Maternal-fetal immunology and autoimmune disease: is some autoimmune disease auto-alloimmune or allo-autoimmune?

Microchimeric cells promote production of rheumatoid arthritis-specific autoantibodies

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Molecular Mechanisms in Autoimmune Thyroid Disease

The most common cause of acquired thyroid dysfunction is autoimmune thyroid disease, which is an organ-specific autoimmune disease with two presentation phenotypes: hyperthyroidism (Graves-Basedow disease) and hypothyroidism (Hashimoto’s thyroiditis). Hashimoto’s thyroiditis is distinguished by the presence of autoantibodies against thyroid peroxidase and thyroglobulin. Meanwhile, autoantibodies against the TSH receptor have been found in Graves-Basedow disease. Numerous susceptibility genes, as well as epigenetic and environmental factors, contribute to the pathogenesis of both diseases. This review summarizes the most common genetic, epigenetic, and environmental mechanisms involved in autoimmune thyroid 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.

Nonendocrine mechanisms of sex bias in rheumatic diseases

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

Autoimmune connective tissue diseases and pregnancy

Autoimmune connective tissue-diseases are more frequent in women and deserve a multidisciplinary approach in which the dermatologist play a major role together with other physicians. Pregnancy in these patients has to be considered a high-risk situation, because of possible worsening of the mother's disease and increased morbility and mortality for the fetus; also, therapies have to be chosen carefully because some drugs cannot be used during pregnancy. For all these reasons, the decision to become pregnant needs to consider the type of disease, stage of disease, age and clinical condition, and requires a multidisciplinary approach. A correct counselling, a close monitoring, a specific approach based on the risks involved and the use of appropriate therapies are the keys to obtain optimal pregnancy outcomes.

Mother-child histocompatibility and risk of rheumatoid arthritis and systemic lupus erythematosus among mothers

The study objective was to test the hypothesis that having histocompatible children increases the risk of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), possibly by contributing to the persistence of fetal cells acquired during pregnancy. We conducted a case control study using data from the UC San Francisco Mother Child Immunogenetic Study and studies at the Inova Translational Medicine Institute. We imputed human leukocyte antigen (HLA) alleles and minor histocompatibility antigens (mHags). We created a variable of exposure to histocompatible children. We estimated an average sequence similarity matching (SSM) score for each mother based on discordant mother-child alleles as a measure of histocompatibility. We used logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals. A total of 138 RA, 117 SLE, and 913 control mothers were analyzed. Increased risk of RA was associated with having any child compatible at HLA-B (OR 1.9; 1.2-3.1), DPB1 (OR 1.8; 1.2-2.6) or DQB1 (OR 1.8; 1.2-2.7). Compatibility at mHag ZAPHIR was associated with reduced risk of SLE among mothers carrying the HLA-restriction allele B*07:02 (n = 262; OR 0.4; 0.2-0.8). Our findings support the hypothesis that mother-child histocompatibility is associated with risk of RA and SLE.

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.

Chimeric maternal cells in offspring do not respond to renal injury, inflammatory or repair signals

Maternal microchimerism (MMc) can persist for years in a child, and has been implicated in the pathogenesis of chronic inflammatory autoimmune diseases. Chimeric cells may either contribute to disease by acting as immune targets or expand in response to signals of injury, inflammation or repair. We investigated the role of maternal cells in tissue injury in the absence of autoimmunity by quantifying MMc by quantitative PCR in acute and chronic models of renal injury: (1) reversible acute renal injury, inflammation and regeneration induced by rhabdomyolysis and (2) chronic injury leading to fibrosis after unilateral ureteral obstruction. We found that MMc is common in the mouse kidney. In mice congenic with their mothers neither acute nor chronic renal injury with fibrosis influenced the levels or prevalence of MMc. Maternal cells expressing MHC antigens not shared by offspring (H2(b/d)) were detected at lower levels in all groups of homozygous H2(b/b) or H2(d/d) offspring, with or without renal injury, suggesting that partial tolerance to low levels of alloantigens may regulate the homeostatic levels of maternal cells within tissues. Maternal cells homozygous for H2(b) were lost in H2(b/d) offspring only after acute renal failure, suggesting that an inflammatory stimulus led to loss of tolerance to homozygous maternal cells. The study suggests that elevated MMc previously found in association with human autoimmune diseases may not be a response to non-specific injury or inflammatory signals, but rather a primary event integral to the pathogenesis of autoimmunity.

