Major histocompatibility complex restriction of maternally induced suppression in young adult mice.

This study focused on the mode in which maternal T cells induce suppression of plaque-forming cell (PFC) response in offspring. The maternal T cells of C57BL/6J pregnant mice, which had been intraperitoneally injected with 2 x 10(8) of sheep red blood cells (SRBC) on day 12 of gestation, were transferred, 5 days after immunization, into (C3H/HeJ x C57BL/6J)F1 normal pregnant mice on day 12 of gestation. The (C3H/HeJ x C57BL/6J)F1 x C3H/HeJ offspring of (C3H/HeJ x C57BL/6J)F1 recipient pregnant mice were reared to more than 6 weeks of age, and their anti-SRBC PFC responses were examined. Suppression of anti-SRBC PFC response was observed in H-2bxk but not H-2k offspring. Thus, maternal T cells of SRBC-immunized pregnant mice induce suppression of anti-SRBC PFC in offspring with restriction to major histocompatibility complex (MHC) haplotype utilized in maternal T-cell responses during pregnancy. Maternal CD4+ T cells are responsible for the MHC-restricted induction of PFC suppression in offspring. Furthermore we demonstrated, in this report, using adoptive transfer of maternal T cells from SRBC-immunized pregnant mice and in vitro secondary PFC assay in the offspring, that maternal T-cell-mediated suppression results from the development of CD4+ suppressor T cells in offspring. Moreover, the activation of suppressor T cells in offspring depends on the recognition of SRBC antigens presented in association with the same MHC haplotype as that utilized in the maternal T-cell response during pregnancy. Thus, the maternal T cells of SRBC-immunized pregnant mice generate a repertoire of suppressor T cells in their offspring.     

The Effect of Maternal Antigenic Stimulation Upon the Active Immune Responsiveness of Their Offspring: Suppression Induced by Soluble Protein Antigen,Ovalbumin, in Mice

ABSTRACT: The active immune responsiveness of the offspring of pregnant mice stimulated with heterologous protein antigen was investigated by measuring the plaque-forming cells (PFC). Mice (C57BL/10;B10) immunized once in pregnancy with ovalbumin (OVA) in the form of Al(OH)3 gel (in alum) or in a soluble form (in saline) developed no anti-OVA PFC response. The anti-OVA PFC response suppression induced in the offspring was high in the offspring of alum-treated mothers and low in those of saline-treated mothers. The optimal dose of OVA in alum that induces the highest immunological memory in pregnant mice caused the complete suppression of PFC development in their offspring. The same dose of OVA in saline induced a negative immunological memory in pregnant mice and partial suppression in the offspring. On the other hand, mice primed prior to conception and boosted during pregnancy developed anti-OVA PFC in significant numbers, and only a partial suppression was established in their young. Based on these data, we discussed the possible mechanisms concerned with the specific suppression induced in the young B10 mice stimulated by OVA.     

The H-Y Response in Mid-Gestation and Long After Delivery in Mice Primed Before Pregnancy

The mechanisms underlying maternal tolerance of the semi-allogeneic fetus are not completely understood. The maternal immune system's response to the male antigen, H-Y is an example of the conflicting evidence that both supports and refutes the idea that the immune system in pregnant females is fundamentally different from that in non-pregnant females. Although multiple pregnancies may inactivate H-Y specific T cells, the immune system of the pregnant female can also generate a cytotoxic response to this antigen. To help understand this apparent conflict, we immunized female mice against H-Y with male spleen cells before pregnancy and examined the subsequent anti H-Y response during mid-pregnancy. The pregnant mice studied were able to mount cytotoxic immune responses to H-Y that were equivalent to those generated in their non-pregnant counterparts. Moreover the experience of pregnancy did not impair the ability to maintain immunologic memory to H-Y. The data support the idea that pregnancy does not violate general rules of antigen specific immunity, even if the antigen is expressed on the fetus.     

