Fetal stem cell microchimerism: natural-born healers or killers?

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.

Fetomaternal microchimerism and genetic diagnosis: On the origins of fetal cells and cell-free fetal DNA in the pregnant woman

During pregnancy several types of fetal cells and fetal stem cells, including pregnancy-associated progenitor cells (PAPCs), traffic into the maternal circulation. Whereas they also migrate to various maternal organs and adopt the phenotype of the target tissues to contribute to regenerative processes, fetal cells also play a role in the pathogenesis of maternal diseases. In addition, cell-free fetal DNA (cffDNA) is detectable in the plasma of pregnant women. Together they constitute the well-known phenomenon of fetomaternal microchimerism, which inspired the concept of non-invasive prenatal testing (NIPT) using maternal blood. An in-depth knowledge concerning the origins of these fetal cells and cffDNA allows a more comprehensive understanding of the biological relevance of fetomaternal microchimerism and has implications for the ongoing expansion of resultant clinical applications.

Male origin microchimerism and ovarian cancer

BACKGROUND

Reduced risk of ovarian cancer is commonly ascribed to reduced exposure to endogenous hormones during pregnancy, using oral contraceptives or not using hormone replacement therapy. However, exposure to hormones alone account for less than half of all cases. Many women carry small amounts of male cells-known as male origin microchimerism-in their circulation and remarkable impacts of these cells on women's health are being published. Here, we pursue the possibility that male origin microchimerism has a role in reducing ovarian cancer risk.

METHODS

We conducted a prospective case-cohort study using blood samples and questionnaire data from 700 women participating in the Danish Diet, Cancer, and Health cohort. Blood samples were analysed for Y chromosome presence as a marker of male microchimerism. We evaluated the association between male microchimerism and ovarian cancer, using weighted Cox regression models reporting hazard ratios (HRs) and corresponding 95% confidence intervals (CIs).

RESULTS

Male microchimerism was detected in 46% of cases and 65.9% of controls. Women testing positive for male microchimerism had a reduced hazard rate of ovarian cancer compared with women testing negative (HR = 0.44, 95% CI: 0.29-0.68). We found no evidence of interaction with measures of hormonal exposures (P = 0.50).

CONCLUSIONS

For the first time we report that women who test positive for male microchimerism in their circulation have reduced rates of ovarian cancer compared with women who test negative. Although the underlying mechanisms are presently unknown, we believe male microchimerism is potent in preventing ovarian cancer.

Forever Connected: The Lifelong Biological Consequences of Fetomaternal and Maternofetal Microchimerism

BACKGROUND

Originally studied as a mechanism to understand eclampsia-related deaths during pregnancy, fetal cells in maternal blood have more recently garnered attention as a noninvasive source of fetal material for prenatal testing. In the 21st century, however, intact fetal cells have been largely supplanted by circulating cell-free placental DNA for aneuploidy screening. Instead, interest has pivoted to the ways in which fetal cells influence maternal biology. In parallel, an increasing appreciation of the consequences of maternal cells in the developing fetus has occurred.

CONTENT

In this review, we highlight the potential clinical applications and functional consequences of the bidirectional trafficking of intact cells between a pregnant woman and her fetus. Fetal cells play a potential role in the pathogenesis of maternal disease and tissue repair. Maternal cells play an essential role in educating the fetal immune system and as a factor in transplant acceptance. Naturally occurring maternal microchimerism is also being explored as a source of hematopoietic stem cells for transplant in fetal hematopoietic disorders.

SUMMARY

Future investigations in humans need to include complete pregnancy histories to understand maternal health and transplant success or failure. Animal models are useful to understand the mechanisms underlying fetal wound healing and/or repair associated with maternal injury and inflammation. The lifelong consequences of the exchange of cells between a mother and her child are profound and have many applications in development, health, and disease. This intricate exchange of genetically foreign cells creates a permanent connection that contributes to the survival of both individuals.

Incognito: Are Microchimeric Fetal Stem Cells that Cross Placental Barrier Real Emissaries of Peace?

Chimerism occurs naturaly throughout gestation and can also occur as a consequence of transfusion and transplantation therapy. It consists of the acquisition and long-term persistence of a genetically distinct population of allogenic cells inside another organism. Previous reports have suggested that feto-maternal microchimerism could exert a beneficial effect on the treatment of hematological and solid tumors in patients treated by PBSCT. In this review we report the mechanism of transplacental fetal stem cell trafficking during pregnancy and the effect of their long-term persistence on autoimmunity, GVHD, PBSCT, cancer and stem cell treatment.

