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Roi Gazit

Publications and source records attributed to Roi Gazit.

At least 19 recordsLinked to original sources
PubMed2006

Decidual NK cells regulate key developmental processes at the human fetal-maternal interface.

Human CD56(bright) NK cells accumulate in the maternal decidua during pregnancy and are found in direct contact with fetal trophoblasts. Several mechanisms have been proposed to explain the inability of NK cells to kill the semiallogeneic fetal cells. However, the actual functions of decidual NK (dNK) cells during pregnancy are mostly unknown. Here we show that dNK cells, but not peripheral blood-derived NK subsets, regulate trophoblast invasion both in vitro and in vivo by production of the interleukin-8 and interferon-inducible protein-10 chemokines. Furthermore, dNK cells are potent secretors of an array of angiogenic factors and induce vascular growth in the decidua. Notably, such functions are regulated by specific interactions between dNK-activating and dNK-inhibitory receptors and their ligands, uniquely expressed at the fetal-maternal interface. The overall results support a 'peaceful' model for reproductive immunology, in which elements of innate immunity have been incorporated in a constructive manner to support reproductive tissue development.

Angiogenesis Inducing Agents↗
PubMed2006

Reduced KIR2DL1 recognition of MHC class I molecules presenting phosphorylated peptides.

As initially described by K. Karre and colleagues in the missing self hypothesis, cells expressing self-MHC class I proteins are protected from NK cells attack. In contrast, reduction in the expression of MHC class I molecules due to viral infection or tumor transformation result in the killing of these "abnormal" cells by NK cells via NK-activating receptors. Thus, NK killing of target cells is determined by both negative signals coming from MHC class I proteins and by positive signals derived from the activating ligands. The bound peptide in MHC class I play an important role in the balanced recognition of NK cells. The peptide stabilizes the MHC complex and interacts directly with the NK inhibitory receptors, thus participating in the determination of the fate of the target cells. In this study we demonstrate that posttranslational modifications such as phosphorylation of the presented peptide altered the ability of NK cells to recognize MHC class I molecules. By using a consensus peptide (QYDDAVYKL) that binds HLA-Cw4 in which different positions in the bound peptide were modified by serine phosphorylation, we observed a reduction in KIR2DL1 binding that led to decreased protection from NK killing. Therefore, it might be possible that alteration in the phosphorylation pattern during tumor transformation or viral infection may result in less inhibition and, consequently, improved NK cell killing.

Acids↗
PubMed2006

Lethal influenza infection in the absence of the natural killer cell receptor gene Ncr1.

The elimination of viruses and tumors by natural killer cells is mediated by specific natural killer cell receptors. To study the in vivo function of a principal activating natural killer cell receptor, NCR1 (NKp46 in humans), we replaced the gene encoding this receptor (Ncr1) with a green fluorescent protein reporter cassette. There was enhanced spread of certain tumors in 129/Sv but not C57BL/6 Ncr1(gfp/gfp) mice, and influenza virus infection was lethal in both 129/Sv and C57BL/6 Ncr1(gfp/gfp) mice. We noted accumulation of natural killer cells at the site of influenza infection by tracking the green fluorescent protein. Our results demonstrate a critical function for Ncr1 in the in vivo eradication of influenza virus.

Animals↗
PubMed2005

The CD85J/leukocyte inhibitory receptor-1 distinguishes between conformed and beta 2-microglobulin-free HLA-G molecules.

For a proper development of the placenta, maternal NK cells should not attack the fetal extravillous cytotrophoblast cells. This inhibition of maternal NK cells is partially mediated via the nonclassical MHC class I molecule HLA-G. Recently, we demonstrated that HLA-G forms disulfide-linked high molecular complexes on the surface of transfected cells. In the present study, we demonstrate that HLA-G must associate with beta(2)m for its interaction with CD85J/leukocyte Ig-like receptor-1 (LIR-1). Although HLA-G free H chain complexes are expressed on the surface, they are not recognized and possibly interfere with CD85J/LIR-1 and HLA-G interaction. The formation of these complexes on the cell surface might represent a novel mechanism developed specifically by the HLA-G protein aimed to control the efficiency of the CD85J/LIR-1-mediated inhibition. We also show that endogenous HLA-G complexes are expressed on the cell surface. These findings provide novel insights into the delicate interaction between extravillous cytotrophoblast cells and NK cells in the decidua.