The H-Y response in mid-gestation and long after delivery in mice primed before pregnancy

The mechanisms underlying maternal tolerance of the semi-allogeneic fetus are not completely understood. The maternal immune system's response to the male antigen, H-Y is an example of the conflicting evidence that both supports and refutes the idea that the immune system in pregnant females is fundamentally different from that in non-pregnant females. Although multiple pregnancies may inactivate H-Y specific T cells, the immune system of the pregnant female can also generate a cytotoxic response to this antigen. To help understand this apparent conflict, we immunized female mice against H-Y with male spleen cells before pregnancy and examined the subsequent anti H-Y response during mid-pregnancy. The pregnant mice studied were able to mount cytotoxic immune responses to H-Y that were equivalent to those generated in their non-pregnant counterparts. Moreover the experience of pregnancy did not impair the ability to maintain immunologic memory to H-Y. The data support the idea that pregnancy does not violate general rules of antigen specific immunity, even if the antigen is expressed on the fetus.     

Gestational immunosuppression is mediated by specific Lyt 2+ T cells.

Female BALB/c mice were tested during the first week of pregnancy for their lymphocyte-mediated cytotoxic response to paternal alloantigens. Spleen or uterine regional lymph node cells were not spontaneously cytotoxic against concanavalin A-activated paternal target lymphocytes. Female mice immunized i.p. with paternal H-2-matched or third-party allogeneic cells on the fifth day and tested on the 12th day of pregnancy demonstrated total suppression of cell-mediated cytotoxicity to paternal alloantigens and partial suppression to third-party alloantigens. A generalized non-specific immunosuppression to alloantigens seems to be associated with pregnancy, which may indicate that soluble factors were involved in mediating the suppressive effect. Cocultures of spleen cells from virgin mice and the whole population of spleen or regional lymph node cells from allogeneic pregnant female mice demonstrated specifically suppressed responses to alloantigens. Similar cocultures with Thy 1.2- and Lyt 2.2-depleted populations restored the cytotoxicity levels of activated spleen cells. We conclude that antigen-specific Lyt 2+ T cells were activated during pregnancy to regulate the female T-cell response to paternal alloantigens.     

Maternal tolerance is not critically dependent on interleukin-4

Pregnant animals can generate and maintain immune responses to fetal antigens. This however, does not usually lead to fetal loss. At least two types of immune response are recognized. T helper type 1 (Th1) responses support the generation of cellular cytotoxicity. In contrast, Th2-type responses support the production of non-cytotoxic antibody and suppress the Th1-type. One attempt to explain why the fetus is not generally rejected has been to suggest that during pregnancy Th2-type responses are dominant. These responses rely heavily on interleukin-4 (IL-4) for both functions. This work focuses on maternal immunity to the male antigen H-Y, which is expressed in male fetuses. When injected with male spleen cells, female mice of certain strains mount a cytotoxic immune response to H-Y. However, pregnant females immunized in this way do not deliver litters with fewer males. To help delineate the possible role of IL-4 in such maternal tolerance, female mice genetically deficient in IL-4 were studied. The results show that: (1) deficiency in maternal IL-4 does not affect fertility, (2) deficiency in IL-4 is not associated with selective loss of male offspring in unimmunized mice, (3) pregnancy does not obliterate anti-H-Y reactivity in immunized mice and (4) maternal immunity to H-Y in the absence of IL-4 does not result in loss of male offspring. The results suggest that IL-4-dependent Th2-type responses are not critical to maternal tolerance. Other cytokines must be examined for their role in this phenomenon.     

Effects of Immunization of Mothers on the Immune Reaction of Their Offspring: Inhibition of Immune Responses of Offspring Caused by Antibody Imported Through the Milk

ABSTRACT: Effects of immunization of pregnant AKR mice with nucleated chicken erythrocytes (CRBC) on immune responses of their offspring were examined. Antigen-specific reduction of generation of cytotoxicity and plaque forming cells (PFC) was demonstrated in the offspring at 8 weeks after birth, and lasted for 15 weeks. Cross-fostering experiments and cell transfer experiments showed that such suppression would be induced by antibody contained in the milk of immunized mothers rather than suppressor cells. Activities to enhance opsonization and to mediate antibody-dependent cell-mediated cytotoxicity (AI)CC) were demonstrated in the serum of such offspring before challenge with CRBC. Delayed footpad reaction (DFR) was maintained at the normal level in such offspring of immunized mice.     

