IL-12 producing monocytes and IFN-γ and TNF-α producing T-lymphocytes are increased in placentas infected by Plasmodium falciparum

https://doi.org/10.1016/j.jri.2006.10.001Get rights and content

Abstract

Placental Plasmodium falciparum sequestration is associated with dysregulated immune function. Placental inflammatory responses via IFN-γ and TNF-α are implicated in functional damage. However, they are needed during placental infection to control asexual stage parasites. To test the hypothesis that placental immunomodulation associated with malaria disturbs cytokine secretion differently in monocytes and lymphocytes, we have determined the proportion of monocytes and/or lymphocytes secreting IFN-γ, TNF-α, IL-10 and IL-12.

Intervillous and peripheral blood monocyte (CD14+) and lymphocyte (CD3/CD4+; CD3/CD8+) cytokine production was compared between 17 P. falciparum-infected and 12 non-infected Senegalese women. After culture with phorbolmyristate acetate/ionomycin (PMA/iono), lipopolysaccharide (LPS) or P. falciparum-infected erythrocytes (IE), the intracellular expression of cytokines in lymphocytes (IFN-γ, TNF-α) and monocytes (IL-10, IL-12, TNF-α), was detected. In response to IE, CD4+ and CD8+ T-cells produced IFN-γ and TNF-α at similar rates in both compartments. In response to PMA/iono, the frequencies of CD4+ and CD8+ T-cells producing IFN-γ and TNF-α were similar in both compartments, but increased in P. falciparum-infected placentas. In response to LPS or IE, IL-12 secreting monocytes were increased in infected women, while the frequency of TNF-α secreting monocytes was decreased compared to that in non-infected placenta.

The monocyte IL-12 response is not impaired in infected women. IL-12 is an important factor for inducing IFN-γ in T-cells. Thus, IL-12 and IFN-α responses may synergistically allow a protective immune response in placental malaria. TNF-α production by CD4+ and CD8+ T-cells is up-regulated in P. falciparum-infected placentas, suggesting that T-cells actively participate to inflammatory responses.

Introduction

Because of pregnancy-related immunomodulation, pregnant women are more susceptible to various infectious pathologies, including malaria. The materno-fetal interface is a complex network where numerous cytokines are secreted. Pregnancy immunomodulation was first considered to result from a Th1/Th2 shift to a decrease of Th1-type cytokines (TNF-α and IFN-γ) (Krishnan et al., 1996) and an increase of Th2-type cytokines (IL-4, IL-10, TGF-β) to allow the fetal allograft to develop (Chaouat et al., 1999, Wegmann et al., 1993). However, this modulation was proposed to result from a state of monocyte activation and lymphocyte inhibition (Dudley et al., 1996, Sacks et al., 1998). A wide variety of cytokines are present at the maternal–fetal interface, but the cellular complexity of the placenta has made it difficult to determine which cells produce which cytokines. Normal pregnancy is characterized by a split tolerance illustrated by normal B cells’ or monocytes’ responses, and T-cells’ anergy or clonal deletion. The main mechanisms implicated in this immunomodulation are Fas/Fas ligand interaction (Kauma et al., 1999), soluble HLA-G1 and G2, and suppressor factor (Clark, 2005). Importantly, this immunomodulation is not specific for malarial antigens, and it is still unclear whether it is related to lymphocyte inhibition (Spina et al., 1998) or functional alteration of antigen-presenting cells, such as monocytes and macrophages (Fievet et al., 1995). It has been reported that Fas ligand on trophoblastic cells can induce apoptosis of activated placental lymphocytes (Kauma et al., 1999). In addition, several studies have suggested inhibition of monocyte/macrophage functions and a defect in antigen presentation during Plasmodium falciparum infection (Schwarzer et al., 1998, Scorza et al., 1999). Hemozoin pigment may also impair monocyte/macrophage function by reducing the expression of MHC II or CD54. Moreover, placental cytokines can modulate antigen-presenting cell function by inhibiting or increasing the expression of various molecules on the monocyte surface. Monocyte MHC II expression is increased by IL-13, IFN-γ, and TNF-α (de Waal Malefyt et al., 1993), and is reduced by IL-10 (Moreau et al., 1999).

