Acquisition of the rheumatoid arthritis HLA shared epitope through microchimerism

Microchimeric cells promote production of rheumatoid arthritis-specific autoantibodies

BACKGROUND

Women are more likely to develop autoimmune diseases than men. Contribution from microchimerism (Mc) has been proposed, as women naturally acquire Mc from more sources than men because of pregnancy. Women with Rheumatoid Arthritis (RA) who lack RA-associated HLA alleles have been found to harbor Mc with RA-associated HLA alleles in higher amounts than healthy women in prior work. However, an immunological impact of Mc remains to be elucidated.

OBJECTIVES

To test the hypothesis that Mc with RA-risk associated HLA alleles can result in the production of RA-associated autoantibodies, when host genetic risk is absent.

METHODS

DBA/2 mice are unable to produce RA-specific anti-citrullinated autoantibodies (ACPAs) after immunization with the enzyme peptidyl arginine deiminase (PAD) in a previously developed model. DBA/2 females were mated with C57BL/6 males humanized to express HLA-DR4, which is associated with RA-risk and production of ACPAs, to evaluate DR4+ fetal Mc contribution. Next, DBA/2 females born of heterozygous DR4+/- mothers were evaluated for DR4+ Mc of maternal or littermate origin. Finally, DBA/2 females from DR4+/- mothers were crossed with DR4+ males, to evaluate the contribution of any Mc source to ACPA production.

RESULTS

After PAD immunization, between 20 % and 43 % of DBA/2 females (otherwise unable to produce ACPAs) had detectable ACPAs (CCP2 kit) after exposure to sources of Mc with RA-associated HLA alleles, compared to 0 % of unmated/unexposed DBA/2 females. Further the microchimeric origin of the autoantibodies was confirmed by detecting a C57BL/6-specific immunoglobulin isotype in the DBA/2 response.

CONCLUSION

Our study demonstrates that Mc cells can produce "autoantibodies" and points to a role of Mc in the biology of autoimmune diseases, including RA.

Pregnancy and the Autoimmune Patient

PURPOSE OF REVIEW

This article will review the current understanding of the immunologic changes that occur during pregnancy. It will discuss the impact of pregnancy on the disease activity of autoimmune or inflammatory rheumatic diseases (AIRD). Lastly, it will highlight the most recent data on pre-conception and pregnancy management practices that can improve pregnancy outcomes in autoimmune patients.

RECENT FINDINGS

Pregnancy is an immunologically complex and dynamic state that may affect the activity of AIRDs, with more patients having active disease during pregnancy than previously thought. Uncontrolled inflammatory diseases are associated with poor pregnancy outcomes such as preeclampsia, small for gestational age infants, and prematurity. Pre-conception counseling and early pregnancy planning discussions can help ensure optimal disease control and medication management prior to attempting conception. Adequate control of AIRDs on pregnancy-compatible medications during the pre-conception, pregnancy, and postpartum periods is required for optimal pregnancy outcomes.

Ultrasensitive chimerism enhances measurable residual disease testing after allogeneic hematopoietic cell transplantation

Increasing mixed chimerism (reemerging recipient cells) after allogeneic hematopoietic cell transplant (allo-HCT) can indicate relapse, the leading factor determining mortality in blood malignancies. Most clinical chimerism tests have limited sensitivity and are primarily designed to monitor engraftment. We developed a panel of quantitative polymerase chain reaction assays using TaqMan chemistry capable of quantifying chimerism in the order of 1 in a million. At such analytic sensitivity, we hypothesized that it could inform on relapse risk. As a proof-of-concept, we applied our panel to a retrospective cohort of patients with acute leukemia who underwent allo-HCT with known outcomes. Recipient cells in bone marrow aspirates (BMAs) remained detectable in 97.8% of tested samples. Absolute recipient chimerism proportions and rates at which these proportions increased in BMAs in the first 540 days after allo-HCT were associated with relapse. Detectable measurable residual disease (MRD) via flow cytometry in BMAs after allo-HCT showed limited correlation with relapse. This correlation noticeably strengthened when combined with increased recipient chimerism in BMAs, demonstrating the ability of our ultrasensitive chimerism assay to augment MRD data. Our technology reveals an underappreciated usefulness of clinical chimerism. Used side by side with MRD assays, it promises to improve identification of patients with the highest risk of disease reoccurrence for a chance of early intervention.

Do Fetal Microchimeric Cells Influence Experimental Autoimmune Myocarditis?

Objective: We investigated the presence and influence of fetal microchimerism in the cardiac tissue of mated female mice submitted to experimental autoimmune myocarditis. Materials and methods: Nulliparous BALB/c females and BALB/c females mated with either BALB/c males (syngeneic mating) or C57BL/6 males (allogeneic mating) were immunized with cardiac myosin peptide MyHC-α_614-629 or kept as non-immunized controls. Immunization occurred 6-8 weeks after delivery and mice were assessed after 21 days. Results: Immunized mice of allogeneic mating had a lower production of anti-MyHC-α_614-629 antibodies compared to immunized nulliparous mice. Immunized nulliparous females had an intense mononuclear inflammatory infiltrate in cardiac tissue, associated with fibroplasia, while mated females had a lower inflammatory reaction. An increase in the frequency of microchimeric fetal cells was observed in mice submitted to allogeneic mating following immunization. Conclusion: Allogeneic cells of fetal origin could contribute to mitigating the inflammatory response in experimental myocarditis.

What is the impact of sex hormones on the pathogenesis of rheumatoid arthritis?

Rheumatoid arthritis (RA) is the most common inflammatory rheumatic disease and has a female predominance of around 3:1. The relationship between sex hormones and RA has been of great interest to researchers ever since Philip Hench's observations in the 1930's regarding spontaneous disease amelioration in pregnancy. Extensive basic scientific work has demonstrated the immunomodulatory actions of sex hormones but this therapeutic potential has not to date resulted in successful clinical trials in RA. Epidemiological data regarding both endogenous and exogenous hormonal factors are inconsistent, but declining estrogen and/or progesterone levels in the menopause and post-partum appear to increase the risk and severity of RA. This review assimilates basic scientific, epidemiological and clinical trial data to provide an overview of the current understanding of the relationship between sex hormones and RA, focusing on estrogen, progesterone and androgens.

