8%), and 10 of polymyositis (PM, 3.1%) in this cohort. Compared to patients with PBC only, the PBC + SS patients were more likely to have fever and elevated erythrocyte sedimentation rate (ESR), higher serum immunoglobulin G (IgG) levels and more frequent rheumatoid factor (RF) and interstitial lung disease (ILD) incidences; PBC + SSc patients had higher frequency of ILD; PBC + SLE patients had lower white blood cell (WBC) count, hemoglobin (Hb), platelet count, γ-glutamyl transpeptidase and immunoglobulin M levels, but higher frequency of renal involvement; PBC + RA patients had lower Hb, higher serum IgG, alkaline phosphatase, faster ESR and a higher ratio of RF positivity; PBC + PM patients had higher WBC count and a tendency towards myocardial involvement.

CONCLUSION: Besides the common liver manifestation of PBC, systemic involvement and overlaps with other CTDs are not infrequent in Chinese patients. When overlapping with other CTDs, PBC patients manifested some special clinical and laboratory features which may have effect on the prognosis.

Up-regulation of transcription factor Blimp1 in systemic lupus erythematosus

PURPOSE

B lymphocyte induced maturation protein 1 (Blimp1) is a transcription factor that is critical for differentiation and antibody production in plasma cells. In order to understand the mechanism of systemic lupus erythematosus (SLE), the role of Blimp1 expression was studied in patients with SLE and in healthy control subjects. And Blimp1 tissue distribution in MRL/lpr lupus mice was also investigated.

METHODS

The mRNA expression level of Blimp1 was analyzed by fluorescent real time PCR and compared between the 40 SLE patients and 30 control subjects. Expression of CD138, CD27 and CD19 in peripheral blood cells was analyzed by flow cytometry. Blimp1 mRNA and protein expression levels and tissue distribution in the kidneys, spleen and lymph nodes of MRL/lpr lupus and normal mice were analyzed.

RESULTS

Blimp1 mRNA expression level was 2.1 times greater in the SLE group as compared to the control group. The increased mRNA expression of Blimp1 seemed to be related to SLE disease activity and anti-nuclear antibody (ANA) titer. In SLE patients, the CD138+ plasma cells increased as the CD27+ cells decreased. Compared with normal mice, Blimp1 was strongly expressed in the kidneys, lymph nodes and spleen of MRL/lpr lupus mice. The expression level of Blimp1 mRNA in the kidneys, lymph nodes and spleen of MRL/lpr lupus mice was much higher than normal mice (1.76, 2.02, and 2.05 times greater, respectively, P<0.05). Similarly, protein levels in the above mentioned organs were also much higher (1.54, 1.99, and 2.21 times greater, respectively, P<0.05).

CONCLUSIONS

The elevated expression of Blimp1 in SLE patients and in the lupus mouse model is correlated with increases in plasma cells, autoantibodies and disease activity. It is closely related to differentiation of B-lymphocytes, antibody production and renal lesions. Blimp1 may play a role in SLE disease development.

The long-term marriage between autoimmunity and internal medicine: a homage to Manuel Carlos Dias

Our understanding of autoimmune diseases results from the perfect combination of basic and clinical scientific research, and the figure that is closest to the proposed autoimmunology specialist is certainly the internist. The role of B cells in rheumatoid arthritis, the immunological mechanisms to fibrosis or to tissue specific damage, the classification of Bechet's syndrome, the clinical outcomes of antiphospholid syndrome, and new biomarkers for vascular complications in systemic sclerosis constitute, among others, are ideal examples of this combination. For these reason, this issue includes comprehensive reviews in all these areas and is dedicated to Dr. Manuel Carlos Dias and his career in the perfectioning and teaching of the clinical skills necessary to manage autoimmune disease. We are convinced that these discussions are likely of interest to basic scientists and clinicians alike for the proposed translational applications.

Cutting-edge issues in autoimmunity and allergy of the digestive system

Autoimmunity and allergy involving the digestive system may be considered as paradigmatic for numerous common themes of complex diseases secondary to tolerance breakdown. Among gastrointestinal autoimmune diseases, for example, we encounter diseases in which a clear environmental trigger is identified (i.e., celiac disease), serum autoantibodies are most specific (i.e., primary biliary cirrhosis), or in which the disease pathophysiology is clearly understood (i.e., autoimmune gastritis). Similarly, it is intriguing that the gastrointestinal tract and the liver circulation represent the crucial environment for the development of immune tolerance. This issue is dedicated to the discussion of recent concepts while identifying two major common issues, i.e., the need for serum biomarkers and the role of vitamin D. Other common themes characterize the etiology and effector mechanisms of these and other autoimmune diseases and are discussed in each cutting-edge overview.

