The same immunoregulatory molecules contribute to successful pregnancy and transplantation

Decidual macrophages in recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is defined as two or more pregnancy loss, affecting the happiness index of fertility couples. The mechanisms involved in the occurrence of RSA are not clear to date. The primary problem for the maternal immune system is how to establish and maintain the immune tolerance to the semi-allogeneic fetuses. During the pregnancy, decidual macrophages mainly play an important role in the immunologic dialogue. The purpose of this study is to explore decidual macrophages, and to understand whether there is a connection between these cells and RSA by analyzing their phenotypes and functions. Pubmed, Web of Science and Embase were searched. The eligibility criterion for this review was evaluating the literature about the pregnancy and macrophages. Any disagreement between the authors was resolved upon discussion and if required by the judgment of the corresponding author. We summarized the latest views on the phenotype, function and dysfunction of decidual macrophages to illuminate its relationship with RSA.

The Role of CD200-CD200 Receptor in Human Blood and Lymphatic Endothelial Cells in the Regulation of Skin Tissue Inflammation

CD200 is a cell membrane glycoprotein that interacts with its structurally related receptor (CD200R) expressed on immune cells. We characterized CD200–CD200R interactions in human adult/juvenile (j/a) and fetal (f) skin and in in vivo prevascularized skin substitutes (vascDESS) prepared by co-culturing human dermal microvascular endothelial cells (HDMEC), containing both blood (BEC) and lymphatic (LEC) EC. We detected the highest expression of CD200 on lymphatic capillaries in j/a and f skin as well as in vascDESS in vivo, whereas it was only weakly expressed on blood capillaries. Notably, the highest CD200 levels were detected on LEC with enhanced Podoplanin expression, while reduced expression was observed on Podoplanin-low LEC. Further, qRT-PCR analysis revealed upregulated expression of some chemokines, including CC-chemokine ligand 21 (CCL21) in j/aCD200⁺ LEC, as compared to j/aCD200⁻ LEC. The expression of CD200R was mainly detected on myeloid cells such as granulocytes, monocytes/macrophages, T cells in human peripheral blood, and human and rat skin. Functional immunoassays demonstrated specific binding of skin-derived CD200⁺ HDMEC to myeloid CD200R⁺ cells in vitro. Importantly, we confirmed enhanced CD200–CD200R interaction in vascDESS in vivo. We concluded that the CD200–CD200R axis plays a crucial role in regulating tissue inflammation during skin wound healing.

Understanding Asthma and Allergies by the Lens of Biodiversity and Epigenetic Changes

Exposure to different organisms (bacteria, mold, virus, protozoan, helminths, among others) can induce epigenetic changes affecting the modulation of immune responses and consequently increasing the susceptibility to inflammatory diseases. Epigenomic regulatory features are highly affected during embryonic development and are responsible for the expression or repression of different genes associated with cell development and targeting/conducting immune responses. The well-known, "window of opportunity" that includes maternal and post-natal environmental exposures, which include maternal infections, microbiota, diet, drugs, and pollutant exposures are of fundamental importance to immune modulation and these events are almost always accompanied by epigenetic changes. Recently, it has been shown that these alterations could be involved in both risk and protection of allergic diseases through mechanisms, such as DNA methylation and histone modifications, which can enhance Th2 responses and maintain memory Th2 cells or decrease Treg cells differentiation. In addition, epigenetic changes may differ according to the microbial agent involved and may even influence different asthma or allergy phenotypes. In this review, we discuss how exposure to different organisms, including bacteria, viruses, and helminths can lead to epigenetic modulations and how this correlates with allergic diseases considering different genetic backgrounds of several ancestral populations.

CD200:CD200R Interactions and Their Importance in Immunoregulation

The molecule CD200, described many years ago as a naturally occurring immunomodulatory agent, capable of regulating inflammation and transplant rejection, has attracted additional interest over the past years with the realization that it may also serve as an important marker for progressive malignancy. A large body of evidence also supports the hypothesis that this molecule can contribute to immunoregulation of, among other diseases, infection, autoimmune disease and allergy. New data have also come to light to characterize the receptors for CD200 (CD200R) and their potential mechanism(s) of action at the biochemical level, as well as the description of a novel natural antagonist of CD200, lacking the NH₂-terminal region of the full-length molecule. Significant controversies exist concerning the relative importance of CD200 as a ligand for all reported CD200Rs. Nevertheless, some progress has been made in the identification of the structural constraints determining the interaction between CD200 and CD200R, and this information has in turn proved of use in developing novel small molecule agonists/antagonists of the interaction. The review below highlights many of these newer findings, and attempts to place them in the broad context of our understanding of the role of CD200-CD200R interactions in a variety of human diseases.

Is there a Role of Intravenous Immunoglobulin in Immunologic Recurrent Pregnancy Loss?

Recurrent pregnancy loss (RPL) commonly refers to three or more miscarriages that occur before 20 weeks of pregnancy. The immunological cause of RPL could be either an auto- or alloimmune-related event or both. Because of the discovery of immunological abnormalities in RPL patients in clinical practice, several immunomodulatory therapies were introduced to maintain the immune balance at the maternal-fetal interface. Intravenous immunoglobulin (IVIg) is one of the immunomodulators. In recent years, several studies have analyzed the therapeutic effect of IVIg on RPL patients with antiphospholipid syndrome (APS) or unexplained RPL. However, their results are controversial. IVIg can be used in RPL patients with APS who have previously failed in other treatments. It is recommended that IVIg infusion could be considered used before conception in RPL patients who have cellular immune abnormalities such as increased natural killer (NK) cell counts, NK cell cytotoxicity, or increased T helper (Th)1/Th2 ratio, depending on the cut-off values of each hospital. The aim of this review was to summarize the mechanisms, efficacy, pharmacokinetics, and side effects associated with passive immunization using IVIg in immunologic RPL, according to the literature published in recent years. We hope that more obstetricians will be able to understand the timing and indication of IVIg properly in immunologic RPL patients and effectively enhance pregnancy outcomes for mothers and neonates.

Role of Macrophages in Pregnancy and Related Complications

Macrophages (MФs) are the leukocytes produced from differentiation of monocytes and are located in almost all tissues of human body. They are involved in various processes, such as phagocytosis, innate and adaptive immunity, proinflammatory (M1) and anti-inflammatory (M2) activity, depending on the tissue microenvironment. They play a crucial role in pregnancy, and their dysfunction or alteration of polarity is involved in pregnancy disorders, like preeclampsia, recurrent spontaneous abortion, infertility, intrauterine growth restriction, and preterm labor. About 50-60% of decidual leukocytes are natural killer (NK) cells followed by MФs (the second largest population). MФs are actively involved in trophoblast invasion, tissue and vascular remodeling during early pregnancy, besides their role as major antigen-presenting cells in the decidua. These cells have different phenotypes and polarities in different stages of pregnancy. They have also been observed to enhance tumor growth by their anti-inflammatory activity (M2 type) and prevent immunogenic rejection. Targeted alteration of polarity (M1-M2 or vice versa) could be a major focus in the future treatment of pregnancy complications. This review is focused on the role of MФs in pregnancy, their involvement in pregnancy disorders, and decidual MФs as possible therapeutic targets for the treatment of pregnancy complications.