Endoplasmic Reticulum Stress, Oxidative Stress, and Rheumatic Diseases

Background: The endoplasmic reticulum (ER) is a multi-functional organelle responsible for cellular homeostasis, protein synthesis, folding and secretion. It has been increasingly recognized that the loss of ER homeostasis plays a central role in the development of autoimmune inflammatory disorders, such as rheumatic diseases. Purpose/Main contents: Here, we review current knowledge of the contribution of ER stress to the pathogenesis of rheumatic diseases, with a focus on rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We also review the interplay between protein folding and formation of reactive oxygen species (ROS), where ER stress induces oxidative stress (OS), which further aggravates the accumulation of misfolded proteins and oxidation, in a vicious cycle. Intervention studies targeting ER stress and oxidative stress in the context of rheumatic diseases are also reviewed. Conclusions: Loss of ER homeostasis is a significant factor in the pathogeneses of RA and SLE. Targeting ER stress, unfolded protein response (UPR) pathways and oxidative stress in these diseases both in vitro and in animal models have shown promising results and deserve further investigation.

Fetal‐placental antigens and the maternal immune system: Reproductive immunology comes of age

Reproductive physiology and immunology as scientific disciplines each have rich, largely independent histories. The physicians and philosophers of ancient Greece made remarkable observations and inferences to explain regeneration as well as illness and immunity. The scientific enlightenment of the renaissance and the technological advances of the past century have led to the explosion of knowledge that we are experiencing today. Breakthroughs in transplantation, immunology, and reproduction eventually culminated with Medawar’s discovery of acquired immunological tolerance, which helped to explain the transplantation success and failure. Medawar’s musings also keenly pointed out that the fetus apparently breaks these newly discovered rules, and with this, the field of reproductive immunology was launched. As a result of having stemmed from transplantation immunology, scientist still analogizes the fetus to a successful allograft. Although we now know of the fundamental differences between the two, this analogy remains a useful tool to understand how the fetus thrives despite its immunological disparity with the mother. Here, we review the history of reproductive immunology, and how major and minor histocompatibility antigens, blood group antigens, and tissue‐specific “self” antigens from the fetus and transplanted organs parallel and differ.

Chimerism in health and potential implications on behavior: A systematic review

In this review, we focus on the phenomenon of chimerism and especially microchimerism as one of the currently underexplored explanations for differences in health and behavior. Chimerism is an amalgamation of cells from two or more unique zygotes within a single organism, with microchimerism defined by a minor cell population of <1%. This article first presents an overview of the primary techniques employed to detect and quantify the presence of microchimerism and then reviews empirical studies of chimerism in mammals including primates and humans. In women, male microchimerism, a condition suggested to be the result of fetomaternal exchange in utero, is relatively easily detected by polymerase chain reaction molecular techniques targeting Y-chromosomal markers. Consequently, studies of chimerism in human diseases have largely focused on diseases with a predilection for females including autoimmune diseases, and female cancers. We detail studies of chimerism in human diseases and also discuss some potential implications in behavior. Understanding the prevalence of chimerism and the associated health outcomes will provide invaluable knowledge of human biology and guide novel approaches for treating diseases.

Nonendocrine mechanisms of sex bias in rheumatic diseases

Rheumatic diseases affect a wide range of individuals of all ages, but the most common diseases occur more frequently in women than in men, at ratios of up to ten women to one man. Despite a growing number of studies on sex bias in rheumatic diseases, sex-specific health care is limited and sex specificity is not systematically integrated into treatment regimens. Women and men differ in three major biological points: the number of X chromosomes per cell, the type and quantities of sex hormones present and the ability to be pregnant, all of which have immunological consequences. Could a greater understanding of these differences lead to a new era of personalized sex-specific medicine? This Review focuses on the main genetic and epigenetic mechanisms that have been put forward to explain sex bias in rheumatic diseases, including X chromosome inactivation, sex chromosome aneuploidy and microchimerism. The influence of sex hormones is not discussed in detail in this Review, as it has been well described elsewhere. Understanding the sex-specific factors that contribute to the initiation and progression of rheumatic diseases will enable progress to be made in the diagnosis, treatment and management of all patients with these conditions.

Immunogenicity of a rheumatoid arthritis protective sequence when acquired through microchimerism

HLA class II genes provide the strongest genetic contribution to rheumatoid arthritis (RA). HLA-DRB1 alleles encoding the sequence DERAA are RA-protective. Paradoxically, RA risk is increased in women with DERAA⁺ children born prior to onset. We developed a sensitive qPCR assay specific for DERAA, and found 53% of DERAA^-/- women with RA had microchimerism (Mc; pregnancy-derived allogeneic cells) carrying DERAA (DERAA-Mc) vs. 6% of healthy women. DERAA-Mc quantities correlated with an RA-risk genetic background including DERAA-binding HLA-DQ alleles, early RA onset, and aspects of RA severity. CD4⁺ T cells showed stronger response against DERAA⁺ vs. DERAA^- allogeneic cell lines in vitro, in line with an immunogenic role of allogeneic DERAA. Results indicate a model where DERAA-Mc activates DERAA-directed T cells that are naturally present in DERAA^-/- individuals and can have cross-reactivity against joint antigens. Moreover, we provide an explanation for the enigmatic observation that the same HLA sequence differentially affects RA risk through Mendelian inheritance vs. microchimeric cell acquisition.

