Damián Muzzio

B Cell Development Undergoes Profound Modifications and Adaptations During Pregnancy in Mice

ABSTRACT Pregnancy hides an immunological riddle combining two antagonistic characteristics of immunology: the existence of a tolerance that allows the gestation of a semiallogeneic fetus and proper protection against pathogens threatening the health of the immunocompromised mother. Despite the fundamental role that B cells play in orchestrating an immune response, their behavior in the context of pregnancy has been barely investigated. Here we demonstrate that numbers of pre/pro and immature B cells were progressively diminished in the bone marrow (BM) of pregnant mice, leading to a reduced influx of B cells in blood and spleen. Correspondingly, lower levels of B cell-activating factor of the TNF family were observed in serum of pregnant mice. In contrast to immature B cells, mature B cells were accumulated in the BM during pregnancy. Accordingly, higher numbers of mature B cells were observed in the lymph nodes draining the uterus as well as in the peritoneal cavity of pregnant mice, both tissues in close contact with the fetuses. Despite an increase in spleen size, pregnant mice showed lower numbers of splenic B cells, which was mirrored by lower numbers of immature and FO B cells. However, marginal zone B cells in the spleen increased during pregnancy. Additionally, serum IgM, IgA, and IgG3 titers were elevated in pregnant mice. Collectively, our data show how the B cell compartment adapts to the presence of the semiallogeneic fetus during gravidity.

Regulatory B10 Cells Restore Pregnancy Tolerance in a Mouse Model

ABSTRACT During mammalian pregnancy, the immune system defies a double challenge: to tolerate the foreign growing fetus and to fight off infections that could affect both mother and fetus. Minimal disturbances to the fine equilibrium between immune activation and tolerance would compromise fetal survival. Here, we show that regulatory B10 cells are important for pregnancy tolerance in mice. The frequency of these cells increases during normal murine pregnancies, while mice presenting spontaneous abortion do not show elevated levels of regulatory B10 cells. When B10 cells are transferred to the abortion-prone mice, dendritic cells are kept in an immature state, and regulatory T cells increase, thus avoiding immunological rejection of the fetuses. In vitro, we could identify IL-10 secreted by B10 cells as the main mediator of these salutary effects. Our data add an important piece of information to the complex immune crosstalk during pregnancy. This study opens novel lines of work to better understand how to help women who have trouble in maintaining a pregnancy.

B-1a B Cells Regulate T Cell Differentiation Associated with Pregnancy Disturbances

During pregnancy, the maternal immune system faces a double dilemma: tolerate the growing semi-allogeneic fetus and at the same time protect the mother and the progeny against pathogens. This requires a fine and extremely regulated equilibrium between immune activation and tolerance. As professional antigen presenting cells, B cells and in particular B-1a B cells, can activate or tolerize T cells and thus participate in the generation or regulation of the immune response. B-1a B cells were involved in the humoral immune response leading to pre-eclampsia, one of the main medical complications during pregnancy. Here we demonstrated that B-1a B cells are additionally involved in cellular immune mechanisms associated with pregnancy complications. Using a mouse model of pregnancy disturbances, we showed that B-1a B cells from animals suffering pregnancy disturbances but not from those developing normal pregnancies induce the differentiation of naïve T cells into Th17 and Th1 cells. This differential role of B-1a B cells during pregnancy seems to be associated with the co-stimulatory molecule CD86 as normal pregnant mice showed lower percentages of CD86 expressing B-1a B cells as compared to pregnant mice developing pregnancy disturbances or to non-pregnant animals. Our data bring to light a new and not explored role of B-1a B cells in the context of pregnancy.

