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.     

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.     

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.     

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

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

High frequency of fetal cells within a primitive stem cell population in maternal blood

BACKGROUND: During pregnancy, fetal cells enter the maternal bloodstreamresulting in fetal cell microchimerism. The fetal cells persistin the mother for decades and colonize a variety of maternalorgans. They are associated with maternal autoimmune diseasesand may also participate in tissue repair. The identity of themicrochimeric cells is not certain but they must be able topersist long-term and have potential for multitissue differentiation. METHODS AND RESULTS: Here we tested the hypothesis that the fetal microchimeric cellsare primitive stem cells, represented by CD34+ adherent cells,which have a wide potential for differentiation. We isolatedthese stem cells from the blood of pregnant females (n = 25)and detected fetal cells of the correct gender, using fluorescencein situ hybridization, in a high proportion (71% male fetusesand 90% female fetuses; false positive rate 11%, false negativerate 29%) of cases. By RT–PCR, we demonstrated that thecells express Oct-4, Nanog and Rex-1. No fetal cells were detectedin the mononuclear or total CD34+ cell populations but highfrequencies (mean 11.8%) of fetal cells were detected in theadherent CD34+ cell population. CONCLUSIONS: These results identify adherent CD34+ stem cells as candidatefetal microchimeric cells, which are capable of sustaining thefetal cell population in the long term and have the abilityto colonize multiple tissues and organs.     

Fetal-maternal microchimerism: impact on hematopoietic stem cell transplantation

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

Increased Microchimeric CD4 T Lymphocytes in Peripheral Blood from Women with Systemic Sclerosis

Recent studies have demonstrated the presence of microchimeric cells in peripheral blood and skin lesions from patients with systemic sclerosis (SSc). In a previous study we found that some peripheral blood CD3⁺ cells from female patients with SSc contained male DNA. Here, peripheral blood samples from 47 patients with SSc (30 with diffuse cutaneous SSc and 17 with limited cutaneous SSc) and 22 healthy controls were sorted for CD4⁺ and CD8⁺ T cells. Both positively and negatively selected populations were analyzed for male DNA by quantitative PCR. Analysis of Y chromosome sequences in the sorted cells demonstrated the presence of microchimerism in 82.9% of SSc patients compared to 63.6% of controls. The numbers of CD4⁺ and CD8⁺ T cells were found to be significantly higher in the SSc patients than in controls. Furthermore, patients with dcSSc were observed to have significantly more CD4⁺ microchimeric T cells than the controls. In the CD8⁺ T-cell population, there was a trend toward more microchimeric cells in the patients but this did not reach significance. These results support the hypothesis that microchimeric CD4⁺ T cells may be involved in the pathogenesis of SSc.     

Prospective assessment of fetal-maternal cell transfer in miscarriage and pregnancy termination

BACKGROUND Fetal cells (microchimerism) are acquired by women during pregnancy. Fetal microchimerism persists decades later and includes cells with pluripotent capacity. Persistent microchimerism has the capacity for both beneficial and detrimental maternal health consequences. Both miscarriage and termination of pregnancy can result in fetal microchimerism. We sought to determine whether cellular fetal microchimerism is acquired during management of pregnancy loss and further explored factors that could influence fetal cell transfer, including viability of fetal tissue, surgical versus medical management and gestational age. METHODS Pregnant women (n= 150 samples from 75 women) with singleton pregnancies undergoing a TOP (n= 63) or treatment for embryonic or fetal demise (miscarriage, n= 12) were enrolled. Mononuclear cells were isolated from blood samples drawn before, and 30 min after, treatment. Fetal cellular microchimerism concentrations were determined using quantitative PCR for a Y chromosome-specific sequence, expressed as genome equivalents of fetal DNA per 100 000 maternal cell equivalents (gEq/10(5)). Detection rate ratios were determined according to clinical characteristics. RESULTS Cellular fetal microchimerism was found more often in post- compared with pretreatment samples, 24 versus 5% (P= 0.004) and at higher concentrations, 0-36 versus 0-0.7 gEq/10(5) (P< 0.001). Likelihood of microchimerism was higher in surgical than medical management, detection rate ratio 24.7 (P= 0.02). The detection rate ratio for TOP versus miscarriage was 16.7 for known male fetuses (P= 0.02). Microchimerism did not vary with gestational age. CONCLUSIONS Significant fetal cell transfer occurs during miscarriage and TOP. Exploratory analyses support relationships between obstetric clinical factors and acquisition of fetal cellular microchimerism; however, our limited sample size precludes definitive analysis of these relationships, and confirmation is needed. In addition, the long-term persistence and potential consequences of fetal microchimerism on maternal health merit further investigation.     