Disease progression in relation to pre-onset parity among women with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) often ameliorates during pregnancy and flares postpartum, but the relationship of pregnancy and childbirth to RA prognosis is unclear. We examined RA severity for association with parity prior to RA onset and asked whether time from birth (latency) and/or the mother's HLA genotype influenced results.

METHODS

A cohort study was conducted of 222 women previously identified in a prospective study of newly diagnosed RA, who returned for follow-up evaluation a median of 8 years later. Stratified analyses using Mantel-Haenszel methods were conducted to evaluate 5 RA severity measures based on hand and wrist radiographs, physical exams, and Health Assessment Questionnaires for association with parity.

RESULTS

Overall, we observed little evidence of altered risk of progression to severe RA in relation to pre-onset parity, adjusting for RA onset age and time to follow-up. Stratifying parous women who had only live births by latency (<15 years/15+ years) showed no difference in risk of severe RA compared to nulligravid women. Live birth deliveries were significantly protective for women with 0 but not for those with 1 or 2 copies of the RA risk-associated HLA-DRB1 shared epitope sequence for erosion score (RR 0.26 95% CI 0.09-0.89) and joint count (RR 0.28 95% CI 0.09-0.87).

CONCLUSION

We observed little evidence of difference in severe RA by pre-onset parity overall. However, among women not predisposed to RA by possessing the risk-associated HLA genotype, parous women who had only live births had lower risk of progression to severe RA as measured by erosion score and joint count.

Feto-Maternal Microchimerism: The Pre-eclampsia Conundrum

Feto-maternal microchimerism (FMM) involves bidirectional cross-placental trafficking during pregnancy, leading to a micro-chimeric state that can persist for decades. In this manner a pregnant woman will harbor cells from her mother, as well as, cells from her child. Historically, eclampsia, a severe disorder of pregnancy provided the basis for FMM following the detection of trophoblast cells in the lungs of deceased women. Bi-directional cell trafficking between mother and fetus is also altered in pre-eclampsia and has been suggested to contribute to the underlying etiology. FMM has been implicated in tolerance promotion, remission of auto-inflammatory disorders during pregnancy, or the development of autoimmune conditions post-partum. The underlying mechanism whereby the host immune system is modulated is unclear but appears to involve HLA class II molecules, in that incompatibility between mother and fetus promotes remission of rheumatoid arthritis, whereas feto-maternal HLA compatibility may assist in the post-partum initiation of scleroderma. Couples having a high degree of HLA class II compatibility have an increased risk for pre-eclampsia, while the occurrence of scleroderma and rheumatoid arthritis is greater in pre-eclamptic cases than in women with normal pregnancies, suggesting a long term autoimmune predisposition. Since pregnant women with pre-eclampsia exhibit significantly lower levels of maternally-derived micro-chimerism, the question arises whether pre-eclampsia and post-partum development of autoimmune conditions occur due to the failure of the grandmothers cells to adequately regulate an inappropriate micro-chimeric constellation.

Specific Donor HLA-DR Types Correlate With Altered Susceptibility to Development of Chronic Lung Allograft Dysfunction

BACKGROUND

The greatest challenge to long-term graft survival is the development of chronic lung allograft dysfunction. Th17 responses to collagen type V (colV) predispose lung transplant patients to the severe obstructive form of chronic lung allograft dysfunction, known as bronchiolitis obliterans syndrome (BOS). In a previous study cohort (n = 54), pretransplant colV responses were increased in recipients expressing HLA-DR15, consistent with the high binding avidity of colV (α1) peptides for HLA-DR15, whereas BOS incidence, which was known to be strongly associated with posttransplant autoimmunity to colV, was higher in patients who themselves lacked HLA-DR15, but whose lung donor expressed it.

METHODS

To determine if this DR-restricted effect on BOS incidence could be validated in a larger cohort, we performed a retrospective analysis of outcomes for 351 lung transplant recipients transplanted between 1988 and 2008 at the University of Wisconsin. All subjects were followed until graft loss, death, loss to follow-up, or through 2014, with an average follow-up of 7 years. Comparisons were made between recipients who did or did not develop BOS. Grading of BOS followed the recommendations of the international society for heart and lung transplantation.

RESULTS

Donor HLA-DR15 was indeed associated with increased susceptibility to severe BOS in this population. We also discovered that HLA-DR7 expression by the donor or HLA-DR17 expression by the recipient decreased susceptibility.

CONCLUSIONS

We show in this retrospective study that specific donor HLA class II types are important in lung transplantation, because they are associated with either protection from or susceptibility to development of severe BOS.

Unravelling the biological secrets of microchimerism by single-cell analysis

The presence of microchimeric cells is known for >100 years and well documented since decades. Earlier, microchimeric cells were mainly used for cell-based non-invasive prenatal diagnostics during early pregnancy. Microchimeric cells are also present beyond delivery and are associated to various autoimmune diseases, tissue repair, cancer and immune tolerance. All these findings were based on low complexity studies and occasionally accompanied by artefacts not allowing the biological functions of microchimerism to be determined. However, with the recent developments in single-cell analysis, new means to identify and characterize microchimeric cells are available. Cell labelling techniques in combination with single-cell analysis provide a new toolbox to decipher the biology of microchimeric cells at molecular and cellular level. In this review, we discuss how recent developments in single-cell analysis can be applied to determine the role and function of microchimeric cells.

Microchimerism: Defining and redefining the prepregnancy context - A review

Bidirectional transplacental exchange characterizes human pregnancy. Cells exchanged between mother and fetus can durably persist as microchimerism and may have both short- and long-term consequences for the recipient. The amount, type, and persistence of microchimerism are influenced by obstetric characteristics, pregnancy complications, exposures to infection, and other factors. A reproductive-aged woman enters pregnancy harboring previously acquired microchimeric "grafts," which may influence her preconception health and her subsequent pregnancy outcomes. Many questions remain to be answered about microchimerism with broad-ranging implications. This review will summarize key aspects of this field of research and propose important questions to be addressed moving forward.

