Possible contribution of microchimerism to the pathogenesis of Sjögren's syndrome

Fetal-origin cells in maternal circulation correlate with placental dysfunction, fetal sex, and severe hypertension during pregnancy

Fetal microchimerism (FMc) arises when fetal cells enter maternal circulation, potentially persisting for decades. Increased FMc is associated with fetal growth restriction, preeclampsia, and anti-angiogenic shift in placenta-associated proteins in diabetic and normotensive term pregnancies. The two-stage model of preeclampsia postulates that placental dysfunction causes such shift in placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFLt-1), triggering maternal vascular inflammation and endothelial dysfunction. We investigated whether anti-angiogenic shift, fetal sex, fetal growth restriction, and severe maternal hypertension correlate with FMc in hypertensive disorders of pregnancy with new-onset features (n = 125). Maternal blood was drawn pre-delivery at > 25 weeks' gestation. FMc was detected by quantitative polymerase chain reaction targeting paternally inherited unique fetal alleles. PlGF and sFlt-1 were measured by immunoassay. We estimated odds ratios (ORs) by logistic regression and detection rate ratios (DRRs) by negative binomial regression. PlGF correlated negatively with FMc quantity (DRR = 0.2, p = 0.005) and female fetal sex correlated positively with FMc prevalence (OR = 5.0, p < 0.001) and quantity (DRR = 4.5, p < 0.001). Fetal growth restriction no longer correlated with increased FMc quantity after adjustment for correlates of placental dysfunction (DRR = 1.5, p = 0.272), whereas severe hypertension remained correlated with both FMc measures (OR = 5.5, p = 0.006; DRR = 6.3, p = 0.001). Our findings suggest that increased FMc is independently associated with both stages of the two-stage preeclampsia model. The association with female fetal sex has implications for microchimerism detection methodology. Future studies should target both male and female-origin FMc and focus on clarifying which placental mechanisms impact fetal cell transfer and how FMc impacts the maternal vasculature.

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.

Male microchimerism in peripheral blood from women with multiple sclerosis in Isfahan Province

Multiple sclerosis (MS) is referred to as an organ-specific T-cell-mediated autoimmune disease of the central nervous system (CNS). Different genetic and environmental factors increase the risk of developing MS. In recent years, microchimerism (Mc) has been widely studied in autoimmune diseases, although the exact role of this phenomenon in human health is not known well. Microchimerism is the low level presence of DNA or cells from one individual into the tissue or circulation of another individual. In the current study, we evaluated the association of fetal microchimerism (FMc) with MS in Isfahan province. In this study, we enrolled 68 women in four groups. Two groups were MS patients with or without a pregnancy for a son, and the other two groups were MS-negative patients with or without a pregnancy for a son. The presence of the male genome assessed and compared in these groups. Four millilitres of peripheral blood were collected from all subjects in the tube containing EDTA and DNA was extracted. Real-time PCR assay was used for the DAZ (deleted in azoospermia) region Yq 11.23 as a marker for male microchimerism in all subjects. Our results showed that the percentage of DAZ (male genome)-positive women was significantly higher in MS-positive women given birth to a son in comparison with the other three groups. Our results also revealed no significant correlation between the percentage of DAZ-positive women and Expanded Disability Status Scale (EDSS) score and age of onset in the patients' group. For future studies, we suggest enrolling subjects who MS diagnosis occurred before and after pregnancy with a son. Comparing FMc in these two groups might provide a better understanding of the possible role of FMc in later development of MS.

Microchimerism: A new concept

Microchimerism is the presence of cells from one individual in another genetically distinct individual. Pregnancy is the main cause of natural microchimerism through transplacental bi-directional cell trafficking between mother and fetus. In addition to a variety of cell-free substances, it is now well-recognized that some cells are also exchanged in pregnancy. Furthermore, it is now known that microchimerism persists decades later both in mother and in her progeny. The consequences of pregnancy-related microchimerism are under active investigation. However, many authors have suggested a close relationship linking fetal microchimerism and the development of autoimmune diseases. Fetal microchimerism is emerging as a potential contributing factor in certain diseases, including cancer. Parallel studies in animal and human pregnancy suggest that microchimeric fetal cells play a role in wound healing. Role of these microchimeric cells in human health and disease is discussed here.

Sex differences in Sjögren's syndrome: a comprehensive review of immune mechanisms

Autoimmune diseases (ADs) are estimated to affect between 5 and 8 % of the US population, and approximately 80 % of these patients are women. Sjögren’s syndrome (SS) is an AD that occurs predominately in women over men (16:1). The hallmark characteristic of SS is diminished secretory production from the primary exocrine gland and the lacrimal or salivary glands resulting in symptoms of dry eye and mouth. The disease is believed to be mediated by an inflammatory and autoantibody response directed against salivary and lacrimal gland tissues. This review will examine the literature on sex differences in the immune response of patients and animal models of Sjögren’s syndrome in order to gain a better understanding of disease pathogenesis.

