Laura Fraccaroli

Modulation and recruitment of inducible regulatory T cells by first trimester trophoblast cells.

Citation Ramhorst R, Fraccaroli L, Aldo P, Alvero AB, Cardenas I, Leirós CP, Mor G. Modulation and recruitment of inducible regulatory T cells by first trimester trophoblast cells. Am J Reprod Immunol 2012; 67: 17–27

A potential tolerogenic immune mechanism in a trophoblast cell line through the activation of chemokine-induced T cell death and regulatory T cell modulation

BACKGROUND Successful implantation is followed by a local pro-inflammatory and Th1 response, subsequently controlled by Th2. Regulated upon activation, normal T cell expressed and secreted (RANTES) promotes a Th1 response and is implicated as a physiologic tolerogenic factor; therefore, we studied its potential role in the trophoblast-maternal leukocyte dialog. METHODS We performed co-cultures of immortalized trophoblast cell line (Swan 71) and peripheral blood mononuclear cells (PBMCs) from fertile women (n = 23) or with recurrent spontaneous abortions (n = 18, RSA). After 24 and 48 h, supernatant and cells were analyzed by enzyme-linked immunosorbent assay, fluorescence-activated cell sorting, Western blot and apoptosis assay. To investigate the physiological effects at peripheral level, we co-cultured maternal and paternal PBMCs with conditioned media from Swan cells and progesterone. RESULTS Following interaction of maternal PBMCs and trophoblast cells, RANTES production increased (P < 0.05) and was accompanied by low levels of interferon gamma, interleukin-12 p70 and high levels of tumor necrosis factor-alpha, nitrites and leukemia-inhibitory factor. RANTES production resulted in elevated apoptosis of potentially deleterious maternal CD3+ lymphocytes, accompanied by a decrease in the proliferative maternal response. During fetal-maternal dialog, the anti-RANTES antibody significantly reduced the frequency of CD4+CD25+Foxp3+ cells (P < 0.05) and was associated with trophoblast cell survival. However, co-cultures of Swan cells and RSA-PBMCs displayed a differential RANTES kinetics, lower levels of regulatory T cells (Tregs) and CD3+annexin-V+cells, accompanied by higher levels of apoptotic trophoblast cells. CONCLUSIONS RANTES promotes an adequate pro-implantatory microenvironment that influences trophoblast cell survival and modulates the balance of maternal Treg/T effector lymphocytes in favor of maternal tolerance.

VIP modulates the pro‐inflammatory maternal response, inducing tolerance to trophoblast cells

Background and purpose:  Successful embryo implantation is followed by a local pro‐inflammatory and Th1 response, subsequently controlled by a Th2 response. Vasoactive intestinal peptide (VIP) has anti‐inflammatory effects and promotes tolerogenic/Th2 responses while favouring embryonic development. We investigated the potential regulatory role of VIP on human trophoblast cells, maternal pro‐inflammatory responses and trophoblast‐maternal leukocyte interactions.

Galectin-1 confers immune privilege to human trophoblast: implications in recurrent fetal loss

Mechanisms accounting for the protection of the fetal semi-allograft from maternal immune cells remain incompletely understood. In previous studies, we showed that galectin-1 (Gal1), an immunoregulatory glycan-binding protein, hierarchically triggers a cascade of tolerogenic events at the mouse fetomaternal interface. Here, we show that Gal1 confers immune privilege to human trophoblast cells through the modulation of a number of regulatory mechanisms. Gal1 was mainly expressed in invasive extravillous trophoblast cells of human first trimester and term placenta in direct contact with maternal tissue. Expression of Gal1 by the human trophoblast cell line JEG-3 was primarily controlled by progesterone and pro-inflammatory cytokines and impaired T-cell responses by limiting T cell viability, suppressing the secretion of Th1-type cytokines and favoring the expansion of CD4(+)CD25(+)FoxP3(+) regulatory T (T(reg)) cells. Targeted inhibition of Gal1 expression through antibody (Ab)-mediated blockade, addition of the specific disaccharide lactose or retroviral-mediated siRNA strategies prevented these immunoregulatory effects. Consistent with a homeostatic role of endogenous Gal1, patients with recurrent pregnancy loss showed considerably lower levels of circulating Gal1 and had higher frequency of anti-Gal1 auto-Abs in their sera compared with fertile women. Thus, endogenous Gal1 confers immune privilege to human trophoblast cells by triggering a broad tolerogenic program with potential implications in threatened pregnancies.