Antigens, CD↗
PubMed2005

The involvement of NK cells in ankylosing spondylitis.

A role for NK cells in the regulation of autoimmunity has been demonstrated. Since there is a strong association between Ankylosing Spondylitis (AS) and HLA-B27, which is specifically recognized by the NK-inhibitory receptor KIR3DL1, this study evaluated the potential involvement of NK cells in AS. We studied 19 AS patients and 22 healthy volunteer donors and assessed the percentage, activity and receptor expression of peripheral blood NK cells. We also evaluated candidate-inflammatory mediators in sera. We found that AS patients have significantly higher percentages of NK cells. However, we found no differences between the ability of NK cells derived from AS and healthy controls to recognize target cells expressing HLA-B27. Remarkably, we observed that the NK-inhibitory receptor CEACAM1 (carcino-embryonic antigen-cell adhesion molecule) is highly expressed among AS-derived NK cells. Furthermore, engagement of CEACAM1 inhibited NK activity in these patients. Finally, we demonstrated that CEACAM1 expression is induced by IL-8 and SDF-1 (stromal cell derived factor), both of which are present in high levels in the sera of AS patients. These results may indicate that NK cells and CEACAM1 play a role in AS pathogenesis and implicate chemokines in the mechanism of CEACAM1 expression.

Adult↗
PubMed2005

Inhibition of the NKp30 activating receptor by pp65 of human cytomegalovirus.

Human cytomegalovirus, a chief pathogen in immunocompromised people, can persist in a healthy immunocompetent host throughout life without being eliminated by the immune system. Here we show that pp65, the main tegument protein of human cytomegalovirus, inhibited natural killer cell cytotoxicity by an interaction with the activating receptor NKp30. This interaction was direct and specific, leading to dissociation of the linked CD3zeta from NKp30 and, consequently, to reduced killing. Thus, pp65 is a ligand for the NKp30 receptor and demonstrates a unique mechanism by which an intracellular viral protein causes general suppression of natural killer cell cytotoxicity by specific interaction with an activating receptor.

Animals↗
PubMed2004

Differential regulation of Th1/Th2 cytokine responses by placental protein 14.

The potency of TCR signaling during primary CD4+ T cell activation influences initial cytokine expression patterns and subsequent polarization toward either Th1 or Th2 subsets. In this study, we demonstrate that the T cell inhibitor placental protein 14 (PP14; glycodelin) preferentially inhibits Th1 cytokine responses and chemokine expression when present during ex vivo priming of CD4+ T cells. PP14 synergizes with exogenously added IL-4 in skewing T cell responses. Significantly, PP14 impairs the down-regulation of GATA-3 transcriptional regulator expression that normally accompanies T cell activation, which is a prerequisite for Th1 development. Taken together, these data document for the first time the ability of PP14 to skew Th responses.

Amniotic Fluid↗
PubMed2004

Membrane-associated heparan sulfate proteoglycans are involved in the recognition of cellular targets by NKp30 and NKp46.

Lysis of virus-infected and tumor cells by NK cells is mediated via natural cytotoxicity receptors (NCRs). We have recently shown that the NKp44 and NKp46 NCRs, but not the NKp30, recognize viral hemagglutinins. In this study we explored the nature of the cellular ligands recognized by the NKp30 and NKp46 NCRs. We demonstrate that target cell surface heparan sulfate proteoglycans (HSPGs) are recognized by NKp30 and NKp46 and that 6-O-sulfation and N-acetylation state of the glucose building unit affect this recognition and lysis by NK cells. Tumor cells expressing cell surface heparanase, CHO cells lacking membranal heparan sulfate and glypican-1-suppressed pancreatic cancer cells manifest reduced recognition by NKp30 and NKp46 and are lysed to a lesser extent by NK cells. Our results are the first clue for the identity of the ligands for NKp30 and NKp46. Whether the ligands are particular HSPGs, unusual heparan sulfate epitopes, or a complex of HSPGs and either other protein or lipid moieties remains to be further explored.

