Colette Kanellopoulos-Langevin

Tolerance of the fetus by the maternal immune system: role of inflammatory mediators at the feto-maternal interface

The adaptive immune system of placental mammals has evolved to tolerate the fetus. Rejection of the fetus by adaptive immune responses is therefore a rare event, with abortion being caused more frequently by inflammation in the placenta. This review will cover recent aspects of immune privilege and the innate immune system at the feto-maternal interface, citing examples of the role played by microbial infections in fetal demise.

Affinity-Dependent Alterations of Mouse B Cell Development by Noninherited Maternal Antigen

Abstract We have examined the passage of maternal cells into the fetus during the gestation and postpartum in mice. Using enhanced green fluorescent protein (EGFP)-transgenic females, we showed that maternal cells frequently gain access to the fetus, mostly in syngeneic pregnancies, but also in allogeneic and outbred crosses. EGFP-transgenic cells, including B, T, and natural killer cells, can persist until adulthood, primarily in bone marrow and thymus. We then asked whether maternal cells, bearing antigens not inherited by the fetus, influence the development of fetal and neonatal B lymphocytes. We have used the B cell receptor 3-83 µ/δ transgenic mouse model, whose B cells recognize the major histocompatibility complex class I molecules H-2Kk and H-2Kb, with a high or moderate affinity, respectively. The fate of transgenic B cells in animals exposed to noninherited H-2Kk or H-2Kb maternal antigens (NIMA) during gestation and lactation was compared with those of nonexposed controls. In H-2Kk-exposed fetuses, NIMA-specific transgenic B cells are partially deleted during late gestation. Nondeleted cells have downmodulated their B cell receptor. In contrast, in NIMA H-2Kb-exposed neonates, transgenic B cells present an activated phenotype, including proliferation, upregulation of surface CD69, and preferential localization in the T cell zone of splenic follicles. This state of activation is still clearly detectable up to 3 wk of age. Thus, we show that fetal and neonatal B cell development is affected by maternal cells bearing antigens noninherited by the fetus and that this phenomenon is highly dependent on the affinity of the B cell receptor for the NIMA.

Transgenic Major Histocompatibility Complex Class I Antigen Expressed in Mouse Trophoblast Affects Maternal Immature B Cells

Abstract We have produced transgenic mice using the mouse placental lactogen type II promoter to force and restrict the expression of the mouse major histocompatibility complex (MHC) class I molecule, H-2Kb, to the placenta. We show that the transgenic MHC antigen H-2Kb is expressed exclusively in trophoblast giant cells from Day 10.5 until the end of gestation. This expression affects neither the fetal development nor the maternal tolerance to the fetus in histoincompatible mothers. We have used the 3.83 B cell receptor (BcR) transgenic mouse line to follow the fate of H-2Kb-specific maternal B cells in mothers bearing H-2Kb-positive placentas. Our results suggest that transgenic H-2Kb molecules on trophoblast giant cells are recognized by 3.83 BcR-transgenic B cells in the bone marrow of pregnant females. This antigen recognition triggers the deletion of a bone marrow B cell subpopulation, including immature and transitional B cells. Their percentage decreases during the second half of gestation and is down to 8% on Day 17.5, compared to 22% in the (3.83 Tg female × Fvb) control group. This deletion might contribute to the process of maternal tolerance of the conceptus.

Placental Anomalies and Fetal Loss in Mice, After Administration of Doxycycline in Food for Tet-system Activation

During the course of a study aiming to obtain a tetracycline (Tet)-inducible transgene expression restricted to the placenta, we have observed a toxicity of doxycycline (dox) given in the food at doses of 2.5–10 mg/g to pregnant mice from two different inbred strains. During the second half of gestation, dox-fed non-transgenic mice presented placental anomalies and impaired fetal development proportional to the dose of antibiotic. Thus, dox administered in commonly used food doses can have an adverse effect on pregnancy. These observations are important for studies of placental or fetal development using inducible gene promoters.