Natural killer 1.1(+) alpha beta T cells in the periimplantation uterus

When the developing embryo implants into the uterine wall, resident maternal immune cells may encounter antigens present on the fetal tissues. The nature and constituents of the ensuing maternal immune response, and its regulation, are of considerable interest in understanding normal and abnormal pregnancy. Here, we report the presence of natural killer (NK)1.1(+) alpha beta T cells in the murine periimplantation uterus. These cells account for a large portion of both the T-cell and natural killer cell populations in early pregnancy, while their numbers in the non-pregnant uterus and later in pregnancy are greatly reduced. Phenotypically, these NK1.1+ alpha beta T cells belong to a previously described subset of cells that bear a V alpha 14-J alpha 281-encoded T-cell receptor. Unlike other organs, where both CD4(+) and CD4(-)/CD8(-) NK1.1(+) alpha beta T cells are found, the placental/decidual population appears to be entirely CD4(-)/CD8(-). The V beta repertoire of the placental/decidual population is also altered from that of other organs, with a majority of cells expressing V beta 3. Together, these features suggest the possibility of local development. NK1.1(+) alpha beta T cells are known to recognize the class I-like CD1 molecule. Consistent with this association, we demonstrate CD1 expression by tissues within the pregnant uterus. Our findings define an additional organ-specific immune environment where NK1.1(+) alpha beta T cells may play a role, and continue to demonstrate the specialized nature of the maternal intrauterine immune system during pregnancy.     

Maternal cell traffic bounds for immune modulation: tracking maternal H-2 alleles in spleens of baby mice by DNA fingerprinting

We have previously reported that the immunization of pregnant mice with T-dependent antigens successfully induced suppression of the antigen-specific plaque-forming cell (PFC) response to the relevant antigens in the offspring. This suppression was not caused by the administered antigens, the antibodies produced by the pregnant mother, or lactational transfer, but was dependent on the presence of the intact maternal T cells. It was major histocompatibility complex (MHC)-restricted manner tolerance, which continued for at least one-sixth of the murine life. Traditionally, the placenta acts as a natural barrier, not allowing the cells to pass through. However, the results presented strongly suggested that maternal T cells pass through the placenta and subsequently induce tolerance. In this present study, we attempted to substantiate the presence of maternal cells in the fetal circulation through the use of molecular techniques. We found that a highly polymorphic microsatellite sequence within the class II Eb gene of the H-2 complex is useful for the molecular detection of various H-2 alleles. DNA polymorphic analysis was used for tracking maternal H-2 alleles in the spleens of baby mice. The main procedure involved polymerase chain reaction amplification and restriction fragment length polymorphism analysis of the DNA sequence encompassing the H-2-specific microsatellite from the genomic DNA of baby mice. The results indicated that maternal T cells of immunized pregnant mice cross the placenta into the fetus, eventually inducing antigen-specific immunological tolerance in the offspring.     

Serum exosomes in pregnancy-associated immune modulation and neuroprotection during CNS autoimmunity

In multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), relapses are markedly reduced during pregnancy. Exosomes are lipid-bound vesicles and are more abundant in the serum during pregnancy. Using murine EAE, we demonstrate that serum exosomes suppress T cell activation, promote the maturation of oligodendrocyte precursor cells (OPC), and pregnancy exosomes facilitate OPC migration into active CNS lesions. However, exosomes derived from both pregnant and non-pregnant mice reduced the severity of established EAE. Thus, during pregnancy, serum exosomes modulate the immune and central nervous systems and contribute to pregnancy-associated suppression of EAE.     

Pregnancy Does not Deter the Development of a Potent Maternal Protective CD8+ T-Cell Acquired Immune Response Against Listeria Monocytogenes Despite Preferential Placental Colonization

Listeria monocytogenes (LM) preferentially colonizes the placenta and causes fetal loss and systemic disease during pregnancy. As systemic CD8⁺ T-cell memory is critical in controlling LM infection, we addressed the issue as to whether it is modulated during pregnancy.