Animals↗
PubMed2004

MHC class I-independent recognition of NK-activating receptor KIR2DS4.

Natural killer cells are capable of killing tumor and virus-infected cells. This killing is mediated primarily via the natural cytotoxicity receptors, including NKp46, NKp44, NKp30, and by the NKG2D receptor. Killer cell Ig-like receptors (KIRs) are mainly involved in inhibiting NK killing (inhibitory KIRs) via interaction with MHC class I molecules. Some KIRs, however, have been found to enhance NK killing when interacting with MHC class I molecules (activating KIRs). We have previously demonstrated that KIR2DS4, an activating KIR, recognizes the HLA-Cw4 protein. The interaction observed was weak and highly restricted to HLA-Cw4 only. These findings prompted us to check whether KIR2DS4 might have additional ligand(s). In this study, we show that KIR2DS4 is able to also interact with a non-class I MHC protein expressed on melanoma cell lines and on a primary melanoma. This interaction is shown to be both specific and functional. Importantly, site-directed mutagenesis analysis reveals that the amino acid residues involved in the recognition of this novel ligand are different from those interacting with HLA-Cw4. These results may shed new light on the function of activating KIRs and their relevance in NK biology.

Amino Acid Sequence↗
PubMed2004

Recognition of Mycoplasma hyorhinis by CD99-Fc molecule.

The human CD99 protein is expressed on many cell types and is mostly abundant on lymphocytes and on several tumors. Different functions were attributed to the CD99 receptor, including adhesion, apoptosis and activation. However, until now the only ligand suggested to be recognized by CD99 was CD99 itself. In order to identify possible new CD99 ligands we constructed a CD99 protein fused to human IgG1. Surprisingly, a pronounced specific staining of melanoma cell lines that were infected with mycoplasmas was observed whereas clean cells were not recognized. Staining was specific, as other fusion proteins did not recognize the mycoplasma-infected cells. Sequencing of the 23s-16s region revealed that the contaminating agent is Mycoplasma hyorhinis. The CD99 interaction with M. hyorhinis was direct since it was blocked by anti-CD99 monoclonal antibody and by M. hyorhinis. It was also strain-specific as other mycoplasmas were not recognized. Our results show that CD99 interacts with a novel ligand of M. hyorhinis.

12E7 Antigen↗
PubMed2004

Biological function of the soluble CEACAM1 protein and implications in TAP2-deficient patients.

Interactions of natural killer (NK) cells with MHC class I proteins provide the main inhibitory signals controlling NK killing activity. It is therefore surprising to learn that TAP2-deficient patients suffer from autoimmune manifestations only occasionally in later stages of life. We have previously described that the CEACAM1-mediated inhibitory mechanism of NK cytotoxicity plays a major role in controlling NK autoreactivity in three newly identified TAP2-deficient siblings. This novel mechanism probably compensates for the lack of MHC class I-mediated inhibition. The CEACAM1 protein can also be present in a soluble form and the biological function of the soluble form of CEACAM1 with regard to NK cells has not been investigated. Here we show that the homophilic CEACAM1 interactions are abrogated in the presence of soluble CEACAM1 protein in a dose-dependent manner. Importantly, the amounts of soluble CEACAM1 protein detected in sera derived from the TAP2-deficient patients were dramatically reduced as compared to healthy controls. This dramatic reduction does not depend on the membrane-bound metalloproteinase activity. Thus, the expression of CEACAM1 and the absence of soluble CEACAM1 observed in the TAP2-deficient patients practically maximize the inhibitory effect and probably help to minimize autoimmunity in these patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Novel APC-like properties of human NK cells directly regulate T cell activation.

