Daniel Rukavina

Protection against inflammation- and autoantibody-caused fetal loss by the chemokine decoy receptor D6

Fetal loss in animals and humans is frequently associated with inflammatory conditions. D6 is a promiscuous chemokine receptor with decoy function, expressed in lymphatic endothelium, that recognizes and targets to degradation most inflammatory CC chemokines. Here, we report that D6 is expressed in placenta on invading extravillous trophoblasts and on the apical side of syncytiotrophoblast cells, at the very interface between maternal blood and fetus. Exposure of D6−/− pregnant mice to LPS or antiphospholipid autoantibodies results in higher levels of inflammatory CC chemokines and increased leukocyte infiltrate in placenta, causing an increased rate of fetal loss, which is prevented by blocking inflammatory chemokines. Thus, the promiscuous decoy receptor for inflammatory CC chemokines D6 plays a nonredundant role in the protection against fetal loss caused by systemic inflammation and antiphospholipid antibodies.

Dendritic Cells: Key to Fetal Tolerance?

Abstract Pregnancy is a unique event in which a fetus, despite being genetically and immunologically different from the mother (a hemi-allograft), develops in the uterus. Successful pregnancy implies avoidance of rejection by the maternal immune system. Fetal and maternal immune cells come into direct contact at the decidua, which is a highly specialized mucous membrane that plays a key role in fetal tolerance. Uterine dendritic cells (DC) within the decidua have been implicated in pregnancy maintenance. DC serve as antigen-presenting cells with the unique ability to induce primary immune responses. Just as lymphocytes comprise different subsets, DC subsets have been identified that differentially control lymphocyte function. DC may also act to induce immunologic tolerance and regulation of T cell-mediated immunity. Current understanding of DC immunobiology within the context of mammalian fetal-maternal tolerance is reviewed and discussed herein.

Increased inflammation in mice deficient for the chemokine decoy receptor D6

Chemokines are chemotactic cytokines with a key role in the control of cell trafficking and positioning under homeostatic and inflammatory conditions. D6 is a promiscuous 7‐transmembrane‐domain receptor expressed on lymphatic vessels which recognizes most inflammatory, but not homeostatic, CC chemokines. In vitro experiments demonstrated that D6 is unable to signal after ligand engagement, and it is structurally adapted to sustain rapid and efficient ligand internalization and degradation. These unique functional properties lead to the hypothesis that D6 may be involved in the control of inflammation by acting as a decoy and scavenger receptor for inflammatory chemokines. Consistent with this hypothesis, here we report that D6–/– mice showed an anticipated and exacerbated inflammatory response in a model of skin inflammation. Moreover, the absence of D6 resulted in increase cellularity and inflammatory‐chemokine levels in draining lymph nodes. Thus, D6 is a decoy receptor structurally adapted and strategically located to tune tissue inflammation and control transfer of inflammatory chemokines to draining lymph nodes.

Critical and differential roles of NKp46- and NKp30-activating receptors expressed by uterine NK cells in early pregnancy.

In early human pregnancy, uterine decidual NK cells (dNK) are abundant and considered as cytokine producers but poorly cytotoxic despite their cytolytic granule content, suggesting a negative control of this latter effector function. To investigate the basis of this control, we examined the relative contribution to the cytotoxic function of different activating receptors expressed by dNK. Using a multicolor flow cytometry analysis, we found that freshly isolated dNK exhibit a unique repertoire of activating and inhibitory receptors, identical among all the donors tested. We then demonstrated that in fresh dNK, mAb-specific engagement of NKp46-, and to a lesser extent NKG2C-, but not NKp30-activating receptors induced intracellular calcium mobilization, perforin polarization, granule exocytosis and efficient target cell lysis. NKp46-mediated cytotoxicity is coactivated by CD2 but dramatically blocked by NKG2A coengagement, indicating that the dNK cytotoxic potential could be tightly controlled in vivo. We finally found that in dNK, mAb-specific engagement of NKp30, but not NKp46, triggered the production of IFN-γ, TNF-α, MIP-1α, MIP-1β, and GM-CSF proinflammatory molecules. These data demonstrate a differential, controlled role of NKp46- and NKp30-activating receptors expressed by dNK that could be critical for the outcome of pregnancy and the killing of uterine cells infected by pathogens.