Parity and HLA alleles in risk of rheumatoid arthritis

Specific HLA II alleles are associated with rheumatoid arthritis (RA) risk and others with protection. Risk-associated alleles encode similar amino acid sequences from 70 through 74 of HLA-DRβ1 (QKRAA, QRRAA, RRRAA), referred to as the "shared epitope" (SE) and protective alleles encode DERAA at the same location. Fetal-maternal cell exchange results in long-term microchimerism i.e. harboring small numbers of genetically disparate cells. Women with RA who lack the SE were recently found to harbor microchimerism with the SE more often than healthy women. This finding raises the question whether microchimerism with DERAA confers benefit against RA and is underscored by the observation that overall parity reduces RA risk. While there is currently no test for microchimerism with DERAA, we conducted studies to ask whether parity benefits women at risk for RA, either because they have the SE or lack the protective DERAA sequence. HLA genotyping was conducted for 310 RA and 571 healthy women. Parity was associated with reduced RA risk in women aged <45 years (RR 0.53, 95% CI 0.34-0.82) and further analyses examined this group. RA risk reduction with parity was greater among women with the SE than SE-negative women (RR 0.42, 95%CI 0.22-0.79 vs. RR 0.79, 0.38-1.64). Among women without DERAA, RA risk was significantly reduced with parity (RR 0.44, 95% CI 0.26-0.74) but not among DERAA-positive women (RR 0.95 95% CI 0.34-2.65). In summary, results indicate the effect of parity varied according to a woman's HLA-genotype, and women at increased risk of RA benefited most.

Rheumatoid arthritis: Forward and reverse inheritance - the yin and the yang

The theory of Mendelian inheritance states that half our genes are maternal and half are paternal. This view is incomplete, as maternal–fetal exchange creates a legacy of non-native cells within an individual that can affect their health for better or worse, including contributing to their risk of developing autoimmune disease.

Number of parity and the risk of rheumatoid arthritis in women: A dose-response meta-analysis of observational studies

AIM

The association between parity and rheumatoid arthritis (RA) risk has been investigated, but results are controversial. Thus, our aim was to systematically analyze the effect of number of parity on the risk of RA in women.

METHODS

Relevant published studies were identified using PubMed and embase databases through 1 April 2016. We pooled the relative risks (RR) and 95% confidence intervals (CI) using random-effects models.

RESULTS

In all, 12 studies with a total of 2 497 580 participants and 11 521 RA cases were included. A borderline significant inverse association was observed when we compared parity with nulliparity for RA, with summarized RR = 0.90 (95%CI: 0.79-1.02; I²  = 58.5%, P_{heterogeneity}  = 0.010). In dose-response analysis, we observed a significant nonlinear (P_nonlinearity  = 0.000) relation between parity number and the risk of RA. Compared with null parity, the pooled RR of RA were 0.89 (95%CI: 0.86-0.93), 0.84 (95%CI: 0.79-0.89), 0.85 (95%CI: 0.79-0.90), 0.88 (95%CI: 0.81-0.95), 0.90 (95%CI: 0.83-0.97), 0.92 (95%CI: 0.84-1.02), and 0.94 (95%CI: 0.83-1.07) for 1, 2, 3, 4, 5, 6, and 7 live births, respectively. Subgroup and sensitivity analyses showed similar associations. No publication bias was found.

CONCLUSION

The findings from the current meta-analysis indicate that parity was related to decreased risk of RA. The greatest risk reduction appeared when the parity number reached two. Further studies are warranted to confirm our findings.

Juvenile idiopathic arthritis in relation to perinatal and maternal characteristics: a case control study

BACKGROUND

Existing data on associations between maternal and early childhood exposures and juvenile idiopathic arthritis (JIA) risk is scant and inconsistent with previous studies showing potential role for prematurity, number of siblings and infections. We explored JIA and International League of Associations for Rheumatology (ILAR) JIA categories in relation to selected infant (birthweight, size-for-gestational-age, gestational age), and maternal (parity, delivery type, prior fetal loss) characteristics that may be markers for exposures related to two pathways (hygiene hypothesis, microchimerism) potentially associated with autoimmune disorder occurrence.

METHODS

A case-control analysis with 1,234 JIA cases and 5,993 birth year-matched controls was conducted. Exposure information was obtained from WA state birth certificates. Multivariable logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) for associations with maternal and early life exposures for JIA and JIA categories.

RESULTS

Greater maternal parity was associated with a decreased OR for JIA (most marked for persistent oligoarticular JIA, OR 0.32, 95% CI 0.15; 0.71, p for trend = 0.0001). Prior fetal loss (except for oligoarticular JIA) was associated with an increased OR for JIA. Prematurity was associated with increased risk of enthesitis related arthritis (OR 1.9, 95% CI: 1.3-2.9) and rheumatoid factor positive polyarticular JIA (OR 2.2, 95% CI: 1.0-4.8).

CONCLUSIONS

We observed associations of selected maternal factors with JIA, some of which varied across JIA categories. The findings of decreased ORs for JIA in relation to greater maternal parity may be consistent with the hygiene and microchimerism hypotheses. Future studies with biomarkers relevant to these hypotheses will help elucidate any associations.

Increased risk of rheumatoid arthritis among mothers with children who carry DRB1 risk-associated alleles

OBJECTIVE

To investigate whether a child's genotype affects a mother's risk of rheumatoid arthritis (RA) beyond the risk associated with her genotype and to test whether exposure to fetal alleles inherited from the father increases risk of RA among mothers without risk alleles.

METHODS

A case-control study was conducted among 1165 mothers (170 cases/995 controls) and their respective 1482 children. We tested the association between having any child with alleles encoding amino acids (AAs) associated with RA including the 'shared epitope' (SE) and DERAA AA sequences at positions 70-74; AA valine, lysine and alanine at positions 11, 71 and 74 of HLA-DRB1; aspartic acid at position 9 of HLA-B and phenylalanine at position 9 of DPB1. We used logistic regression models to estimate OR and 95% CI for each group of alleles, adjusting for maternal genotype and number of live births.