Fetal microchimerism and maternal health: a review and evolutionary analysis of cooperation and conflict beyond the womb

The presence of fetal cells has been associated with both positive and negative effects on maternal health. These paradoxical effects may be due to the fact that maternal and offspring fitness interests are aligned in certain domains and conflicting in others, which may have led to the evolution of fetal microchimeric phenotypes that can manipulate maternal tissues. We use cooperation and conflict theory to generate testable predictions about domains in which fetal microchimerism may enhance maternal health and those in which it may be detrimental. This framework suggests that fetal cells may function both to contribute to maternal somatic maintenance (e.g. wound healing) and to manipulate maternal physiology to enhance resource transmission to offspring (e.g. enhancing milk production). In this review, we use an evolutionary framework to make testable predictions about the role of fetal microchimerism in lactation, thyroid function, autoimmune disease, cancer and maternal emotional, and psychological health.

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Microchimerism in alopecia areata

BACKGROUND

Autoimmunity is the main etiopathogenetic factor in alopecia areata. Microchimerism is the existence of allogeneic DNA in a living creature. There are variable studies investigating the role of microchimerism on the etiopathogenesis of autoimmune diseases. To our knowledge, no report has investigated the relationship between microchimerism and alopecia areata.

OBJECTIVE

We aimed to investigate the possible role of microchimerism on alopecia areata.

METHODS

We analyzed SRY gene levels as indicators of fetal microchimerism in our patient group. The patients were 29 women with alopecia areata, over 18 years old, who had visited our clinic between 2010 and 2013. Patients were divided into two groups; group 1 consisted of 14 patients having a son and group 2, 15 patients either nulliparous or having a daughter.

RESULTS

Seventeen of 29 patients (58.6%) and four of 103 controls (3.9%) showed presence of an SRY gene. The difference between the patient and control groups was statistically significant (P < 0.001).

CONCLUSION

As a result of our study, microchimerism may be associated with the etiopathogenesis of alopecia areata. However, we think there is a need for a larger series of studies to support this hypothesis.

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.

Immune recognition of transplacentally acquired lymphoid allografts selects for increased major histocompatibility polymorphism

The extreme polymorphism of mammalian major histocompatibility (MHC) Class I and Class II alleles has been attributed to inbreeding avoidance, heterozygote advantage and pathogen driven selection for rare MHC alleles. However, MHC alleles can be classified into a limited number of allele supertypes based on the specificity of their peptide binding grooves (about 10 supertypes in the case of human MHC Class I alleles). The paradox is that if antigen presentation can be accomplished by a limited number of binding groove motifs, why are these loci so polymorphic? An unexplored driver of this complexity may be selection pressure to enhance the antigenicity and immune recognition of transplacentally acquired lymphoid allografts during pregnancy. The exchange of lymphoid cells between mother and fetus probably occurs in all pregnancies and may lead to fetal and/or maternal lymphoid microchimerism, a known cause of autoimmune disease. Natural selection may have favoured increased polymorphism at MHC Class I and Class II loci in order to improve immune surveillance of these cells and thereby reduce the incidence of maternal and fetal autoimmune disease. At the same time, selection may have favoured the retention of a limited set of allele supertypes which optimally present immunodominant antigens.

Fetal microchimerism as an explanation of disease

Fetal cell microchimerism is defined as the persistence of fetal cells in the mother after birth without any apparent rejection. Fetal microchimeric cells (FMCs) engraft into the maternal bone marrow for decades after delivery and are able to migrate to blood and tissues. This phenomenon was hypothesized to have a detrimental role in autoimmune diseases, but data are still controversial and debated. In malignant tumors, fetal cell microchimerism has been postulated to have a positive effect on tumor burden, although some evidence suggests that FMCs may be involved in neoplastic progression. At the peripheral level, circulating FMCs are less frequently detected in patients with thyroid cancer, breast cancer or other solid, hematologic malignancies than in healthy individuals, which suggests a protective role for fetal cell microchimerism. In tissues, FMCs have been found in tumor sections from malignancies such as thyroid, breast, cervix, lung cancers and melanomas and have been shown to differentiate into epithelial, hematopoietic, endothelial and mesenchymal cells. FMCs with hematopoietic differentiation have been postulated to have a role in destroying the tumor, whereas mesenchymal and epithelial cells could participate in repair processes. Endothelial cells, on the other hand, are believed to play a part in tumor progression. This Review provides an overview of the role of fetal cell microchimerism in autoimmune and benign or malignant nonautoimmune diseases. Moreover, the mechanisms by which fetal cell microchimerism is believed to modulate the protection against cancer or tumor progression will be discussed, together with future research directions.