Fetomaternal cell trafficking: A new cause of disease?

Isolation of fetal cells from maternal blood is under active investigation as a noninvasive method of prenatal diagnosis. In the context of studying cell surface antigens expressed on fetal cells we discovered that fetal cells from a prior pregnancy also could be detected. This led to the appreciation of the persistence of fetal cells in maternal blood for as long as 27 years postpartum, and the realization that following pregnancy, a woman becomes a chimera. Quantitative polymerase chain reaction analyses have shown that a term pregnancy is not required for the subsequent development of fetal cell microchimerism. As many as 500,000 fetal nucleated cells are transfused following an elective first trimester termination of pregnancy. The relationship between fetal cell microchimerism and maternal disease is currently being explored. During pregnancy, fetal cells in the maternal skin are related to polymorphic eruptions of pregnancy and increased fetomaternal trafficking is detectable in cases of preeclampsia. After delivery, more male DNA of presumed fetal origin is present in the blood and skin of women with scleroderma as compared with healthy controls. Scleroderma is of particular interest because it shows a strong female predilection and it is an autoimmune disease with clinical similarities to graft‐versus‐host disease. Fetomaternal cell trafficking provides a potential explanation for the increased prevalence of autoimmune disorders in adult women following their childbearing years. Am. J. Med. Genet. 91:22–28, 2000. © 2000 Wiley‐Liss, Inc.     

Blood fetal microchimerism in primary biliary cirrhosis

The autoimmune nature of primary biliary cirrhosis (PBC) is well established. We tested the hypothesis that fetal microchimerism indicated by the persistence of circulating fetal cells in women years after pregnancy might contribute to the aetiopathogenesis of PBC through a graft-versus-host-like response. We extracted DNA from the peripheral blood cells of 36 women carefully selected from 173 consecutive PBC patients, who were matched with 36 healthy women by age, age of last son, and number of children. Both patients and controls had to have male offspring, and no history of miscarriages or blood transfusions; they could not be twins. We tested all of the samples for the presence of two specific Y-chromosome sequences (SY154 and SRY) by amplifying DNA in a nested polymerase chain reaction. Y-chromosome-specific DNA was detected in the peripheral blood cell DNA of 13 (36%) of the 36 women with PBC and in 11 (31%) of the 36 healthy controls. The two groups of PBC patients with and without male DNA sequences were similar in terms of their clinical, biochemical, and serological features. Y-chromosome sequences were found in three of the four PBC women with associated systemic sclerosis. All of the 24 Y-positive samples contained SY154 sequences, but only three PBC patients and six controls showed the presence of both SY154 and SRY sequences. This discrepancy may suggest that not only fetal cells but also fragments of fetal DNA are present in maternal circulation. Overall, our data do not support the hypothesis that fetal microchimerism plays a significant role in the onset or progression of PBC.     

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.     

CAR T cells for brain tumors: Lessons learned and road ahead

Malignant brain tumors, including glioblastoma, represent some of the most difficult to treat of solid tumors. Nevertheless, recent progress in immunotherapy, across a broad range of tumor types, provides hope that immunological approaches will have the potential to improve outcomes for patients with brain tumors. Chimeric antigen receptors (CAR) T cells, a promising immunotherapeutic modality, utilizes the tumor targeting specificity of any antibody or receptor ligand to redirect the cytolytic potency of T cells. The remarkable clinical response rates of CD19‐targeted CAR T cells and early clinical experiences in glioblastoma demonstrating safety and evidence for disease modifying activity support the potential of further advancements ultimately providing clinical benefit for patients. The brain, however, is an immune specialized organ presenting unique and specific challenges to immune‐based therapies. Remaining barriers to be overcome for achieving effective CAR T cell therapy in the central nervous system (CNS) include tumor antigenic heterogeneity, an immune‐suppressive microenvironment, unique properties of the CNS that limit T cell entry, and risks of immune‐based toxicities in this highly sensitive organ. This review will summarize preclinical and clinical data for CAR T cell immunotherapy in glioblastoma and other malignant brain tumors, including present obstacles to advancement.     