RESULTS

We found increased risk of RA among mothers who had any child with SE (OR 3.0; 95% CI 2.0 to 4.6); DERAA (OR 1.7; 95% CI 1.1 to 2.6); or valine (OR 2.3; 95% CI 1.6 to 3.5), lysine (OR 2.3; 95% CI 1.5 to 3.4) and alanine (OR 2.8; 95% CI 1.2 to 6.4) at DRB1 positions 11, 71 and 74, respectively. Among non-carrier mothers, increased risk of RA was associated with having children who carried DERAA (OR 1.7; 95% CI 1.0 to 2.7) and alleles encoding lysine at DRB1 position 71 (OR 2.3; 95% CI 1.5 to 4.8).

CONCLUSION

Findings support the hypothesis that a child's genotype can contribute independently to risk of RA among mothers.

Impact of HIV-1 infection on the feto-maternal crosstalk and consequences for pregnancy outcome and infant health

Adaptation of the maternal immune system to establish maternal/fetal equilibrium is required for a successful pregnancy. Viral infections, including HIV-1 infection, can alter this maternal/fetal equilibrium, with significant consequences for pregnancy outcome, including miscarriages, impaired fetal growth, and premature delivery. Furthermore, maternal HIV-1 infection has been shown to have a long-term impact on the developing fetal immune system also when the infant is not infected with the virus. In this review, we discuss the consequences of maternal HIV-1 infection and antiretroviral therapy on pregnancy outcome and the health of the uninfected HIV-1-exposed infant.

Strategies and methods to study female-specific cardiovascular health and disease: a guide for clinical scientists

BACKGROUND

In 2001, the Institute of Medicine's (IOM) report, "Exploring the Biological Contributions to Human Health: Does Sex Matter?" advocated for better understanding of the differences in human diseases between the sexes, with translation of these differences into clinical practice. Sex differences are well documented in the prevalence of cardiovascular (CV) risk factors, the clinical manifestation and incidence of cardiovascular disease (CVD), and the impact of risk factors on outcomes. There are also physiologic and psychosocial factors unique to women that may affect CVD risk, such as issues related to reproduction.

METHODS

The Society for Women's Health Research (SWHR) CV Network compiled an inventory of sex-specific strategies and methods for the study of women and CV health and disease across the lifespan. References for methods and strategy details are provided to gather and evaluate this information. Some items comprise robust measures; others are in development.

RESULTS

To address female-specific CV health and disease in population, physiology, and clinical trial research, data should be collected on reproductive history, psychosocial variables, and other factors that disproportionately affect CVD in women. Variables related to reproductive health include the following: age of menarche, menstrual cycle regularity, hormone levels, oral contraceptive use, pregnancy history/complications, polycystic ovary syndrome (PCOS) components, menopause age, and use and type of menopausal hormone therapy. Other factors that differentially affect women's CV risk include diabetes mellitus, autoimmune inflammatory disease, and autonomic vasomotor control. Sex differences in aging as well as psychosocial variables such as depression and stress should also be considered. Women are frequently not included/enrolled in mixed-sex CVD studies; when they are included, information on these variables is generally not collected. These omissions limit the ability to determine the role of sex-specific contributors to CV health and disease. Lack of sex-specific knowledge contributes to the CVD health disparities that women face.

CONCLUSIONS

The purpose of this review is to encourage investigators to consider ways to increase the usefulness of physiological and psychosocial data obtained from clinical populations, in an effort to improve the understanding of sex differences in clinical CVD research and health-care delivery for women and men.

Exosomes: The missing link between microchimerism and acquired tolerance?

It has become increasingly clear that the immune system of viviparous mammals is much more in the business of acquiring tolerance to non-self antigens, than it is in rejecting cells that express them (for a recent review, highlighting the role of Treg cells, see ref. (1) ). It is also clear that both self-tolerance, and acquired tolerance to non-self is a dynamic process, with a natural ebb and flow. As has been often said of an effective team defense in sports, tolerance will "bend but does not break." How microchimerism, defined as the presence of extremely rare [1/10(4)-1/10(6)] cells of a genetically different individual, can induce either new immunogenetic pressures that push self-tolerance to the breaking point, or alternatively, provide relief from pre-existing immunogenetic risk, preventing development of autoimmune disease, remains a mystery. Indeed, the inability to directly correlate DNA-level microchimerism detected in blood samples by qPCR, with naturally occurring regulation to minor H and MHC alloantigens expressed by the rare cells themselves, has been frustrating to researchers in this field. (2) [Haynes, W.J. et al, this issue] However, recent developments in the areas of transplantation and reproductive immunology offer clues to how the effects of microchimerism can be amplified, and how a disproportionate immune impact might occur from a very limited cell source.

The effect of maternal Inflammation on foetal programming of metabolic disease

Maternal obesity during pregnancy increases the child's risk of developing obesity and obesity-related diseases later in life. Key components in foetal programming of metabolic risk remain to be identified; however, chronic low-grade inflammation associated with obesity might be responsible for metabolic imprinting in the offspring. We have therefore surveyed the literature to evaluate the role of maternal obesity-induced inflammation in foetal programming of obesity and related diseases. The literature on this topic is limited, so this review also includes animal models where maternal inflammation is mimicked by single injections with lipopolysaccharide (LPS). An LPS challenge results in an immunological response that resembles the obesity-induced immune profile, although LPS injections provoke a stronger response than the subclinical obesity-associated response. Maternal LPS or cytokine exposures result in increased adiposity and impaired metabolic homeostasis in the offspring, similar to the phenotype observed after exposure to maternal obesity. The cytokine levels might be specifically important for the metabolic imprinting, as cytokines are both transferable from maternal to foetal circulation and have the capability to modulate placental nutrient transfer. However, the immune response associated with obesity is moderate and therefore potentially weakened by the pregnancy-driven immune modulation, dominated by anti-inflammatory Treg and Th2 cells. We know from other low-grade inflammatory diseases, such as rheumatoid arthritis, that pregnancy can improve disease state. If pregnancy is also capable of suppressing the obesity-associated inflammation, the immunological markers might be less likely to affect metabolic programming in the developing foetus than otherwise implied.

