The impact of abnormal autoimmune function on reproduction: maternal and fetal consequences

The impact of abnormal autoimmune function on reproductive success has remained a highly controversial issue. This is, at least partially, due to the relative lack of demographic data from women with established autoimmune diseases. We, therefore, investigated 163 women with proven autoimmune diseases and 73 controls in a demographic study of reproductive success and impact of abnormal autoimmunity on pregnancy and offspring. Women with autoimmune diseases experienced fewer pregnancies overall (p=0.04) and fewer pregnancy losses (p=0.05). Offspring from women with autoimmune diseases demonstrated a significantly increased prevalence of confirmed autoimmune diseases (p=0.04; OR 3.759; 95%CL 1.04-1.27), which increased further if suspected, but not yet confirmed, cases were added (p=0.001; OR 8.592; 95%CL 1.05-55.0). Women with autoimmune diseases exhibited a trend towards lower cesarean section delivery during their own birth and a significantly increased prevalence of disease in vaginally delivered offspring (p=0.014; OR 6.041; 95%CL 1.32-38.22). Autoimmune diseases impair female fecundity even before the diseases become clinically overt. Offspring are at increased risk to develop autoimmune diseases, though they may differ from those of their mothers. This risk appears to correlate with mode of delivery and may be the consequence of varying cell traffic dynamics with vaginal and cesarean section deliveries.     

Autoimmune Disease During Pregnancy and the Microchimerism Legacy of Pregnancy

Pregnancy has both short-term effects and long-term consequences on the maternal immune system. For women who have an autoimmune disease and subsequently become pregnant, pregnancy can induce amelioration of the mother's disease, such as in rheumatoid arthritis, while exacerbating or having no effect on other autoimmune diseases like systemic lupus erythematosus. That pregnancy also leaves a long-term legacy has recently become apparent by the discovery that bi-directional cell trafficking results in persistence of fetal cells in the mother and of maternal cells in her offspring for decades after birth. The long-term persistence of a small number of cells (or DNA) from a genetically disparate individual is referred to as microchimerism. While microchimerism is common in healthy individuals and is likely to have health benefits, microchimerism has been implicated in some autoimmune diseases such as systemic sclerosis. In this paper, we will first discuss short-term effects of pregnancy on women with autoimmune disease. Pregnancy-associated changes will be reviewed for selected autoimmune diseases including rheumatoid arthritis, systemic lupus erythematosus and autoimmune thyroid disease. The pregnancy-induced amelioration of rheumatoid arthritis presents a window of opportunity for insights into both immunological mechanisms of fetal-maternal tolerance and pathogenic mechanisms in autoimmunity. A mechanistic hypothesis for the pregnancy-induced amelioration of rheumatoid arthritis will be described. We will then discuss the legacy of maternal-fetal cell transfer from the perspective of autoimmune diseases. Fetal and maternal microchimerism will be reviewed with a focus on systemic sclerosis (scleroderma), autoimmune thyroid disease, neonatal lupus and type I diabetes mellitus.     

Autoimmune disease during pregnancy and the microchimerism legacy of pregnancy

Pregnancy has both short-term effects and long-term consequences on the maternal immune system. For women who have an autoimmune disease and subsequently become pregnant, pregnancy can induce amelioration of the mother's disease, such as in rheumatoid arthritis, while exacerbating or having no effect on other autoimmune diseases like systemic lupus erythematosus. That pregnancy also leaves a long-term legacy has recently become apparent by the discovery that bi-directional cell trafficking results in persistence of fetal cells in the mother and of maternal cells in her offspring for decades after birth. The long-term persistence of a small number of cells (or DNA) from a genetically disparate individual is referred to as microchimerism. While microchimerism is common in healthy individuals and is likely to have health benefits, microchimerism has been implicated in some autoimmune diseases such as systemic sclerosis. In this paper, we will first discuss short-term effects of pregnancy on women with autoimmune disease. Pregnancy-associated changes will be reviewed for selected autoimmune diseases including rheumatoid arthritis, systemic lupus erythematosus and autoimmune thyroid disease. The pregnancy-induced amelioration of rheumatoid arthritis presents a window of opportunity for insights into both immunological mechanisms of fetal-maternal tolerance and pathogenic mechanisms in autoimmunity. A mechanistic hypothesis for the pregnancy-induced amelioration of rheumatoid arthritis will be described. We will then discuss the legacy of maternal-fetal cell transfer from the perspective of autoimmune diseases. Fetal and maternal microchimerism will be reviewed with a focus on systemic sclerosis (scleroderma), autoimmune thyroid disease, neonatal lupus and type I diabetes mellitus.     