Method of study

Pregnant mice were infected with LM and their immune response was quantified relative to the non-pregnant cohort using advanced immunological techniques.

Results

Pregnant mice exhibited progressive and massive placental LM infection leading to fetal resorptions. In contrast, they harbored significantly lower bacteria in spleen and liver relative to non-pregnant controls, and rapidly cleared systemic infection. Both pregnant and non-pregnant mice exhibited similar activation of systemic innate immunity. Moreover, LM infection in pregnant and non-pregnant hosts evoked strong antigen-specific cytolytic CD8⁺ T cells that produced IFN-γ. Consequently, LM infection initiated during pregnancy afforded long-term protective memory to secondary infection.

Conclusion

Maternal hosts generate a normal Listeria -specific adaptive immunity in particular CD8⁺ T-cell memory response suggesting that systemic listeriosis during pregnancy may be an immunopathology associated with placental infection.     

The H‐Y Response in Mid‐Gestation and Long After Delivery in Mice Primed Before Pregnancy

The mechanisms underlying maternal tolerance of the semi‐allogeneic fetus are not completely understood. The maternal immune system's response to the male antigen, H‐Y is an example of the conflicting evidence that both supports and refutes the idea that the immune system in pregnant females is fundamentally different from that in non‐pregnant females. Although multiple pregnancies may inactivate H‐Y specific T cells, the immune system of the pregnant female can also generate a cytotoxic response to this antigen. To help understand this apparent conflict, we immunized female mice against H‐Y with male spleen cells before pregnancy and examined the subsequent anti H‐Y response during mid‐pregnancy. The pregnant mice studied were able to mount cytotoxic immune responses to H‐Y that were equivalent to those generated in their non‐pregnant counterparts. Moreover the experience of pregnancy did not impair the ability to maintain immunologic memory to H‐Y. The data support the idea that pregnancy does not violate general rules of antigen specific immunity, even if the antigen is expressed on the fetus.     

T and B lymphocyte subsets in patients with unexplained recurrent spontaneous abortion: IVIG versus placebo treatment

PROBLEM: To investigate circulating lymphocyte subsets in women with recurrent spontaneous abortion (RSA) in relation to pregnancy outcome and to treatment with intravenous immunoglobulin (IVIG). METHOD OF STUDY: Forty-one women with a history of unexplained RSA were examined during first trimester of pregnancy before IVIG or placebo treatment and after pregnancy. The results were compared with five healthy, non-pregnant women and five women in the first trimester of normal pregnancy. Circulating lymphocyte subsets with focus on T-cell subpopulations were determined by flow cytometry. RESULTS: The proportions of human leukocyte antigen (HLA)-DR positive T cells (CD3+ HLA-DR+), T-killer/effector cells (CD8+ S6F1+) and B cells (CD19+) were increased, whereas the proportion of T-suppressor/inducer cells (CD4+ CD45RA+) was decreased during first trimester pregnancy of RSA women compared with pregnant normal controls. T and B lymphocyte subsets did not correlate with pregnancy outcome on either IVIG or placebo group. CONCLUSIONS: In RSA patients, the immune system seems to be activated in contrast to the suppression noted in normal pregnancy.     

Maternal antigenic stimulation actively produces suppressor activity in offspring

Pregnant B10.A(3R) and B10.A(5R) mice were immunized with heterologous erythrocyte and protein antigens and the active immune responsiveness of their offspring was investigated by the plaque-forming cell (PFC) assay. In offspring derived from mothers which were stimulated with optimal amounts of antigens and which had fully developed antibody-forming cells, there was a clear-cut suppression in development of specific PFC over a significant period after delivery. In order to characterize the suppressor cell population, spleen cells were prepared from offspring whose mothers were immunized and thereafter treated by anti I-Jk or anti I-Jb monoclonal antibody and complement (C') followed by adoptive transfer to normal corresponding mouse strain. Only the group that received 3R spleen cells treated with anti I-Jb monoclonal antibody and C' had no suppressed PFC. To clarify the suppressor site in offspring, precursor B-cells of experimental offspring responded as hapten specific antibody forming cells by employing homologous hapten and heterologous carrier antigens. These results suggest mechanisms for suppression in offspring whose mothers were stimulated during pregnancy.     