[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 labial salivary glands of hematopoietic stem cell transplanted patients

OBJECTIVE

Microchimerism has been extensively investigated in autoimmune diseases, which display similarities with graft-vs-host disease. This study was conducted to investigate the presence of microchimerism in minor salivary glands of hematopoietic stem cell transplanted patients, one of the targets of graft-vs-host disease.

METHODS

Labial salivary glands biopsy specimens from 11 stem cell transplanted patients were analysed. The samples were grouped in control (five specimens from a female-to-female transplantation) and study group (five glands from male-to-female transplantation). One male transplanted patient was used as a positive control. Fluorescence in situ hybridization with Y-chromosome probe and immunofluorescence with anticytokeratin AE1/AE3 and CD45 were used to identify Y-chromosome positive glandular epithelial cells from allogeneic hematopoietic stem cell transplanted patients.

RESULTS

In the study group, all samples were positive to Y-chromosome and cytokeratin AE1/AE3, in agreement with the pattern exhibited by male labial salivary gland. None of the samples from control group were positive to Y-chromosome despite being positive to cytokeratin AE1/AE3. Positivity to CD45 was not relevant.

CONCLUSION

Microchimerism in the labial salivary glands of sex-mismatched stem cell transplanted patients is a real phenomenon. Further studies are necessary to elucidate the impact of this phenomenon on the clinical status of stem cell transplanted patients.

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.

Fetal cell microchimerism in human cancers

The transfer of fetal cells into the maternal circulation occurs normally during pregnancy and the post-partum persistence of these cells in the maternal blood and tissues, known as fetal cell microchimerism, has been clearly demonstrated. However, the long-term consequences of this phenomenon are only beginning to be appreciated. In particular, whether microchimerism could be involved in the carcinogenetic process or whether fetal microchimeric cells could be able to differentiate in host tissues, participating in the maternal response to injury, is still matter of study. In this review, the possible role and the consequences of fetal cell microchimerism, as emerged from studies in animal models and in women with different types of cancer, will be presented.

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.

Fetal cell microchimerism in papillary thyroid cancer: a possible role in tumor damage and tissue repair

Fetal cells enter the maternal circulation during pregnancy and can persist in the maternal blood or tissues for decades, creating a physiologic microchimerism. Because papillary thyroid cancer (PTC) is more frequent in women, the role of persisting fetal male cells in this tumor has been investigated. Tumor tissue specimens were obtained from 63 women with PTC who had a male pregnancy before the diagnosis. Male cells, identified by PCR amplification of a male-specific gene, the sex-determining region Y, was detected in 47.5% of women. By fluorescence in situ hybridization (FISH) analyses, the total number of microchimeric cells was significantly higher in neoplastic tissue than in controlateral normal sections. By combined FISH and immunohistochemistry (immuno-FISH), male cells expressing thyroglobulin were found in tumor and normal tissues, whereas male microchimeric cells stained with the CD45 antigen were detected only in tumor sections. Microchimeric cells negative for either marker were detected both in tumor and normal tissues. Moreover, both CD45(+) and Tg(+) fetal cells did not express MHC II antigens. In conclusion, fetal microchimerism has been documented in a high proportion of women with PTC. The immuno-FISH studies indicate that CD45(+)/MHC II(-) male cells found in neoplastic tissues might be committed to destroy tumor cells, whereas Tg(+)/MHC II(-) cells could have a repair function. Finally, microchimeric cells negative for either CD45 or Tg could have "progenitor-like" properties able to transdifferentiate in different cellular types. Although a pathogenetic mechanism cannot be excluded, the whole of the present results indicates a protective role of microchimerism in thyroid cancer.

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.

The influence of pregnancy on the development of autoimmunity in chronic lymphocytic leukemia

To examine whether pregnancy influences the development of autoimmunity in chronic lymphocytic leukemia (CLL), we studied 591 consecutive CLL patients (202 post-menopausal women and 389 men). The mean observation time for all patients was 3.8 years, corresponding to approximately 2200 person-years of follow-up. Autoimmune manifestations were analyzed in 194 women with known obstetric history and known number of long-term sexual partners, and in the 389 male CLL patients for comparison. One hundred and fifty-nine of the CLL patients exhibited autoimmune manifestations, 38% in females and 21% in men. In female CLL patients, the frequency of autoimmunity and the number of pregnancies and the number of partners were strongly correlated. Each of the major autoimmune types approximately doubled in frequency for each additional pregnancy. The impact of pregnancy on expressed autoimmunity increased with each additional sexual partner (the odds of autoimmunity increased 11 times with each long-term sexual partner). The average numbers of pregnancies in female CLL patients with and without autoimmunity were 4.92 and 2.24, respectively (P < 0.001). Coombs' positive autoimmune anemia, a gastric ulcer with parietal cell autoantibodies and idiopathic thrombocytopenic purpura were equally common in women and men, whereas autoimmune thyroiditis, Sjögren's syndrome, rheumatoid arthritis and systemic lupus erythematosus were seen in higher rates in women than in men. The spectrum of autoimmunity suggests that pregnancy-related alloimmunization may be involved in the development of autoimmunity in CLL.