Fetal-maternal microchimerism: impact on hematopoietic stem cell transplantation

Reciprocal cell traffic between mother and fetus during pregnancy gives rise to postpartum fetal-maternal lymphohematopoietic microchimerism, which is frequently detected in blood or tissue from healthy individuals. Although such microchimerism has been implicated in the pathogenesis of autoimmune diseases and tissue repair, recent clinical experiences have suggested the association of microchimerism with acquired immunologic hyporesponsiveness to non-inherited maternal HLA antigens (NIMAs) or inherited paternal HLA antigens (IPAs); T cell-replete HLA-haploidentical hematopoietic stem cell transplantation from a microchimeric IPA/NIMA-mismatched donor confers relatively lower incidence of severe graft-versus-host disease. The underlying mechanisms by which fetal-maternal microchimerism contributes to IPA/NIMA-specific tolerance are still elusive, although emerging experimental evidence suggests an involvement of the central deletion of IPA/NIMA-reactive T cells, the induction of peripheral regulatory T cells, and affinity-dependent modulation of NIMA-reactive B cells.     

Fetal microchimerism and autoimmune disease

Microchimerism is defined by the presence of circulating cells, bi-directionally transferred from one genetically distinct individual to another. The acquisition and persistence of fetal cell microchimerism, small numbers of genetically disparate cells from the fetus in the mother, is now a well-recognized consequence of normal pregnancy. Some of the autoimmune diseases that show a predilection for women in their child-bearing years and beyond are linked to fetal microchimerism from previous pregnancies. Microchimerism has been investigated in different autoimmune disorders, such as systemic sclerosis, systemic lupus erythematosus, autoimmune thyroid diseases, and primary biliary cirrhosis. Recent data have demonstrated the promising role of microchimeric cells in the maternal response to tissue injuries by differentiating into many lineages. Therefore, further understanding of fetal-maternal microchimerism may help in anticipating its implications in disease as well as in more general women's health issues.     

Microchimerism in Human Health and Disease

During pregnancy some cells traffic between the fetus and the mother. Recent investigative work indicates a low level of fetal cells commonly persists in the maternal circulation for years, or even indefinitely, after pregnancy has been completed. The term microchimerism refers to one individual harboring DNA or cells at a low level that derive from another individual. Chronic graft-versus-host disease (cGvHD) shares similarities with some autoimmune diseases and is an iatrogenic form of chimerism, occurring as a complication of hematopoietic stem cell transplantation. The HLA genes of the donor and the host are known to be of central importance to the development of cGvHD. When also considered in light of the female predilection to autoimmunity, these series of observations led to the hypothesis that microchimerism and HLA genes of host and non-host cells are involved in some autoimmune diseases. The hypothesis can also apply to men, children, and women who have not been pregnant because there are other sources of microchimerism. Persistent microchimerism can follow a blood transfusion, or can occur from transfer between twins in utereo. Additionally, maternal cells have recently been found to persist in her immune competent progeny. A number of studies have investigated a potential role of microchimerism in human diseases including systemic sclerosis (SSc), primary biliary cirrhosis (PBC), Sjögren's syndrome, polymorphic eruption of pregnancy, myositis, and thyroid disease. While some studies lend support to the concept that microchimerism is involved in the pathogenesis of selected autoimmune diseases, studies also indicate microchimerism is not uncommon in other human conditions and in healthy individuals.     