Marginal zone B cells emerge as a critical component of pregnancy well-being

The success of eutherian mammal evolution was certainly supported by the ability of the already existing immune system to adapt to the presence of the semi-allogeneic fetus without losing the capability to defend the mother against infections. This required the acquisition of highly regulated and coordinated immunological mechanisms. Failures in the development of these strategies not only lead to the interruption of pregnancy but also compromise maternal health. Alongside changes on the cytokine profile - expansion of tolerogenic dendritic and regulatory T cells - a profound adaptation of the B cell compartment during pregnancy was recently described. Among others, the suppression of B cell lymphopoiesis and B cell lymphopenia were proposed to be protective mechanisms tending to reduce the occurrence of autoreactive B cells that might recognize fetal structures and put pregnancy on risk. On the other hand, expansion of the pre-activated marginal zone (MZ) B cell phenotype was described as a compensatory strategy launched to overcome B cell lymphopenia thus ensuring a proper defense. In this work, using an animal model of pregnancy disturbances, we demonstrated that the suppression of B cell lymphopoiesis as well as splenic B cell lymphopenia occur independently of pregnancy outcome. However, only animals undergoing normal pregnancies, but not those suffering from pregnancy disturbances, could induce an expansion and activation of the MZ B cells. Hence, our results clearly show that MZ B cells, probably due to the production of natural protective antibodies, participate in the fine balance of immune activation required for pregnancy well-being.

Cytochrome P450 17A1 inhibitor abiraterone attenuates cellular growth of prostate cancer cells independently from androgen receptor signaling by modulation of oncogenic and apoptotic pathways

Abiraterone provides significant survival advantages in prostate cancer (PC), however, the current understanding of the molecular mechanisms of abiraterone is still limited. Therefore, the abiraterone impact on androgen receptor (AR)-positive LNCaP and AR-negative PC-3 cells was assessed by cellular and molecular analyses. The present study demonstrated, that abiraterone treatment significantly decreased cell growth, AR expression, and AR activity of AR-positive LNCaP cells. Notably, AR-negative PC-3 cells exhibited comparable reductions in cellular proliferation, associated with DNA fragmentation and pro-apoptotic modulation of p21, caspase-3, survivin, and transforming growth factor β (TGFβ). Our observations suggest that the attenuation of AR signaling is not the only rationale to explain the abiraterone anticancer activity. Abiraterone efficacy may play a more global role in PC progression control than originally hypothesized. In this regard, abiraterone is not only a promising drug for treatment of AR-negative PC stages, even more, abiraterone may represent an alternative for treatment of other malignancies besides prostate cancer.

Progesterone and estradiol exert an inhibitory effect on the production of anti-inflammatory cytokine IL-10 by activated MZ B cells

The main message of this work is the fact that female sex hormones, progesterone and estradiol, whose levels significantly rise during pregnancy, inhibit the production of anti-inflammatory cytokine IL-10 with no apparent effect on pro-inflammatory cytokine TNF-α by activated MZ B cells. This is an important piece of information and helps to better understand how the maternal immune system controls the balance between immune tolerance and immune activation during pregnancy leading to the simultaneously acceptance of the semi-allogeneic fetus and the proper defense of the mother against pathogens during this critical period of time.

Expression analysis of cannabinoid receptors 1 and 2 in B cells during pregnancy and their role on cytokine production.

The endocannabinoid system consists in a family of lipids that binds to and activates cannabinoid receptors. There are two receptors so far described, the cannabinoid receptor 1 (CB1) and 2 (CB2). In the context of pregnancy, the endocannabinoid system was shown participates in different key aspects of reproductive events. B-lymphocytes are pleiotropic cells belonging to the adaptive arm of the immune system. Besides immunoglobulin production, B-lymphocytes were recently shown to be actively involved in antigen presentation as well as cytokine production, thus playing a central role in immunity. In this study we first aimed to characterize the expression of CB1 and CB2 receptors in B cells during pregnancy and then analyze the impact of their activation in term of cytokine production by B cells from pregnant and non-pregnant mice. We observed that the expression of CB1 and CB2 receptors in B-lymphocytes is differentially regulated during pregnancy. While CB2 expression is down regulated CB1 is augmented in B-lymphocytes of pregnant mice. Additionally, the treatment of activated B-lymphocytes with specific CB1 and CB2 agonists, showed a different response in term of cytokine production. Particularly, CB1 against boosted the production of the anti-inflammatory cytokine IL-10 by activated B-lymphocytes from pregnant mice.

