Y chromosome microchimerism in rheumatic autoimmune disease

Feto-maternal microchimerism: Memories from pregnancy

There is a bidirectional transplacental cell trafficking between mother and fetus during pregnancy in placental mammals. The presence and persistence of fetal cells in maternal tissues are known as fetal microchimerism (FMc). FMc has high multilineage potential with a great ability to differentiate and functionally integrate into maternal tissue. FMc has been found in various maternal tissues in animal models and humans. Its permanence in the maternal body up to decades after delivery suggests it might play an essential role in maternal pathophysiology. Studying the presence, localization, and characteristics of FMc in maternal tissues is key to understanding its impact on the woman's body. Here we comprehensively review the existence of FMc in different species and organs and tissues, aiming to better characterize their possible role in human health and disease. We also highlight several methodological considerations that would optimize the detection, quantification, and functional determination of FMc.

Soluble HLA-G Expression Inversely Correlates With Fetal Microchimerism Levels in Peripheral Blood From Women With Scleroderma

Women with scleroderma (SSc) maintain significantly higher quantities of persisting fetal microchimerism (FMc) from complete or incomplete pregnancies in their peripheral blood compared to healthy women. The non-classical class-I human leukocyte antigen (HLA) molecule HLA-G plays a pivotal role for the implantation and maintenance of pregnancy and has often been investigated in offspring from women with pregnancy complications. However data show that maternal HLA-G polymorphisms as well as maternal soluble HLA-G (sHLA-G) expression could influence pregnancy outcome. Here, we aimed to investigate the underlying role of maternal sHLA-G expression and HLA-G polymorphisms on the persistence of FMc. We measured sHLA-G levels by enzyme linked immunosorbent assay in plasma samples from 88 healthy women and 74 women with SSc. Male Mc was quantified by DYS14 real-time PCR in blood samples from 58 women who had previously given birth to at least one male child. Furthermore, eight HLA-G 5'URR/3'UTR polymorphisms, previously described as influencing HLA-G expression, were performed on DNA samples from 96 healthy women and 106 women with SSc. Peripheral sHLA-G was at lower concentration in plasma from SSc (76.2 ± 48.3 IU/mL) compared to healthy women (117.5 ± 60.1 IU/mL, p < 0.0001), independently of clinical subtypes, autoantibody profiles, disease duration, or treatments. Moreover, sHLA-G levels were inversely correlated to FMc quantities (Spearman correlation, p < 0.01). Finally, women with SSc had lower sHLA-G independently of the eight HLA-G 5'URR/3'UTR polymorphisms, although they were statistically more often homozygous than heterozygous for HLA-G polymorphism genotypes -716 (G/T), -201 (G/A), 14 bp (ins/del), and +3,142 (G/A) than healthy women. In conclusion, women with SSc display less sHLA-G expression independently of the eight HLA-G polymorphisms tested. This decreased production correlates with higher quantities of persisting FMc commonly observed in blood from SSc women. These results shed some lights on the contribution of the maternal HLA-G protein to long-term persistent fetal Mc and initiate new perspectives in this field.

Lack of detectable fetal microchimerism in psoriasis vulgaris lesions and in non-affected skin in spite of its presence in peripheral blood CD34-positive and CD34-negative cells

BACKGROUND

Microchimerism is defined as a stable presence of low numbers of cells derived from a different individual due to cell transfer between twins or between mother and fetus during pregnancy.

OBJECTIVE

Fetal cells in the organism of the mother (FMc) are postulated to play a role in autoimmune diseases. Psoriasis is a disease which has an autoimmune component, but no study on microchimerism in this disease has been reported.

METHODS

The easiest way to detect microchimerism is to look for male cells in blood or other tissues of a woman who previously delivered a son. Here, we looked for the presence of male cells in mononuclear cell subpopulations from peripheral blood and in skin samples of women with psoriasis and of healthy women.

RESULTS

We detected FMc in similar proportions of patients and controls in CD4+, CD8+ and CD34+ cells, whereas in CD34- cells they were present in higher fraction of controls, and similar but non-significant difference was observed in CD19+ cells. No microchimeric cells were detected in patients' skin samples, both from affected and non-affected skin, or in skin tissue from healthy control individuals.

CONCLUSION

Our result does not prove the involvement of microchimerism in the aetiology of psoriasis.

Microchimeric cells in systemic lupus erythematosus: targets or innocent bystanders?

During pregnancy maternal and fetal cells commute back and forth leading to fetal microchimerism in the mother and maternal microchimerism in the child that can persist for years after the birth. Chimeric fetal and maternal cells can be hematopoietic or can differentiate into somatic cells in multiple organs, potentially acting as targets for ‘autoimmunity' and so have been implicated in the pathogenesis of autoimmune diseases that resemble graft-versus-host disease after stem cell transplantation. Fetal cells have been found in women with systemic lupus erythematosus, both in the blood and a target organ, the kidney, suggesting that they may be involved in pathogenesis. Future studies will address how the host immune system normally tolerates maternal and fetal cells or how the balance may change during autoimmunity.