Initiation of the adaptive immune response is dependent on the priming of naive T cells by APCs. Proteomic analysis of unactivated and activated human NK cell membrane-enriched fractions demonstrated that activated NK cells can efficiently stimulate T cells, since they upregulate MHC class II molecules and multiple ligands for TCR costimulatory molecules. Furthermore, by manipulating antigen administration, we show that NK cells possess multiple independent unique pathways for antigen uptake. These results highlight NK cell-mediated cytotoxicity and specific ligand recognition by cell surface-activating receptors on NK cells as unique mechanisms for antigen capturing and presentation. In addition, we analyzed the T cell-activating potential of human NK cells derived from different clinical conditions, such as inflamed tonsils and noninfected and CMV-infected uterine decidual samples, and from transporter-associated processing antigen 2-deficient patients. This in vivo analysis revealed that proinflammatory, but not immune-suppressive, microenvironmental requirements can selectively dictate upregulation of T cell-activating molecules on NK cells. Taken together, these observations offer new and unexpected insights into the direct interactions between NK and T cells and suggest novel APC-like activating functions for human NK cells.

Antigen-Presenting Cells↗
PubMed2004

Math1 controls cerebellar granule cell differentiation by regulating multiple components of the Notch signaling pathway.

Cerebellar granule cells (CGC) are the most abundant neurons in the mammalian brain, and an important tool for unraveling molecular mechanisms underlying neurogenesis. Math1 is a bHLH transcription activator that is essential for the genesis of CGC. To delineate the effects of Math1 on CGC differentiation, we generated and studied primary cultures of CGC progenitors from Math1/lacZ knockout mice. Rhombic lip precursors appeared properly positioned, expressed CGC-specific markers, and maintained Math1 promoter activity in vivo and in vitro, suggesting that Math1 is not essential for the initial stages of specification or survival of CGC. Moreover, the continuous activity of Math1 promoter in the absence of MATH1, indicated that MATH1 was not necessary for the activation of its own expression. After 6, but not 3, days in culture, Math1 promoter activity was downregulated in control cultures, but not in cells from Math1 null mice, thus implying that Math1 participates in a negative regulatory feedback loop that is dependent on increased levels of MATH1 generated through the positive autoregulatory feedback loop. In addition, Math1 null CGC did not differentiate properly in culture, and were unable to extend processes. All Notch signaling pathway receptors and ligands tested were expressed in the rhombic lip at embryonic date 14, with highest levels of Notch2 and Jag1. However, Math1-null rhombic lip cells presented conspicuous downregulation of Notch4 and Dll1. Moreover, of the two transcriptional repressors known to antagonize Math1, Hes5 (but not Hes1) was downregulated in Math1-null rhombic lip tissue and primary cultures, and was shown to bind MATH1, thus revealing a negative regulatory feedback loop. Taken together, our data demonstrate that CGC differentiation, but not specification, depends on Math1, which acts by regulating the level of multiple components of the Notch signaling pathway.

Animals↗
PubMed2003

The mechanisms controlling the recognition of tumor- and virus-infected cells by NKp46.

The destruction of viral-infected and tumor cells is mediated in part via the lysis receptor of natural killer (NK) cells, NKp46. The nature, however, of its lysis ligands expressed on target cells is poorly defined. Recently, we have identified a novel functional interaction between the lysis receptors NKp46 and NKp44 and the hemagglutinin of influenza and hemagglutinin-neuroaminidase of Sendai viruses. This recognition depends on the sialylation of NKp46 and NKp44 receptors. In this study, we expand the significance of these observations by demonstrating a conserved pattern of NKp46 and NKp44 recognition by various hemagglutinins derived from different viral strains. We further establish that this recognition is direct and mainly mediated via alpha2,6-linked sialic acid carried by NKp46. In addition, we demonstrate that the ability of NKp46 to recognize target cells is confined to the membrane proximal domain, and largely relies on the highly conserved sugar-carrying residue, Thr 225. This residue plays a critical dual role in NKp46 interactions with both viral hemagglutinins and the unknown tumor ligands via different mechanisms. These results may explain the ability of NK cells to kill such a broad spectrum of viral-infected and tumor cells.