Fetomaternal microchimerism: Some answers and many new questions

The transfer of fetal cells into mothers during pregnancy and their organ specific integration is a well recognized phenomenon in placental vertebrates. Recently, it has been reported that some fetal cells found in the mothers have progenitor cell-like features such as multilineage differentiation potential and as a consequence they were termed pregnancy associated progenitor cells (PAPC). The multilineage differentiation potential suggested some level of cellular plasticity, which these cells share with other stem or progenitor cells. In this context, we have shown that PAPCs indeed express neural stem cell and markers for developing neurons in the brain and that PAPCs morphologically mature into neurons over time. The stem/progenitor properties of PAPCs raises the hope that they might be valuable for studying the functional integration of foreign cells into preexisting tissues and organs, for example in cellular therapies. The functional integration of transplanted cells and their connectivity to the host circuitry is still a major bottleneck in cellular therapies particularly for the brain. The animal models of fetomaternal microchimerism might provide valuable insights into the mechanism how cells survive, migrate, integrate and differentiate in a foreign environment of a host. This review discusses some of the recent findings in the field of fetomaternal microchimerism. It also tries to identify some major gaps of knowledge and raises some questions resulting from the recent advances. Studying fetomaternal microchimerism and the properties of PAPCs in greater detail might pave the way to advance cell based regenerative medicine as well as transplantation medicine.

Signatures of reproductive events on blood counts and biomarkers of inflammation: Implications for chronic disease risk

Whether inflammation mediates how reproductive events affect chronic-disease risk is unclear. We studied inflammatory biomarkers in the context of reproductive events using National Health and Nutrition Examination Survey (NHANES) data. From 15,986 eligible women from the 1999–2011 data cycles, we accessed information on reproductive events, blood counts, C-reactive protein (CRP), and total homocysteine (tHCY). We calculated blood-count ratios including: platelet-lymphocyte (PLR), lymphocyte-monocyte (LMR), platelet-monocyte (PMR), and neutrophil-monocyte (NMR). Using sampling weights per NHANES guidelines, means for counts, ratios, or biomarkers by reproductive events were compared using linear regression. We performed trend tests and calculated p-values with partial sum of squares F-tests. Higher PLR and lower LMR were associated with nulliparity. In postmenopausal women, lower PMR was associated with early age at first birth and higher NMR with later age at and shorter interval since last birth. Lower PNR and higher neutrophils and tHCY were associated with early natural menopause. In all women, the neutrophil count correlated positively with CRP; but, in premenopausal women, correlated inversely with tHCY. Reproductive events leave residual signatures on blood counts and inflammatory biomarkers that could underlie their links to chronic disease risk.

A Child's HLA-DRB1 genotype increases maternal risk of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) disproportionately affects women of reproductive age. During pregnancy, women are exposed to various sources of fetal material possibly constituting a significant immunologic exposure relevant to the development of SLE. The objective of this study was to investigate whether having any children who carry DRB1 alleles associated with SLE increase the risk of maternal SLE. This case-control study is based on the University of California, San Francisco Mother-Child Immunogenetic Study and from studies at the Inova Translational Medicine Institute. Analyses were conducted using data for 1304 mothers (219 cases/1085 controls) and their respective 1664 children. We selected alleles based on their known association with risk of SLE (DRB1*03:01, *15:01, or *08:01) or Epstein-Barr virus (EBV) glycoproteins (*04:01) due to the established EBV association with SLE risk. We used logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (CI) for each allele of interest, taking into account maternal genotype and number of live births. We found an increase in risk of maternal SLE associated with exposure to children who inherited DRB1*04:01 from their father (OR 1.9; 95% CI, 1.1-3.2), among *04:01 allele-negative mothers. Increased risk was only present among mothers who were positive for one or more SLE risk-associated alleles (*03:01, *15:01 and/or *08:01). We did not find increased risk of maternal SLE associated with any other tested allele. These findings support the hypothesis that a child's alleles inherited from the father influence a mother's subsequent risk of SLE.

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.

Women and primary biliary cirrhosis

Primary biliary cirrhosis occurs more frequently in women, and previous studies indicated that the average age of primary biliary cirrhosis (PBC) onset makes pregnancy in PBC patients uncommon. However, more recently, improved diagnostic testing has enabled detection of PBC in younger women, including those of childbearing age. This has led investigators to become increasingly interested in the relationship between the ontogeny of PBC and pregnancy. Published cases indicate that the typical age for pregnant women to be diagnosed with PBC is in the early 30s, and that during gestation, pruritus and jaundice are the most common symptoms. During gestation, susceptible women may experience onset of PBC resulting from the drastic changes in female hormones; this would include not only the mitochondrial damage due to accumulation of bile acids but also changes in the immune response during the different stages of pregnancy that might play an important role in the breakdown of self-tolerance. The mechanisms underlying the potential relationship between PBC and pregnancy warrant further investigation. For women first diagnosed with PBC during gestation, or those for whom first appearance of a flare up occurs during and postpartum, investigation of the immune response throughout gestation could provide new avenues for immunologic therapeutic intervention and the discovery of new treatment strategies for PBC.