Prion Protein and Shadoo Are Involved in Overlapping Embryonic Pathways and Trophoblastic Development

The potential requirement of either the Prion or Shadoo protein for early mouse embryogenesis was recently suggested. However, the current data did not allow to precise the developmental process that was affected in the absence of both proteins and that led to the observed early lethal phenotype. In the present study, using various Prnp transgenic mouse lines and lentiviral vectors expressing shRNAs that target the Shadoo-encoding mRNA, we further demonstrate the specific requirement of at least one of these two PrP-related proteins at early developmental stages. Histological analysis reveals developmental defect of the ectoplacental cone and important hemorrhage surrounding the Prnp-knockout-Sprn-knockdown E7.5 embryos. By restricting the RNA interference to the trophoblastic cell lineages, the observed lethal phenotype could be attributed to the sole role of these proteins in this trophectoderm-derived compartment. RNAseq analysis performed on early embryos of various Prnp and Sprn genotypes indicated that the simultaneous down-regulation of these two proteins affects cell-adhesion and inflammatory pathways as well as the expression of ectoplacental-specific genes. Overall, our data provide biological clues in favor of a crucial and complementary embryonic role of the prion protein family in Eutherians and emphasizes the need to further evaluate its implication in normal and pathological human placenta biology.

Heredity—Venturing Beyond Genetics

Abstract Our knowledge of heredity has recently undergone major upheaval. Heredity transmits considerably more than just genetic elements. First, the oocyte is full of maternal cytoplasmic components that subsequently are present in each new cell. Second, maternal cells can pass to the progeny, where they remain active into adult life (microchimerism). Here, we examine the notion that the transmission of characters involves at least two processes in addition to that of mendelian heredity, long considered to be the only hereditary mechanism. These processes all involve epigenetic processes, including the transmission of macromolecules, subcellular organelles, and living cells solely from the mother to her offspring, whether female or male, during pregnancy and lactation. We postulate that cytoplasmic heredity and maternal transmission of cells leading to a long-term state of microchimerism in progeny are two good examples of matrilineal, nonmendelian heredity. A mothers important contribution to the development and health of her progeny seems to possess many uncharted depths.

Transplantation Tolerance to a Single Noninherited MHC Class I Maternal Alloantigen Studied in a TCR-Transgenic Mouse Model

The mechanisms underlying tolerance to noninherited maternal Ags (NIMA) are not fully understood. In this study, we designed a double-transgenic model in which all the offspring’s CD8+ T cells corresponded to a single clone recognizing the Kb MHC class I protein. In contrast, the mother and the father of the offspring differed by the expression of a single Ag, Kb, that served as NIMA. We investigated the influence of NIMA exposure on the offspring thymic T cell selection during ontogeny and on its peripheral T cell response during adulthood. We observed that anti-Kb thymocytes were exposed to NIMA and became activated during fetal life but were not deleted. Strikingly, adult mice exposed to NIMA accepted permanently Kb+ heart allografts despite the presence of normal levels of anti-Kb TCR transgenic T cells. Transplant tolerance was associated with a lack of a proinflammatory alloreactive T cell response and an activation/expansion of T cells producing IL-4 and IL-10. In addition, we observed that tolerance to NIMA Kb was abrogated via depletion of CD4+ but not CD8+ T cells and could be transferred to naive nonexposed mice via adoptive transfer of CD4+CD25high T cell expressing Foxp3 isolated from NIMA mice.

Selective loss of mouse embryos due to the expression of transgenic major histocompatibility class I molecules early in embryogenesis

