Immunoactive products of placenta. V. Immunoregulatory properties of a low molecular weight compound obtained from human placental cultures

Immunometabolic adaptation in monocytes underpins functional changes during pregnancy

Metabolic heterogeneity is a determinant of immune cell function. The normal physiological metabolic reprogramming of pregnancy that ensures the fuel requirements of mother and baby are met, might also underpin changes in immunity that occur with pregnancy and manifest as altered responses to pathogens and changes to autoimmune disease symptoms. Using peripheral blood from pregnant women at term, we reveal that monocytes lose M2-like and gain M1-like properties accompanied by reductions in mitochondrial mass, maximal respiration, and cardiolipin content in pregnancy; glycolysis is unperturbed. We establish that muramyl dipeptide (MDP)-stimulated cytokine production relies on oxidative metabolism, then show in pregnancy reduced cytokine production in response to MDP but not LPS. Overall, mitochondrially centered metabolic capabilities of late gestation monocytes are down-regulated revealing natural plasticity in monocyte phenotype and function that could reveal targets for improving pregnancy outcomes but also yield alternative therapeutic approaches to diverse metabolic and/or immune-mediated diseases beyond pregnancy.

Specific Isolation of Placenta-Derived Exosomes from the Circulation of Pregnant Women and Their Immunoregulatory Consequences

PROBLEM

One immunoregulatory pathway receiving little attention is placental exosome release. In normal pregnancy, as factors linked with early immunomodulation decline, placental exosomes become critical in modulating T-cell activation, suppressing effector T cells by enhancing lymphocyte apoptosis and CD3-zeta loss.

METHOD OF STUDY

Placental exosomes were specifically isolated from the maternal peripheral circulation by a chromatographic/immunosorbent procedure. Exosomal suppression of T-cell signaling molecules on unfractionated T cells and T subsets was analyzed by Western immunoblot. The role of Fas ligand (FasL) was defined by use of Fas-blocking antibody.

RESULTS

While exosomes of lymphoid origin could be demonstrated in all women, placenta-derived exosomes were only identified in pregnant patients. Placental exosomes suppressed T-cell expression of CD3-zeta and JAK3, while inducing SOCS-2. This downregulation of CD3-zeta was partially reversed by pre-incubating T cells with ZB4 antibody. Using T subsets, the level of CD3-zeta on CD8+ cells was inhibited 1.43-fold more than in CD4+ cells. On CD4+ CD25+ cells, CD3-zeta was not significantly inhibited.

CONCLUSION

Placental exosomes suppressed T-cell signaling components; however, while exosomal FasL is an important contributor, it does not appear to be the sole mediator. The additional expression of PD-L1 may explain immunoregulatory consequences of exosomes with low or absent FasL.

Engraftment potential of human amnion and chorion cells derived from term placenta

BACKGROUND

Fetal membranes are tissues of particular interest for several reasons, including their role in preventing rejection of the fetus and their early embryologic origin. which may entail progenitor potential. The immunologic reactivity and the transplantation potential of amnion and chorion cells, however, remain to be elucidated.

METHODS

Amnion and chorion cells were isolated from human term placenta and characterized by immunohistochemistry, flow cytometric analysis, and expression profile of relevant genes. The immunomodulatory characteristics of these cells were studied in allogeneic and xenogeneic mixed lymphocyte reactions and their engraftment potential analyzed by transplantation into neonatal swine and rats. Posttransplant chimerism was determined by polymerase chain reaction analysis with probes specific for human DNA.

RESULTS

Phenotypic and gene expression studies indicated mesenchymal stem cell-like profiles in both amnion and chorion cells that were positive for neuronal, pulmonary, adhesion, and migration markers. In addition, cells isolated both from amnion and chorion did not induce allogeneic nor xenogeneic lymphocyte proliferation responses and were able to actively suppress lymphocyte responsiveness. Transplantation in neonatal swine and rats resulted in human microchimerism in various organs and tissues.

CONCLUSIONS

Human amnion and chorion cells from term placenta can successfully engraft neonatal swine and rats. These results may be explained by the peculiar immunologic characteristics and mesenchymal stem cell-like phenotype of these cells. These findings suggest that amnion and chorion cells may represent an advantageous source of progenitor cells with potential applications in a variety of cell therapy and transplantation procedures.