Fetal cell microchimerism: a protective role in autoimmune thyroid diseases

OBJECTIVE

The physiological persistence of fetal cells in the circulation and tissue of a previously pregnant woman is called fetal cell microchimerism (FCM). It has been hypothesized to play a role in systemic autoimmune disease; however, only limited data are available regarding its role in autoimmune thyroid disease (AITD).

DESIGN

Circulating FCM was analyzed in a large series of previously pregnant women with Graves' disease (GD), Hashimoto's thyroiditis (HT), or no disease (healthy controls (HCs)). To exclude the possible bias related to placental factors, the polymorphic pattern of human leukocyte antigen-G (HLA-G) gene, which is known to be involved in the tolerance of fetal cells by the maternal immune system, was investigated.

METHODS

FCM was evaluated by PCR in the peripheral blood, and the Y chromosome was identified by fluorescence in situ hybridization in some GD tissues. HLA-G polymorphism typing was assessed by real-time PCR.

RESULTS

FCM was significantly more frequent in HC (63.6%) than in GD (33.3%) or HT (27.8%) women (P=0.0004 and P=0.001 respectively). A quantitative analysis confirmed that circulating male DNA was more abundant in HC than it was in GD or HT. Microchimeric cells were documented in vessels and in thyroid follicles. In neither GD/HT patients nor HC women was the HLA-G typing different between FCM-positive and FCM-negative cases.

CONCLUSION

The higher prevalence of FCM in HC as compared to GD and HT patients suggests that it plays a possible protective role in autoimmune thyroid disorders. Placental factors have been excluded as determinants of the differences found. The vascular and tissue localization of microchimeric cells further highlights the ability of those cells to migrate to damaged tissues.

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.

Maternal microchimerism in biliary atresia: are maternal cells effector cells, targets, or just bystanders?

The etiology of biliary atresia (BA) is unknown; however, the liver histology is similar to that observed in immune-mediated hepatic disorders. Liver fibrosis in BA progresses even after bile drainage has been achieved by the Kasai operation. Maternal microchimerism has been purported to play a part in the pathogenesis of BA as well as certain autoimmune diseases. However, the role of maternal cells has not yet been determined in BA. Specifically, it is unknown whether these maternal cells function as maternal effector T lymphocytes, or targets or bystanders. We currently hypothesize that the first hit is due to GvHD interaction by engrafted maternal effector T lymphocytes. Furthermore, we suggest that the secondary effects that are manifested by progressive cirrhosis are caused either by maternal chimeric effector T lymphocytes (e.g., GvHD interaction) or targets (e.g., HvGD interaction). Based on our hypothesis, mixed lymphocyte reactions between patients and their mothers might shed light on the etiopathogenesis and prognostic indicators.

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

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

Peripheral blood mononuclear cell microchimerism in Turkish female patients with systemic sclerosis

OBJECTIVES

To investigate microchimerism (Mc) in peripheral blood mononuclear cells (PBMC) taken from female patients with systemic sclerosis (SSc) and healthy females. We also intended to research the association between Mc and the clinical subsets.

METHODS

This study included 50 females with lcSSc, 30 females with dcSSc and 40 healthy females. The Y-chromosome sequences were studied by RT-PCR in DNA obtained from PBMC.

RESULTS

Mc was found in 28 (35 %) patients and 8 (20 %) healthy controls as well as in 6 dcSSc patients with son(s) (27.3 %), 10 lcSSc patients with son(s) (32.3 %) and 7 control females with son(s) (18.9 %) (p > 0.05). Mc was detected in 6 nulliparous lcSSc patients (31.6 %) and in 1 nulliparous dcSSc patient (11.1 %) (p > 0.05). The mean time elapsed between the first pregnancy and the diagnosis of SSc was 3.5 (0-49) years in the Mc-positive patients and 14 (0-55) years in the negative patients (p = 0.020). The mean modified Rodnan skin scores (ModRSS) of the patients with and without Mc was 10 (4-24) and 13 (4-26), respectively (p = 0.038). The relationship between Mc and the system involvement, disease severity, autoantibody profile, number of children and age of children was not found.