Heterogeneity of Stem Cells: A Brief Overview

Stem cells possess the extraordinary capacity of self-renewal and differentiation to various cell types, thus to form original tissues and organs. Stem cell heterogeneity including genetic and nongenetic mechanisms refers to biological differences amongst normal and stem cells originated within the same tissue. Cell differentiation hierarchy and stochasticity in gene expression and signaling pathways may result in phenotypic differences of stem cells. The maintenance of stemness and activation of differentiation potential are fundamentally orchestrated by microenvironmental stem cell niche-related cellular and humoral signals.

Characterization of Mesenchymal-Fibroblast Cells Using the Col1a2 Promoter/Enhancer

Excessive deposition of extracellular matrix (ECM) is a common hallmark of fibrotic diseases in various organs. Chiefly among this ECM are collagen types I and III, secreted by local fibroblasts, and other mesenchymal cells recruited for repair purposes. In the last two decades, the search for a fibroblast-specific promoter/enhancer has intensified in order to control the regulation of ECM in these cells and limit the scarring of the fibrotic process. In our previous work, we characterized an enhancer region 17 kb upstream of the Col1a2 gene transcription start site. This enhancer in transgenic mice is expressed mainly in mesenchymal cells during development and in adults upon injury. When driving transgenes such as beta-galactosidase or luciferase, this construct acts as an informative reporter of collagen transcription and is predictive of collagen type I deposition. In this chapter, we provide detailed protocols for identifying similar enhancers and using the sequence to generate a construct for transfection and producing transgenic animals. We also provided information on the use of luminescence in transgenic mice, tissue processing, as well as using cre/lox system to obtain conditional gain and loss of function in mice.

A molecular classification of human mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are widely used for the study of mesenchymal tissue repair, and increasingly adopted for cell therapy, despite the lack of consensus on the identity of these cells. In part this is due to the lack of specificity of MSC markers. Distinguishing MSC from other stromal cells such as fibroblasts is particularly difficult using standard analysis of surface proteins, and there is an urgent need for improved classification approaches. Transcriptome profiling is commonly used to describe and compare different cell types; however, efforts to identify specific markers of rare cellular subsets may be confounded by the small sample sizes of most studies. Consequently, it is difficult to derive reproducible, and therefore useful markers. We addressed the question of MSC classification with a large integrative analysis of many public MSC datasets. We derived a sparse classifier (The Rohart MSC test) that accurately distinguished MSC from non-MSC samples with >97% accuracy on an internal training set of 635 samples from 41 studies derived on 10 different microarray platforms. The classifier was validated on an external test set of 1,291 samples from 65 studies derived on 15 different platforms, with >95% accuracy. The genes that contribute to the MSC classifier formed a protein-interaction network that included known MSC markers. Further evidence of the relevance of this new MSC panel came from the high number of Mendelian disorders associated with mutations in more than 65% of the network. These result in mesenchymal defects, particularly impacting on skeletal growth and function. The Rohart MSC test is a simple in silico test that accurately discriminates MSC from fibroblasts, other adult stem/progenitor cell types or differentiated stromal cells. It has been implemented in the www.stemformatics.org resource, to assist researchers wishing to benchmark their own MSC datasets or data from the public domain. The code is available from the CRAN repository and all data used to generate the MSC test is available to download via the Gene Expression Omnibus or the Stemformatics resource.

Fetal endothelial and mesenchymal progenitors from the human term placenta: potency and clinical potential

Since the isolation of fetal stem cell populations from perinatal tissues, such as umbilical cord blood and placenta, interest has been growing in understanding their greater plasticity compared with adult stem cells and exploring their potential in regenerative medicine. The phenomenon of fetal microchimerism (FMC) naturally occurring during pregnancy through the transfer of fetal stem/progenitor cells to maternal blood and tissues has been integral in developing this dogma. Specifically, microchimeric mesenchymal stem cells and endothelial progenitors of fetal origin have now demonstrated a capacity for tissue repair in the maternal host. However, the use of similar fetal stem cells in therapy has been significantly hampered by the availability of clinically relevant cell numbers and/or contamination with cells of maternal origin, particularly when using the chorionic and decidual placenta. In the present prospective review, we highlight the importance of FMC to the field of fetal stem cell biology and issues of maternal contamination from perinatal tissues and discuss specific isolation strategies to overcome these translational obstacles.