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.

Progesterone-induced blocking factor inhibits degranulation of natural killer cells

PROBLEM: During the first trimester of pregnancy, nonclassical (CD3—, CD56+, CD16—, perforin [P]bright +) natural killer (NK) cells comprise the major decidual lymphocyte population. These cells, in spite of their high perforin content, exert a low cytolytic activity. Peripheral blood lymphocytes of healthy pregnant women produce progesterone‐induced blocking factor (PIBF), which inhibits NK activity. PIBF‐producing cells are likely to be present in decidua and might contribute to low decidual NK activity.

Decrease in CD3-negative-CD8dim+ and Vδ2/Vγ9 TcR + peripheral blood lymphocyte counts, low perforin expression and the impairment of natural killer cell activity is associated with chronic hepatitis C virus infection

BACKGROUND/AIMS As chronic hepatitis C virus (HCV) infection is associated with impaired natural killer (NK) cell cytotoxicity, we examined the phenotypes and perforin expression of peripheral blood lymphocytes, as well as the effect of interferon-alpha2b (IFN-alpha2b) therapy. METHODS Thirty-three patients had chronic hepatitis C, and of them 12 had been on IFN-alpha2b treatment. Eleven individuals had been treated earlier with IFN-alpha2b and completely cured, and eight were HCV carriers with persistently normal serum alanine aminotransferase. Three-colour flow cytometry was used to measure the percentage of CD3(+/-)CD8+, CD3+CD4+, gammadeltaTcR+, Vdelta2 TcR+, Vgamma9 TcR+, Vdelta1 TcR+, CD3-CD16+, CD3-CD56+, CD19+ and perforin-positive cells. NK cell activity was assessed by single cell cytotoxic and flow cytometric assay. RESULTS Patients with chronic hepatitis C showed an impaired NK cytotoxicity, decreased percentage of CD3-negative-CD8dim-positive (NK subtype) and Vgamma9/Vdelta2 TcR+ as well as perforin-positive T lymphocytes, compared to controls and to those who were cured from HCV infection. IFN-alpha2b increased NK cell cytotoxicity and the percentage of perforin-positive lymphocytes. CONCLUSIONS Our findings suggest that in chronic HCV infection a decreased percentage of CD3(-)CD8+, Vgamma9/Vdelta2 TcR+ and perforin-positive T cells and simultaneous decreased peripheral NK activity may contribute to the impaired cellular immune response and the chronicity of the disease.

Characteristics of Perforin Expressing Lymphocytes Within the First Trimester Decidua of Human Pregnancy

PROBLEM: The number of perforin (P)‐positive cells in decidua of pregnancy is larger than that observed in any other pathological condition. The aim was to investigate the distribution and the phenotype of P+ cells.

Abundant perforin expression at the maternal–fetal interface: guarding the semiallogeneic transplant?

Abstract The pregnant uterus harbors the highest concentration of perforin known to occur in any physiological or pathological condition. This cytolytic molecule might therefore subserve an immune surveillance function protecting both mother and fetus.

An immunohistochemical study of leucocytes in human endometrium, first and third trimester basal decidua

An immunohistochemical quantitative study of leucocyte subpopulations on fresh human endometrium and on biopsy specimens of first and third trimester basal decidua in normal (uncomplicated) pregnancies was performed. The most prominent population in endometrial and decidual stroma of basal decidua are macrophages. B cells as well as gamma/delta T cell receptor positive cells were found occasionally, scattered throughout the endometrial/decidual stroma. CD3+ cells were present in a relatively small number in the endometrium as well as in the first trimester basal decidua, but their number was elevated (doubled) in the third trimester of pregnancy. CD2+ cells showed a slight increase in first trimester basal decidua when compared with both endometrium and third trimester basal decidua. Cells with positive NKH-1 marker (CD56+) showed a significant increase in the first trimester, while in the third trimester their number diminished drastically. CD56:CD3 cell ratio increased to more than five times in first trimester basal decidua, while in the third trimester basal decidua decreased drastically. The mentioned increase of CD56+ cells in the first trimester and that of CD3+ cells at term suggests that these cells could have some specific function(s). However, it still has to be established whether the described quantitative changes of decidual leucocytes in basal decidua during pregnancy are of any importance for the mechanism(s) for the fetal allograft protection.