Naturally acquired microchimerism: implications for transplantation outcome and novel methodologies for detection

Microchimerism represents a condition where one individual harbors genetically distinct cell populations, and the chimeric population constitutes <1% of the total number of cells. The most common natural source of microchimerism is pregnancy. The reciprocal cell exchange between a mother and her child often leads to the stable engraftment of hematopoietic and non-hematopoietic stem cells in both parties. Interaction between cells from the mother and those from the child may result in maternal immune cells becoming sensitized to inherited paternal alloantigens of the child, which are not expressed by the mother herself. Vice versa, immune cells of the child may become sensitized toward the non-inherited maternal alloantigens of the mother. The extent of microchimerism, its anatomical location, and the sensitivity of the techniques used for detecting its presence collectively determine whether microchimerism can be detected in an individual. In this review, we focus on the clinical consequences of microchimerism in solid organ and hematopoietic stem cell transplantation, and propose concepts derived from data of epidemiologic studies. Next, we elaborate on the latest molecular methodology, including digital PCR, for determining in a reliable and sensitive way the extent of microchimerism. For the first time, tools have become available to isolate viable chimeric cells from a host background, so that the challenges of establishing the biologic mechanisms and function of these cells may finally be tackled.

Lack of Evidence That Male Fetal Microchimerism is Present in Endometriosis

INTRODUCTION

Fetal microchimerism has been implicated in the etiology of autoimmune diseases. This study was done to test the hypothesis that male fetal microchimerism is present in eutopic and ectopic endometrium (EM) obtained from women with endometriosis but not in eutopic EM from women without endometriosis.

METHODS

A total of 31 patients were selected, including women with endometriosis (paired eutopic and ectopic EM; n = 19) and women without endometriosis (eutopic EM; n = 12). Tricolor interphase fluorescence in situ hybridization analysis was performed by cohybridization of CEP Y SpectrumAqua and CEP X SpectrumGreen (SG)/CEP Y SpectrumOrange probes.

RESULTS

Ectopic EM from women with endometriosis had 75% XX chromosomes (double SG signals) and 25% X chromosomes (single SG signal). Y chromosomes were not observed in any of the eutopic/ectopic endometrial tissues from cases or controls.

CONCLUSIONS

We were unable to confirm our hypothesis that male fetal microchimerism is present in eutopic and/or ectopic EM obtained from women with endometriosis.

[Sex-specific differences of the immune system]

BACKGROUND

Sex-specific differences in the prevalence and severity of immune disorders are well-known phenomena; however, it is only recently that we have begun to understand the possible causes of such differences.

MATERIAL AND METHODS

A literature search on this topic was carried out and the results are summarized.

RESULTS

In the last few years research has been guided by technological advances in gene sequencing and new insights into the microbiome of the gut, as well as an awareness of sex- and gender-specific risk factors for infections and autoimmunity.

CONCLUSION

The knowledge acquired in recent years will not only improve diagnostics and early identification of these disorders but also influence future research, prevention and therapy of infections and autoimmune diseases.

Fetal microchimerism in kidney biopsies of lupus nephritis patients may be associated with a beneficial effect

Introduction

Microchimeric male fetal cells (MFCs) have been associated with systemic lupus erythematosus, and published studies have further correlated MFC with lupus nephritis (LN). In the present study, we evaluated the frequency of MFC in the renal tissue of patients with LN.

Methods

Twenty-seven renal biopsies were evaluated: Fourteen were from women with clinical and laboratory findings of LN, and thirteen were from controls. Genomic DNA was extracted from kidney biopsies, and the male fetal DNA was quantified using real-time quantitative polymerase chain reactions for the detection of specific Y chromosome sequences.

Results

MFCs were detected in 9 (64%) of 14 of patients with LN, whereas no MFCs were found in the control group (P = 0.0006). No differences in pregnancy history were found between patients with LN and the control group. Significantly higher amounts of MFCs were found in patients with LN with serum creatinine ≤1.5 mg/dl. Furthermore, women with MFCs had significantly better renal function at the time of biopsy (P = 0.03). In contrast, patients with LN without MFCs presented with more severe forms of glomerulonephritis (World Health Organization class IV = 60% and class V = 40%).

Conclusions

Our data indicate a high prevalence of MFCs in renal biopsy specimens from women with LN, suggesting a role for MFCs in the etiology of LN. The present report also provides some evidence that MFCs could have a beneficial effect in this disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0615-4) contains supplementary material, which is available to authorized users.

Pregnancy outcomes in a patient with Sjögren's disease with renal involvement

BACKGROUND

Maternal and fetal outcome in pregnancy with renal failure is unpredictable, where each condition can adversely affect the other. We present a case of steroid sensitive Sjögren's nephritis worsened by pregnancy, demonstrated over the course of multiple pregnancies and investigated the aetiology.

CASE

A 28-year-old nullipara with a diagnosis of primary Sjögren's syndrome presented with a deterioration of renal function. A diagnosis of secondary tubulo-interstitial nephritis was made on renal biopsy. Her first pregnancy ended in the second trimester with a decision to deliver a female infant at 27 weeks due to worsening maternal renal function. Renal function improved immediately. A second pregnancy ended in a first trimester miscarriage. The third and fourth pregnancies delivered male infants at 35 and 34 weeks, with worsening renal function in each pregnancy, reaching end stage. Repeat biopsy showed extensive glomerulosclerosis and male cells were identified.