Monocytes from Sjögren's syndrome patients display increased vasoactive intestinal peptide receptor 2 expression and impaired apoptotic cell phagocytosis

Sjögrens syndrome (SS) is a chronic autoimmune disease characterized by salivary and lacrimal gland dysfunction. Clinical observations and results from animal models of SS support the role of aberrant epithelial cell apoptosis and immune homeostasis loss in the glands as triggering factors for the autoimmune response. Vasoactive intestinal peptide (VIP) promotes potent anti‐inflammatory effects in several inflammatory and autoimmune disease models, including the non‐obese diabetic (NOD) mouse model of SS. With the knowledge that VIP modulates monocyte function through vasoactive intestinal peptide receptors (VPAC) and that immune homeostasis maintenance depends strongly upon a rapid and immunosuppressant apoptotic cell clearance by monocytes/macrophages, in this study we explored VPAC expression on monocytes from primary SS (pSS) patients and the ability of VIP to modulate apoptotic cell phagocytic function and cytokine profile. Monocytes isolated from individual pSS patients showed an increased expression of VPAC2 subtype of VIP receptors, absent in monocytes from control subjects, with no changes in VPAC1 expression. VPAC2 receptor expression could be induced further with lipopolysaccharide (LPS) in pSS monocytes and VIP inhibited the effect. Moreover, monocytes from pSS patients showed an impaired phagocytosis of apoptotic epithelial cells, as evidenced by reduced engulfment ability and the failure to promote an immunosuppressant cytokine profile. However, VIP neither modulated monocyte/macrophage phagocytic function nor did it reverse their inflammatory profile. We conclude that monocytes from pSS patients express high levels of VPAC2 and display a deficient clearance of apoptotic cells that is not modulated by VIP.

Trophoblast cells induce a tolerogenic profile in dendritic cells.

BACKGROUND Dendritic cells (DCs), which are biased toward a tolerogenic profile, play a pivotal role in tissue-remodeling processes and angiogenesis at the maternal-fetal interface. Here, we analyzed the effect of trophoblast cells on the functional profile of DCs to gain insight on the tolerogenic mechanisms underlying the human placental-maternal dialog at early stages of gestation. METHODS DCs were differentiated from peripheral blood monocytes obtained from fertile women (n = 21), in the presence of interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor during 5 days in culture. Then, DCs were cultured with trophoblast cells (Swan-71 cell line obtained from normal cytotrophoblast, at 7 weeks) for 24 h and for an additional 24 h in the absence or presence of lipopolysaccharide (LPS) from Escherichia coli. DCs were recovered and used for flow cytometry, enzyme-linked immunosorbent assay, RT-PCR and suppression and migration assays. RESULTS Trophoblast cells significantly prevented the increase in CD83 expression induced by LPS without affecting the expression of CD86, CD40 and human leukocyte antigen-DR (P < 0.05). Trophoblast cells significantly decreased the production of IL-12p70 and tumor necrosis factor-α, while it increased the production of IL-10 (P < 0.05). No changes were observed in the production of IL-6 and monocyte chemotactic protein-1. The culture of DCs with trophoblast cells, also suppressed the stimulation of the allogeneic response triggered by LPS (P < 0.05). Conditioned DCs were able to increase the frequency of CD4 + CD25 + Foxp3 cells and this effect was accompanied by an increase in indoleamine 2, 3-dioxygenase expression in DCs (P < 0.05). CONCLUSIONS The interaction of DCs with trophoblast cells promotes the differentiation of DCs into cells with a predominantly tolerogenic profile that could contribute to a tolerogenic microenvironment at the maternal-fetal interface.

Modulation of maternal LIF producers T cells by trophoblast and paternal antigens.

Citation Fraccaroli L, Grasso E, Zeitler E, Lombardi E, Gogorza S, Etchepareborda JJ, Nagle C, Cortelezzi M, Leirós CP, Ramhorst R. Modulation of maternal LIF producers T cells by trophoblast and paternal antigens. Am J Reprod Immunol 2011; 65: 133–145

VIP boosts regulatory T cell induction by trophoblast cells in an in vitro model of trophoblast-maternal leukocyte interaction.