CONCLUSIONS

Various etiological factors rather than just one play a role in the development of scleroderma. Mc is thought to be one factor that shortens the elapsed time of disease development in SSc. Mc is inversely related to the ModRSS, and no association was detected between Mc and autoantibodies or the clinical subsets.

Pregnancy and perinatal outcomes among women with multiple sclerosis: a retrospective case-controlled study in South Hungary

OBJECTIVE

The aim of this study was to investigate the connections between multiple sclerosis (MS) and fertility, pregnancy.

METHODS

The case histories and pregnancy complications in a sample of 65 treatment-naive pregnant women with MS in the period 1998-2012 were compared with an age-matched case-controlled analysis. Comparisons were made between primigravidas and multigravidas subjects.

RESULTS

Our results revealed a higher rate of miscarriage (18.46%) in the first trimester in women with MS, and intrauterine death (7.69%) in the third trimester, as compared with women without MS (p < 0.001 and p = 0.035).

CONCLUSIONS

These findings suggest that, the risk of miscarriages and intrauterine death may be disease-related not drug-related feature. Further studies are needed to determine to possible associated factors of miscarriages.

Fetal microchimeric cells in blood and thyroid glands of women with an autoimmune thyroid disease

Persistence of fetal microchimeric cells may result in the development of autoimmune thyroid diseases (AITD) such as Hashimoto thyroiditis (HT) or Graves disease (GD). In women, HT and GD show an increased incidence in the years following parturition. Although fetal cells have already been shown to be more common in the thyroid glands of patients with an AITD compared with controls, these cells haven’t been described in blood of these patients. Our study detected fetal cells in blood of all patients with an AITD. Moreover, fetal cells were immune cells potentially capable of initiating a graft vs. host reaction and suggest a potential role of these cells in the pathogenesis of AITD. Our study indicates the value and need for further research in this field.

Fetal microchimeric cells in autoimmune thyroid diseases: harmful, beneficial or innocent for the thyroid gland?

Autoimmune thyroid diseases (AITD) show a female predominance, with an increased incidence in the years following parturition. Fetal microchimerism has been suggested to play a role in the pathogenesis of AITD. However, only the presence of fetal microchimeric cells in blood and in the thyroid gland of these patients has been proven, but not an actual active role in AITD. Is fetal microchimerism harmful for the thyroid gland by initiating a Graft versus Host reaction (GvHR) or being the target of a Host versus Graft reaction (HvGR)? Is fetal microchimerism beneficial for the thyroid gland by being a part of tissue repair or are fetal cells just innocent bystanders in the process of autoimmunity? This review explores every hypothesis concerning the role of fetal microchimerism in AITD.

Transfusion-associated microchimerism: the hybrid within

Microchimerism, the coexistence of genetically disparate populations of cells in a receptive host, is well described in both clinical and physiological settings, including transplantation and pregnancy. Microchimerism can also occur after allogeneic blood transfusion in traumatically injured patients, where donor cells have been observed decades after transfusion. To date, transfusion-associated microchimerism (TA-MC) appears confined to this clinical subset, most likely due to the immune perturbations that occur after severe trauma that allow foreign donor cells to survive. Transfusion-associated microchimerism appears to be unaffected by leukoreduction and has been documented after transfusion with an array of blood products. The only significant predictor of TA-MC to date is the age of red cells, with fresher units associated with higher risk. Thus far, no adverse clinical effect has been observed in limited studies of TA-MC. There are, however, hypothesized links to transfusion-associated graft vs host disease that may be unrecognized and consequently underreported. Microchimerism in other settings has gained increasing attention owing to a plausible link to autoimmune diseases, as well as its diagnostic and therapeutic potential vis-a-vis antenatal testing and adoptive immunotherapy, respectively. Furthermore, microchimerism provides a tool to further our understanding of immune tolerance and regulation.

Laminin-1 (LM-111) in preeclampsia and systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of antibodies. SLE has been associated with placental pathology, a finding that is also the determinant in preeclampsia (PE). Genetic evidence and serologic reports suggest laminin-1 (LM-111) as an immunogenic molecule and its polymorphic gene as a candidate gene for both disorders.

OBJECTIVE

To evaluate the association between LAMA1 (rs543355) and LAMC1 (rs20563) polymorphisms and the presence of SLE and PE as well as to determine serum levels of anti-LM-111 autoantibodies in the PE group.

METHODS

Group A: 169 women with PE and 172 healthy pregnant women. Group B: 204 women with SLE and 204 healthy women. Anti-LM-111 for group A was measured by ELISA and the genotyping was done by using a PCR system.