CONCLUSIONS

This case of Sjögren's syndrome with renal disease demonstrated the increased risk of fetal and maternal adverse pregnancy outcomes. Renal function worsened in each pregnancy and progressed to end-stage renal disease. Fetal microchimerism offers an interesting mechanism for our patient's renal failure and its apparent relationship to her pregnancies.

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.

HLA-targeted flow cytometric sorting of blood cells allows separation of pure and viable microchimeric cell populations

Microchimerism is defined by the presence of low levels of nonhost cells in a person. We developed a reliable method for separating viable microchimeric cells from the host environment. For flow cytometric cell sorting, HLA antigens were targeted with human monoclonal HLA antibodies (mAbs). Optimal separation of microchimeric cells (present at a proportion as low as 0.01% in artificial mixtures) was obtained with 2 different HLA mAbs, one targeting the chimeric cells and the other the background cells. To verify purity of separated cell populations, flow-sorted fractions of 1000 cells were processed for DNA analysis by HLA-allele-specific and Y-chromosome-directed real-time quantitative PCR assays. After sorting, PCR signals of chimeric DNA markers in the positive fractions were significantly enhanced compared with those in the presort samples, and they were similar to those in 100% chimeric control samples. Next, we demonstrate applicability of HLA-targeted FACS sorting after pregnancy by separating chimeric maternal cells from child umbilical cord mononuclear cells. Targeting allelic differences with anti-HLA mAbs with FACS sorting allows maximal enrichment of viable microchimeric cells from a background cell population. The current methodology enables reliable microchimeric cell detection and separation in clinical specimens.

[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.

Naturally acquired microchimerism

Bi-directional transplacental trafficking occurs routinely during the course of normal pregnancy, from fetus to mother and from mother to fetus. In addition to a variety of cell-free substances, it is now well recognized that some cells are also exchanged. Microchimerism refers to a small number of cells (or DNA) harbored by one individual that originated in a genetically different individual. While microchimerism can be the result of iatrogenic interventions such as transplantation or transfusion, by far the most common source is naturally acquired microchimerism from maternal-fetal trafficking during pregnancy. Microchimerism is a subject of much current interest for a number of reasons. During pregnancy, fetal microchimerism can be sought from the mothers blood for the purpose of prenatal diagnosis. Moreover, studies of fetal microchimerism during pregnancy may offer insight into complications of pregnancy, such as preeclampsia, as well as insights into the pathogenesis of autoimmune diseases such as rheumatoid arthritis which usually ameliorates during pregnancy. Furthermore, it is now known that microchimerism persists decades later, both fetal microchimerism in women who have been pregnant and maternal microchimerism in her progeny. Investigation of the long-term consequences of fetal and maternal microchimerism is another exciting frontier of active study, with initial results pointing both to adverse and beneficial effects. This review will provide an overview of microchimerism during pregnancy and of current knowledge regarding long-term effects of naturally acquired fetal and maternal microchimerism.

Fetal microchimerism: the cellular and immunological legacy of pregnancy

During pregnancy there is transplacental traffic of fetal cells into the maternal circulation. Remarkably, cells of fetal origin can then persist for decades in the mother and are detectable in the circulation and in a wide range of tissues. Maternal CD8 T cell responses directed against fetal antigens can also be detected following pregnancy. However, the impact that the persistence of allogenic cells of fetal origin and the maternal immune response towards them has on the mother's health remains unclear and is the subject of considerable investigation. The potentially harmful effects of fetal microchimerism include an association with autoimmune disease and recurrent miscarriage. Beneficial effects that have been explored include the contribution of persistent fetal cells to maternal tissue repair. A link between fetal microchimerism and cancer has also been proposed, with some results supporting a protective role and others, conversely, suggesting a role in tumour development. The phenomenon of fetal microchimerism thus provokes many questions and promises to offer further insights not only into the biology of pregnancy but fields such as autoimmunity, transplantation biology and oncology.

Fetal-maternal exchange of multipotent stem/progenitor cells: microchimerism in diagnosis and disease

The biological concept of microchimerism, the bidirectional trafficking and stable long-term persistence of small numbers of allogeneic (fetal and maternal) cells in a genetically different organ, has gained considerable attention. Microchimerism is a common phenomenon in many species, including humans, and microchimeric cells can modify immunological recognition or tolerance, affect the course and outcome of various diseases and demonstrate stem cell-like or regenerative potential. Here, we review current knowledge of the biology of microchimerism and show how long-term allogeneic co-existence within an organism can impact on existing paradigms in chronic disease, cancer biology, regenerative medicine and fetal-maternal immunology. We discuss diagnostic challenges, clinical applications and future research directions in this exciting and rapidly emerging field of allogeneic fetal-maternal cell exchange.

Sex-specific genetic architecture of human disease

Sexual dimorphism in anatomical, physiological and behavioural traits are characteristics of many vertebrate species. In humans, sexual dimorphism is also observed in the prevalence, course and severity of many common diseases, including cardiovascular diseases, autoimmune diseases and asthma. Although sex differences in the endocrine and immune systems probably contribute to these observations, recent studies suggest that sex-specific genetic architecture also influences human phenotypes, including reproductive, physiological and disease traits. It is likely that an underlying mechanism is differential gene regulation in males and females, particularly in sex steroid-responsive genes. Genetic studies that ignore sex-specific effects in their design and interpretation could fail to identify a significant proportion of the genes that contribute to risk for complex diseases.