Treatment with intravenous immunoglobulin in patients with recurrent pregnancy loss: An update

Intravenous immunoglobulin (IVIg) has a documented clinical effect in many autoimmune diseases and has so far been tested in >10 randomised controlled trials (RCTs) in women with recurrent pregnancy loss (RPL). The results of the RCTs have, however, been very divergent. In meta-analyses of all trials, no significant impact on live birth rate has been reported. In contrast, in sensitivity analyses, IVIg significantly increased live birth rates when initiated prior to conception and it had a borderline significant therapeutic effect in women with secondary RPL. Higher dosages of IVIg and serological signs of autoimmunity in the treated patients tended to increase the success rate after treatment. A follow-up study of patients from our recent RCT also supports a significant therapeutic effect in patients who had received IVIg before conception. The lessons learned from the published trials and meta-analyses should be incorporated in the design of future RCTs of IVIg in the treatment of RPL.

Deciphering the Contribution of γδ T Cells to Outcomes in Transplantation

γδ T cells are a subpopulation of lymphocytes expressing heterodimeric T-cell receptors composed of γ and δ chains. They are morphologically and functionally heterogeneous, innate yet also adaptive in behavior, and exhibit diverse activities spanning immunosurveillance, immunomodulation, and direct cytotoxicity. The specific responses of γδ T cells to allografts are yet to be fully elucidated with evidence of both detrimental and tolerogenic roles in different settings. Here we present an overview of γδ T-cell literature, consider ways in which their functional heterogeneity contributes to the outcomes after transplantation, and reflect on methods to harness their beneficial properties.

Changes in the cellular immune system and circulating inflammatory markers of stroke patients

This study was designed to investigate dynamic changes in the cellular immune system and circulating inflammatory markers after ischemic stroke. Blood was collected from 96 patients and 99 age-matched control subjects for detection of lymphocyte subpopulations and inflammatory markers. We observed decreases in B cells, Th cells, cytotoxic T cells, and NK cells and an increase in regulatory T (Treg) cells in stroke patients on days 1, 3, and 7. Serum levels of TNF-α, C-reactive protein (CRP), IL-4, IL-6, IL-10, IL-17, IL-23, and TGF-β increased, whereas serum level of IFN-γ decreased at all time points after stroke. Stroke patients with infection exhibited a similar tendency toward changes in some lymphocyte subpopulations and inflammatory markers as stroke patients without infection. After controlling for NIH Stroke Scale (NIHSS), we observed no differences in lymphocyte subpopulations between patients with anterior circulation stroke and those with posterior circulation stroke at any time point. The splenic volume correlated positively with the percentages of B cells, Th cells, and cytotoxic T cells, but negatively with Treg cells on day 3 after stroke. Infections were associated with splenic volume, leukocyte counts, percentage of Treg cells, and serum levels of CRP, IL-10, and IFN-γ on day 3. Lesion volume correlated positively with CRP, IL-6, and IL-23, but negatively with IFN-γ on day 3. The NIHSS showed a positive relation with IL-6 and IL-10 on day 3. Ischemic stroke has a profound effect on the systemic immune system that might explain the increased susceptibility of stroke patients to infection.

Human CD200 suppresses macrophage-mediated xenogeneic cytotoxicity and phagocytosis

PURPOSE

Various strategies, such as the generation of alpha-1,3-galactosyltransferase knocked-out pigs and CD55 transgenic pigs, have been investigated to inhibit pig to human xenogeneic rejection. Our aim is to develop strategies to overcome the hurdle of not only hyper acute rejection, but also that of cellular xenogeneic rejection (CXR). Although macrophages have been well known to play a critical role in CXR, monocyte/macrophage-mediated xenogeneic rejection has not been well studied. In this study, we evaluated the effect of CD200 in xenogeneic rejection by macrophages.

METHODS

Naïve swine endothelial cells (SEC) and SEC/CD200 were co-cultured with M0 macrophages and the cytotoxicity was measured by a WST-8 assay. The phagocytosis of SEC and SEC/CD200 by macrophages was analyzed by flow cytometry.

RESULTS

While CD200 failed to suppress a significant amount of cytotoxicity against SEC by monocytes, M0 macrophage-mediated cytotoxicity was significantly suppressed by human CD200. The phagocytosis by M0 macrophages was also tested. The phagocytosis assay revealed that human CD200 suppresses M0 macrophage-mediated phagocytosis.

CONCLUSIONS

Our findings indicate that human CD200 suppresses the xenogeneic rejection by CD200R⁺ macrophages and that the generation of hCD200 transgenic pigs for use in xenografts is very attractive for preventing the macrophage-mediated rejection.

The Predominant Th1 Cytokine Profile in Maternal Plasma of Preeclamptic Women Is Not Reflected in the Choriodecidual and Fetal Compartments

OBJECTIVE

Human pregnancy disorders such as preeclampsia are thought to involve variations in cytokine levels. It has been proposed that, in preeclamptic women, a balance favoring the Th1-type over the Th2-type cytokine profile determines local or systemic immunologic responses to pregnancy and that this may cause defective placental implantation and placental ischemia, which activate systemic endothelial cells. The purpose of this study was to determine whether cytokine expression differs in the maternal, choriodecidual, and fetal compartments, and between women with or without preeclampsia.

METHODS

Plasma concentrations of interferon gamma (IFNgamma), interleukin (IL)-2, IL-4, and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA) in samples obtained from maternal peripheral blood (MPB), choriodecidual (CD), and fetal cord (FC) blood compartments of 17 women with preeclampsia and in 15 normotensive women. Intracellular concentrations of IFNgamma and IL-2 in T lymphocytes were assessed by flow cytometry.

RESULTS

Plasma IFNgamma concentrations in both MPB and CD compartments were significantly higher in preeclamptic than in normotensive women. Maternal plasma IL-4 concentration was significantly lower in preeclamptic than in normotensive women. Intracellular IFNgamma and IL-2 concentrations did not differ significantly between preeclamptic and normotensive women.

CONCLUSIONS

The dominant Th1-type over Th2-type cytokine profile is evident in MPB, but not in the CD and FC blood compartments. This might reflect the complex cytokine networks in the fetal-placental interface and might involve trophoblasts or decidual and endothelial cells, which could account for the increased plasma IFNgamma concentration and T-helper cell number.

Association of peripheral blood dendritic cells with recurrent pregnancy loss: a case-controlled study

PROBLEM

Dendritic cells (DCs) have been reported to play an important role in pregnancy. However, the role of DCs in recurrent pregnancy loss (RPL) has not been investigated well.

METHOD OF STUDY

Forty-three women affected by RPL and 16 fertile controls were recruited from June 2013 to December 2014. The peripheral blood DCs subsets, including myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), the levels (%) of CD80(+) , CD86(+) , and CD200(+) DCs were analyzed using flow cytometry.

RESULTS

The levels of total DCs, mDCs, and CD86(+) DCs were significantly higher (all P<.05); however, the level of CD200(+) DCs in the RPL group was significantly lower than that of the control group (P<.05). The logistical regression analyses showed that the elevated level of mDCs was significantly associated with RPL after adjustment for age (OR: 1.14, 95% CI, 1.01-1.29, P<.05).

CONCLUSION

The elevated level of mDCs was significantly associated with RPL, which might lead to the intervention of targeted immunosuppression in women with RPL.