[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.

Syndrome de Gougerot-Sjögren en gynécologie obstétrique

Sjogren syndrome (SS) is an immune disease characterized by a progressive degeneration of exocrine glands. It leads to dryness of mucosa and conjunctivitis. Gynecologists and obstetricians may encounter this disease in women at any age, including during pregnancy. Knowledge of the main characteristics is required for early diagnosis and multidisciplinary program. In the event of secondary Sjögren syndrome occurring during pregnancy, treatment focuses on the associated disease, mainly systemic lupus erythematosus. In primary Sjögren syndrome, pregnancy does not appear to influence disease course. However, patients with both primary and secondary Sjögren syndrome must be monitored carefully. There is a risk of neonatal lupus and congenital atrioventricular bloc associated with high morbidity and mortality. These patients should benefit from multidisciplinary care in a hospital with a neonatal intensive care unit.

Sjogren's syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease affecting the exocrine glands, primarily the salivary and lacrimal glands. It has been suggested that exogenous agents may trigger SS in genetically predisposed individuals. However, at present, the etiology of SS is far from being understood, and no direct evidence for any of these triggers has been presented. The salivary and lacrimal glands from patients with SS harbor unique and highly selected T- and B-cell populations. Disturbance in glandular cell apoptosis may be one possible explanation for the sicca symptoms in SS. However, discrepancies between glandular destruction and salivary flow give rise to processes causing glandular dysfunction preceding or triggering glandular cell destruction. Recent reports suggested autoantibodies inhibiting neuronal innervation of acinar cells and defective water transport to be implicated in salivary secretion deficiency observed in SS. Several types of autoantibodies have been suggested to contribute to the pathogenesis of SS. However, how the tolerance to these structures is broken down is unknown at present. Studies on B-cell activating factor indicated that diminished apoptosis and disturbed B-cell maturation could be responsible for the occurrence of autoreactive B-cells and B-cell hyperreactivity. B-cell activation may also provide a basis for lymphoma development observed in up to 5% of the patients with SS.

Fetal cells in mother rats contribute to the remodeling of liver and kidney after injury

Fetal microchimerism indicates a mixture of cells of maternal and fetal origin seen in maternal tissues during and after pregnancy. Controversy exists about whether persistent fetal microchimerism is related with some autoimmune disorders occurring during and after pregnancy. In the current experiment, an animal model in which EGFP positive cells were taken as fetal-origin cells was designed to detect the fetal microchimerism in various maternal organs. Ethanol drinking and gentamicin injection were adopted to induce liver and kidney injury simultaneously. EGFP positive cells were engrafted not only in the maternal circulation and bone marrow, but also in the liver and kidney as hepatocytes and tubular cells, respectively. These results indicate that fetal cells are engrafted to maternal hematopoietic system without apparent injury and they also contribute to the repairing process of maternal liver and kidney.

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.

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.

New concepts in the pathogenesis of Sjögren syndrome: many questions, fewer answers

Although a modified European-American consensus classification of Sjögren syndrome has been introduced during the last year, the etiopathogenesis of this disease characterized by chronic lymphocytic inflammation, impaired function, and, finally, destruction of the salivary and lacrimal glands as well as systemic manifestations remains to be elucidated. Recent insights into the pathogenesis of Sjögren syndrome resulting from immunogenetic, hormonal, and epidemiologic evaluations as well as animal and in vitro studies are highlighted by this review. Evidence confirms that lymphocytic disturbances, including ectopic germinal center formation and aberrations of cellular signaling play a significant role in Sjögren syndrome. Although some of these features are unique to Sjögren syndrome, others are also found in a number of systemic autoimmune diseases, such as systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. The underlying cause of Sjögren syndrome remains largely enigmatic. However, distinct characteristics may provide the basis for the classification of the disease entities. Finally, an enhanced risk of lymphomagenesis is a well-known hallmark of primary Sjögren syndrome, indicating the central role of derangement of lymphocyte regulation. As demonstrated by the introduction of the new targeted therapeutic approaches in rheumatoid arthritis, solid insights into the pathogenesis of Sjögren syndrome may pave the way toward new therapeutic approaches.

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.