Origins of the breast milk-derived cells; an endeavor to find the cell sources

Fresh human breast milk consists of a heterogeneous population of cells that may offer a non-invasive source of cells for therapeutic proposes. The aims of this study were to characterize the breast milk-derived cells cultured in vitro. To do this, the cells from human breast milk were cultured and the expression of the CD markers along with the embryonic stem cell markers, endothelial and luminal mammary epithelial cell markers was evaluated by flow cytometry and immunofluorescence. The presence of fetal microchimerism among the isolated cells was also determined by the presence of SRY gene. They were also differentiated into adipocytes and osteoblasts. The results showed that a remarkable number of cells expressed the mesenchymal stem cell (MSC) markers such as CD90, CD44, CD271, and CD146. A subpopulation of the human breast milk-derived cells (HBMDC) also expressed the embryonic stem cell markers, such as TRA 60-1, Oct4, Nanog and Sox2 but not SSEA1 or 4. The frequencies of the cells which expressed the endothelial, hematopoietic cell markers were negligible. SRY gene was not detected in the breast milk isolated cells. A subpopulation of the cells also expressed cytokeratin 18, the marker of luminal mammary epithelial cells. These cells showed the capability to differentiate into adipocytes and osteoblasts. In conclusion, these finding highlighted the presence of cells with various sources in the breast milk. Different stem cells including MSCs or embryonic stem cell-like cell along with the exfoliated cells from luminal epithelial cells were found among the isolated cells. The breast milk-derived stem cells might be considered as a non-invasive source of the stem cells for therapeutic purpose.

Assessment of fetal cell chimerism in transgenic pig lines generated by Sleeping beauty transposition

Human cells migrate between mother and fetus during pregnancy and persist in the respective host for long-term after birth. Fetal microchimerism occurs also in twins sharing a common placenta or chorion. Whether microchimerism occurs in multiparous mammals such as the domestic pig, where fetuses have separate placentas and chorions, is not well understood. Here, we assessed cell chimerism in litters of wild-type sows inseminated with semen of transposon transgenic boars. Segregation of three independent monomeric transposons ensured an excess of transgenic over non-transgenic offspring in every litter. Transgenic siblings (n = 35) showed robust ubiquitous expression of the reporter transposon encoding a fluorescent protein, and provided an unique resource to assess a potential cell trafficking to non-transgenic littermates (n = 7) or mothers (n = 4). Sensitive flow cytometry, fluorescence microscopy, and real-time PCR provided no evidence for microchimerism in porcine littermates, or piglets and their mothers in both blood and solid organs. These data indicate that the epitheliochorial structure of the porcine placenta effectively prevents cellular exchange during gestation.

The occurrence of fetal microchimeric cells in endometrial tissues is a very common phenomenon in benign uterine disorders, and the lower prevalence of fetal microchimerism is associated with better uterine cancer prognoses

This is the first study carried out to describe the role of fetal microchimerism (FM) in the pathogenesis of uterine cancer. The prevalence and concentration of male fetal microchimeric cells (FMCs) were examined in endometrial tissues in relation to subtypes of uterine cancer, and the histological grade and stage of the tumor. FM occurrence was analyzed in relation to risk factors, including hypertension, obesity, type 2 diabetes, dyslipidemia, age at cancer diagnosis, and patient pregnancy history. The prevalence and concentration of FMCs were examined in endometrial tissues using real-time polymerase chain reaction, SRY and β-globin sequences as markers for male fetal FMCs and total DNA. The studied group involved 47 type 1 endometrial cancers, 28 type 2 endometrial cancers, and 41 benign uterine diseases. While the prevalence of FM was decreased only in type 1 endometrial cancer, compared with benign uterine disorders (38.3% vs.70.7%; odds ratio [OR]=0.257, 95% confidence interval [CI]: 0.105 to 0.628, p=0.003), FMC concentrations did not differ within examined groups. The lower FM prevalence was detected in low-grade (grade 1 and grade 2) endometrioid cancer (38.3% vs. 70.7%, OR=0.256, 95% CI: 0.105 to 0.627, p=0.003) and in FIGO 1 tumors (40.7% vs. 70.7%, OR=0.285, 95% CI: 0.120 to 0.675, p=0.004). No correlation between FM prevalence or FMC concentrations and risk factors was demonstrated. A lower prevalence of male FM seemed to be associated with better prognoses in uterine cancer based on tumor subtype, histological grade, and stage of the tumor.