Among the numerous hypotheses proposed to explain the absence of fetal rejection by the mother in mammals, it has been suggested that regulation of expression of the polymorphic major histocompatibility complex (MHC) at the fetal‐maternal interface plays a major role. In addition to a lack of MHC gene expression in the placenta throughout gestation, the absence of polymorphic MHC molecules on the early embryo, as well as their low level of expression after midgestation, could contribute to this important biologic phenomenon. In order to test this hypothesis, we have produced transgenic mice able to express polymorphic MHC class I molecules early in embryogenesis. We have placed the MHC class Ia gene H‐2Kb under the control of a housekeeping gene promoter, the hydroxy‐methyl‐glutaryl coenzyme A reductase (HMG) gene minimal promoter. This construct has been tested for functionality after transfection into mouse fibroblast L cells. The analysis of three founder transgenic mice and their progeny suggested that fetoplacental units that could express the H‐2Kb heavy chains are unable to survive in utero beyond midgestation. We have shown further that a much higher resorption rate, on days 11 to 13 of embryonic development, is observed among transgenic embryos developing from eggs microinjected at the one‐cell stage with the pHMG‐Kb construct than in control embryos. This lethality is not due to immune phenomena, since it is observed in histocompatible combinations between mother and fetus. These results are discussed in the context of what is currently known about the regulation of MHC expression at the fetal‐maternal interface and in various transgenic mouse models. Mol. Reprod. Dev. 50:35–44, 1998.

CD1d-restricted NKT cells modulate placental and uterine leukocyte populations during chlamydial infection in mice.

Invariant CD1d-restricted natural killer T cells play an important immunoregulatory role and can influence a broad spectrum of immunological responses including against bacterial infections. They are present at the fetal-maternal interface and although it has been reported that experimental systemic iNKT cell activation can induce mouse abortion, their role during pregnancy remain poorly understood. In the present work, using a physiological Chlamydia muridarum infection model, we have shown that, in vaginally infected pregnant mice, C. muridarum is cleared similarly in C57BL/6 wild type (WT) and CD1d(-/-) mice. We have also shown that infected- as well as uninfected-CD1d(-/-) mice have the same litter size as WT counterparts. Thus, CD1d-restricted cells are required neither for the resolution of chlamydial infection of the lower-genital tract, nor for the maintenance of reproductive capacity. However, unexpected differences in T cell populations were observed in uninfected pregnant females, as CD1d(-/-) placentas contained significantly higher percentages of CD4(+) and CD8(+) T cells than WT counterparts. However, infection triggered a significant decrease in the percentages of CD4(+) T cells in CD1d(-/-) mice. In infected WT pregnant mice, the numbers of uterine CD4(+) and CD8(+) T cells, monocytes and granulocytes were greatly increased, changes not observed in infected CD1d(-/-) mice. An increase in the percentage of CD8(+) T cells seems independent of CD1d-restricted cells as it occurred in both WT and CD1d(-/-) mice. Thus, in the steady state, the lack of CD1d-restricted NKT cells affects leukocyte populations only in the placenta. In Chlamydia-infected pregnant mice, the immune response against Chlamydia is dampened in the uterus. Our results suggest that CD1d-restricted NKT cells play a role in the recruitment or homeostasis of leukocyte populations at the maternal-fetal interface in the presence or absence of Chlamydia infection.

A New Marker on Chicken Hematopoietic Cells isDefined by a Monoclonal Antibody Raised Against a V ßChain of the Human TCR

In this paper, we show that a mouse monoclonal antibody, 111-427, specific for the V ß 5.3 chain of the human T-cell receptor (TCR) for antigen, also reacts with chicken hematopoietic cells. Our data indicate that the majority of 111-427 positive cells among peripheral blood leucocytes (PBL) are thrombocytes. This antibody also recognizes two in vitro cell lines, III-C5, an IL-2-dependent T-cell-line and HD11, a macrophage cell line. In addition, erythrocytes and a minor subpopulation of thymus and spleen cells are also stained by the monoclonal antibody (mAb). No specific immunoprecipitation could be detected from 125I radiolabeled cell lysates. By Western blotting techniques, the 111- 427 mAb identifies a single band of apparent molecular weight 91 kD, unaffected by reduction, from III-C5 and HD11 cell lysates. This band is absent in negative cell control lysates. On thrombocytes, the apparent molecular weight of the band is shifted to 87 kD. These results indicate that the mAb does not recognize the chicken T-cell receptor for antigen, but a cell surface marker shared primarily between thrombocytes and erythrocytes. This new chicken cell marker is compared to other cell surface markers in avian or mammalian species that present some analogies in their tissue distribution.