CD200/CD200R Paired Potent Inhibitory Molecules Regulating Immune and Inflammatory Responses; Part II : CD 200/CD200R Potential Clinical Applications

CD200 and its receptor were recognized as having the multiple immunoregulatory functions. Their immunoregulatory, suppressive, and tolerogenic potentials could be very effectively exploited in the treatment of many diseases, e.g. Alzheimer disease, rheumatoid arthritis, and allergy to name only some. Many research projects are aimed to develop clinically valuable methods being based on the structure and function of these paired molecules. In this review, we would like to introduce CD200/CD200R functions in a clinical context.

Influence of inflammation on the immunological profile of adult-derived human liver mesenchymal stromal cells and stellate cells

BACKGROUND AIMS

Stem cell therapy for liver diseases has recently emerged as a promising alternative to liver transplantation. Eligible cells should have an appropriate immunophenotype. The aim of the present study was to define the immunological profile of two human liver-derived mesenchymal stromal cell populations, namely, stem cells (ADHLSC) and hepatic stellate cells (HSC).

METHODS

The study was conducted under normal and inflammatory conditions with the use of human bone marrow mesenchymal stromal cells (BM-MSC) as reference.

RESULTS

Like BM-MSC and ADHLSC, HSC were negative for hematopoietic (CD45) and endothelial (CD34) markers but positive for stromal markers. All cell types were constitutively positive for HLA class I and negative for human leukocyte antigen (HLA) class II and co-stimulatory molecules (CD80, CD86, CD134 and CD252). Inflammation induced the expression of CD40 in all cell types, but the highest values were observed on HSCs; high CD252 expression was only observed on HSC as compared with ADHLSC and BM-MSC. The expression of various adhesion molecules (CD54, CD58, CD106 and CD166) was dissimilar in these three cell types and was differentially influenced by inflammation as well. ADHLSC and HSC constitutively expressed the immunosuppressive molecule HLA-G, whereas CD274 expression was induced by inflammation, as in the case of BM-MSC. Moreover, all cell types expressed the two major natural killer ligands CD112 and CD115.

CONCLUSIONS

Toll-like receptors (TLR) 1, 3, 4 and 6 messenger RNA was expressed by both cell types, whereas TLR 2, 5, 7, 9 and 10 were only expressed by ADHLSC. Inflammation increased the expression of TLR 2 and 3 by ADHLSC and HSC. Finally, both liver-derived cell types were immunosuppressive because they inhibited the proliferation of mitogen-activated T cells.

Reduced CD200 and CD200R1 expression in human chorionic villi contributes to early spontaneous abortion

OBJECTIVE

To examine the expression of CD200 and its receptor (CD200R) in human chorionic villi during the first trimester of normal pregnancy and early spontaneous abortion (ESA).

DESIGN

Prospective study.

METHODS

Expression of CD200 and CD200R in the chorionic villi was determined using streptavidin-peroxidase immunohistochemistry, confocal laser scanning microscopy and real-time polymerase chain reaction.

POPULATION

Thirty-five women diagnosed with ESA and 30 women experiencing a healthy pregnancy in a medical university hospital in China were enrolled in this study between 2011 and 2013.

MAIN OUTCOME MEASURES

CD200 and CD200R expression.

RESULTS

The expression of CD200 in syncytiotrophoblast cells was significantly higher during normal pregnancy than in ESA (0.51 ± 0.05 vs. 0.35 ± 0.05). In contrast, expression of CD200 in cytotrophoblast cells and CD200R in stromal cells was significantly lower during normal pregnancy when compared with ESA (CD200: 0.16 ± 0.02 vs. 0.32 ± 0.03; CD200R: 0.19 ± 0.03 vs. 0.22 ± 0.02). In villi, the expression of both CD200 protein and CD200R transcripts were significantly higher in healthy first-trimester pregnancy than in ESA (CD200: 156.89 ± 105.65 vs. 37.51 ± 17.62).

CONCLUSIONS

There is an increase in inhibitory properties of human chorionic villi during normal pregnancy. The mechanism underlying ESA might be associated with enhanced expression of CD200 and CD200R in the trophoblast, leading to an upregulation of the immune response during the first trimester of pregnancy.

Amniotic fluid CD200 levels in pregnancies complicated by preterm prelabor rupture of the membranes

OBJECTIVE

To determine the amniotic fluid CD200 levels in uncomplicated pregnancies and in preterm prelabor rupture of the membranes (PPROM) according to microbial invasion of the amniotic cavity and histological chorioamnionitis and its association with neonatal outcomes.

METHODS

One hundred and fifty-nine women with singleton pregnancies were included in this study. Amniotic fluid was collected, and CD200 levels were determined using ELISA.

RESULTS

No difference was found in CD200 levels between women in the second trimester and women at term without labor. Women at term with labor had higher CD200 levels than women in the second trimester and women at term without labor. The presence of funisitis in PPROM pregnancies was associated with higher CD200 levels independent of gestational age (with funisitis: median 197.5 pg/mL versus without funisitis: median 61.0 pg/mL; p = 0.003). The need for tracheal intubation and the development of bronchopulmonary dysplasia were associated with higher CD200 levels.

CONCLUSIONS

Amniotic fluid CD200 levels remained stable in advanced pregnancy and they were increased during parturition. Elevated CD200 levels in the presence of funisitis suggest the involvement of negative regulatory mechanisms of innate immunity. CD200 may play a role in the development of pulmonary aspects of neonatal morbidity.

B7h (ICOS-L) maintains tolerance at the fetomaternal interface

In a successful pregnancy, the semiallogeneic fetus is not rejected by the maternal immune system, which implies tolerance mechanisms protecting fetal tissues from maternal immune attack. Here we report that the ICOS-B7h costimulatory pathway plays a critical role in maintaining the equilibrium at the fetomaternal interface. Blockade of this pathway increased fetal resorption and decreased fetal survival in an allogeneic pregnancy model (CBA female × B6 male). Locally in the placenta, levels of regulatory markers such as IDO and TGF-β1 were reduced after anti-B7h monoclonal antibody treatment, whereas levels of effector cytokines (eg, IFN-γ) were significantly increased. In secondary lymphoid organs, enhanced IFN-γ and granzyme B production (predominantly by CD8(+) T cells) was observed in the anti-B7h-treated group. The deleterious effect of B7h blockade in pregnancy was maintained only in CD4 knockout mice, not in CD8 knockout mice, which suggests a role for CD8(+) T cells in immune regulation by the ICOS-B7h pathway. In accord, regulatory CD8(+) T cells (in particular, CD8(+)CD103(+) cells) were significantly decreased after anti-B7h monoclonal antibody treatment, and adoptive transfer of this subset abrogated the deleterious effect of B7h blockade in fetomaternal tolerance. Taken together, these data support the hypothesis that B7h blockade abrogates tolerance at the fetomaternal interface by enhancing CD8(+) effector response and reducing local immunomodulation mediated by CD8(+) regulatory T cells.

CD200:CD200R-Mediated Regulation of Immunity

The type 1 membrane glycoprotein CD200, widely expressed on multiple cells/tissues, uses a structurally similar receptor (CD200R1), whose expression is more restricted to cells of the myeloid and lymphoid lineages, to transmit signals affecting responses in multiple physiological systems. Thus CD200 expression is reported to exert effects on cancer growth, autoimmune and allergic disorders, infection, transplantation, bone development and homeostasis, and reproductive biology. It was initially thought, based on the idea that CD200R1 was mostly expressed on cells of myeloid origin, that CD200:CD200R1 interactions were primarily dedicated to controlling myeloid cell function. However additional members of the CD200R family have now also been identified, although their function(s) remain unclear, and CD200R1 itself is now known to be expressed by subsets of T cells and other cells. Together these observations add layers of complexity to our understanding of CD200-related regulation. In common with a number of physiological systems, the mechanism(s) of CD200-induced signaling seem to fit within a similar framework of opposing actions of kinases and phosphatases. This paper highlights the advances in our knowledge of immunoregulation achieved following CD200:CD200R interaction and the potential clinical applicability of that information.