New insights on the molecular identification of specific P. falciparum ligands involved in cytoadhesion to the syncytiotrophoblast lead to a better knowledge of anti-malarial immunity acquired during pregnancy (Beeson et al., 2005). However, the questions of how an effective cellular immune response can be mounted in the placenta and the implication of this cellular response in the immunopathology are not completely understood. Pregnant women, particularly primigravidae, are more susceptible to malaria. During pregnancy-associated malaria (PAM), adhesion of P. falciparum-infected erythrocytes (IE) to syncytiotrophoblast leads to parasite sequestration in the intervillous spaces. One reason for this is that the parasite adheres specifically to chondroitin sulfate-A expressed on syncytiotrophoblast (Fried and Duffy, 1996, Reeder et al., 2000). P. falciparum development in the placenta causes an imbalance in the immune response with an increase of Th1-type cytokines, IFN-γ and TNF-α (Fievet et al., 2001, Fried et al., 1998, Moormann et al., 1999), which explains why immunomodulation is more important in placental blood than in the peripheral blood (Diouf et al., 2004). This inflammatory response is responsible for functional damage in placental villi, and disturbs feto-maternal exchange, leading to low birth weight (Menendez et al., 2000, Ordi et al., 1998). IFN-γ secretion by intervillous blood (IVB) mononuclear cells is associated with protection against PAM, suggesting a role for the cellular response in this protection (Moore et al., 1999). However, the role of IL-12 and IL-18 in regulation of IFN-γ secreting cells (natural killer; CD4+ and CD8+ T-cells) in the placenta is not yet well defined. A single study describes a disturbance of placental IL-12 secretion during HIV/malaria co-infection (Chaisavaneeyakorn et al., 2002). All studies quantified cytokines in the plasma or in the supernatant of in vitro culture of cells. In the present study, we have used flow cytometric analysis and intracellular staining to allow identification and quantification of the secreting cells. To test the hypothesis that placental immunomodulation associated with PAM disturbs cytokine secretion differently in monocytes and lymphocytes, we determined the proportion of monocytes and/or lymphocytes secreting IFN-γ, TNF-α, IL-10 and IL-12. To confirm cytokine changes occurring during PAM, we quantified and compared cytokine secretion in peripheral and placental blood from P. falciparum infected and non-infected women. We choose to investigate the immune responses in two blood compartments, peripheral and intervillous. This was based on the fact that the placenta is the site where the adhesion and multiplication of P. falciparum takes place and it is where inflammatory responses might be the most damaging for feto-maternal exchanges during pregnancy.

Section snippets

Study site, subjects and blood sample collection

This study took place in Pikine-Guédiawaye, 15 km northeast of Dakar, a suburb in full demographic expansion with a population estimated at 1 million. Malaria is hypo-endemic, with an average of one infecting bite/person/year. Malaria transmission is perennial, with an increase during the rainy season from September to January. The main malaria vector is Anopheles arabiensis, and P. falciparum is the most widespread malaria species (98% of cases). Subjects were enrolled in maternity wards of the

Study population

A total of 29 pregnant women were enrolled. They were 15–37 years old with a mean (±S.D.) age of 23.3 ± 6.4 years. Parity varied from 1 to 8, with a mean of 2.4 ± 2.1. Primiparae represented 48.3% of all women, while great multiparae (more than five pregnancies) were 20.7%. Placental thick blood smear examination revealed that 17 women were infected by P. falciparum and 12 were not. Parasitological results from peripheral and intervillous blood were in agreement. Among infected women, parasite

Discussion

The aim of the present study was to evaluate placental immune responses at the cellular level in P. falciparum-infected mothers. Because of both the specific localization and multiplication of P. falciparum in the placenta during pregnancy, and the particular modulation of the immune response within the placenta, it was important to investigate cell responses in both peripheral and intervillous blood compartments. The intervillous blood compartment is the strategic place where specific immune

Acknowledgements

We acknowledge the strong support of the staff of the maternity clinic of Centre de Santé Roi Baudoin de Guédiawaye who were in charge of the collection of biological samples and other data, and specifically to Bineta, Ndéye Amy, Pape Ndiaye and Boubacar. We are very grateful to all the mothers. We are grateful also to Gérard Chaouat, Julie Myers and Jim Keenan for scientific advice, and to Guillaume Roussel for technical assistance. This work was supported by IMEA and the French Ministry of

References (45)

  • S. Chaisavaneeyakorn et al.

    Immunity to placental malaria. III. Impairment of interleukin(IL)-12, not IL-18, and interferon-inducible protein-10 responses in the placental intervillous blood of human immunodeficiency virus/malaria-coinfected women

    J. Infect. Dis.

    (2002)
  • G. Chaouat et al.

    Localization of the Th2 cytokines IL-3, IL-4 IL-10 at the fetomaternal interface during human and murine pregnancy and lack of requirement for Fas/Fas ligand interaction for a successful allogeneic pregnancy

    Am. J. Reprod. Immunol.

    (1999)
  • G. Chaouat et al.

    The emerging role of IL-10 in pregnancy

    Am. J. Reprod. Immunol.

    (1996)
  • D.A. Clark

    Tolerance signaling molecules

    Chem. Immunol. Allergy

    (2005)
  • R. de Waal Malefyt et al.

    Effects of IL-13 on phenotype, cytokine production, and cytotoxic function of human monocytes Comparison with IL-4 and modulation by IFN-γ or IL-10

    J. Immunol.

    (1993)
  • I. Diouf et al.

    Monocyte activation and T cell inhibition in Plasmodium falciparum-infected placenta

    J. Infect. Dis.

    (2004)
  • N. Fievet et al.

    Malaria and pregnancy in cameroonian primigravidae—humoral and cellular immune responses to Plasmodium falciparum blood-stage antigens

    Am. J. Trop. Med. Hyg.

    (1995)
  • N. Fievet et al.