Dendritic cells: a family portrait at mid-gestation

Recent advances in our understanding of dendritic cells (DCs) and their role in tolerance and immunity has fuelled study of their normal development and function within the reproductive tract. The common hypothesis that pregnancy is a state of immune suppression or deviation now includes the idea that alterations in DC phenotype and function are critical for maternal tolerance. We chose to study DCs in the uterus and lymphoid tissue in non-pregnant and pregnant mice at mid-gestation to understand what DC-related factors may be involved in premature birth. We used a mouse model where the mother's immune system has been shown to respond to the male antigen H-Y. Observed differences among DCs in the uterus, uterine draining nodes and spleen, even in non-pregnant mice, suggest the existence of a specialized uterus-specific subset of DCs. We further found that, amongst CD45(+) CD11c(+) cells in the uterus and peripheral lymphoid tissue of pregnant mice, expression of major histocompatibility complex class II (MHC II) and costimulatory molecules (i.e. CD80) was similar to that in the non-pregnant state. Moreover, there was no pregnancy-related decrease in the proportion of CD11c(+) cells in the uterus or in the uterine node that were CD11b(-) CD8(+). Pregnancy increased the CD11b(+) subsets and the expression of chemokine (C-C motif) ligand 6 (CCL6) in DCs of the uterine draining nodes. Finally, DC subsets showed variable expression, with respect to tissue and pregnancy, of the cytokine interleukin-15, which is important in lymphoid cell homeostasis. For DCs, pregnancy is not a state of immune paralysis, but of dynamic developmental change.     

Effect of Maternal Antigenic Stimulation on the Active Immune Responses of Their Offspring

Pregnant mice were stimulated by heterologous erythrocyte and protein antigen, and the active immune responses of their offspring as measured by plaque-forming cells (PFC) were investigated. In offspring derived from mothers immunized by a suitable amount of T-dependent antigen, clear-cut suppression of development of specific PFC in spleen was observed over a significant period after delivery. The mechanism of this suppression was investigated, and the following results were obtained. When the heterologous erythrocyte was used as antigen, the more the specific PFC developed in the mother spleen, the stronger the suppression of PFC observed in their offspring. However, it is worthy of note that passive administration of antibody to pregnant mice did not induce suppression in their young. In case of the protein antigen ovalbumin (OVA), pregnant mice had to be injected with a suitable amount of antigen, along with aluminium hydroxide, for either primary or secondary stimulus to induce the suppression of specific PFC in their offspring. Soluble OVA administered to pregnant mice was not effective for inducing suppression in the offspring. Based on these results, some possible mechanisms are discussed concerning specific PFC suppression in the offspring when pregnant mice are stimulated.     

Regulatory T cells protect from autoimmune arthritis during pregnancy

Pregnancy frequently has a beneficial effect on the autoimmune disease Rheumatoid Arthritis, ranging from improvement in clinical symptoms to complete remission. Despite decades of study, a mechanistic explanation remains elusive. Here, we demonstrate that an analogous pregnancy-induced remission can be observed in a mouse model of arthritis. We demonstrate that during pregnancy mice are protected from collagen-induced arthritis, but are still capable of launching normal immune responses to influenza infections. We examine the role of regulatory T (T(R)) cells in this beneficial effect. T(R) cells are essential for many aspects of immune tolerance, including the suppression of autoimmune responses. Remarkably, transfer of regulatory T cells from pregnant 'protected' mice was sufficient to confer protection to non-pregnant mice. These results suggest that regulatory T cells are responsible for the pregnancy-induced amelioration of arthritis.     