Characterization and functionality of the CD200-CD200R system during mesenchymal stromal cell interactions with T-lymphocytes

Mesenchymal stromal cells (MSCs) possess a specific immunological profile that makes them potentially useful for immune-based therapies. Adipose tissue (AT) and Wharton's jelly (WJ) are considered to be valuable alternatives to bone marrow (BM) as sources of MSCs. These MSCs exhibit strong immunomodulatory properties that affect lymphocyte responses. The CD200/CD200R axis has been reported to be important in regulating the immune responses. Engagement of CD200R by CD200 initiates an inhibitory pathway that displays immunosuppressive effects. Because the CD200/CD200R axis is involved in immunoregulation, we investigated the expression and role of this ligand/receptor pair in MSCs and T-lymphocytes during co-culture. CD200 is differently expressed and modulated on MSCs depending on the tissue of origin and the culture conditions. Among the different MSC sources, WJ-MSCs express CD200 in the greatest proportion. This high constitutive CD200 expression may represent a distinctive marker for WJ-MSCs. A pro-inflammatory environment and IFN-γ in particular induce an increase in CD200 expression by BM-MSCs. In T-lymphocytes, CD200R and CD200 are differently distributed between the CD4(+) and CD8(+) T-cell subsets. During co-culture, blocking CD200-CD200R interactions does not prevent MSC-mediated inhibition of lymphocyte proliferation. However, depending on their origin, MSCs are able to modulate the expression of both CD200 and CD200R on some T-cells. Further study is required to understand the function of CD200 expression by nonmyeloid cells such MSCs and the significance of CD200 and C200R expression by T-cells. The findings presented here support bidirectional communication between MSCs and T-lymphocytes. Understanding the role of this ligand-receptor pair during co-culture will improve and increase the clinical use of MSCs.

IDO induces expression of a novel tryptophan transporter in mouse and human tumor cells

IDO is the rate-limiting enzyme in the kynurenine pathway, catabolizing tryptophan to kynurenine. Tryptophan depletion by IDO-expressing tumors is a common mechanism of immune evasion inducing regulatory T cells and inhibiting effector T cells. Because mammalian cells cannot synthesize tryptophan, it remains unclear how IDO(+) tumor cells overcome the detrimental effects of local tryptophan depletion. We demonstrate that IDO(+) tumor cells express a novel amino acid transporter, which accounts for ∼50% of the tryptophan uptake. The induced transporter is biochemically distinguished from the constitutively expressed tryptophan transporter System L by increased resistance to inhibitors of System L, resistance to inhibition by high concentrations of most amino acids tested, and high substrate specificity for tryptophan. Under conditions of low extracellular tryptophan, expression of this novel transporter significantly increases tryptophan entry into IDO(+) tumors relative to tryptophan uptake through the low-affinity System L alone, and further decreases tryptophan levels in the microenvironment. Targeting this additional tryptophan transporter could be a way of pharmacological inhibition of IDO-mediated tumor escape. These findings highlight the ability of IDO-expressing tumor cells to thrive in a tryptophan-depleted microenvironment by expressing a novel, highly tryptophan-specific transporter, which is resistant to inhibition by most other amino acids. The additional transporter allows tumor cells to strike the ideal balance between supply of tryptophan essential for their own proliferation and survival, and depleting the extracellular milieu of tryptophan to inhibit T cell proliferation.

Potent immunosuppression by a bivalent molecule binding to CD200R and TGF-betaR

BACKGROUND

The novel immunosuppressive molecule, CD200, has been reported to induce immunoregulation after interaction with its receptor(s), CD200R(s), in part at least through augmented induction of regulatory T-cell populations. Independent studies have also described increased expression of indoleamine-2,3-dioxygenase after CD200R triggering, whereas others have provided evidence that TGF-beta is important for the induction or function of many populations of regulatory T cells. We have asked whether a hybrid molecule in which a soluble fusion protein containing CD200, CD200Fc, was linked to TGF-beta through a glycine linker (Gly6) functions as a superior immunosuppressant molecule when compared with CD200Fc or TGF-beta alone, or in combination.

METHODS

The hybrid molecule CD200FcGly6TGF-beta was expressed by transient transfection in CHO cells and purified over a protein A column. Functional activity of this and recombinant CD200Fc or TGF-beta alone were assessed in mixed leukocyte cultures (MLCs) and in skin graft rejection in vivo.

RESULTS

Immunosuppression mediated by CD200FcGly6TGF-beta is dependent on both functional CD200 and TGF-beta moieties, as indicated by inhibition of suppression using anti-CD200 or anti-TGF-beta antibodies. Using as responder cells, using antigen-presenting cell from mice with a deletion of the CD200R gene and responder T cells from mice with siRNA-mediated suppression of expression of the TGF-betaII receptor, we show that suppression follows binding to TGF-betaRII on T cells, and CD200R1 on antigen-presenting cells. Indoleamine-2,3-dioxygenase inhibitors did not attenuate suppression by CD200FcGly6TGF-beta.

CONCLUSION

CD200FcGly6TGF-beta is a potent immunosuppressant in vivo and in vitro.

Alternative splicing of CD200 is regulated by an exonic splicing enhancer and SF2/ASF

CD200, a type I membrane glycoprotein, plays an important role in prevention of inflammatory disorders, graft rejection, autoimmune diseases and spontaneous fetal loss. It also regulates tumor immunity. A truncated CD200 (CD200_tr) resulting from alternative splicing has been identified and characterized as a functional antagonist to full-length CD200. Thus, it is important to explore the mechanism(s) controlling alternative splicing of CD200. In this study, we identified an exonic splicing enhancer (ESE) located in exon 2, which is a putative binding site for a splicing regulatory protein SF2/ASF. Deletion or mutation of the ESE site decreased expression of the full-length CD200. Direct binding of SF2/ASF to the ESE site was confirmed by RNA electrophoretic mobility shift assay (EMSA). Knockdown of expression of SF2/ASF resulted in the same splicing pattern as seen after deletion or mutation of the ESE, whereas overexpression of SF2/ASF increased expression of the full-length CD200. In vivo studies showed that viral infection reversed the alternative splicing pattern of CD200 with increased expression of SF2/ASF and the full-length CD200. Taken together, our data suggest for the first time that SF2/ASF regulates the function of CD200 by controlling CD200 alternative splicing, through direct binding to an ESE located in exon 2 of CD200.