Microchimerism in human health and disease

During pregnancy some cells traffic between the fetus and the mother. Recent investigative work indicates a low level of fetal cells commonly persists in the maternal circulation for years, oreven indefinitely, after pregnancy has been completed. The term microchimerism refers to one individual harboring DNA or cells at a low level that derive from another individual. Chronic graft-versus-host disease (cGvHD) shares similarities with some autoimmune diseases and is an iatrogenic form of chimerism, occurring as a complication of hematopoietic stem cell transplantation. The HLA genes of the donor and the host are known to be of central importance to the development of cGvHD. When also considered in light of the female predilection to autoimmunity, these series of observations led to the hypothesis that microchimerism and HLA genes of host and non-host cells are involved in some autoimmune diseases. The hypothesis can also apply to men, children, and women who have not been pregnant because there are other sources of microchimerism. Persistent microchimerism can follow a blood transfusion, or can occur from transfer between twins in utereo. Additionally, maternal cells have recently been found to persist in her immune competent progeny. A number of studies have investigated a potential role of microchimerism in human diseases including systemic sclerosis (SSc), primary biliary cirrhosis (PBC), Sj?gren's syndrome, polymorphic eruption of pregnancy, myositis, and thyroid disease. While some studies lend support to the concept that microchimerism is involved in the pathogenesis of selected autoimmune diseases, studies also indicate microchimerism is not uncommon in other human conditions and in healthy individuals.     

Impact of fetal-maternal tolerance in hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is known to cure various hematological disorders; however, its widespread use is limited due to a lack of histocompatible donors. Reciprocal cell traffic between the mother and fetus during pregnancy gives rise to postpartum fetal-maternal lymphohematopoietic microchimerism, which is frequently detected in the blood or tissue of healthy individuals. Studies in clinical and experimental transplantation provide evidence that exposure to non-inherited maternal antigens (NIMAs) during pregnancy may result in long-lasting fetomaternal microchimerism and tolerance induction. Studies of HLA-mismatched HSCT have suggested a relatively lower incidence of severe graft-versus-host disease (GVHD) after transplantation from a NIMA-mismatched donor. Studies using a mouse model have also demonstrated a “child-to-mother” bone marrow transplantation from an NIMA-exposed donor to reduce the morbidity and mortality of GVHD in an antigen-specific manner while preserving the graft-versus-leukemia effects and favoring the immune reconstitution, thus resulting in a marked improvement in outcome after HSCT. Prospective clinical studies are therefore warranted to confirm these beneficial effects of fetal-maternal tolerance in allogeneic HSCT.     

Non-myeloablative stem cell transplantation for autoimmune diseases

Treatment of life-threatening autoimmune diseases in animal models with induced or spontaneous autoimmune diseases can be accomplished by a 2-step procedure involving elimination of self-reactive lymphocytes with an immune ablative conditioning regimen followed by infusion of autologous or allogeneic stem cells, respectively. In animal models it was shown that using such a strategy, autoimmunity could be adequately controlled. It is speculated that de-novo development of the T and B cell repertoire from uncommitted progenitor cells in the presence of the autoantigens may be the best recipe for re-induction of self-tolerance, similarly to the normal ontogeny of the immune system during the induction of self tolerance in fetal stage. For both autologous and allogeneic hematopoietic stem cell transplantation, a non-myeloablative stem cell transplantation (NST) regimen may be used for safer lymphoablation rather than myeloablation. In addition, for allogeneic hematopoietic stem cell transplantation engraftment of disease resistant donor stem cells will alter the genetic predisposition towards autoimmune disease susceptibility.     