RESULTS

Group A: Levels of anti-LM-111 was similar in women with PE and the control group (p = 0.3). The allelic frequencies and genotypes did not show statistically significant differences for LAMA1 and LAMC1 polymorphisms. Group B: Significant differences between SLE patients and controls for rs543355 polymorphism were not observed. Nevertheless, LAMC1 rs20563 A-allele provided protection against the development of SLE (OR 0.73, 95%CI 0.55-0.96).

CONCLUSIONS

Serum levels of anti-LM-111 at the third trimester of gestation do not seem to have any direct relationship with the presence of PE, and the SNPs evaluated are not associated with the risk of developing this disorder. LAMC1 polymorphism could be a protective factor for SLE.

Chimerism in women with end stage renal diseases: Who's who?

Many sources of foreign or semi foreign cells, known as microchimerism (Mc), can be found in healthy individuals. We have recently shown in women with end stage renal disease (ESRD) that Mc frequencies and levels are exacerbated prior to kidney transplantation. Is Mc arising from pregnancy a protective factor for renal diseases explaining lower incidence in women? Is Mc helpful in slowing down disease progression? However, natural Mc is not the only actor as post blood transfusion Mc is also found at high levels in women with ESRD. The difficulty is therefore to distinguish the different types of Mc and this is made even more complicated when the recipient receives a potentially chimeric organ. What part does each source of chimerism play in disease and transplant fate, and can one decipher each role knowing that one chimerism may hide another?

A mouse model for fetal maternal stem cell transfer during ischemic cardiac injury

Fetal cells enter the maternal circulation during pregnancies and can persist in blood and tissues for decades, creating a state of physiologic microchimerism. Microchimerism refers to acquisition of cells from another individual and can be due to bidirectional cell traffic between mother and fetus during pregnancy. Peripartum cardiomyopathy, a rare cardiac disorder associated with high mortality rates has the highest recovery rate amongst all etiologies of heart failure although the reason is unknown. Collectively, these observations led us to hypothesize that fetal cells enter the maternal circulation and may be recruited to the sites of myocardial disease or injury. The ability to genetically modify mice makes them an ideal system for studying the phenomenon of microchimerism in cardiac disease. Described here is a mouse model for ischemic cardiac injury during pregnancy designed to study microchimerism. Wild-type virgin female mice mated with eGFP male mice underwent ligation of the left anterior descending artery to induce a myocardial infarction at gestation day 12. We demonstrate the selective homing of eGFP cells to the site of cardiac injury without such homing to noninjured tissues suggesting the presence of precise signals sensed by fetal cells enabling them to target diseased myocardium specifically.

Maternal microchimerism in muscle biopsies from children with juvenile dermatomyositis

OBJECTIVE

Recent advances in molecular techniques have revealed that there is bi-directional transfer of cells between mother and child during pregnancy, and the presence of a mother's cells in her child has been termed maternal microchimerism (MMc). There is the potential for maternal cells to provoke inappropriate immune responses in the child, which could be a factor in autoimmunity including JDM. The aim of this study was to determine whether maternal (female) cells could be detected in frozen muscle sections from seven males (age range 3-13 years) with JDM participating in the Juvenile Dermatomyositis National (U.K. and Ireland) Cohort Biomarker Study and Repository for Idiopathic Inflammatory Myopathies and sections of muscle controls (age range 2-12 years).

METHODS

At least 1000 cells from each section underwent FISH and confocal imaging through each nucleus. Concomitant IF for CD45 was used to determine whether MMc in muscle were lymphocytes. A non-parametric Mann-Whitney U-test was used to detect statistical differences.

RESULTS

The frequency of MMc was higher in JDM muscle (0.42-1.14%) than in controls (0.08-0.42%) P = 0.01. No CD45+ MMc were observed.

CONCLUSION

These data confirm an increased frequency of MMc in JDM. More detailed characterization of MMc is required, particularly using phenotypic markers, to explain the role of these cells in JDM.

The otherness of self: microchimerism in health and disease

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

Microchimerism in graves' disease

Microchimerism is the presence of cells from one individual in another genetically distinct individual. Pregnancy is the main cause of natural microchimerism through transplacental bidirectional cell trafficking between mother and fetus. 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. It has been more than ten years now since the demonstration of the presence of a significant high number of fetal microchimeric cells residing in thyroid glands from operated patients with Graves' disease. This intrathyroidal fetal microchimerism is an attractive candidate mechanism for the modulation of Graves' disease in pregnancy and the postpartum period.