Mechanisms and pathophysiology of autoimmune disease

The first textbook on autoimmunity was published by Ian Mackay and McFarland Burnett in 1963. It was the first attempt to summarize existing knowledge on human autoimmunity. Since that time, there have been tens of thousands of experimental papers and numerous textbooks that focus on the diagnosis and treatment of human autoimmunity. There have been at least as many, if not more, directed at similar issues in animal models. Enormous strides have been made not only in diagnosis, but also in the pathophysiology and especially in treatment. We have gone from the era of simple HLA typing to deep sequencing and, more recently, epigenetic analysis. We have gone from the era of white blood cell differentials to detailed lymphoid phenotyping. We have gone from the era of simple antinuclear antibodies to detailed and sophisticated immunodiagnosis with recombinant autoantigens and disease-specific epitopes. We have gone from the era of using only corticosteroids to selective biologic agents. Diseases that were previously considered idiopathic are now very much understood as autoimmune. We are in the era of autoinflammatory reactions and the concept of both innate versus adaptive immunity in mediating immunopathology. In this edition of Clinical Reviews in Allergy and Immunology, we focus on key and cutting-edge issues in the pathophysiology of autoimmunity. The issues are very much oriented and driven by hypothesis, i.e., a prediction of events expected to occur based on observations. It is not meant to be a complete summary of potential mechanisms of autoimmunity, but rather an attempt to accelerate discussion and better understanding. The primary goal is obviously to help our patients with autoimmune disease.

Primary biliary cirrhosis and Sjögren's syndrome: autoimmune epithelitis

Primary biliary cirrhosis (PBC) has been often coined a model autoimmune disease based on the homogeneity amongst patients, the frequency and similarity of antimitochondrial antibodies, including the highly directed immune response to pyruvate dehydrogenase (PDC-E2). A significant number of patients with PBC suffer from sicca and amongst these, there are patients who also have classic Sjögren's syndrome. Indeed, both PBC and Sjögren's syndrome are characterized by inflammation of target epithelial elements. Both diseases can be considered on the basis of a number of other related clinical aspects, including proposed unique apoptotic features of the target tissue, the role of secretory IgA, and the frequency with which both diseases overlap with each other. Indeed, PBC may be considered a Sjögren's syndrome of the liver, whereas Sjögren's syndrome can be equally discussed as PBC of the salivary glands. Dissection of the genetic predispositions for both diseases and especially the molecular basis of effector mechanisms, will become critical elements in developing new therapies.

Gender and the regulation of longevity: implications for autoimmunity

For humans and other animals, gender has an influence not only on their physical attributes, but also on life span. In humans, females have a longer life span than males. The reasons for this are not entirely clear. The role of gender in the regulation of longevity may be linked to gender specific genetic differences, including the expression of sex hormone patterns and the changes in these patterns during an individual's lifetime. In addition, the effect of sex hormones on other physiologic responses to environmental influences on cellular stress and oxidative damage may play a role in longevity. Gender can impact many disease states, including autoimmune diseases, and the factors that affect the development of autoimmune diseases and the regulation of longevity may share common mechanistic pathways. Other factors that may play a role include telomere and telomerase related differences, caloric restriction and changes in mitochondrial DNA. Inflammatory and regulatory pathways such as insulin/IGF signaling and Target of Rapamycin (TOR) signaling may also play a role in longevity and aging-related diseases such as Alzheimer's. The role of gender differences in the regulation of these pathways or factors is not entirely clear. The role of X-chromosome inactivation in longevity has also yet to be fully elucidated.

The X chromosome and the sex ratio of autoimmunity

The number of human conditions that are currently considered to be autoimmune diseases (AID) has been steadily growing over the past decades and it is now estimated that over 10 million people are affected in the United States. One of the major shared features among AID is the predominance in the female sex which in some cases changes with the age at disease diagnosis. Numerous hypotheses have been formulated based on intuitive scientific backgrounds to justify this sex imbalance, i.e. sex hormones and reproductive factors, fetal microchimerism, other sex-related environmental factors, a skewing of the X-chromosome inactivation patterns, and major defects in sex chromosomes. Nevertheless, none of these hypotheses has thus far gathered enough convincing evidence and in most cases data are conflicting, as well illustrated by the reports on fetal microchimerism in systemic sclerosis or primary biliary cirrhosis. The present article will critically discuss the main hypotheses (loss of mosaicism, reactivation, and haploinsufficiency) that have been proposed based on findings in female patients with specific AID along with two additional mechanisms (X-chromosome vulnerability and X-linked polyamine genes) that have been observed in AID models. Further, recent data have significantly shifted the paradigm of X chromosome inactivation by demonstrating that a large number of genes can variably escape silencing on one or both chromosomes. As a result we may hypothesize that more than one mechanism may contribute to the female susceptibility to tolerance breakdown while the possibility that unknown factors may indeed protect men from AID should not be overlooked.