Advancing the detection of maternal haematopoietic microchimeric cells in fetal immune organs in mice by flow cytometry

Maternal microchimerism, which occurs naturally during gestation in hemochorial placental mammals upon transplacental migration of maternal cells into the fetus, is suggested to significantly influence the fetal immune system. In our previous publication, we explored the sensitivity of quantitative polymerase chain reaction and flow cytometry to detect cellular microchimerism. With that purpose, we created mixed cells suspensions in vitro containing reciprocal frequencies of wild type cells and cells positive for enhanced green fluorescent protein or CD45.1⁺, respectively. Here, we now introduce the H-2 complex, which defines the major histocompatibility complex in mice and is homologous to HLA in human, as an additional target to detect maternal microchimerism among fetal haploidentical cells. We envision that this advanced approach to detect maternal microchimeric cells by flow cytometry facilitates the pursuit of phenotypic, gene expression and functional analysis of microchimeric cells in future studies.

Adverse pregnancy outcomes and risk of subsequent rheumatoid arthritis

OBJECTIVE

Pregnancy and reproductive outcomes have been associated with altered risk of some autoimmune diseases, including rheumatoid arthritis (RA). We sought to determine whether prior pregnancy resulting in a low birth weight (LBW) infant or preterm birth is associated with a risk of subsequent RA in the mother.

METHODS

We conducted an analysis of RA risk in parous women from a population-based prospective study of newly diagnosed cases of RA and age-matched healthy controls. The primary outcome measure was disease status (RA versus control), with exposures of prior preterm birth and prior delivery of an infant with LBW (≤2,500 gm), very low birth weight (VLBW; ≤1,500 gm), or extremely low birth weight (ELBW; ≤1,000 gm). A preplanned analysis including only rheumatoid factor (RF)-positive RA cases was also conducted.

RESULTS

A total of 202 RA cases and 1,102 controls were analyzed. Prior delivery of an infant with ELBW was associated with RA in the mother (relative risk [RR] 3.7 [95% confidence interval (95% CI) 1.0-13.2]). Prior VLBW (RR 4.0 [95% CI 1.3-11.4]) and ELBW (RR 5.5 [95% CI 1.4-22.5]) infants were associated with RF-positive RA. Prior LBW deliveries and preterm births were more common among RA cases than controls, but the differences were not statistically significant.

CONCLUSION

Compared to those with uncomplicated pregnancies, women with a prior VLBW or ELBW delivery had a higher risk of RA, particularly RF-positive RA. This association may reflect common risk factors for pregnancy complications and RA. Alternatively, complicated pregnancy itself may confer risk of subsequent RA.

Comparative sensitivity analyses of quantitative polymerase chain reaction and flow cytometry in detecting cellular microchimerism in murine tissues

Cellular microchimerism is defined as the presence of small populations of cells from one individual in another genetically distinct individual. The pivotal role of cellular microchimerism in a variety of immune settings is increasingly recognized, e.g. in context of pregnancy, transplantation and cancer. However, the detection of chimeric cells is overshadowed by technical limitations. This study aimed to overcome these limitations by testing the sensitivity and detection limit of a molecular biology approach (quantitative polymerase chain reaction, qPCR) and a cellular approach (flow cytometry) in order to identify experimentally induced cellular microchimerism in mice. Leukocytes isolated from lymph nodes or spleens of transgenic enhanced green fluorescent protein (eGFP) and CD45.1 mice respectively were used as targets to be detected as microchimeric cells among wild type (wt) or haploidentical cells. The detection limit of microchimeric cells by flow cytometry was 0.05% or lower for the respective eGFP(+) or CD45.1(+) cell subsets, which equals 48 cells or fewer per 1×10(5) wt cells. The detection limit of CD45.1(+) and CD45.2(+) cells among haploidentical CD45.1(+)2(+) cells by flow cytometry was 48 cells (0.05%) and 198 cells (0.2%), respectively. Using qPCR, a detection limit of 198 eGFP(+) cells per 1×10(5) wt cells, respective 0.2%, could be achieved. We here introduce two technical approaches to reliably detect low number of chimeric cells at a low detection limit and high sensitivity in transgenic mouse systems.

Long-term persistence and effects of fetal microchimerisms on disease onset and status in a cohort of women with rheumatoid arthritis and systemic lupus erythematosus

Background

The discovery of a fetal cells transfer to the mother is a phenomenon with multiple implications for autoimmunity and tolerance. The prevalence and meaning of the feto-maternal microchimerism (MC) in rheumatic diseases has not been thoroughly investigated. The aim of this study was to analyze the prevalence of fetal MC in patients with inflammatory rheumatic diseases and to investigate the association of MC with disease onset and current status.

Methods

A total of 142 women who gave birth to at least one male offspring were recruited: 72 women with rheumatoid arthritis (RA), 16 women with systemic lupus erythematosus (SLE), and 54 healthy women. For the detection of fetal microchimerism a nested PCR method was used to amplify a Y chromosome specific sequence (TSPY1). For characterization of disease activity we analyzed autoantibody profiles and X-rays in RA, and in addition complement levels in SLE respectively.