A role for microchimerism in obesity and evolution?

Cells exchanged between individuals, such as those passing the placenta from the mother to the child and vice versa, may survive in the fetal or maternal circulation and tissues for decades and result in microchimerism. Microchimeric cells may play a role in tissue repair, but they have also been implicated as inducers of chronic inflammation, leading to autoimmunity or even cancer. Here we propose that microchimerism may play a more fundamental role in health and evolution by setting a limit to genomic variability within populations. This means that microchimerism allows immune recognition of genomic differences between donor and host which may, depending on the level of variability, cause chronic inflammation. Since chronic inflammation has been experimentally linked to metabolic syndrome, we propose that genomic variability could affect the individual's weight. Thus, metabolic syndrome, which is a growing health problem, may not only result from our lifestyle, but in part be caused by global migration and the increasingly diverse origin of the present human population. Moreover, since in nature weight gain is associated with an increased risk of predation, we discuss the possibility that immunological incompatibility normally promotes the continuous development of new species.

Indirect evidence that maternal microchimerism in cord blood mediates a graft-versus-leukemia effect in cord blood transplantation

During pregnancy women can develop B- and T-cell immunity against the inherited paternal antigens (IPAs) of the fetus, such as HLA, peptides of minor histocompatibilty antigens, and possibly onco-fetal antigens. The biological and pathological role of these pregnancy-induced immunological events is only understood in part. However, anti-IPA immunity in the mother persists for many decades after delivery and may reduce relapse in offspring with leukemia after HLA-haploidentical transplantation of maternal hematopoietic stem cells (HSC). We hypothesized that maternal anti-IPA immune elements cross the placenta and might confer a potent graft-versus-leukemia effect when cord blood (CB) is used in unrelated HSC transplantation. In a retrospective study of single-unit CB recipients with all grafts provided by the New York Blood Center, we show that patients with acute myeloid or lymphoblastic leukemia (n = 845) who shared one or more HLA-A, -B, or -DRB1 antigens with their CB donor's IPAs had a significant decrease in leukemic relapse posttransplantation [hazard ratio (HR) = 0.38, P < 0.001] compared with those that did not. Remarkably, relapse reduction in patients receiving CB with one HLA mismatch (HR = 0.15, P < 0.001) was not associated with an increased risk of severe acute graft-versus-host disease (HR = 1.43, P = 0.730). Our findings may explain the unexpected low relapse rate after CB transplantation, open new avenues in the study of leukemic relapse after HSC transplantation (possibly of malignancies in general), and have practical implications for CB unit selection.

Fetal microchimeric cells in blood of women with an autoimmune thyroid disease

Context

Hashimoto's thyroiditis (HT) and Graves' disease (GD), two autoimmune thyroid diseases (AITD), occur more frequently in women than in men and show an increased incidence in the years following parturition. Persisting fetal cells could play a role in the development of these diseases.

Objective

Aim of this study was to detect and characterize fetal cells in blood of postpartum women with and without an AITD.

Participants

Eleven patients with an AITD and ten healthy volunteers, all given birth to a son maximum 5 years before analysis, and three women who never had been pregnant, were included. None of them had any other disease of the thyroid which could interfere with the results obtained.

Methods

Fluorescence in situ hybridization (FISH) and repeated FISH were used to count the number of male fetal cells. Furthermore, the fetal cells were further characterized.

Results

In patients with HT, 7 to 11 fetal cells per 1.000.000 maternal cells were detected, compared to 14 to 29 fetal cells in patients with GD (p = 0,0061). In patients with HT, mainly fetal CD8⁺ T cells were found, while in patients with GD, fetal B and CD4⁺ T cells were detected. In healthy volunteers with son, 0 to 5 fetal cells were observed, which was significantly less than the number observed in patients (p<0,05). In women who never had been pregnant, no male cells were detected.

Conclusion

This study shows a clear association between fetal microchimeric cells and autoimmune thyroid diseases.

Review: The feto-placental unit, pregnancy pathology and impact on long term maternal health

Pregnancy induces a number of alterations to maternal physiology to accommodate the increased demands made by the developing fetus and placenta. These alterations appear at least in part to be driven by products derived from the feto-placental unit, including microchimeric cells, as well as placental exosomes and microparticles, inducing changes to maternal physiology both during pregnancy and beyond. Further, increasing evidence suggests that some of these alterations are dependent on the sex of the fetus. Pre-eclampsia and asthma represent two common pregnancy complications that have provided valuable insight into how the feto-placental unit influences maternal physiology in a sex-specific manner. Pregnancy-induced alterations in maternal physiology may expose pre-existing subclinical pathologies and provide insight into future maternal health and disease. While most pregnancy-induced alterations to the maternal system are reversed following delivery, some can persist after parturition leading to cardiovascular, metabolic and autoimmune disease and increased risk of early mortality.