Fetal microchimerism and maternal health during and after pregnancy

Trafficking of fetal cells into the maternal circulation begins very early in pregnancy and the effects of this cell traffic are longlasting. All types of fetal cells, including stem cells, cross the placenta during normal pregnancy to enter maternal blood, from where they may be recovered in pregnancy for the purpose of genetic prenatal diagnosis. Fetal cells can also be located in maternal tissues during and after pregnancy, and persist as microchimeric cells for decades in marrow and other organs. Although persistent fetal cells were first implicated in autoimmune disease, subsequent reports routinely found microchimeric cells in healthy tissues and in non-autoimmune disease. Parallel studies in animal and human pregnancy now suggest instead that microchimeric fetal cells play a role in the response to tissue injury. However, it is still not clear whether microchimeric fetal cells persisting in the mother are an incidental finding, are naturally pathogenic or act as reparative stem cells, and the environmental or biological stimuli that determine microchimeric cell fate are as yet undetermined. Future studies must also focus on investigating whether fetal cells create functional improvement in response to maternal injury and whether this response can be manipulated. The pregnancy-acquired low-grade chimeric state of women could have far-reaching implications, influencing recovery after injury or surgery, ageing, graft survival after transplantation, survival after cancer as well as deciding the protective effect of pregnancy against diseases later in life. Lifelong persistence of fetal cells in maternal tissues may even explain why women live longer than men.

Chimerism occurs in thyroid, lung, skin and lymph nodes of women with sons

Chimerism indicates the presence of cells from one individual in another. Pregnancy and blood transfusions are considered the main sources for chimerism. Chimeric cells have been attributed a pathogenic role in various autoimmune diseases. However, data on the occurrence of chimeric cells in normal organs are scarce. In order to gain insight into the possible pathogenic potential of chimeric cells in autoimmune disease, it is necessary to determine the prevalence of chimeric cells in organs not affected by autoimmune disease. In situ hybridization for the Y-chromosome was performed on organs obtained at autopsy of 51 women. We investigated 44 thyroid, 38 lung, 21 skin and 7 lymph node samples. All women had sons, and data from their blood transfusion histories were retrieved for at least 10 years before death. Slides were scored semi-quantitatively for chimerism as low (1-3 Y-chromosome-positive cells per slide), moderate (4-10 positive cells per slide) or high (more than 10 positive cells per slide). Y-chromosome-positive cells were found in 8 thyroid, 10 lung, 3 skin and 1 lymph node samples of 18 women. There was no association between the presence of chimeric cells and blood transfusion history. Most organs in which chimerism was present contained a small to moderate level. Thus, chimerism can occur in normal organs of women without autoimmune disease. Our results indicate that chimerism is not necessarily associated with disease.

Impact of fetal-maternal microchimerism on women's health--a review

Microchimerism is defined by the presence of circulating cells, bi-directionally transferred from one genetically distinct individual to another. It occurs either physiologically during pregnancy, or iatrogenically after blood transfusion and organ transplants. The migrated cells may persist for decades. Much controversy exists around the role of microchimeric cells in the pathogenesis of various diseases and around their role in tissue repair. Microchimerism has been investigated in different autoimmune disorders, such as systemic sclerosis, systemic lupus erythematosus, autoimmune thyroid diseases, primary biliary cirrhosis and juvenile inflammatory myopathies. 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.

Peripartum cardiomyopathy: a comprehensive review

Peripartum cardiomyopathy (PPCM) is a rare disorder in which left ventricular dysfunction and symptoms of heart failure occur in the peripartum period in previously healthy women. Incidence of PPCM ranges from 1 in 1300 to 1 in 15,000 pregnancies. The etiology of PPCM is unknown, but viral, autoimmune, and idiopathic causes may contribute. The diagnostic criteria are onset of heart failure in the last month of pregnancy or in first 5 months postpartum, absence of determinable cause for cardiac failure, and absence of a demonstrable heart disease before the last month of pregnancy. Risk factors for PPCM include advanced maternal age, multiparity, African race, twinning, gestational hypertension, and long-term tocolysis. The clinical presentation of patients with PPCM is similar to that of patients with dilated cardiomyopathy. Early diagnosis and initiation of treatment are essential to optimize pregnancy outcome. Treatment is similar to medical therapy for other forms of dilated cardiomyopathy. About half the patients of PPCM recover without complications. The prognosis is poor in patients with persistent cardiomyopathy. Persistence of disease after 6 months indicates irreversible cardiomyopathy and portends worse survival.