Results

A significant higher prevalence of fetal MC was found in RA (18%) and SLE (31%) compared to controls (3.7%) (p = 0.02 and p = 0.006, resp.). The mean age at disease onset was comparable in MC + and MC- RA patients. Disease onset occurred 18.7 (MC +) and 19.8 (MC-) years post partum of the first son, respectively. The presence of anti-CCP and RF did not differ significantly, anti-CCP were found in 75% of MC + and 87% of MC- patients, RF in 75% of both MC + and MC- patients. A slightly higher mean Steinbrocker score in MC + patients was associated with longer disease duration in MC + compared to MC- RA. In SLE patients the mean age at disease onset was 42.6 years in MC + and 49.1 years in MC- patients. Disease onset occurred 24.0 and 26.4 years post partum of the first son for MC + and MC- patients, respectively. The presence of ANA and anti-dsDNA antibodies, C3, C4 and CH50 did not differ significantly.

Conclusion

Our results indicate a higher frequency of long-term male MC in RA and SLE patients compared with controls without impact on disease onset and status in RA and SLE.

Maternal floor infarction/massive perivillous fibrin deposition: a manifestation of maternal antifetal rejection?

OBJECTIVE

Massive perivillous fibrin deposition (MPFD) and maternal floor infarction (MFI) are related placental lesions often associated with fetal death and fetal growth restriction. A tendency to recur in subsequent pregnancies has been reported. This study was conducted to determine whether this complication of pregnancy could reflect maternal antifetal rejection.

METHODS

Pregnancies with MPFD were identified (n = 10). Controls consisted of women with uncomplicated pregnancies who delivered at term without MPFD (n = 175). Second-trimester maternal plasma was analyzed for panel-reactive anti-HLA class I and class II antibodies. The prevalence of chronic chorioamnionitis, villitis of unknown etiology, and plasma cell deciduitis was compared between cases and controls. Immunohistochemistry was performed on available umbilical vein segments from cases with MPFD (n = 4) to determine whether there was evidence of complement activation (C4d deposition). Specific maternal HLA-antibody and fetal HLA-antigen status were also determined in paired specimens (n = 6). Plasma CXCL-10 concentrations were measured in longitudinal samples of cases (n = 28 specimens) and controls (n = 749 specimens) by ELISA. Linear mixed-effects models were used to test for differences in plasma CXCL-10 concentration.

RESULTS

(i) The prevalence of plasma cell deciduitis in the placenta was significantly higher in cases with MPFD than in those with uncomplicated term deliveries (40% versus 8.6%, P = 0.01), (ii) patients with MPFD had a significantly higher frequency of maternal anti-HLA class I positivity during the second trimester than those with uncomplicated term deliveries (80% versus 36%, P = 0.01); (iii) strongly positive C4d deposition was observed on umbilical vein endothelium in cases of MPFD, (iv) a specific maternal antibody against fetal HLA antigen class I or II was identified in all cases of MPFD; and 5) the mean maternal plasma concentration of CXCL-10 was higher in patients with evidence of MPFD than in those without evidence of MFPD (P < 0.001).

CONCLUSION

A subset of patients with MPFD has evidence of maternal antifetal rejection.

Microchimerism in the rheumatoid nodules of patients with rheumatoid arthritis

OBJECTIVE

The rheumatoid nodule is a lesion commonly found on extraarticular areas prone to mechanic trauma. When present with inflammatory symmetric polyarthritis, it is pathognomonic of rheumatoid arthritis (RA), an autoimmune disease in which naturally acquired microchimerism has previously been described and can sometimes contribute to RA risk. Since RA patients harbor microchimerism in the blood, we hypothesized that microchimerism is also present in rheumatoid nodules and could play a role in rheumatoid nodule formation. This study was undertaken to investigate rheumatoid nodules for microchimerism.

METHODS

Rheumatoid nodules were tested for microchimerism by real-time quantitative polymerase chain reaction (qPCR). The rheumatoid nodules of 29 female patients were tested for a Y chromosome-specific sequence. After HLA genotyping of patients and family members, rheumatoid nodules from 1 man and 14 women were tested by HLA-specific qPCR, targeting a nonshared HLA allele of the potential microchimerism source. Results were expressed as genome equivalents of microchimeric cells per 10(5) patient genome equivalents (GE/10(5)).

RESULTS

Rheumatoid nodules from 21% of the female patients contained male DNA (range <0.5, 10.3 GE/10(5)). By HLA-specific qPCR, 60% of patients were microchimeric (range 0, 18.5 GE/10(5)). Combined microchimerism prevalence was 47%. A fetal or maternal source was identified in all patients who tested positive by HLA-specific qPCR. Unexpectedly, a few rheumatoid nodules also contained microchimerism without evidence of a fetal or maternal source, suggesting alternative sources.

CONCLUSION

Our findings indicate that microchimerism is frequently present in the rheumatoid nodules of RA patients. Since microchimerism is genetically disparate, whether microchimerism in rheumatoid nodules serves as an allogeneic stimulus or allogeneic target warrants further investigation.

The otherness of self: microchimerism in health and disease

Microchimerism (Mc) refers to the harboring of a small number of cells (or DNA) that originated in a different individual. Naturally acquired Mc derives primarily from maternal cells in her progeny, or cells of fetal origin in women. Both maternal and fetal Mc are detected in hematopoietic cells including T and B cells, monocyte/macrophages, natural killer (NK) cells and granulocytes. Mc appears also to generate cells such as myocytes, hepatocytes, islet β cells and neurons. Here, the detrimental and beneficial potential of Mc is examined. The prevalence, diversity and durability of naturally acquired Mc, including in healthy individuals, indicates that a shift is needed from the conventional paradigm of 'self versus other' to a view of the normal 'self' as constitutively chimeric.