Fetal-cell microchimerism, lymphopoiesis, and autoimmunity

During all human and murine pregnancies, fetal cells enter the maternal circulation and tissues and may persist there for decades. The immune consequences of this phenomenon have been explored for many years as a potential origin of autoimmunity or protection from cancer in women after pregnancy. The leading hypothesis, suggesting that semi-allogenic fetal T cells may trigger a graft-versus-host type of disease, has been supported by several studies showing an increased frequency of fetal-cell microchimerism (FMc) in women affected with systemic sclerosis. However, a large proportion of healthy women or women affected with non-immune disorders also display fetal T cells, challenging the direct pathogenic role of such cells. In addition, recent evidence showing the transfer of various fetal progenitor cells to the mother during gestation has shed new light on the interpretation of microchimerism in autoimmunity. This review discusses the functional capacity of fetal hematopoietic progenitors to form T and B cells in maternal hematopoietic tissues, where they undergo an educational process probably resulting in tolerance to maternal antigens. Therefore, hypotheses other than the transfer of fetal cells to the mother’s circulation should be considered in explaining the observed association of FMc and autoimmune disorders.     

Possible roles and determinants of microchimerism in autoimmune and other disorders

Microchimerism is the presence of a low level of non-host stem cells or their progeny in an individual. The most common source of microchimerism is pregnancy. During pregnancy, bi-directional trafficking of hematopoietic cells occurs through the placenta and these microchimeric cells persist for decades after childbirth. A possible role of microchimerism in the pathogenesis of some (systemic sclerosis, systemic lupus erythematosus, primary biliary cirrhosis, autoimmune thyroid diseases and juvenile myositis) but not all autoimmune diseases has been suggested by recent studies. Contradictory reports exist regarding HLA allelic associations with persistent T lymphocyte microchimerism. Although much of the focus of past studies has been on microchimerism in the effector arm of the immune system, increasing evidence suggests that microchimeric cells may differentiate into many lineages in different tissues raising additional possible roles for these cells. The possibility of microchimerism in many organs should induce an exploration of how persistent mixtures of cells of different genetic backgrounds throughout the body may influence diverse physiologic processes during life. In the present review, we discuss possible influencing factors and roles of all forms of microchimerism in autoimmune and non-autoimmune diseases. A better understanding of the immune mechanisms, along with the identification of environmental and genetic risk factors, is crucial for further deciphering the many possible implications of maternal-fetal and fetal-maternal cell trafficking in health and disease.     

The implications of autoimmunity and pregnancy

There are multiple epidemiological studies that document the potential adverse affects of autoimmunity on nearly every aspect of reproduction, even in the absence of clinically manifest autoimmune disease. Two decades ago, it was suggested that women with autoimmune diseases avoid pregnancy due to inordinate risks to the mother and the child. In contrast, newer epidemiological data demonstrated that advances in the treatment of autoimmune diseases and the management of pregnant women with these diseases have similarly improved the prognosis for mother and child. In particular, if pregnancy is planned during periods of inactive or stable disease, the result often is giving birth to healthy full-term babies without increased risks of pregnancy complications. Nonetheless, pregnancies in most autoimmune diseases are still classified as high risk because of the potential for major complications. These complications include disease exacerbations during gestation and increased perinatal mortality and morbidity in most autoimmune diseases, whereas fetal mortality is characteristic of the anti-phospholipid syndrome (APS). In this review, we will discuss these topics, including issues of hormones, along with potential long-term effects of the microchimerism phenomenon. With respect to pregnancy and autoimmune diseases, epidemiological studies have attempted to address the following questions: 1) Is it safe for the mother to become pregnant or are there acute or chronic effects of pregnancy on the course of the disease? 2) Does the disease alter the course and/or the outcome of a pregnancy and thereby represent an inordinate risk for the fetus and infant? And do new therapeutic and management approaches improve the pregnancy outcomes in women with autoimmune diseases? 3) Does passage of maternal autoantibodies represent a risk to the child? 4) Do pregnancy, parity, or other factors influencing hormonal status explain the female predominance of many autoimmune diseases, and is the pregnancy effect related to microchimerism? Answering these questions has taken on additional importance in recent decades as women in western countries now frequently choose to delay pregnancies and have some or all of their pregnancies after disease onset. In this paper, we primarily focus on APS, systemic lupus erythematosus (SLE), multiple sclerosis (MS), rheumatoid arthritis (RA), and type 1 diabetes (T1D).     