Chimerism in systemic lupus erythematosus—three hypotheses

Systemic lupus erythematosus (SLE) is an immune-mediated disease characterized by the presence of autoantibodies and a wide array of clinical symptoms. Despite intensive research, the aetiology of SLE is still unknown and is probably multifactorial. Both genetic and environmental factors have been associated with SLE, but these factors alone are insufficient to explain the onset of SLE. Recently, it has been suggested that chimerism plays a role in the pathogenesis of autoimmune diseases, including SLE. Chimerism indicates the presence of cells from one individual in another individual. In an experimental mouse model, the injection of chimeric cells induces a lupus-like disease. In addition, chimerism is found more often in kidneys of women with SLE than in healthy controls. There are several mechanisms by which chimeric cells could be involved in the pathogenesis of SLE. In this review, three hypotheses on the role of chimerism in SLE are discussed. The first two hypotheses describe the possibilities that chimeric cells induce either a graft-vs-host reaction in the host (comparable with reactions seen after bone marrow transplantation) or a host-vs-graft reaction (comparable with reactions seen after solid organ transplantation). The third hypothesis discusses the possible beneficial role chimeric cells may play in repair mechanisms due to their stem cell-like properties. This review provides insights into the mechanisms by which chimerism may be involved in SLE and proposes several lines of inquiry to further investigate chimerism in SLE.

Chimerism occurs twice as often in lupus nephritis as in normal kidneys

OBJECTIVE

Systemic lupus erythematosus (SLE) is an immune-mediated disease that particularly affects the kidneys, causing lupus nephritis. In experimental mouse models, lupus nephritis can be mimicked by inducing a chimeric state through the injection of parental T cells in offspring. In humans, pregnancy-induced chimerism may play a role in the pathogenesis of autoimmune diseases such as SLE, but it is likely that only certain chimeric cells have pathogenic potential. In this study, we investigated whether the distribution of chimeric cells is different in the kidneys of women with SLE from that in normal kidneys, and we examined the phenotype of chimeric cells in women with SLE.

METHODS

The presence of chimeric cells was investigated by in situ hybridization targeting the Y chromosome in 57 renal biopsy samples from 49 women with lupus nephritis. Fifty-one kidney autopsy specimens without histomorphologic lesions served as controls. Double-staining for the Y chromosome in combination with CD3 and CD34 markers was performed in 5 kidney specimens with lupus nephritis to identify the phenotype of the chimeric cells.

RESULTS

Y chromosome-positive cells were found in 27 of 49 patients with lupus nephritis and in 13 of 51 normal controls (P < 0.01). Both CD3+ and CD34+ chimeric cells were identified in lupus nephritis kidney specimens.

CONCLUSION

Chimeric cells are present significantly more often in kidneys with lupus nephritis than in normal kidneys, and some of these chimeric cells are T cells. This finding is interesting in light of experimental models demonstrating that lupus nephritis is initiated by chimeric T cells.

Association between microchimerism and multiple sclerosis in Canadian twins

Microchimerism, the persistence of foreign cells thought to derive from previous pregnancies, has been associated with autoimmune diseases. A maternal parent-of-origin effect in MS remains unexplained. We tested for microchimerism in monozygotic and dizygotic twin-pairs with MS. Microchimerism was associated with MS in affected females from monozygotic concordant pairs when compared to both affected (p=0.020) and unaffected (p=0.025) females in monozygotic discordant pairs. Microchimerism was increased in affected females of dizygotic discordant pairs (p=0.059). The rate of microchimerism was significantly higher in affected twins than in unaffected co-twins (p=0.0059). These observations show an association in twins between the presence of microchimerism and having MS.

[Fetal microchimerism in rheumatic diseases]

Fetal microchimerism is the presence of fetal cells inmaternal tissues and vice versa, i.e., the coexistence of2 different cellular populations from genetically differentindividuals within a single person. The most frequentcause of microchimerism is pregnancy, in which there is abi-directional fetal-maternal interchange of cells duringpregnancy and delivery. Fetal cells have been demonstrated in the tissues ofpatients with rheumatic, endocrine or infectious diseases,as well as in those of healthy individuals. Microchimerism has been most extensively studied insystemic sclerosis. It seems that during pregnancyallogenic fetal or maternal cells cross the placenta bidirectionallyand persist in the systemic circulation andtissues of both mother and child. Subsequently, they areactivated, resulting in is a graft-against-host reactionassociated with the onset of clinical manifestations.Microchimerism has been also studied in otherconnective tissue diseases.

Pathophysiology of fetal microchimeric cells

Microchimerism has been defined by the presence of a low number of circulating cells transferred from one individual to another. The transfer of microchimeric cells naturally takes place during pregnancy and occurs bi-directionally between the mother and fetus. Further, microchimerism can also be a result of blood transfusions and organ transplants. Microchimeric cells have been implicated in health and disease. Fetal microchimerism has been correlated with the hyporesponsiveness of the maternal immune system towards a fetal allograft and with the longevity of organ transplants. However, microchimeric cells have been implicated in the pathogenesis of autoimmune diseases including systemic sclerosis. In contrast, microchimeric cells were found to contribute to tissue repair. Much controversy exists around the role of microchimeric cells in the pathogenesis of certain diseases, and these cells in tissues may be a consequence rather than the cause of disease.

Maternal - offspring HLA-DRB1 compatibility in multiple sclerosis

Major histocompatibility complex (MHC) compatibility has been reported to facilitate the long-term tolerance of fetal or maternally derived stem cells exchanged during pregnancy. Furthermore, such compatibility has been suggested to play a role in fetal viability. An increase in maternal - fetal human leukocyte antigen (HLA) compatibility for class II DR alleles has previously been observed in the autoimmune disease scleroderma. Here, we examined the hypothesis that increased maternal - fetal MHC class II DR compatibility was associated with multiple sclerosis (MS) risk. HLA-DRB1 typing was performed in 2170 affected individuals and 2894 unaffected relatives from 1006 families with MS in at least two members. We found no evidence for increased HLA compatibility between affected individuals and their mothers, compared with unaffected individuals and their mothers, nor compared with affected individuals and their fathers. We also observed no excess of homozygosity of mothers compared with fathers of individuals with MS. In families in which the father shared exactly one allele with the mother, we found no excess in transmission of this allele to affected or unaffected offspring. These findings do not support a role for an excess maternal - fetal HLA-DRB1 compatibility in MS susceptibility.