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.

Y-chromosome DNA is present in the blood of female dogs suggesting the presence of fetal microchimerism

Fetal microchimerism has been suggested to play contradictory roles in women’s health, with factors including age of the recipient, time elapsed since microchimerism occurred, and microchimeric cell type modulating disease. Both beneficial and harmful effects have been identified in wound healing and tissue regeneration, immune mediated disease, and cancer. This area of research is relatively new, and hindered by the time course from occurrence of fetal microchimerism to the multi-factorial development of disease. Dogs represent an excellent model for study of fetal microchimerism, as they share our environment, have a naturally condensed lifespan, and spontaneously develop immune-mediated diseases and cancers similar to their human counterparts. However, fetal microchimerism has not been described in dogs. These experiments sought preliminary evidence that dogs develop fetal microchimerism following pregnancy. We hypothesized that Y chromosomal DNA would be detected in the peripheral blood mononuclear cells of female dogs collected within two months of parturition. We further hypothesized that Y chromosomal DNA would be detected in banked whole blood DNA samples from parous female Golden Retrievers with at least one male puppy in a prior litter. Amplification of DNA extracted from five female Golden Retrievers that had whelped within the two months prior to collection revealed strong positive bands for the Y chromosome. Of banked, parous samples, 36% yielded positive bands for the Y chromosome. This is the first report of persistent Y chromosomal DNA in post-partum female dogs and these results suggest that fetal microchimerism occurs in the canine species. Evaluation of the contributions of fetal microchimeric cells to disease processes in dogs as a model for human disease is warranted.

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.

High male chimerism in the female breast shows quantitative links with cancer

Clinical observations suggest that pregnancy provides protection against cancer. The mechanisms involved, however, remain unclear. Fetal cells are known to enter the mother's circulation during pregnancy and establish microchimerism. We investigated if pregnancy-related embryonic/fetal stem cell integration plays a role in breast cancer. A high-sensitivity Y-chromosome assay was developed to trace male allogeneic cells (from male fetus) in females. Fixed-embedded samples (n = 206) from both normal and breast cancer patients were screened for microchimerism. The results were combined with matching clinicopathological and histological parameters and processed statistically. The results show that in our samples (182 informative) more than half of healthy women (56%) carried male cells in their breast tissue for decades (n = 68), while only one out of five in the cancer sample pool (21%) (n = 114) (odds ratio = 4.75, CI at 95% 2.34-9.69; p = 0.0001). The data support the notion that a biological link may exist between chimerism and tissue-integrity. The correlation, however, is non-linear, since male microchimerism in excess ("hyperchimerism") is also involved in cancer. The data suggest a link between hyperchimerism and HER2-type cancers, while decreased chimerism ("hypochimerism") associates with ER/PR-positive (luminal-type) breast cancers. Chimerism levels that correlate with protection appear to be non-random and share densities with the mammary progenitor components of the stem cell lineage in the breast. The results suggest that protection may involve stem/progenitor level interactions and implicate novel quantitative mechanisms in chimerism biology.

Amniotic fluid stem cells and fetal cell microchimerism

Fetal cells (and cell-free, fetal DNA used for non-invasive prenatal diagnosis) are known to exist in the circulation of pregnant women. These cells exhibit stem cell properties when they differentiate at the site of injured maternal tissue, but the origin of these fetal, natural, and probably reparative cells is unknown. During pregnancy, mobilized pluripotent fetal stem cells of yet unidentified in vivo significance float in the amniotic fluid, and we argue that circulating fetal cells and the pluripotent amniotic fluid cells might share a common origin.