Dialogue materno-fœtal et implantation embryonnaire humaine : des concepts qui évoluent

Multiple immunogical mechanisms allow fetal allograft tolerance. In this review, we first describe the maternal and embryological side in order to expose the dangers for the embryo enabling the development of materno-fetal strategies that will allow fetal survival and growth.

A corpus luteum is not a prerequisite for the expression of progesterone induced blocking factor by T-lymphocytes a week after implantation

PURPOSE

To determine if production of the immunomodulatory protein, progesterone induced blocking factor (PIBF), requires merely progesterone or whether other factors made by the corpus luteum are required.

METHODS

The percentage of peripheral lymphocytes expressing PIBF was determined by obtaining a blood sample from women 9-12 days after embryo transfer. The embryos were either fresh ones following hyperstimulation and oocyte retrieval or were frozen-thawed embryos. Preparation for frozen embryo transfer required corpus luteum suppression with exogenous estrogen. The percentage of lymphocytes expressing PIBF was determined by an immunocytochemistry method.

RESULTS

PIBF expression (>1%) was found in 20.5% of COH and 13.3% of frozen embryo transfer cycles. There either was a significant difference or a trend for higher pregnancy rates when PIBF expression was detected.

CONCLUSIONS

These data corroborate previous conclusions that PIBF is detected in a minority of women in the late luteal phase. A corpus luteum is not required for its expression.

Effects of the chromatographic fractions of the pig placental trophoblast on graft-versus-host reaction

The trophoblast has a significant role in regulation of immune reactions at the materno-fetal interface by producing biologically active substances. In our previous studies five fractions with immunomodulatory activities were isolated by gel chromatography from trophoblast of pig placentas. To confirm the immunomodulatory effect of these trophoblast fractions on allogeneic in vivo systems and to obtain more evidence for the relevance of their activity on the maternofetal interface, their effect was studied on graft-versus-host reaction (GVHR). To assess the GVHR, the primary and secondary popliteal lymph nodes assay was used in mice. In the primary GVHR, 100 microg protein of Fraction 2-5, mixed with 5 x 10(6) allogeneic spleen cells (C57BL/6), were injected into one of the foot pads of recipient (BALB/c) mice. The secondary GVHR was induced in F1 (BALB/c x C57BL/6) mice by injection of spleen cells of BALB/c mice intraperitoneally preimmunized with allogeneic cells. The GVHR was measured by the weight of lymph nodes and by the lymphocyte proliferation. Flow cytometric analyses of the cells in the nodes with GVHR and under the influence of Fraction 4 or 5 were performed using monoclonal antibodies. In the primary GVHR, Fraction 4 or 5, injected simultaneously with allogeneic spleen cells, significantly suppressed the lymph nodes reactivity. Fractions 4 and 5 inhibited the ability of the spleen cells of mice intraperitoneally preimmunized with allogeneic cells to induce secondary GVHR in F1 mice. The Fraction 2 and 3 had no effect on GVHR. The results revealed that a group of proteins with Mr 37-7 kDa, isolated from trophoblast of pig placenta, strongly suppressed popliteal lymph node reactivity in the primary and secondary GVHR. The data provide convincing evidence for these fractions in vivo activity, for their effect across the species barrier and suggest the relevance of the same reactions on the materno-fetal interface.

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

PROBLEM

Th2 cytokines and Fas/Fas ligand interactions are proposed to be part of the placental barrier that contribute to the success of allogeneic pregnancy. To fully understand the role regulation of Th2 cytokines, we must isolate and identify the cells that produce them. We also need to assess the requirement for Fas/Fas ligand interaction in facilitating a successful allogeneic pregnancy.

METHOD OF STUDY

To assess the site of production of Th2 cytokines, we used immunohistochemistry sections from placental and decidual tissue obtained at various stages of gestation in mice and humans. We used mice that are genetically deficient in Fas/Fas ligand interactions and raised specific anti-paternal CTLs by anti-paternal immunization of the mother before mating.

RESULTS

The detailed results show that in both species the bulk of Th2 production may come from non-lymphoid tissues in the placenta and decidua, with a major role for trophoblasts. This raises questions about the mechanism(s) by which alloimmunization enhances local Th2 cytokine production. This issue is discussed.

CONCLUSIONS

The success of allopregnancy in mice with circulating anti-paternal CTLs and deficient Fas/Fas ligand interactions rules out a mandatory role for such a mechanism in ensuring the success of allogeneic pregnancy.