Interaction of pregnancy and autoimmune rheumatic disease

During pregnancy, the fetus represents a natural allograft that is not normally rejected. While the maternal immune system retains the ability to respond to foreign antigens, tolerance mechanisms are up-regulated to protect the fetus from immunologic attacks by the mother. The profound immunologic adaptations during and after pregnancy do influence maternal autoimmune rheumatic diseases in several ways. One is triggering the onset of a rheumatic disease in the post partum period, the other influencing disease activity of established rheumatic disease. The review will discuss the mechanisms of increased susceptibility of rheumatoid arthritis (RA) in the first year post partum with a specific emphasis on the role of fetal cells or antigens persisting in the maternal circulation (so called microchimerism). Furthermore, the different influences of pregnancy on established rheumatic diseases will be highlighted. A marked beneficial effect of pregnancy is observed on RA whereas several other rheumatic diseases as ankylosing spondylitis (AS) and systemic lupus erythematosus (SLE) show either no particular effect or an aggravation of symptoms during pregnancy. Differences emerging in regard to modulation of disease symptoms during pregnancy seem related to response to hormones, the type of cytokine profile and immune response prevailing as well as further downstream interactions of molecular pathways that are important in disease pathogenesis.

Maternal HLA panel-reactive antibodies in early gestation positively correlate with chronic chorioamnionitis: evidence in support of the chronic nature of maternal anti-fetal rejection

PROBLEM

Maternal tolerance of the fetus is essential for viviparity, yet anti-fetal rejection occurs in several pregnancy complications. Chronic chorioamnionitis is a feature of anti-fetal cellular rejection. There is a robust association between chronic chorioamnionitis and maternal seropositivity for anti-human leukocyte antigen (HLA) panel-reactive antibodies (PRA) at the time of delivery. This longitudinal study was performed to assess maternal HLA PRA status in early gestation and the temporal evolution of maternal HLA PRA in the context of chronic chorioamnionitis and, thereby, to determine whether HLA PRA during the course of pregnancy is useful for the detection of anti-fetal rejection.

METHOD OF STUDY

Maternal sera obtained before 16 weeks of gestation and at delivery were analyzed for HLA PRA in cases with (N = 100) and without (N = 150) chronic chorioamnionitis.

RESULTS

IgG (but not IgM) HLA class I and II PRA positivity at delivery was higher in cases with chronic chorioamnionitis than in those without chronic chorioamnionitis. IgG HLA class I PRA positivity before 16 weeks of gestation was higher in cases with chronic chorioamnionitis than in those without (30.3 versus 13.3%; P = 0.001). Positive conversion (negative HLA PRA before 16 weeks of gestation but positive at delivery) of IgG HLA class I and II PRA was significantly associated with chronic chorioamnionitis. Fetal HLA class I antigen-specific antibodies were confirmed in 12 of 16 mothers tested who were sensitized to HLA class I antigens before 16 weeks of gestation.

CONCLUSION

Positive maternal HLA PRA before 16 weeks of gestation and the temporal evolution of maternal HLA PRA are associated with the presence of chronic chorioamnionitis at the time of delivery. Maternal IgG HLA PRA has the potential to be a monitoring tool of anti-fetal rejection. Furthermore, the findings herein indicate that subsets of fetuses are exposed to alloimmune HLA antibodies for months, especially in cases with chronic chorioamnionitis.

[Systemic autoimmune disorders and pregnancy]

The coincidence of systemic autoimmune diseases and pregnancy may modify the outcome of the disease and the pregnancy due to the background immunologic and hormonal processes. The great majority of patients with autoimmune diseases are young females in their reproductive years, willing to have babies. Consequently, we have to prepare for this special situation. Our concept on childbearing in autoimmune women has changed within the last 30 years. Earlier, systemic lupus erythematosus flared in about 50% of patients during pregnancy, but the flare rate has significantly decreased recently. This improvement can be attributed to increased attention to low diseases activity at the time of conception, which might reduce to the half of the risk for flare. Tight control of patients and appropriate use of corticosteroids also contribute to the better results. The adequate use of anti-thrombotic agents resulted in a significant amelioration of pregnancy outcome in antiphospholipid syndrome. The earlier use of methotrexate and the introduction of tumor necrosis factor-alpha inhibitors in the treatment of rheumatoid arthritis have changed the natural characteristics of the disease. The increase in remission rate indirectly has beneficial effect on the number of planned and carried out pregnancies. Authors review the connection between systemic autoimmune disorders and pregnancy as well as the possibilities of medical treatment of such diseases during pregnancy.

Genetics of rheumatoid arthritis: time for a change!

PURPOSE OF REVIEW

To review recent progress in the genetics of rheumatoid arthritis (RA) and discuss the implications for understanding the pathogenesis of the disease as well as clinical application.

RECENT FINDINGS

Protection against anticitrullinated protein antibody (ACPA) positive RA was shown to be associated wit DRB1*1301. Genome-wide association studies (GWASs) added about 10 new loci to the list of already more than 20 loci associated with RA, so the list is now over 30. Typing for the known risk loci is not helpful for prediction of the risk for RA. It is remarkable how few functional studies have been published.

SUMMARY

Known genetic factors explain 50-60% of the genetic variance for susceptibility to ACPA-positive and 30-50% for ACPA-negative RA. Searching for the remaining missing or hidden heritability is in all probability not going to yield much for prediction and/or targeted intervention. Therefore, I conclude that if you want to find more genes you should have a lot of patience, time and money, stop with convential GWAS and invest in large-scale sequencing of selected patients and controls. I have a better suggestion, however: use the information that is already available to perform functional studies in order to understand the mechanism of the known associations!

Can maternal microchimeric cells influence the fetal response toward self antigens?

The origins of autoimmunity are still elusive despite significant advances in immunology. There is cumulative evidence that, beyond simple genetics, the maternal environment plays a critical role in the development of common autoimmune disorders, such as multiple sclerosis or diabetes. In recent years, the trafficking of maternal cells to the offspring has been clearly demonstrated. This microchimerism represents the very first immunological event in fetal life. The number of persisting maternal cells has been associated with several autoimmune disorders such as systemic sclerosis, juvenile dermatomyositis and diabetes. The precise role of the maternal cells in these disorders remains unclear. Based on recent experimental work in an animal model of juvenile diabetes, we will discuss the possibility of maternal cells modifying the response of the developing fetal immunity towards self.