Chronic Graft-versus-Host-Disease-Like Dermopathy in a Child with CD4+ Cell Microchimerism

We report the case of an 11-year-old boy suffering from a severe progressive chronic skin disease with clinical features of progressive systemic scleroderma, systemic lupus erythematosus and dermatomyositis. Skin biopsies revealed fibrosis and lichenoid changes and muscle biopsy a myositis. Immunohistology of the skin showed a lichen-ruber-like pattern. Despite repeated extensive investigations, no autoantibodies were detectable. Some of these findings looked like those described in juvenile dermatomyositis. Finally, it could be demonstrated that the boy showed microchimerism with approximately 1% maternal CD4+ lymphocytes in his peripheral blood leukocytes. Furthermore maternal cells could be demonstrated in inflamed muscle tissue. So a graft-versus-host-disease-like pathomechanism appears to be likely. Several systemic therapies have been used with limited success to improve the condition including corticosteroids, azathioprine, cyclosporine A and mycophenolate mofetil. A distinct improvement of erythemas and sclerosis could be achieved by means of low-dose UVA1 phototherapy which was applied with escalating single doses of 3-12 J/cm2 for 35 consecutive days.

Microchimerism and systemic sclerosis

PURPOSE OF REVIEW

Although 6 years have elapsed since the initial report describing the presence of microchimeric cells in affected tissues from patients with systemic sclerosis, a mechanism by which these cells might contribute to the pathogenesis of the disease is still unknown. This article reviews the published literature related to the possible role of microchimeric cells in the pathogenesis of systemic sclerosis.

RECENT FINDINGS

Numerous studies have reported the identification or quantification of microchimeric cells in the peripheral blood or tissues from systemic sclerosis patients; however, only one study to date has investigated their function. Recent investigations have demonstrated microchimeric cells in the clinically uninvolved tissues from patients with systemic sclerosis, suggesting that these cells are present in early disease. However, after the identification of microchimeric cells in blood and tissues of patients with systemic sclerosis, these cells have been found in organs affected by nonautoimmune conditions. These cells are also commonly detected in the peripheral blood of healthy people.

SUMMARY

These observations have raised questions about whether microchimeric cells are responsible for the pathologic events in systemic sclerosis or are merely remnants of a pregnancy remote in time, and it has been suggested that they might also have beneficial effects for the host.

Fetomaternal cell traffic, pregnancy-associated progenitor cells, and autoimmune disease

Fetal cells in maternal blood are a potential source of fetal genetic material that can be obtained non-invasively. Efforts to isolate these cells from maternal peripheral blood are limited by their low circulating numbers (approximately 1 per ml of maternal blood in euploid pregnancies). Expansion of these cells by culture would provide more cells for diagnosis and give an opportunity to study fetal metaphase chromosomes. Despite extensive optimization of culture conditions, many groups have failed reproducibly to grow fetal cells from pre-procedural maternal samples. An unexpected benefit of this research has been the discovery of a novel population of fetal cells, the pregnancy-associated progenitor cell (PAPC), which remains in maternal blood and tissue for decades following delivery. These cells might play a role in some autoimmune diseases, such as scleroderma. PAPCs appear to have stem cell characteristics, such as the ability to proliferate and differentiate. Recently developed animal models will help to ascertain whether these cells cause disease, respond to disease, or have therapeutic applications.

Microchimerism in children with rheumatic disorders: What does it mean?

Bidirectional cell trafficking occurs between a mother and fetus during pregnancy. This trafficking is associated with the persistence of non-self cells and is termed chimerism or, because of the low levels of non-self cells, microchimerism. Persistence of these cells has been demonstrated for many years after birth in the child and mother. Children with juvenile dermatomyositis, juvenile idiopathic inflammatory myositis, and healthy adults have all demonstrated persistence of maternal microchimerism, which is increased in the diseased population and thought associated with human leukocyte antigen genes of the offspring and the mother.

Chimerism in myositis

Bidirectional cell trafficking occurs between a mother and fetus during pregnancy. The trafficking is associated with the persistence of non-self cells. Persistence of these cells has been demonstrated after birth for many years in the child and mother. Children and adults with inflammatory myositis are reported to have persistence of microchimeric cells more often than healthy individuals in their peripheral blood and muscle tissue.

Microchimerism in autoimmune disease: more questions than answers?