    Plasmodium falciparum induces a Th1/Th2 disequilibrium, favoring the Th1-type pathway, in the human placenta

    J. Infect. Dis.

    (2001)
  • M. Fried et al.

    Adherence of Plasmodium falciparum to chondroitin sulfate A in the human placenta

    Science

    (1996)
  • M. Fried et al.

    Malaria elicits type 1 cytokines in the human placenta: IFN-γ and TNF-α associated with pregnancy outcomes

    J. Immunol.

    (1998)
  • J. Gysin et al.

    Ex vivo desequestration of Plasmodium falciparum-infected erythrocytes from human placenta by chondroitin sulfate A

    Infect. Immun.

    (1999)
  • S.W. Kauma et al.

    Placental Fas ligand expression is a mechanism for maternal immune tolerance to the fetus

    J. Clin. Endocrinol. Metab.

    (1999)
  • Cited by (40)

    • Immunohistopathological changes in the placenta of malaria-infected women in unstable transmission setting of Aligarh

      2022, Placenta
      Citation Excerpt :

      The accumulation is mainly due to the binding of variant parasite antigens present on the surface of iRBCs with chondroitin sulphate A(CSA) of proteoglycans expressed by syncytiotrophoblast cells [16]. This leads to the invasion of maternal immune cells, mainly neutrophils, monocytes and macrophages in the placenta [17–20]. Several studies reported that the accumulation of iRBCs and inflammatory cells in the intervillous space may result in foetal and placental hypoxia either by utilisation of oxygen by the accumulated cells or by reducing blood flow and surface area for the maternal-foetal exchange [21,22].

    • Panax notoginseng saponin R1 modulates TNF-α/NF-κB signaling and attenuates allergic airway inflammation in asthma

      2020, International Immunopharmacology
      Citation Excerpt :

      TNF-α is an inflammatory cytokine associated with Th1 that plays an important role in the pathogenesis of asthma [32]. It is a neutrophil and monocyte chemotactic factor that increases vascular permeability and activates T cells, eosinophils, and mast cells [33]. A previous study showed that TNF-α is one of key mediators of moraxella catarrhalis triggered exacerbation of allergic airway inflammation [34].

    • Characterization of cAMP as an anti-allergic functional factor in Chinese jujube (Ziziphus jujuba Mill.)

      2019, Journal of Functional Foods
      Citation Excerpt :

      Allergy and inflammation are associated with enhanced production of Th2 cytokines (IL-4, IL-5) and decreased production of Th1 cytokines (IFN-γ, TNF-α) (Quraishi, Davies, & Craig, 2004). T cells activated in the presence of IL-12 differentiate into Th1 cells, which predominantly secrete IFN-γ and TNF-α and promote delayed-type hypersensitivity responses (Diouf et al., 2007). Some studies have shown that the occurrence of allergic symptoms is often associated with a Th1/Th2 imbalance (Romagnani, 2004).

    • Modified nanoparticle mediated IL-12 immunogene therapy for colon cancer

      2017, Nanomedicine: Nanotechnology, Biology, and Medicine
      Citation Excerpt :

      We also found that DMP-pIL12 stimulated lymphocytes activity, and the subsequent higher level of TNF-α and IFN-γ production than the controls. The current results are supported by previous findings: IL-12 could stimulate the production of TNF-α and IFN-γ, which serves to mediate the destruction of cancerous cells by inducing an anti-proliferative state.36–39 Besides, TNF-α is also closely related to the cell apoptosis, inflammation and immunity.40–42

    • Clinical development of a VAR2CSA-based placental malaria vaccine PAMVAC: Quantifying vaccine antigen-specific memory B & T cell activity in Beninese primigravidae

      2017, Vaccine
      Citation Excerpt :

      The choice of these cytokines relies on their purported role in anti-malarial immunity. Placental malaria is associated with an increased frequency of IFN-γ and TNF-α producing T lymphocytes, suggesting an important role of those cells and the cytokines they produce in protection [20]. The concentrations of IL-5, IL-6, IL-10, TNF-α, and IFN-γ in placental and/or peripheral plasma have been shown to be associated with PAM [21–23].

    • Role of some biomarkers in placental malaria in women living in Yaoundé, Cameroon

      2015, Acta Tropica
      Citation Excerpt :

      The selective accumulation of malaria parasites in the intervillous spaces of the placenta often leads to an increased of pro-inflammatory responses mediated by cytokines and chemokines, which contribute to the pathogenesis of PM and its complications (Fried et al., 1998; Suguitan et al., 2003). In fact, studies have shown that cells producing the regulatory cytokine (IL-10) in response to malaria infection during pregnancy can accumulate in the intervillous space of the placenta (Diouf et al., 2007, Suguitan et al., 2003). Although the anti-inflammatory effects of IL-10 are necessary to prevent the genesis of PM, it might also enhance the persistence of malaria parasites (Kevin et al., 2008; Gazzinelli et al., 1992).

    View all citing articles on Scopus

    Informed consent was obtained from all donors. The National Ethics Committee of Senegalese Health Ministry approved this study.

    View full text