Increased incidence of pregnancy complications in women who later develop scleroderma: a case control study

Introduction

Studies have shown that fetal progenitor cells persist in maternal blood or bone marrow for more than 30 years after delivery. Increased trafficking of fetal cells occurs during pregnancy complications, such as hypertension, preeclampsia, miscarriage and intra-uterine growth restriction (IUGR). Women with these pregnancy complications are significantly more often HLA-class II compatible with their spouses. Women who later develop scleroderma also give birth to an HLA-class II child more often. From these prior studies we hypothesized that preeclampsia and other pregnancy complications could be associated with increased levels of fetal cell trafficking, and later be involved in the development of scleroderma.

Methods

This study was a retrospective multi-centre matched case-control study. One-hundred-and-three women with systemic sclerosis (SSc) and 103 women with no history of SSc or other autoimmune disease were given a questionnaire regarding complications during pregnancy, such as hypertension, intra-uterine growth restriction (IUGR) and miscarriage. Conditional logistic regression analysis was used to assess associations.

Results

We found a statistically significantly increased incidence of having had a pregnancy history of hypertension or a fetus with IUGR in women who subsequently developed SSc compared to healthy controls. We found an odds ratio of 2.6 (95% confidence interval (CI): 1.1 to 4.6) for hypertensive complications during pregnancy and an odds ratio of 3.9 (95% CI: 1.2 to 12.3) for intra-uterine growth restriction for women with SSc compared to healthy controls.

Conclusions

This is the first study to show an association between hypertensive complications during pregnancy or IUGR and the development of SSc at a later age. We speculate that the pregnancy abnormalities may have resulted in increased fetomaternal trafficking, which may have played a role in the increased incidence of SSc. Further studies are indicated to examine this putative relationship.

Gimme shelter: the immune system during pregnancy

Antigen-presenting molecules vary between individuals of the same species, making it more difficult for pathogens to evade immune recognition and spread through the whole population. As a result of this genetic diversity, transplants between individuals are recognized as foreign and are rejected. This alloreactivity turns placental viviparity into a major immunological challenge. The maternal immune system has to balance the opposing needs of maintaining robust immune reactivity to protect both mother and fetus from invading pathogens, while at the same time tolerating highly immunogenic paternal alloantigens in order to sustain fetal integrity. Regulatory T cells are responsible for the establishment of tolerance by modulating the immune response, and uterine natural killer cells direct placentation by controlling trophoblast invasion. A variety of other cell types, including decidual stromal cells, dendritic cells, and immunomodulatory multipotent mesenchymal stromal cells, are found at the fetal-maternal interface. These cells conspire to establish a suitable environment for fetal development without compromising systemic immunity. Defects in any of these components can lead to gestational failure despite successful fertilization.

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

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

Pregnancy and the risk of autoimmune disease

Autoimmune diseases (AID) predominantly affect women of reproductive age. While basic molecular studies have implicated persisting fetal cells in the mother in some AID, supportive epidemiological evidence is limited. We investigated the effect of vaginal delivery, caesarean section (CS) and induced abortion on the risk of subsequent maternal AID. Using the Danish Civil Registration System (CRS) we identified women who were born between 1960 and1992. We performed data linkage between the CRS other Danish national registers to identify women who had a pregnancy and those who developed AID. Women were categorised into 4 groups; nulligravida (control group), women who had 1st child by vaginal delivery, whose 1st delivery was by CS and who had abortions. Log-linear Poisson regression with person-years was used for data analysis adjusting for several potential confounders. There were 1,035,639 women aged >14 years and 25,570 developed AID: 43.4% nulligravida, 44.3% had their first pregnancy delivered vaginally, 7.6% CS and 4.1% abortions. The risk of AID was significantly higher in the 1st year after vaginal delivery (RR = 1.1[1.0, 1.2]) and CS (RR = 1.3[1.1, 1.5]) but significantly lower in the 1st year following abortion (RR = 0.7[0.6, 0.9]). These results suggest an association between pregnancy and the risk of subsequent maternal AID. Increased risks of AID after CS may be explained by amplified fetal cell traffic at delivery, while decreased risks after abortion may be due to the transfer of more primitive fetal stem cells. The increased risk of AID in the first year after delivery may also be related to greater testing during pregnancy.