Feto-maternal microchimerism in connective tissue diseases

Fetal progenitor cells traffic to the mother during pregnancy and can persist in the maternal circulation for many years. Feto-maternal microchimerism has been reported in women with scleroderma, but its contribution to the disease pathogenesis remains unclear. Furthermore, the involvement of microchimerism in other connective tissue diseases is controversial. We studied 243 females, 122 of whom had previously carried a male fetus (50 healthy controls, 23 patients with scleroderma, and 49 with other connective tissue diseases). The presence of the male-specific SRY sequence was analyzed using a kinetic quantitative ELISA PCR assay that allows detection of one to three male cells in one million female cells. The percentage of SRY-positive samples was not different among women having borne son(s): 16% (95% confidence interval 0.07-0.29) in healthy controls, 21.7% (0.07-0.44) in patients with scleroderma and 25.5% (0.14-0.40) in patients with connective tissue diseases (p=0.25). The mean number of fetal cells was similar in the three groups. Among the 121 females who never carried a male fetus, no healthy woman was SRY positive. However, 33% of patients with scleroderma and 22.9% of women with connective tissue diseases were chimeric, a phenomenon which might be related to early miscarriage(s). Therefore, feto-maternal microchimerism is a common event in both healthy controls and patients with connective tissue diseases, and is unlikely to represent per se a risk factor for these diseases.     

Preliminary experiences with intraoperative radiation therapy (IORT) for the treatment of brain tumors.

Ten brain tumor patients underwent wide resection of the tumor followed by Intraoperative Radiation Therapy (IORT) at the first surgery or at the second salvage surgery after failure of conventional external beam irradiation. Two patients(1 meningioma, 1 glioblastoma multiforme) were treated at the first surgery and 8 patients(3 anaplastic astrocytoma, 3 glioblastoma multiforme, 1 meningioma, 1 gliosarcoma) were treated after salvage surgery. The IORT doses were ranged from 15-25 Gy depending on the tumor volume and previous radiation therapy. The neurological status(Karnofsky performance status) was improved in 4 cases, not changed in 6 cases after IORT. There were several complications after IORT; radiation necrosis, communicating hydrocephalus, wound infection, and abnormal CT findings such as diffuse low density area in an around operation site. The radiation necrosis was confirmed by operation in a recurrent meningioma patient 12 months after IORT. At follow-up, ranging from 1 to 16 months, there was no deaths. Based on our limited experiences, the IORT might be one of the adjuvant therapeutic modalities especially for the malignant brain tumors and unresectable huge meningioma.     

The tripartite immune conflict in placentals and a hypothesis on fetal-->maternal microchimerism

There is a two-way traffic of immune cells through the placenta; and fetal immune cells are often present in the maternal body even long after giving birth. We present an adaptationist theory to interpret fetal-->maternal microchimerism and the diverse set of concomitant medical phenomena. We handle fetal, maternal, and paternal adaptive interests separately and in interaction with one another. Fetuses may benefit from immunological information gathered by migrant cells in the maternal body, and also from improved maternal defence. However, they may be jeopardized by a selfish maternal usage of fetal-->maternal microchimerism - i.e., some mothers get pregnant only to improve their immune system and then to abort. The use of microchimeric cells by the maternal immune system may contribute to the adaptive benefits of female choosiness and polyandry. While fathers may enjoy an indirect benefit from enhanced fetal and maternal health, they also face the risk of wasting sexual efforts due to selfish pregnancies of cheating females. Paternal alleles acting via clones of microchimeric cells in the maternal body could launch an immunological attack against the non-kin sperm in the female genitalia, or against the non-kin fetus in the womb. Furthermore, an intraspecific version of Zahavi's Mafia Hypothesis could explain a potential interaction between the abortion of fetuses and a subsequent rise of an autoimmune disease. We suggest that males may be capable to provoke microchimerism-induced autoimmune-like diseases in the mother in revenge of selfish pregnancies. This hypothetic paternal threat could increase the maternal costs associated to selfish pregnancies. From a medical point of view, we propose new interpretations for autoimmune-like diseases, infertility, miscarriage, and also for the prevailing connections among them. Specifically, we argue that miscarriages may cause autoimmune diseases, a reversed causality as compared to the currently accepted one.     