The danger hypothesis applied to idiosyncratic drug reactions

The danger hypothesis has had a profound effect on the way immunologists view the immune response. This hypothesis proposes that the major determinant of whether an immune response is mounted against some agent is determined by whether that agent causes some type of cell damage. Assuming that most idiosyncratic drug reactions (IDRs) are immune-mediated, this hypothesis also has the potential to explain many aspects of the mechanism of these adverse drug reactions. For example, most IDRs appear to be caused by chemical metabolites rather than the parent drug, but not all drugs that form reactive metabolites are associated with a significant incidence of IDRs. Therefore, using the danger hypothesis, one feature of a drug candidate that may predict whether it causes an IDR is whether the drug, or more likely its reactive metabolites, cause cell damage. Although the range of molecules that can act as danger signals is unknown, the most attractive candidates are high mobility group box 1 protein (HMGB1), heat shock proteins, and S100 proteins. These molecules act through the same receptors (toll-like receptors) as pathogen-associated molecules that stimulate the immune system. Therefore, other environmental factors such as infections or trauma might determine which patients would be at increased risk for IDRs. Although there are examples where this appears to be the case, in most cases there are no obvious environmental factors that determine IDR risk. In addition, in animal models of immune-mediated reactions, stimulation of toll-like receptors often does not increase the immune response, and depending on the timing, it can actually be protective. Therefore, there may be additional unknown control mechanisms that are involved. A better understanding of these fundamental immune mechanisms has the potential to have a significant impact on many areas of medicine.

Endothelial CD200 is heterogeneously distributed, regulated and involved in immune cell-endothelium interactions

CD200 is a highly glycosylated cell surface protein containing two immunoglobulin superfamily domains in the extracellular region and performs immunosuppressive activities. It is widely distributed in various tissues including the vascular endothelium. We report here the distribution of CD200 in rat endothelia from different vascular beds. Endothelial CD200 immunoreactivity was weakly expressed in most arteries but was intensely expressed in the arterioles, most veins and venules, as well as continuous and fenestrated capillaries. The distribution of CD200 in the sinusoidal and lymphatic endothelia was variable. Immunoelectron microscopic studies revealed that endothelial CD200 varied considerably not only in different microvasculatures but also in the membrane domains at the subcellular level. Endothelial CD200 expression was differentially regulated by lipopolysaccharide in cell types both in vivo and in vitro. Functional assessments of endothelial CD200 suggested that the physical binding between CD200 and CD200 receptor (CD200R) was involved in T-cell adhesion to the endothelium but not in macrophage-endothelium interaction. In the latter, however, CD200 agonist, a synthetic peptide from complementarity-determining region 3 of mouse CD200, may trigger CD200R signaling in macrophages to suppress their adhesion to the endothelium. Our findings demonstrate that the distribution, subcellular localization, and lipopolysaccharide-regulation of endothelial CD200 are heterogeneous, and provide evidence elucidating the functional roles of endothelial CD200 during tissue inflammation.

The FGL2-FcgammaRIIB pathway: a novel mechanism leading to immunosuppression

Fibrinogen-like protein 2 (FGL2) is a multifunctional protein, which has been implicated in the pathogenesis of allograft and xenograft rejection. Previously, FGL2 was shown to inhibit maturation of BM-derived DC and T-cell proliferation. The mechanism of the immunosuppressive activity of FGL2 remains poorly elucidated. Here, we focus on identification of FGL2-specific receptor(s) and their ability to modulate APC activity and allograft survival. Using flow cytometry and surface plasmon resonance analysis, we show that FGL2 binds specifically to Fc gamma receptor (FcgammaR)IIB and FcgammaRIII receptors, which are expressed on the surface of APC, including B lymphocytes, macrophages and DC. Antibody to FcgammaRIIB and FcgammaRIII, or deficiency of these receptors, abrogated FGL2 binding. FGL2 inhibited the maturation of BMDC from FcgammaRIIB+/+ mice but not from FcgammaRIIB(-/-) mice and induced apoptosis in the FcgammaRIIB+ mouse B-cell line (A20) but not the A20IIA1.6 cell line that does not express FcgammaRIIB. Recombinant FGL2 infused into FcgammaRIIB+/+ (C57BL/6J, H-2b) mice but not FcgammaRIIB(-/-) mice inhibited rejection of fully mismatched BALB/cJ (H-2d) skin allografts. The identification of specific receptor binding has important implications for the pathogenesis of immune-mediated disease and suggests a potential for targeted FGL2 therapy.

Syngeneic immune-dependent abortions in mice suggest paternal alloantigen-independent mechanisms

PROBLEM

Recurrent immune-associated miscarriages in humans are thought to result from maternal immune responses to paternal alloantigens. We investigated the role of paternal alloantigens in a mouse model of immune-dependent abortion.

METHOD OF STUDY

Sib-crosses of C57Bl/6J (haplotype b/b) mice heterozygous for a targeted hypomorphic allele of the tbp gene (tbp(deltaN/+)) resulted in selective mid-gestational abortion of 88% of the tbp(deltaN/deltaN) fetuses. In dams lacking mature lymphocytes (rag1-/-), nearly all tbp(deltaN/deltaN) fetuses survived to birth, indicating abortions were immune-dependent. Allogeneic pregnancies bearing tbp(deltaN/deltaN) fetuses were established by either hybridizing the paternal lineage to BALB/cJ (haplotype d/d) and mating hybrid tbp(deltaN/+) sires to haplotype b/b tbp(deltaN/+) C57Bl/6J dams, or by transfer of haplotype b/b zygotes from tbp(deltaN/+)x tbp(deltaN/+) matings into pseudopregnant wild-type CByD2F1/J dams (haplotype d/d).

RESULTS

Neither hemizygous paternal allogeneic loci nor homozygous allogeneic loci, including a haplotype-mismatched major histocompatibility complex (MHC), increased abortion frequencies.

CONCLUSION

Results suggested that mechanisms for maternal tolerance of paternal alloantigens, including mismatched MHC antigens, were intact in these pregnancies, yet maternal immune-dependent paternal antigen-independent abortion of mutants occurred. These data indicate that, in some cases of immune-mediated abortions, the presence of paternal alloantigens can be coincidental and superfluous to the compromising rejection response.

Human embryo immune escape mechanisms rediscovered by the tumor

Towards the end of the 1990s, the two opposing theories on immunosurveillance and immunostimulation were extensively studied by researchers in an attempt to understand the complex mechanisms that regulate the relation between tumors and the host's immune system. Both theories probably have elements that would help us to comprehend how the host can induce anti-tumor clinical responses through stimulation of the immune system and which could also give us a deeper insight into the mechanisms of tumor immunosuppression. The model that most resembles the behavior of tumor cells in terms of growth, infiltration and suppression of the immune system of the environment in which they live is undoubtedly that of the embryonic cell. The fetus behaves like an allogenic transplant within the mother's body, using every means it has to escape from and defend itself against the mother's immune system. The majority of these mechanisms are the same as those found in tumor cells: antigenic loss, lack of expression of classic HLA-I molecules, production of immunosuppressive cytokines, induction of lack of expression of co-stimulatory molecules in antigen presenting cells, and induction of apoptosis in infiltrating lymphocytes, with activation of a type Th2 regulatory lymphocyte response. A careful and comparative study of key mechanisms capable of triggering tolerance or cytotoxicity in both embryonic and tumor cells could prove immensely valuable in designing new strategies for anti-tumor immunotherapy.

Increased mortality and altered immunity in neonatal sepsis produced by generalized peritonitis

Neonates have a higher prevalence of bacterial sepsis and have greater morbidity and mortality from sepsis than other infants and children. Our understanding of the inflammatory and immunological responses to sepsis is hampered by the lack of appropriate neonatal murine models. In the present report, we have developed a cecal slurry model of generalized peritonitis in neonatal mice (age range, 5-7 days) and compared the outcome and the innate and adaptive cellular responses of these animals with those of the young adult animals (age range, 7-10 weeks) with sepsis induced either by cecal slurry administration or by cecal ligation and puncture. Neonatal mice were more susceptible to sepsis and mounted a markedly attenuated systemic inflammatory response compared with young adult animals (specifically, decreased plasma interferon gamma; interleukins 1alpha and 1beta; regulated on activation, normal T expressed and secreted (RANTES); and tumor necrosis factor alpha concentrations). Compared with young adult animals, septic neonatal mice did not lose significant percentage or absolute number of splenic CD4+ T cells. These findings suggest that the cecal slurry model of generalized peritonitis can produce sepsis in neonatal mice with dose-dependent lethality. Inherent differences in the host response to polymicrobial sepsis between neonatal and young adult animals may explain the increased sensitivity of the neonatal mouse to generalized peritonitis.