Impact of in utero Th2 immunity on T cell deviation and subsequent immediate-type hypersensitivity in the neonate

It was the aim of this study to analyze the impact of maternal Th2 immune responses on onset and subsequent development of allergen-specific immunity and immediate-type hypersensitivity in early childhood. In a well characterized mouse model of Th2 immunity, BALB / c mice were sensitized to ovalbumin (OVA) before mating followed by allergen aerosol exposure during pregnancy. At the end of pregnancy mice developed allergen-specific Th2 / Th0 immunity and immediate-type hypersensitivity responses to OVA. T cells from these newborns, when restimulated with PMA / ionomycin, demonstrated a lowered capacity to produce IFN-gamma. To assess whether prenatal allergen exposure favors postnatal onset of a Th2-type immune response, these offspring were immunized to a novel antigen by a single injection of beta-lactoglobulin (BLG). In contrast to offspring from non-sensitized mothers, offspring from OVA-sensitized mice showed both higher anti-BLG immunoglobulin titers and higher frequencies of immediate-type skin test responses. Our data suggest that Th2 / Th0 immunity present during pregnancy has a decisive impact on shaping of the Th1 / Th2 T cell profile in the neonate. Furthermore, this effect favors the development of Th2 immune responses, when mice are exposed to a novel antigen during early childhood.     

CD4+ CD25+ regulatory T cells in human pregnancy: development of a Treg-MLC-ELISPOT suppression assay and indications of paternal specific Tregs

The current study was aimed at developing a one-way mixed leucocyte culture-enzyme-linked immunospot (MLC-ELISPOT) assay for the study of CD4(+) CD25(+) regulatory T (T(reg)) cells and applying this method in the study of antifetal immune reactions during human pregnancy. Twenty-one pregnant women and the corresponding fathers-to-be, and 10 non-pregnant control women and men, participated in the study. CD4(+) CD25(+) cells were isolated from peripheral blood mononuclear cells (PBMC) by immunomagnetic selection. Maternal/control PBMC were stimulated with paternal or unrelated PBMC in MLC. Secretion of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) from responder cells, with or without the presence of autologous T(reg) cells, was analysed by ELISPOT. PBMC from pregnant women showed increased secretion of IL-4 compared to controls. In pregnant and non-pregnant controls, T(reg) cells suppressed IFN-gamma reactivity against paternal and unrelated alloantigens. Interestingly, T(reg) cells suppressed IL-4 secretion against paternal but not unrelated alloantigens during pregnancy. We have successfully developed a model for studying T(reg) cells in antifetal cytokine reactions during pregnancy. Results indicate that T(reg) cells contribute to strict regulation of both T helper type 1-like and type 2-like antifetal immune reactions. Interestingly, T helper type 2-like cells specific to unrelated alloantigens are able to escape the suppression of T(reg) cells, which would allow for IL-4, alongside CD4(+) CD25(+) T(reg) cells, to control potentially detrimental IFN-gamma reactions during pregnancy.     

Suppression of Allergen‐Specific IgE in Offspring After Preconceptional Immunisation: Maternal,Paternal and Genetic Influences

Immunisation of female mice with the allergen ovalbumin (OVA) during pregnancy reduces the OVA‐specific IgE response in adult offspring. To approach primary prevention strategies for allergy, we investigated to what extent genetic, paternal and maternal factors influence this suppressive effect on allergic sensitisation in offspring and investigated the possibility of pregestational immunisation. Maternal allergen immunisation reduced OVA‐specific IgE levels in immunised offspring, even after maternal immunisation up to 8 weeks before conception without further allergen exposure. Immunisation of immunodeficient BALB/c severe combined immune deficiency (SCID) dams mated with wild type males did not lead to IgE suppression in offspring, indicating the importance of a functional maternal immune system. Immunisation of male mice before the relevant spermatogenesis did not cause antibody suppression in offspring. OVA‐specific IgG1, presumably of maternal origin, was present in naïve offspring only from immunised dams and was associated with suppressed IgE responses after offspring immunisation. The IgE‐suppressive effect of maternal immunisation was demonstrated in all three immunocompetent strains tested (NIH/OlaHsd, BALB/cA and C57BL/6 mice). In conclusion, suppression of allergen‐specific IgE production in offspring could not be induced by paternal immunisation, and genetic factors were of minor importance. In contrast, we demonstrate the necessity of maternal factors, possibly allergen‐specific IgG1, resulting from a functional adaptive immune response, for the IgE‐suppressive effect in offspring. These maternal factors could be induced by immunisation of female mice even before conception.