Recent studies indicate cell traffic occurs between the fetus and mother during pregnancy and that low numbers of fetal cells commonly persist in the maternal circulation for years thereafter. Microchimerism refers to a small number of cells or DNA from one individual harbored in another individual. Autoimmune diseases are more common among women and often increase in incidence following reproductive years. Chronic graft vs. host disease is an iatrogenic form of chimerism with similarities to some autoimmune diseases for which the HLA relationship of donor and host are of central importance. When considered together, these observations led to the hypothesis that microchimerism and HLA relationships of host and non-host cells are involved in autoimmune disease. The hypothesis is applicable to men, children and women without pregnancies because there are other sources of microchimerism, including from a twin, the mother or a blood transfusion. Microchimerism has now been investigated in a number of different diseases with some results supporting a potential role in disease pathogenesis. However, fetal and maternal microchimerism are also found in organs affected by non-autoimmune conditions. Moreover, microchimerism is commonly detected in the peripheral blood of healthy individuals raising the intriguing question of whether these cells are simple remnants of pregnancy or whether they might also have beneficial effects for the host.

Fetal cell microchimerism: helpful or harmful to the parous woman?

PURPOSE OF REVIEW

Fetal cells enter the maternal circulation during most pregnancies and can persist in maternal blood and tissues after delivery. Concerns with regard to the histocompatibility of these fetal cells have raised the question of the long-term consequences of an immune response on maternal health. In the past few years, many investigators have demonstrated an association between the persistence of fetal cells in maternal tissues and blood and maternal autoimmune disease, especially systemic sclerosis. In this review we will summarize more recent data that provide a new insight into bi-directional feto-maternal cell trafficking.

RECENT FINDINGS

Persisting fetal cells have been found in the tissue of women affected with endocrine or infectious disease as well as healthy parous women.

SUMMARY

These data suggest the possibility that fetal microchimeric cells may also participate in the maternal physiological response to tissue injury. The medical consequences of pregnancy, therefore, appear to extend well beyond delivery.

Microchimerism and scleroderma: an update

Microchimerism has been defined by the presence of a low number of circulating cells transferred from one individual to another. This transfer takes place naturally during pregnancy, between mother and fetus, or between fetuses in multigestational pregnancies. Furthermore, the establishment of microchimerism can also occur during blood transfusion, as well as during bone marrow and solid-organ transplants. Recently, microchimeric cells have been implicated in the pathogenesis of autoimmune diseases, particularly systemic sclerosis. Studies have demonstrated an increased presence of microchimeric cells in peripheral blood and tissues from patients with systemic sclerosis, and, more recently, microchimeric cells were demonstrated to be specifically activated and capable of recognizing patient human leukocyte antigens.

Microchimerism and human autoimmune diseases

Cells traffic in both directions between the fetus and the mother during pregnancy. Recent studies indicate that a low level of fetal cells commonly persists in the maternal circulation for years after pregnancy completion. The harboring of DNA or cells from another individual at low levels is called microchimerism. Chronic graft-vs-host disease is a condition of human chimerism that shares similarities to some autoimmune diseases and for which the specific HLA genes of donor and host are known to be of central importance. Considered together with the female predilection to autoimmunity, these observations led to the hypothesis that microchimerism and HLA genes of host and non-host cells are involved in autoimmune disease. The hypothesis also extends to men and females who have not been pregnant because there are other sources of microchimerism. Maternal cells are now know to persist in her progeny and microchimerism can also derive from a twin or from a blood transfusion. Studies of systemic sclerosis, primary biliary cirrhosis, Sjögrens syndrome, polymorpyhic eruption of pregnancy, myositis and thyroid disease have both lent support and raised doubts about the role of microchimerism in autoimmune disease.

Detection of maternal-fetal microchimerism in the inflammatory lesions of patients with Sjögren's syndrome

BACKGROUND

A possible relation between maternal-fetal microchimerism and autoimmune diseases with some similarities to chronic graft versus host disease (cGVHD) has been reported.

OBJECTIVE

To investigate whether cells with male DNA exist in female patients with Sjögren's syndrome (SS) as SS has clinical features similar to those of cGVHD.

METHODS

DNA was extracted from 27 samples of peripheral blood mononuclear cells (PBMC), 42 biopsy samples of labial salivary glands (LSG), and nine samples of bronchoalveolar lavage fluid (BALF) cells from 56 female patients with SS. The presence of male DNA was determined by nested polymerase chain reaction (PCR) and by fluorescence in situ hybridisation (FISH).

RESULTS

Among 56 female patients with SS, 42 patients had at least one male child. Among those 42 patients, none of the 22 PBMC but 10/28 (36%) LSG samples tested positive by PCR for the Y chromosome-specific sequence (p=0.0013). The Y chromosome-specific sequence was not detected in the samples of LSG in 10 patients without SS. In the BALF samples 2/9 (22%) patients with SS tested positive by PCR. Cells containing the Y chromosome were shown to exist in all the LSG specimens from three female patients with SS by FISH.

CONCLUSIONS

Maternal-fetal microchimerism was shown for the first time to exist in the salivary glands and lungs of female patients with SS in this study. The presence of non-host cells in the inflammatory lesions but not in the peripheral blood suggests a possible role for maternal-fetal microchimerism in the pathogenesis of SS.