Jeg-3 human choriocarcinoma-induced immunosuppression: downregulation of interleukin-2, interleukin-2 receptor alpha-chain, and its Jak/Stat signaling pathway

PROBLEM

The mechanisms of the immunosuppressive and immunosuppression-inducing capacities of Jeg-3 human choriocarcinoma cell line supernatants (HCSs) are not yet completely understood. The influence on interleukin (IL)-2, IL-4 and interferon (IFN)-gamma production; IL-2 receptor (IL-2R) alpha-, beta-, and gamma-chain; and the signaling pathway molecules Janus kinase (Jak)1, Jak3, signal transducers and activators of transcription (Stat)1, Stat3, and Stat5 should be investigated.

METHOD OF STUDY

For assessment of IL production, whole peripheral venous blood from healthy donors was stimulated with phorbol-myristate-acetate and ionomycine. Secretion of ILs was blocked with monensine. Intracellular ILs were analyzed by flow cytometry. For IL-2R and signaling pathway molecule analysis, peripheral blood lymphocytes were stimulated with phytohemagglutinin (PHA). IL-2R chains were measured by flow cytometry, and Jaks/Stats by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot.

RESULTS

Phorbol-myristate-acetate and ionomycine strongly increase the percent-age of IL-2+ cells; an additional 50% HCSs significantly suppresses the percentage to, or below the level of unstimulated cells. IFN-gamma production is strongly decreased by HCSs in some cases, but not in others. PHA stimulates IL-2R alpha-, beta-, and gamma-chain expression and their signaling pathway molecules Jak1, Jak3, Stat1, Stat3, and Stat5. 50% HCS downregulates the alpha-chain and slightly upregulates the beta-chain. Jak1, Jak3, Stat1, Stat3, and Stat5 expression is suppressed approximately to, or below the level of unstimulated cells.

CONCLUSIONS

HCS forcefully blocks the production of IL-2; the IL-2R alpha-chain; and Jak1, Jak3, Stat1, Stat3, and Stat5 expression. The observed phenomena might be caused by downregulation of an IL-2R regulation gene, and might play a key role in the expansion of choriocarcinoma, and possibly in the survival of the fetal allograft.

Suppression of immunoglobulin secretion by soluble annexin II

Annexin II (AII) belongs to a family of glycoproteins that bind negatively charged phospholipids in the presence of calcium. The annexins exert various biological functions. We have previously shown that soluble AII suppresses mitogen-induced lymphoproliferation in vitro. In this study we address the question of whether soluble AII may also affect immunoglobulin secretion. Mononuclear cells from peripheral blood were stimulated with pokeweed mitogen in vitro and immunoglobulin-secreting cells were quantified using an ELISPOT assay. Retroplacental serum and soluble AII significantly inhibited secretion of IgG and IgM when added at concentrations that did not affect lymphoproliferation or cell viability. The inhibitory effect was dose- and time dependent. Significant suppression was observed when soluble AII was added at concentrations of 0.1 and 0.01 microg/ml. The strongest inhibition was observed when soluble AII or retroplacental serum was added initially. The data demonstrate that soluble AII can suppress immunoglobulin secretion in vitro. AII seems to be a potent immunosuppressive substance. The presence of high levels of soluble AII in retroplacental serum may indicate a possible immunomodulatory role in normal pregnancy.

Immune suppression and Th1/Th2 balance in pregnancy revisited: a (very) personal tribute to Tom Wegmann

PROBLEM

The paradigm of local suppression necessary to understand the survival of the fetal allograft is often compared with the host-tumor relationship.

METHODS

We investigated two components of local immune suppression: placenta-induced immunosuppression, which is mediated at least in part by a soluble factor of low molecular weight that can induce anergy in lymphocytes, and interleukin-10 (IL-10).

RESULTS

We show that enhancement of IL-10 production in the decidua and placenta after alloimmunization requires the presence of Asialo GM1+ cells. Placenta-induced immunosuppression is linked with defects in phosphorylation of some components of the T cell receptor.

CONCLUSION

NK cells could be in fact regulatory cells pushing maternal immune response toward a Th2 profile, beneficial for fetal survival, or toward a Th1 type of immune response, which acts in synergy. Modulation of TcR may represent a new mechanism for maternal-fetal tolerance.