Expression of cysteine protease inhibitors in human gliomas and meningiomas

Increased levels of human cysteine proteases have been implicated in the progression of tumors from the premalignant to the malignant state. The physiological activities of these proteases are regulated by their interactions with specific inhibitors. To our knowledge there have been no previous reports about the cysteine protease inhibitors (CPIs) in human brain tumors. In the study reported here, we determined CPI activity during glioma progression and compared that with normal human brain tissue. We also determined CPI activities in meningioma and glioblastoma cell lines in vitro. This activity was significantly higher in normal brain tissue and low-grade glioma than in anaplastic astrocytoma and glioblastoma. CPI activity was significantly higher in benign and atypical meningioma cell extracts in comparison with those from malignant meningiomas and with those from glioblastoma cell lines. After several passages, one benign meningioma cell line showed reduced levels of CPI and increased levels of cathepsin. Our results suggest that decreases in the activities of CPI may contribute to the malignant properties of brain tumors.     

Intercellular Adhesion Molecule-1 (ICAM-1) Upregulation in Human Brain Tumors as an Expression of Increased Blood-Brain Barrier Permeability

The distribution of intercellular adhesion molecule (ICAM-1) binding sites was studied in the microvasculature of several types of human brain tumor biopsies (angioma, glioblastoma multiforme and meningioma). Immunoelectron microscopy was performed with the application of immuno-HRP or gold probes using a pre-embedding technique. Ultrastructural analysis demonstrated a pronounced ICAM-1 upregulation on the luminal EC and/or perivascular surfaces. Reaction product for ICAM-1 was observed associated with some but not all blood vessels of the tumors examined. The strongest reaction product was noted associated with the angioma cases with lesser expression observed on the glioblastoma multiforme and meningioma cases. The reaction product using immuno-HRP probe was observed most pronounced on the luminal endothelial cell surface and also within vesiculo-tubular structures. Concentrated immunosignals with gold label were often expressed on EC microvilli. These data suggest that several types of brain tumors are actively involved in the process of upregulating ICAM-1, presumably for tumor cell adhesion and trafficking, the process of angiogenesis or both. We suggest that the ICAM-1-positive vesiculo-tubular structures reflect specialized, targeted regions on the ECs for tumor cell adhesion and eventual trans-BBB passage. Further, our studies also provide evidence that adhesion molecules may be a useful tool for the study of blood-brain barrier injury.     

Chimerism of metanephric adenoma but not of carcinoma in kidney transplants

Recipient-derived cells integrate into renal allografts inducing organ-specific microchimerism. Circulating pluripotent progenitor cells with high plasticity for differentiation were suggested as a potential source of allograft chimerism. Whether or not these cells also contribute to tumor formation in renal transplants is unknown. We analyzed six histologically different tumors in renal allografts for the presence of recipient-derived cells. To circumvent dependency on gender mismatch, a polymerase chain reaction assay for highly polymorphic short tandem repeat marker (DNA fingerprinting) in combination with laser microdissection was applied. Pure tumor cell populations were harvested by laser microdissection after immunohistochemical (CD45/CD68) marking of contaminating leukocytes. In cases of gender mismatch (n = 2), results were confirmed by sex chromosome in situ hybridization. Two metanephric adenomas demonstrated microchimerism comprising both donor- and recipient-derived tumor cells. Two clear cell carcinomas, one transitional cell carcinoma, and one renal cortical adenoma were all of donor origin without chimerism. We conclude that except for metanephric adenomas, tumors arising in renal transplants originate completely from graft cells. The mixed derivation of metanephric adenomas indicates an incorporation of recipient-derived progenitor cells. This finding suggests that adult stem cells can assume neoplastic phenotypes.