Male microchimerism in healthy women and women with scleroderma: cells or circulating DNA? A quantitative answer

Male DNA, of presumed fetal origin, can be detected in the maternal circulation decades after delivery and is referred to as fetal microchimerism (FM). We previously found quantitatively greater FM in the circulation of women with the autoimmune disease scleroderma (SSc) than of healthy women. However, it is unknown whether this difference is due to intact circulating cells or free DNA released from breakdown in disease-affected tissues. To distinguish the origin of FM, we developed a real-time quantitative polymerase chain reaction (PCR) assay for the Y-chromosome-specific sequence DYS14, and tested 114 women in peripheral blood mononuclear cells (PBMCs) and/or plasma. Fifty-seven controls and 57 SSc patients were studied, 48 and 43 of whom, respectively, had given birth to at least one son. Circulating FM was quantitatively greater in PBMCs from SSc patients (n = 39; range, 0.0-12.5 male genome-equivalent cells per million maternal cells), compared with healthy women (n = 39; range, 0.0-4.4; P =.03). In contrast, there was no difference between patients (n = 25) and controls (n = 22) in plasma, and no evidence of free DNA. FM was enriched among T lymphocytes compared with PBMCs (P =.01) in controls (n = 14), but not in SSc patients (n = 14); the latter finding was most likely due to immunosuppressive medications. In conclusion, this real-time quantitative assay showed that quantitative differences in the circulation of women with SSc are due to cells and not to free DNA. As FM was not uncommon in healthy women, including among T cells, and because graft-versus-host disease has similarities to SSc, these results also suggest that FM merits investigation in pheresis products used for stem cell transplantation.

Microchimerism and autoimmune diseases

Microchimerism is defined by the presence within an individual of a low level of cells derived from another individual. Systemic sclerosis is clinically similar to chronic graft-versus-host disease, a known condition of chimerism, which has led some authors to explore the hypothesis that microchimerism may contribute to the pathogenesis of systemic sclerosis and other autoimmune disorders. This article reviews early studies that lend support to this hypothesis.

Microchimerism in autoimmunity and transplantation: potential relevance to multiple sclerosis

Microchimerism (MC) is the stable presence of small numbers of non-host cells and appears to be commonly present in parous women. There are several methods of detecting microchimerism and each has advantages for different types of studies, but the risk of contamination and the differing levels of sensitivity lead to difficulties in estimating the proportion of individuals that are microchimeric. Recent observations of an increased frequency of microchimerism in women with scleroderma and Hashimoto's thyroiditis suggest that microchimerism may increase the risk of developing autoimmune disease. Inferences regarding autoimmunity are drawn from the immunological effects of organ and bone-marrow transplantation. Potential research questions regarding microchimerism, human leukocyte antigen (HLA) similarity, and autoimmune diseases in the context of multiple sclerosis (MS) are discussed.

Microchimerism: incidental byproduct of pregnancy or active participant in human health?

It is now well recognized that cells traffic in both directions between fetus and mother during pregnancy. Moreover, fetal cells have been found to persist for years, probably for a lifetime, in the circulation of healthy women. Harboring of cells from another individual at low levels is called microchimerism. Women have a predilection to autoimmune disease, and chronic graft-versus-host disease, a condition of human chimerism, shares similarities with some autoimmune diseases. The specific HLA genes of donor and host are known to be of central importance in graft-versus-host disease, and HLA class II genes are important in autoimmune disease. Considered together, these observations led to the hypothesis that microchimerism and HLA genes of host and non-host cells are involved in autoimmune diseases. Alternative sources of microchimerism include transfer from a twin or the mother during pregnancy, or from blood transfusion. Studies of systemic sclerosis, primary biliary cirrhosis, Sjögrens syndrome, pruritic eruption of pregnancy, myositis, and thyroid disease have both lent support and raised doubts about a potential role of microchimerism in autoimmune disease.

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.

Intrathyroidal fetal microchimerism in pregnancy and postpartum

To investigate a possible relationship between fetal microchimerism and autoimmune thyroiditis, we looked for the presence of fetal cells in the maternal blood and thyroid gland in murine experimental autoimmune thyroiditis (EAT). We used a quantitative PCR-ELISA for products of the SRY locus on the Y chromosome to detect fetal male cells during pregnancy and the postpartum period with a sensitivity of approximately 1 male cell/10(5) female cells. Within the thyroid glands, 12 of 26 (46%) Tg-immunized pregnant mice were SRY positive (range, 1-1700 cells), whereas, in contrast, few SRY transcripts were detected in control thyroids from nonimmunized pregnant mice (P < 0.05). At 5 wk postpartum, although SRY was still detected in the thyroids of 12 of 40 (30%) Tg-immunized mice, the number of male cells was markedly decreased (range, 1-30), and by 10 wk postpartum SRY had disappeared. Using allogeneic male mice heterozygous for green fluorescent protein expression, green fluorescent fetal cells were detected in the blood and bone marrow of pregnant mice. However, green cells were only found in thyroid glands from Tg-immunized pregnant mice that had green fluorescent protein-transgenic green fetuses and not in control nonimmunized pregnant mice. Cytologically, the fetal cells appeared to be of variable origin. Using antibody-mediated affinity purification of thyroid digests we showed this cell population to include fetal cells of T cell and dendritic cell lineage. Hence, fetal cells of immune origin were shown to accumulate within the thyroid glands of mice with EAT during pregnancy and the early postpartum. These data indicated that the inflamed thyroid gland was capable of accumulating fetal cells, including T cells and dendritic cells. Such active immune cells may have a profound regulatory influence on autoimmune thyroiditis in pregnancy and the postpartum period.