Interaction between dendritic cells and natural killer cells during pregnancy in mice

A complex regulation of innate and adaptive immune responses at the maternal fetal interface promotes tolerance of trophoblast cells carrying paternally derived antigens. Such regulatory functions involve uterine dendritic cells (uDC) and natural killer (uNK) cells. The existence of a NK and DC "cross talk" has been revealed in various experimental settings; its biological significance ranging from cooperative stimulation to cell lysis. Little is known about the presence or role of NK and DC cross talk at the maternal fetal interface. The present study shows that mouse NK and DC interactions are subject to modulation by trophoblast cells in vitro. This interaction promotes a tolerogenic microenvironment characterized by downregulation of the expression of activation markers on uNK cells and uDC and dominance of Th2 cytokines. NK and DC interactions would also influence uterine cell proliferation and this process would be strongly modulated by trophoblast-derived signals. Indeed; while low proliferation rates were observed upon regular coculture allowing direct contact between uterine cells and trophoblasts, incubation in a transwell culture system markedly increased uterine cell proliferation suggesting that soluble factors are key mediators in the molecular "dialog" between the mother and the conceptus during the establishment of mouse pregnancy. Our data further reveal that the regulatory functions of trophoblast cells associated with tolerance induction are impaired in high abortion murine matings. Interestingly, we observed that secretion of interleukin-12p70 by uDC is dramatically abrogated in the presence of uNK cells. Taken together, our results provide the first evidence that a delicate balance of interactions involving NK cells, DC, and trophoblasts at the mouse maternal fetal interface supports a successful pregnancy outcome.

Toll-like receptor-4-mediated macrophage activation is differentially regulated by progesterone via the glucocorticoid and progesterone receptors

Macrophage function has been demonstrated to be subject to modulation by progesterone. However, as this steroid hormone can act through the glucocorticoid receptor as well as the progesterone receptor, the mechanism of action has not been precisely characterized. To determine the mode of action, we compared the ability of progesterone, norgestrel (a synthetic progesterone-receptor-specific agonist) and dexamethasone (a synthetic glucocorticoid receptor agonist) to modulate macrophage function following stimulation of the Toll-like receptor-4 (TLR-4) ligand lipopolysaccharide (LPS). The results demonstrate that following stimulation of TLR-4 with LPS and cotreatment with either progesterone or dexamethasone, but not norgestrel, there is a significant reduction in nitric oxide (NO) production, indicating that this progesterone-mediated effect is through ligation of the glucocorticoid receptor. In contrast, LPS-induced interleukin-12 (IL-12) production could be downregulated by all three steroids, indicating that ligation by progesterone of either the glucocorticoid or the progesterone receptors or both could mediate this effect. While progesterone downmodulated NO-mediated killing of Leishmania donovani by activated macrophages in vitro, most probably via the glucocorticoid receptor, it had little effect on Toxoplasma gondii growth in these cells. This would suggest that progesterone-mediated increased susceptibility to T. gondii during pregnancy is more likely to be related to the ability of the hormone to downregulate IL-12 production and a type-1 response utilizing the progesterone as well as the glucocorticoid receptors.

Cyclosporin A improves murine pregnancy outcome in abortion-prone matings: involvement of CD80/86 and CD28/CTLA-4

Immune regulation during pregnancy is complex, and thus an optimal therapy for pregnancy complications is always a big challenge to reproductive medicine. Cyclosporin A (CsA), a potent immunosuppressant, prevents rejection of allografts by hosts, but little is known about the modulating effect of CsA on the materno-fetal relationship. Here, pregnant CBA/J females mated with DBA/2 males as an abortion-prone model were administered with CsA on day 4.5 of gestation, and the pregnant CBA/J females mated with BALB/c males were established as successful pregnancy control. It was demonstrated that administration of CsA at the window of implantation significantly up-regulated the expression of CTLA-4, while down-regulating the levels of CD80, CD86, and CD28 at the materno-fetal interface in the CBA/J×DBA/2 abortion-prone matings, and the embryo resorption rate of the abortion-prone matings reduced significantly after CsA treatment, implying that modulation of costimulatory molecule expression by CsA might contribute to preventing the fetus from maternal immune attack. In addition, treatment with CsA induced enhanced growth and reduced cell apoptosis of the murine trophoblast cells. Together, these findings indicate that CsA has a beneficial effect on the materno-fetal interface in abortion-prone matings, leading to a pregnancy outcome improvement, which might provide new therapeutics for spontaneous pregnancy wastage.

Transfusion-related immunomodulation due to peripheral blood dendritic cells expressing the CD200 tolerance signaling molecule and alloantigen

BACKGROUND

The transfusion of allogeneic blood products containing white cells (WBCs) has been reported to reduce resistance to infection, stimulate the growth of some types of tumors in animal models, and prevent abortion of allogeneic embryos in the CBAxDBA/2 murine model.

STUDY DESIGN AND METHODS

In this study, the issue explored was whether allogeneic BALB/c whole blood given to C57Bl/6 mice by tail vein after injection of syngeneic FSL-10 fibrosarcoma cells increased the number of lung nodules enumerated on Day 21. The effect on the tumor growth-promoting effect produced by allogeneic BALB/c whole blood was then examined by exposure of the allogeneic BALB/c blood to various monoclonal antibodies (MoAbs). The antibodies added to the BALB/c blood included anti-murine CD200 antibodies, anti-lymphoid dendritic cell (DC) antibodies (DEC205), or anti-myeloid DC (anti-CD11c) antibodies.

RESULTS

The tumor growth-promoting effect of the allogeneic BALB/c blood was abrogated by the addition to the BALB/c blood of MoAb either to myeloid DCs (anti-CD11c) or to the CD200 tolerance signaling molecule, but not by adding MoAb to lymphoid DCs (DEC205). BALB/c blood also was shown to increase the percentage of transforming growth factor (TGF)-beta+ splenocytes detected in recipient mice, on Day 12 after transfusion. This effect was abrogated by adding anti-CD200 antibody to the BALB/c donor blood. Moreover, physiologic concentrations of TGF-beta, but not interleukin-10, were shown to stimulate, in cell culture experiments, the proliferation of syngeneic FSL-10 sarcoma cells.

CONCLUSIONS

These data support the hypothesis that the mechanism of the tumor growth-promoting effect of allogeneic blood is mediated by a highly potent population of peripheral blood DCs expressing the CD200 tolerance signaling molecule. These data also indicate that tumor cell growth can be mediated by the stimulation of TGF-beta-producing cells and that TGF-beta may act by tumor cell growth stimulation, rather than by host immunosuppression.