Inducible regulatory T cells (Tregs) exert a timely and efficient immunosuppressive action at the critical peri‐implantation stage essential for maternal tolerance to the conceptus. Vasoactive intestinal peptide (VIP) promotes anti‐inflammatory and tolerogenic profiles through binding to VIP receptors on immune cells. We evaluated whether VIP produced by trophoblast cells induces Tregs during the early interaction of maternal leukocytes with trophoblast cells, thus contributing to maternal tolerance. We used an in vitro model of maternal leukocyte–trophoblast cell interaction represented by cocultures of fertile womens PBMCs with a human trophoblast cell line (Swan‐71) and evaluated the effect of VIP added exogenously and of the endogenous polypeptide. VIP increased the frequency of CD4+CD25+FoxP3+ cells after coculture, and these cells were able to suppress the maternal alloresponse. VIP also increased the frequency of CD4+IL10+ and CD4+TGFβ+ cells, but it did not modulate IFN‐γ or IL‐17 production. Swan‐71 secreted VIP, and their coculture with maternal PBMCs significantly increased the frequency of Tregs. This effect was even more pronounced if the trophoblast cells had been pretreated with VIP. In both situations, the VIP antagonist prevented the increase in the frequency of CD4+Foxp3+ cells, reflecting a specific effect of the polypeptide after the interaction with Swan‐71 cells. Finally, the increase in CD4+CD25+FoxP3+ frequency was prevented by an anti–TGF‐β Ab and a VIP antagonist. These results suggest that VIP could have an active role in the immunoregulatory processes operating in the maternal–placental interface by contributing to the induction of Tregs through a mechanism involving TGF‐β1.

Tissue transglutaminase on trophoblast cells as a possible target of autoantibodies contributing to pregnancy complications in celiac patients.

Women with celiac disease (CD) are often affected by atypical presentations of the disease associated with reproductive disorders as a main extra‐digestive complaint. Here, we analyzed if autoantibodies against tissue transglutaminase (tTG) in sera from CD patients with reproductive disorders could display direct effects through their interaction with tTG expressed on trophoblast cells and phagocytes inducing tissue damage and interfering in the clearance of trophoblast apoptotic bodies.

Defects in the vasoactive intestinal peptide (VIP)/VPAC system during early stages of the placental-maternal leucocyte interaction impair the maternal tolerogenic response.

Successful embryo implantation occurs followed by a local inflammatory/T helper type 1 (Th1) response, subsequently redirected towards a tolerogenic predominant profile. The lack of control of this initial local inflammatory response may be an underlying cause of early pregnancy complications as recurrent spontaneous abortions (RSA). Considering that vasoactive intestinal peptide (VIP) mediates anti‐inflammatory and tolerogenic effects in several conditions we hypothesized that VIP might contribute to tolerance towards trophoblast antigens during the early interaction of maternal leucocytes and trophoblast cells. In this study we investigated VIP/VPAC system activity and expression on maternal peripheral blood mononuclear cells (PBMCs) after interaction with immortalized trophoblast cells (Swan‐71 cell line) as an in‐vitro model of feto–maternal interaction, and we analysed whether it modulates maternal regulatory T cell (Treg)/Th1 responses. We also investigated the contribution of the endogenous VIP/VPAC system to RSA pathogenesis. VIP decreased T‐bet expression significantly, reduced monocyte chemotactic protein‐1 (MCP‐1) and nitrite production in co‐cultures of PBMCs from fertile women with trophoblast cells; while it increased the frequency of CD4+CD25+ forkhead box protein 3 (Foxp3)+ cells, transforming growth factor (TGF)‐β expression and interleukin (IL)‐10 secretion. These effects were prevented by VIP‐specific antagonist. Interestingly, PBMCs from RSA patients displayed significantly higher T‐bet expression, lower Treg frequency and lower frequency of VIP‐producer CD4 lymphocytes after the interaction with trophoblast cells. Moreover, the patients displayed a significantly lower frequency of endometrial CD4+VIP+ cells in comparison with fertile women. VIP showed a Th1‐limiting and Treg‐promoting response in vitro that would favour early pregnancy outcome. Because RSA patients displayed defects in the VIP/VPAC system, this neuropeptide could be a promising candidate for diagnostic biomarker or surrogate biomarker for recurrent spontaneous abortions.