Pregnancy-associated progenitor cells: an under-recognized potential source of stem cells in maternal lung

Novel therapies are needed for the treatment of acute and chronic lung diseases, many of which are incurable. The use of exogenous stem cells has shown promise in both animal models and clinical trials. However, to date, the stem cell literature has under-recognized naturally acquired pregnancy-associated progenitor cells (PAPCs). These cells are found at sites of injury or disease in female tissues. They persist for decades after parturition in maternal blood and organs, with the largest number being found in the maternal lungs. Their presence there may be one explanation for the sex differences observed in the prevalence and prognosis of some lung diseases. Although the clinical significance of these cells is as yet unknown, the literature suggests that some of the PAPCs are stem cells or have stem cell-like properties. PAPCs harvested from the blood or organs of parous women could potentially be used as an alternate source of cells with regenerative properties for the woman herself or her children. Because PAPCs preferentially traffic to the maternal lung they may play a significant role in recovery or protection from lung disease. In this review article, we discuss ongoing research investigating the administration of both adult and placenta-derived stem cells to treat lung disease, and how PAPCs may also play an important future therapeutic role.

Specific maternal microchimeric T cells targeting fetal antigens in β cells predispose to auto-immune diabetes in the child

OBJECTIVE

During pregnancy there is an exchange of cells between the fetus and the mother including T lymphocytes that can persist after delivery. Previous studies have described an increased numbers of maternal cells in children with juvenile diabetes as compared to their unaffected siblings. Our objective was to assess the possibility for these chimeric T cells to trigger an anti-beta cell response.

RESEARCH DESIGN AND METHODS

We mated OT2 transgenic female mice having T cells specifically targeting ovalbumin to RIP-OVA males expressing ovalbumin in pancreatic β cells. This allowed us to examine RIP-OVA progeny from OT2 mothers to assess the consequences of maternal T cells acquired during gestation or lactation. We quantitatively analyzed the pancreas of RIP-OVA mice from OT2 mothers for islet infiltration and compared them to RIP-OVA mice not exposed to OT2 mothers or to wild-type mice from OT2 mothers.

RESULTS

RIP-OVA mice from OT2 mothers had significantly more peri-insulitis (p=0.0083) compared to wild-type littermates. Similarly RIP-OVA mice from OT2 mothers had more peri-insulitis as compared to RIP-OVA mice from RIP-OVA mothers (p=0.0073). Presence and specific anti-ovalbumin activity of maternal OT2 cells in the offsprings' peripheral lymphoid tissues was found in a separate group of mice. In animals presenting islet inflammation, CD3+ infiltrating cells in the pancreas were however derived from the offspring and not from OT2 mothers. In accordance, OT2 and RIP-OVA double transgenic mice with high levels of auto-reactive T cells had more peri-insulitis and sometimes intense insulitis when they were from OT2 mothers as compared to RIP-OVA mothers (p=0.046).

CONCLUSIONS

In highly specific fetal/maternal combinations, maternal T cells with activity against the offspring pancreatic beta cells, presumably chimeric in fetal organs, initiate islet inflammation and may therefore predispose to auto-immune diabetes.

[Fetal microchimerism: self and non-self, finally who are we?]

For a long time, the conventional view was that the fetus and maternal vascular system are kept separate. In fact there is a two-way traffic of immune cells through the placenta and the transplacental passage of cells is in fact the norm. The fetal cells can persist in a wide range of woman's tissue following a pregnancy or an abortion and she becomes a chimera. Fetal cells have been found in the maternal circulation and they were shown to persist for almost three decades in humans, thus demonstrating long-term engraftment and survival capabilities. Microchimerism is a subject of much interest for a number of reasons. Studies of fetal microchimerism during pregnancy may offer explanations for complications of pregnancy, such as preeclampsia, as well as insights into the pathogenesis of autoimmune disease which usually ameliorates during pregnancy. The impact that the persistence of allogenic cells of fetal origin and the maternal immunological response to them has on the mother's health and whether it is detrimental or beneficial to the mother is still not clear. Although microchimerism has been implicated in some autoimmune diseases, fetal microchimerism is common in healthy individuals. On the beneficial side, it has been proposed that genetically disparate fetal microchimerism provides protection against some cancers, that fetal microchimerism can afford the mother new alleles of protection to some diseases she has not, that fetal microchimerism can enlarge the immunological repertoire of the mother improving her defense against aggressor. Fetal cells are often present at sites of maternal injury and may have an active role in the repair of maternal tissues.