Does the Immune System Induce Labor? Lessons from Preterm Deliveries in Women with Autoimmune Diseases

A recent review of the literature suggested that thyroid autoimmunity is statistically associated with preterm delivery. This observation raises a number of follow-up questions, among them whether autoimmune function, in general, predisposes to premature delivery. A review of the English literature for the last 10 years, via PubMed search, finds strong supportive evidence for such a hypothesis. Since the fetal–placental unit represents a (semi) allograft within a maternal (allograft) recipient, it is reasonable to assume that it is subject to similar immunologic tolerance (and failure thereof) as solid organ transplants. As autoimmune responses represent a normal feature of tolerance failure in organ transplantation, similar autoimmune responses can also be expected with failure of tolerance of the fetal–maternal graft. The association of premature (and possibly also term) labor with autoimmune function may, therefore, be the consequence of abnormalities in normal fetal–placental tolerance, leading to uterine activation and labor.     

Is peripartum cardiomyopathy an organ-specific autoimmune disease?

Peripartum cardiomyopathy (PPCM) is a rare and serious heart disease that exclusively afflicts women during childbearing years. Symptoms include rapid onset of cardiovascular insufficiency occurring during pregnancy, initiated anytime between the third trimester until 5 months post-partum in the absence of any other signs or history of heart disease. The rare incidence of PPCM and the absence of any relevant animal models have limited research and understanding of the pathogenic mechanisms involved. Several compelling sets of data support the view that PPCM is a form of autoimmune IDCM. However, PPCM differs from autoimmune IDCM in that (a) it is associated with unique sets of autoantibodies and autoantigens, (b) it has a relatively rapid onset, and (c) it exclusively affects pregnant women. Furthermore, the etiology of PPCM is dependent on the interaction of pregnancy associated factors, e.g. increased hemodynamic stress, vasoactive hormones and fetal microchimerism, that co-operate in the context of essential immune and genetic environments for disease progression. Our model of PPCM attempts to represent how multiple factors, e.g. pregnancy, genetics, immune dysregulation, and fetal microchimerism are held in a complex dynamic balance that can co-operate towards the maintenance of cardiovascular health or disease in the mother (Fig. 1). A more thorough study of the precise nature of the cardiac tissue autoantigens may lead to the identification of the mechanisms of breakdown of self-tolerance and perhaps also the putative etiologic agent(s). Further studies of the precise nature of the cardiac tissue autoantigens and the specific factors governing the balance between tolerance and autoimmunity in the periphery, e.g. expression of PD-L1 on cardiac tissues and the role of regulatory T cells, may help to elucidate the autoimmune mechanisms of PPCM.     

Maternal microchimerism—Allogenic target of autoimmune disease or Normal Biology?

Chimerism is the state of cells from two distinct individuals living within one body. Fetal cells pass into a mother during pregnancy, where they may persist at low levels for years, creating a state of fetal microchimerism. At the same time, maternal cells pass into the fetus, leading to maternal microchimerism that can persist into adulthood. Hematopoietic stem cell transplantation also creates a state of chimerism, and can lead to a complication of chronic multi-organ inflammation called graft-versus-host disease, (GVHD). The similarities between GVHD and some autoimmune diseases like scleroderma, lupus and myositis suggest that chimerism may be involved in the pathogenesis of both. Maternal and fetal microchimerism in the blood and in tissues have been associated with autoimmune diseases. However, many healthy individuals harbor maternal and fetal cells. Human and animal studies have begun to elucidate the mechanisms for normal tolerance to maternal and fetal microchimeric cells, and how this tolerance may be broken in states of chronic inflammatory disease.     

Modulating impact of human chorionic gonadotropin hormone on the maturation and function of hematopoietic cells

hCG hormone is a naturally occurring, immune-modulating agent, which is highly expressed during pregnancy and causes improvements of some autoimmune diseases such as multiple sclerosis and Crohn's disease. Little is known about its immune-modulating effects. This study in MNCs of women who received hCG as preconditioning prior to IVF demonstrates that hCG increases anti-inflammatory IL-27 expression and reduces inflammatory IL-17 expression. In addition, we found increased IL-10 levels and elevated numbers of Tregs in peripheral blood of women after hCG application. Rejection of allogeneic skin grafts was delayed in female mice receiving hCG. We conclude that hCG may be useful for the induction of immune tolerance in solid organ transplantation.     