Comprehensive analysis of genes expressed by rare microchimeric fetal cells in the maternal mouse lung

During pregnancy, cells from each fetus travel into the maternal circulation and organs, resulting in the development of microchimerism. Identification of the cell types in this microchimeric population would permit better understanding of possible mechanisms by which they affect maternal health. However, comprehensive analysis of fetal cells has been hampered by their rarity. In this study, we sought to overcome this obstacle by combining flow cytometry with multidimensional gene expression microarray analysis of fetal cells isolated from the murine maternal lung during late pregnancy. Fetal cells were collected from the lungs of pregnant female mice. cDNA was amplified and hybridized to gene expression microarrays. The resulting fetal cell core transcriptome was interrogated using multiple methods including Ingenuity Pathway Analysis, the BioGPS gene expression database, principal component analysis, the Eurexpress gene expression atlas, and primary literature. Here we report that small numbers of fetal cells can be flow sorted from the maternal lung, facilitating discovery-driven gene expression analysis. We additionally show that gene expression data can provide functional information about fetal cells. Our results suggest that fetal cells in the murine maternal lung are a mixed population, consisting of trophoblasts, mesenchymal stem cells, and cells of the immune system. Detection of trophoblasts and immune cells in the maternal lung may facilitate future mechanistic studies related to the development of immune tolerance and pregnancy-related complications, such as pre-eclampsia. Furthermore, the presence and persistence of mesenchymal stem cells in maternal organs may have implications for long-term postpartum maternal health.

Identification of circulating fetal cell markers by microarray analysis

OBJECTIVE

Different fetal cell types have been found in the maternal blood during pregnancy in the past, but fetal cells are scarce, and the proportions of the different cell types are unclear. The objective of the present study was to identify specific fetal cell markers from fetal cells found in the maternal blood circulation at the end of the first trimester.

METHOD

Twenty-three fetal cells were isolated from maternal blood by removing the red blood cells by lysis or combining this with removal of large proportions of maternal white blood cells by magnetic-activated cell sorting. Fetal cells identified by XY fluorescence in situ hybridization and confirmed by reverse-color fluorescence in situ hybridization were shot off microscope slides by laser capture microdissection. The expression pattern of a subset of expressed genes was compared between fetal cells and maternal blood cells using stem cell microarray analysis.

RESULTS

Twenty-eight genes were identified as fetal cell marker candidates.

CONCLUSION

Of the 28 fetal marker candidate genes, five coded for proteins, which are located on the outer surface of the cell membrane and not expressed in blood. The protein product of these five genes, MMP14, MCAM, KCNQ4, CLDN6, and F3, may be used as markers for fetal cell enrichment.

Fetal microchimerism in skin wound healing

Skin wound healing is a complex regenerative process involving various cell types. We recently investigated whether fetal microchimeric cells (FMCs) acquired during gestation contribute to maternal wound healing and used fetal microchimerism to investigate the recruitment of distant endothelial progenitor cells in skin wounds. Our study showed that fetal progenitor cells are recruited into maternal wounds and participate in inflammation and angiogenesis. These fetal cells might have beneficial effects in situations of maternal defective healing, and might also modify the adult maternal wound environment toward a scarless fetal-like wound healing.

Male microchimerism at high levels in peripheral blood mononuclear cells from women with end stage renal disease before kidney transplantation

Patients with end stage renal diseases (ESRD) are generally tested for donor chimerism after kidney transplantation for tolerance mechanism purposes. But, to our knowledge, no data are available on natural and/or iatrogenic microchimerism (Mc), deriving from pregnancy and/or blood transfusion, acquired prior to transplantation. In this context, we tested the prevalence of male Mc using a real time PCR assay for DYS14, a Y-chromosome specific sequence, in peripheral blood mononuclear cells (PBMC) from 55 women with ESRD, prior to their first kidney transplantation, and compared them with results from 82 healthy women. Male Mc was also quantified in 5 native kidney biopsies obtained two to four years prior to blood testing and in PBMC from 8 women collected after female kidney transplantation, several years after the initial blood testing. Women with ESRD showed statistically higher frequencies (62%) and quantities (98 genome equivalent cells per million of host cells, gEq/M) of male Mc in their PBMC than healthy women (16% and 0.3 gEq/M, p<0.00001 and p = 0.0005 respectively). Male Mc was increased in women with ESRD whether they had or not a history of male pregnancy and/or of blood transfusion. Three out of five renal biopsies obtained a few years prior to the blood test also contained Mc, but no correlation could be established between earlier Mc in a kidney and later presence in PBMC. Finally, several years after female kidney transplantation, male Mc was totally cleared from PBMC in all women tested but one. This intriguing and striking initial result of natural and iatrogenic male Mc persistence in peripheral blood from women with ESRD raises several hypotheses for the possible role of these cells in renal diseases. Further studies are needed to elucidate mechanisms of recruitment and persistence of Mc in women with ESRD.

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.