CD200-dependent and nonCD200-dependent pathways of NK cell suppression by human IVIG

PROBLEM

Intravenous immunoglobulin (IVIG) has been used to suppress autoimmune and inflammatory disorders by a variety of mechanisms. Recently, the CD200 tolerance-promoting signal has been found to play a role in IVIG suppression of blood natural killer (NK) cells. Further, different types of IVIG have been reported to differ in this activity, and that has been related to efficacy (and inefficacy) of treatment of women with pregnancy failure. CD200 acts by binding to CD200 receptors (C200R). The objective of this study was to determine if CD200-dependent NK suppression by IVIG involved direct binding of IVIG-associated CD200 molecules to CD200R on NK cells.

METHOD OF STUDY

Peripheral Blood Lymphocytes isolated from human blood were used as a source of NK cells to lyse Cr(51)-labelled K562 target cells in vitro in 18 and 4 h assays, and three different types of IVIG were tested for suppressive activity in the presence or absence of specific monoclonal anti-huCD200. In some experiments, CD56(+) NK cells were purified using anti-CD56 magnetic beads. Western blotting of IVIG using a specific anti-huCD200 antibody was done. Enzyme-Linked ImmunoSorbent Assays were used to measure cytokine production in NK assays.

RESULTS

Different IVIGs showed significant differences in potency in suppressing NK cytolytic activity in vitro (mg/ml for 60% suppression, Gammagard 4.1, Gamunex 14.1, Gamimmune 20.2). For CD200-dependent suppression, Gammagard was twice as potent as Gamimmune, but equivalent to Gamunex. The presence of suppression in 4 hour assays indicated stimulation of cytokine synthesis was unlikely to explain CD200-dependent suppression. Purification of NK cells led to loss of the CD200-dependent component. Western blotting confirmed that material reactive with anti-CD200 antibody was present in Immunoglobulin G (IgG) preparations, and at a lower level in human serum that contains IgG.

CONCLUSIONS

IVIGs are not all equipotent in suppressing NK cell cytolytic activity. CD200 associated with IVIG is an important component of suppression. CD200-dependent suppression appears to be mediated by a non-NK population that then acts on NK cells by direct contact rather than indirectly through release of immunosuppressive cytokines.

Antigen-presenting cells and materno-fetal tolerance: an emerging role for dendritic cells

During pregnancy, a delicate balance of innate and adaptive immune responses at the maternal-fetal interface promotes survival of the semi-allogeneic embryo and, at the same time, allows effective immunity to protect the mother from environmental pathogens. As in other tissues, antigen handling and processing in the decidualized endometrium constitutes a primary event in the onset of immune responses and is therefore likely to determine their stimulatory or tolerogenic nature. Maternal antigen-presenting cells [macrophages and dendritic cells (DCs)] are scattered throughout the decidualized endometrium during all stages of pregnancy and appear to be important players in this feto-maternal immune adjustment. This review focuses on the characterization of decidual macrophages and DCs, as well as their involvement in cell-cell interactions within the decidual leukocyte network, which are likely to influence uterine and placental homeostasis as well as the local maternal immune responses to the fetus during pregnancy.

Cytokines: Important for implantation?

PROBLEM

Cytokines are obviously very important in an established pregnancy, but what about human embryo implantation?

METHODS

Literature review.

RESULTS

We first discuss the necessity and limits of animal models, and then review the few cytokines which have been demonstrated by knock-out methods to be absolutely necessary for embryo implantation using in animal models. We then review what is known or discussed about the role of other cytokines as deduced from quantitative and/or qualitative dysregulation in animals and in humans.

CONCLUSIONS

Cytokines are indeed involved in implantation as they are in ongoing pregnancy and delivery. Relevance to infertility and recurrent pregnancy loss is discussed.

Transfusion-related immunomodulation (TRIM): an update

Allogeneic blood transfusion (ABT)-related immunomodulation (TRIM) encompasses the laboratory immune aberrations that occur after ABT and their established or purported clinical effects. TRIM is a real biologic phenomenon resulting in at least one established beneficial clinical effect in humans, but the existence of deleterious clinical TRIM effects has not yet been confirmed. Initially, TRIM encompassed effects attributable to ABT by immunomodulatory mechanisms (e.g., cancer recurrence, postoperative infection, or virus activation). More recently, TRIM has also included effects attributable to ABT by pro-inflammatory mechanisms (e.g., multiple-organ failure or mortality). TRIM effects may be mediated by: (1) allogeneic mononuclear cells; (2) white-blood-cell (WBC)-derived soluble mediators; and/or (3) soluble HLA peptides circulating in allogeneic plasma. This review categorizes the available randomized controlled trials based on the inference(s) that they permit about possible mediator(s) of TRIM, and examines the strength of the evidence available for relying on WBC reduction or autologous transfusion to prevent TRIM effects.

Administration of high-dose intact immunoglobulin has an anti-resorption effect in a mouse model of reproductive failure

Administration of high-dose intact human immunoglobulin (IH-Ig) has been applied to treat a variety of inflammatory and autoimmune diseases, and is expected to have beneficial effects on human fecundity. In the present study, we investigated whether Ig had anti-resorption effects using polyinosinic-polycytidylic acid sodium salt [poly (I:C)]-induced enhancement of fetal resorption in the mating of CBA/J x DBA/2J resorption-prone mouse model. Furthermore, we investigated the mechanism of the effect by examining the mRNA expression of interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, IL-10, IL-4 and TGF-beta(1) in spleens and placentas from the resorption-prone model treated with IH-Ig, by reverse transcription (RT)-polymerase chain reaction (PCR). Administration of high-dose IH-Ig significantly reduced the fetal resorption rate from 55% to 10%. This anti-resorption effect, however, was not detected in mice administered with Fab fragments of human Ig. We then performed adoptive transfer experiments to examine whether cellular components could transfer the effect. A remarkable anti-resorption effect was seen in poly (I:C)-injected pregnant recipients transferred with spleen cells from IH-Ig-treated donor mice. The RT-PCR study showed that IH-Ig reduced the expression of IFN-gamma and TNF-alpha mRNA in placentas of poly (I:C)-injected pregnant mice. The present findings demonstrate that intact Ig, particularly its Fc portion, possesses anti-resorption activity. The effect might be attributed to the suppressed production of pro-inflammatory cytokines at the maternofetal interface.

Mice lacking CD200R1 show absence of suppression of lipopolysaccharide-induced tumor necrosis factor-alpha and mixed leukocyte culture responses by CD200

BACKGROUND

CD200:CD200R interactions deliver immunoregulatory signals. A family of CD200Rs (CD200R1-5) has been described, and engagement of CD200R1 by its ligand CD200 suppresses LPS-induced macrophage cytokine production, decreases alloimmune responses in vivo and in vitro, and suppresses collagen-induced arthritis.

METHODS

We generated C57BL/6 mice lacking the genomic exons encoding the extracellular domains of the CD200R1 molecule using transformation of ES cells and explored cell subtypes and immune responses in these mice.

RESULTS

Myeloid cells/splenocytes from CD200R1(-/-) mice were not stained in FACS by anti-CD200R1 mAb. Stimulation of splenic tumor necrosis factor-alpha production by lipopolysaccharide was enhanced relative to control (+/+) mice and was not suppressed by addition of exogenous CD200Fc. Modulation of alloreactivity in mixed leukocyte cultures by CD200Fc depended upon CD200R1+ stimulatory cells, although maximal immunoregulation by CD200Fc occurred only when CD200R1+ T responder cells also were used. CD200Fc failed to suppress graft rejection in CD200R1(-/-) mice.