Animals↗
PubMed2003

Complexes of HLA-G protein on the cell surface are important for leukocyte Ig-like receptor-1 function.

The nonclassical class I MHC molecule HLA-G is selectively expressed on extravillous cytotrophoblast cells at the maternal-fetal interface during pregnancy. HLA-G can inhibit the killing mediated by NK cells via interaction with the inhibitory NK cell receptor, leukocyte Ig-like receptor-1 (LIR-1). Comparison of the sequence of the HLA-G molecule to other class I MHC proteins revealed two unique cysteine residues located in positions 42 and 147. Mutating these cysteine residues resulted in a dramatic decrease in LIR-1 Ig binding. Accordingly, the mutated HLA-G transfectants were less effective in the inhibition of NK killing and RBL/LIR-1 induced serotonin release. Immunoprecipitation experiments demonstrated the involvement of the cysteine residues in the formation of HLA-G protein oligomers on the cell surface. The cysteine residue located at position 42 is shown to be critical for the expression of such complexes. These oligomers, unique among the class I MHC proteins, probably bind to LIR-1 with increased avidity, resulting in an enhanced inhibitory function of LIR-1 and an impaired killing function of NK cells.

Amino Acid Sequence↗
PubMed2003

Enhanced recognition of human NK receptors after influenza virus infection.

The NK cell cytotoxic activity is regulated by both inhibitory and activating NK receptors. Thus, changes in the expression levels and in the affinity or avidity of those receptors will have a major effect on the killing of target cells. In this study, we demonstrate that the binding of NK-inhibitory receptors is enhanced after influenza virus infection. Surprisingly, however, no change in the level of class I MHC protein expression was observed on the surface of the infected cells. The increased binding was general, because it was observed in both the killer cell Ig-like receptor 2 domain long tail 1 and leukocyte Ig-like receptor-1. The increased binding was functional, was not dependent on the interaction with viral hemagglutinin-neuraminidase, was not dependent on the glycosylation site, and was not abolished after mutating the transmembrane or cytosolic portions of the class I MHC proteins. Confocal microscopy experiments showed increased binding of NK receptor-coated beads to infected cells expressing the appropriate class I MHC proteins. In addition, specific cell-free bead aggregates covered with class I MHC proteins were observed only in infected cells. We therefore suggest that the influenza virus use a novel mechanism for the inhibition of NK cell activity. This mechanism probably involves the generation of class I MHC complexes in infected cells that cause increased recognition of NK receptors.

Animals↗
PubMed2003

CXCL12 expression by invasive trophoblasts induces the specific migration of CD16- human natural killer cells.

In the maternal decidua, natural killer (NK) cells, characterized by lack of CD16, are found in direct contact with the fetal extravillous trophoblasts (EVTs). It is yet unknown which factors contribute to the specific homing of this unique NK subset to the decidua. In this study we analyze the chemokine receptor repertoire on various NK populations derived from the peripheral blood and decidua. We show that CXCR4 and CXCR3 receptors are preferentially expressed on CD16- NK subsets derived either from the peripheral blood or the decidua and that these receptors are involved in migration of all NK subsets to their ligands. We further demonstrate in vivo that invading EVTs that eventually perform endovascular invasion express CXCL12, the ligand for CXCR4, but not ligands for CXCR3. Indeed, specific accumulation of the CD16- NK cells at the expense of CD16+ cells was observed only when in vitro migration was performed with ligands for CXCR4. Finally, incubation of the peripheral blood CD16- NK cells with cytokines present in the decidua, especially interleukin 15 (IL-15), resulted in the expression of chemokine receptor repertoire similar to that observed on decidual NK cells, suggesting an additional important regulatory effect of local decidual cytokines.

Blood Vessels↗