Neonatal autoimmune diseases: a critical review

Neonatal autoimmune diseases are distinctly rare. Most neonatal autoimmune diseases result from the transplacental transfer of maternal antibodies directed against fetal or neonatal antigens in various tissues. In neonatal lupus, the heart seems to be particularly susceptible. Primary autoimmunity in newborns, with the exception of familial autoinflammatory diseases, is virtually non-existent. The pathophysiologic basis for the development of neonatal autoimmunity is not entirely clear, but differences in the neonatal immune system compared with the adult immune system, as well as unique characteristics of target antigens in the newborn period may be important factors. Neonatal lupus is the most common presentation of autoimmunity in the newborn. But the characteristics defining neonatal lupus are not well defined and the presentation of neonatal lupus differs from that of classical lupus. Other neonatal autoimmune diseases involving the interaction between maternal antibodies and fetal/neonatal antigens include neonatal anti-phospholipid syndrome, Behcet's disease, neonatal autoimmune thyroid disease, neonatal polymyositis and dermatomyositis, neonatal scleroderma and neonatal type I diabetes mellitus. While autoantibodies have been detected in patients with neonatal autoimmune disease, the pathogenic role of autoantibodies has not been well defined. Other mechanisms may play a role in the development of neonatal autoimmunity, including fetal/maternal microchimerism and aberrant apoptosis of fetal cells. The autoinflammatory syndromes are a completely different category, but are also included in discussion of neonatal autoimmune diseases. The autoinflammatory syndromes include the cryopyrin associated periodic syndromes (CAPS) - familial cold autoinflammatory syndrome (FCAS), neonatal onset multisystem inflammatory disease (NOMID) and Muckle-Wells syndrome, which all share a common pathophysiologic mechanism.     

Impaired B‐cell tolerance checkpoints promote the development of autoimmune diseases and pathogenic autoantibodies

A role for B cells in autoimmune diseases is now clearly established both in mouse models and humans by successful treatment of multiple sclerosis and rheumatoid arthritis with anti‐CD20 monoclonal antibodies that eliminate B cells. However, the underlying mechanisms by which B cells promote the development of autoimmune diseases remain poorly understood. Here, we review evidence that patients with autoimmune disease suffer from defects in early B‐cell tolerance checkpoints and therefore fail to counterselect developing autoreactive B cells. These B‐cell tolerance defects are primary to autoimmune diseases and may result from altered B‐cell receptor signaling and dysregulated T‐cell/regulatory T‐cell compartment. As a consequence, large numbers of autoreactive naive B cells accumulate in the blood of patients with autoimmune diseases and may promote autoimmunity through the presentation of self‐antigen to T cells. In addition, new evidence suggests that this reservoir of autoreactive naive B cells contains clones that may develop into CD27^?CD21^?/lo B cells associated with increased disease severity and plasma cells secreting potentially pathogenic autoantibodies after the acquisition of somatic hypermutations that improve affinity for self‐antigens.     

Genetic lesions in T-cell tolerance and thresholds for autoimmunity

Summary: The cause of common organ‐specific autoimmune diseases is poorly understood because of genetic and cellular complexity in humans and animals. Recent advances in the understanding of the mechanisms of the defects underlying autoimmune disease in autoimmune polyendocrinopathy syndrome type 1 and non‐obese diabetic mice suggest that failures in central tolerance play a key role in predisposition towards organ‐specific autoimmunity. The lessons from such rare monogenic autoimmune disorders and well‐characterized polygenic traits demonstrate how subtle quantitative trait loci can result in large changes in the susceptibility to autoimmunity. These data allow us to propose a model relating efficiency of thymic deletion to T‐cell tolerance and susceptibility to autoimmunity.