CONCLUSION

CD200:CD200R1 plays an immunoregulatory role in vivo.

Effect of interferon-gamma treatment on the expression of interleukin-1beta at the maternal-fetal interface of pregnant rats

In the present study, the possible mechanisms by which interferon (IFN)-gamma affects pregnancy were investigated using the cytokine network model. The IFN-gamma-induced expression of interleukin (IL)-1beta was examined using western blotting, immunohistochemistry and immunofluorescence. The results showed that IFN-gamma treatment significantly decreased the expression of uterine IL-1beta protein during the preimplantation, post-implantation and mid-gestation periods. The expression of IL-1beta protein was increased after IFN-gamma treatment compared with the control group in late pregnancy. In the placenta, IL-1beta protein levels were significantly increased after IFN-gamma treatment in early and mid-pregnancy. In late pregnancy, IFN-gamma treatment significantly decreased placental IL-1beta protein levels. IL-1beta was mainly expressed in the myometrium, uterine arteries, decidua basalis, trophospongium of the junctional layer and trophoblastic epithelium of the labyrinthine layers. IL-1beta was mainly located in the cytoplasm of in vitro cultured endometrial stromal cells (ESCs). IFN-gamma treatment did not affect the distribution of IL-1beta, only the expression of IL-1beta. The effects of IFN-gamma on the proliferation of ESCs were determined using an MTS (a novel tetrazolium compound) assay. IFN-gamma treatment inhibited the proliferation of ESCs and decreased the weight of the fetus and placenta. These results indicate that exogenous IFN-gamma affects the expression of IL-1beta and inhibits ESC proliferation.

Effect of the Immunoregulatory Cytokines on Successful Pregnancy Depends Upon the Control of Graft Rejection Mechanisms

Successful outcomes in allopregnant women depend upon control of graft rejection mechanisms. An understanding of how the fetus escapes the maternal immune system may be relevant for the prevention of transplant rejection. It has been suggested that the same immunosuppressive cytokines contribute to successful pregnancy and transplantation. Recent reports suggest a role for transforming growth factor beta (TGF-beta) in the generation of T-regulatory lymphocytes. In contrast, production of proinflammatory cytokines accompanying intrauterine infection has been associated with fetal rejection or preterm labor. Interleukin-12 (IL-12) is the unique stimulator for differentiation of T-helper lymphocytes (Th) to Th1 cells. It rapidly induces transcription of Th1 cytokines such as interferon-gamma. This study was performed in 70 pregnant women at 21 to 36 weeks gestation, and in 32 healthy nonpregnant controls. An indirect enzyme-linked immunosorbent assay was used to estimate TGF-beta1, and IL-12 in serum. The results showed that TGF-beta1 levels were higher in all pregnant women compared with the nonpregnant controls. No significant changes in serum levels of IL-12 were observed in pregnant compared with the normal control women. The results suggested that the cytokine milieu of the placenta appeared to play a critical role in the maternal acceptance of the fetus, and that TGF-beta1 may function as a regulatory factor in fetal allograft survival during pregnancy.

Dietary protein deficiency in pregnant mice and offspring

Previous studies suggest an association between dermal contact hypersensitivity and preterm delivery. We hypothesized that dietary protein deficiency produces cell-mediated immune hypersensitivity in pregnant animals and their offspring akin to those known to produce tissue damage. We compared the effects of feeding a 20% protein diet (controls) to those of feeding a 10% protein (deficient) diet ad libitum to pregnant BALB/c mice. We measured dermal contact sensitivity to 2,4-dinitrofluorobenzene (DNFB) by the increment in ear skin thickness (swelling) 72 h after immunization and parity by the number of viable pups delivered. Dams fed the protein-deficient diet ingested less food, gained less weight and delivered fewer viable pups than the dams fed the control diet. Greater DNFB-stimulated increment in ear skin thickness was found in the protein-deficient mothers and in their offspring than in the control mothers and their offspring. We conclude that dietary protein deficiency limits parity and induces immune hypersensitivity. These findings suggest the potential for dietary protein deficiency to activate a T-cell-mediated branch of the immune response that may put pregnant animals at risk for preterm delivery.

MD1 expression regulates development of regulatory T cells

Intense interest has centered around the role of a subset of regulatory T cells, CD4+CD25+ Treg, in controlling the development of autoimmune disorders, allograft rejection, infection, malignancy, and allergy. We previously reported that MD1, a molecule known to be important in regulation of expression of RP105, also was important in regulating alloimmunity, and that blockade of expression of MD1 diminished graft rejection in vivo. One mechanism by which an MD1-RP105 complex exerts an effect on immune responses is through interference with an LPS-derived signal delivered through the CD14-MD-2-TLR4 complex. We show below that LPS signaling for Treg induction occurs at higher LPS thresholds that for effector T cell responses. In addition, blockade of MD1 functional activity in dendritic cells (using anti-MD1 mAbs, MD1 antisense deoxyoligonucleotides, or responder cells from mice with deletion of the MD1 gene), resulted in elevated Treg induction in response to allogeneic stimulation (in vivo or in vitro) in the presence of LPS. These data offer one mechanistic explanation for the augmented immunosuppression described following anti-MD1 treatment.

Analysis of endometrial myeloid and lymphoid dendritic cells during mouse estrous cycle

This study was performed to evaluate the frequency and localization of endometrial myeloid (CD11c(+) CD11b(+)) and lymphoid (CD11c(+) CD8alpha(+)) dendritic cells (DCs) at different stages of murine estrous cycle. To address the systemic effect of ovarian hormones fluctuations during estrous cycle, the same variables were studied in splenic DCs as well. Stages of the estrous cycle of Balb/c mice were determined by examination of vaginal smears. Frozen sections of uterus and spleen at each stage of estrous cycle were stained for CD11c and MHC-II. Two-color immunohistochemistry was also carried out using anti-CD11c with one of the antibodies against CD11b, CD8alpha, CD86, and DEC-205. The average density of DCs and relative percentage of myeloid and lymphoid DCs (MDCs and LDCs) were determined at each stage of estrous cycle by morphometric analysis. Our results showed that DCs were present throughout the estrous cycle in mice endometrium, but their frequency was highest at estrus and lowest at proestrus (P<0.005). The lymphoid subset of DCs was more prominent at estrus relative to those at other stages (P<0.005). Conversely, the relative percentage of myeloid DCs at estrus was significantly lower compared to other stages (P<0.005). Nearly all endometrial and splenic DCs expressed CD86 and MHC-II. At proestrus, and particularly at estrus, DCs were more concentrated subadjacent to the luminal and glandular epithelial layers with some scattered throughout the stroma whereas, at metestrus and diestrus, DCs were randomly distributed in stroma and around the glandular and luminal epithelial layers. The number and immunophenotype of splenic DCs were not statistically different between stages of estrous cycle. Our results suggest that endometrial but not splenic myeloid and lymphoid DCs are influenced by steroid hormones during estrous cycle.

Modulation of immunity to respiratory viral infection

Acute respiratory tract infections cause approximately 4 million deaths globally each year. Current strategies to combat these infections include vaccines and antiviral drugs. However, a significant proportion of the pathology and illness induced by respiratory viral infection is attributed to an excessive host immune response, rather than the cytopathic nature of the pathogen. Distinct respiratory viruses elicit common immune mediators and cells, which are subsequently the cause of pathology. Therefore, strategies that seek to attenuate the potency of the host’s immune response may provide generic relief from multiple respiratory infections.