A Kinetic Study of CD83 Reveals an Upregulation and Higher Production of sCD83 in Lymphocytes from Pregnant Mice

For the normal development of pregnancy, a balance between immune tolerance and defense is crucial. However, the mechanisms mediating such a balance are not fully understood. CD83 is a transmembrane protein whose expression has been linked to anti-inflammatory functions of T and B cells. The soluble form of CD83, released by cleavage of the membrane-bound protein, has strong anti-inflammatory properties and was successfully tested in different mouse models. It is assumed that this molecule contributes to the establishment of immune tolerance. Therefore, we postulated that the expression of CD83 is crucial for immune tolerance during pregnancy in mice. Here, we demonstrated that the membrane-bound form of CD83 was upregulated in T and B cells during allogeneic murine pregnancies. An upregulation was also evident in the main splenic B cell subtypes: marginal zone, follicular zone, and transitional B cells. We also showed that there was an augmentation in the number of CD83+ cells toward the end of pregnancy within splenic B and CD4+ T cells, while CD83+ dendritic cells were reduced in spleen and inguinal lymph nodes of pregnant mice. Additionally, B lymphocytes in late-pregnancy presented a markedly higher sensitivity to LPS in terms of CD83 expression and sCD83 release. Progesterone induced a dosis-dependent upregulation of CD83 on T cells. Our data suggest that the regulation of CD83 expression represents a novel pathway of fetal tolerance and protection against inflammatory threats during pregnancy.

Human pregnancy is accompanied by modifications in B cell development and immunoglobulin profile

Though human pregnancy success has been classically linked with a shift into a Th2 immunoglobulin producing cell response, a clear picture concerning B cell development and immunoglobulin profile during human pregnancy is missing. We analyzed in this work the dynamic of different B cell populations in peripheral blood of pregnant women on the first, second and third trimester of pregnancy. As control, age-matched non-pregnant fertile women were included. Additionally, we quantified the levels of immunoglobulin (IgG1, IgG2, IgG3, IgG4, IgM, IgA and IgE) in the serum of pregnant and non-pregnant women. We observed a significant decrease in the percentages of transitional B cells in peripheral blood of pregnant women as compared to non-pregnant control women. Besides, percentages of naïve as well as switched and non-switched memory B cells in peripheral blood of pregnant women were similar to those in non-pregnant control women. Interestingly, although we did not observe differences in the activation status of B cells as well as in the percentages of plasma cells between pregnant and non-pregnant women, we observed significantly higher levels of IgM, IgA, IgG3, more likely natural antibodies, as well IgG4 in serum of pregnant women compared to non-pregnant age matched control women.

3D In Vitro Models of Early Pregnancy: How to Choose the Right Scaffolding Material?

Following fertilization, the blastocyst has to complete two distinct steps to assure further development of pregnancy. After apposition it establishes a firm connection with the luminal epithelium of the endometrium (attachment) and subsequently enters the decidualizing stroma (invasion). If this step is not achieved successfully, fertility problems arise. Development of the placenta ensures an adequate supply of nutrients and gas between the mother and the fetus. Preeclampsia is a prevalent disorder arising from defects in the process of placentation. It is associated with an increase of maternal morbidity and mortality. Numerous attempts have been made in order to elucidate the etiology of the syndrome and identify women at risk. The lack of reliable animal models has turned the attention to the development of in vitro assays, which could provide a better insight into the individual processes that will later trigger preeclampsia symptoms. In particular, 3D in vitro models more closely resemble the complexity of the extracellular environment. The choice of the scaffolding material should be done carefully as cell-matrix interactions are very often as important as cell-cell interactions for the correct attachment, proliferation and differentiation of cells. The following review is aimed to provide a general overview of the scaffolds available for the in vitro modeling of these complicated systems as well as to discuss the importance surrounding the choice of the scaffolding material and its influence on the results obtained.