Showing papers by "Eric Vivier published in 1999"

Differential Roles of N- and C-Terminal Immunoreceptor Tyrosine-Based Inhibition Motifs During Inhibition of Cell Activation by Killer Cell Inhibitory Receptors

Abstract: Killer cell inhibitory receptors (KIRs) inhibit NK and T cell cytotoxicity when recognizing MHC class I molecules on target cells. They possess two tandem intracytoplasmic immunoreceptor tyrosine-based inhibition motifs (ITIMs) that, when phosphorylated, each bind to the two Src homology 2 domain-bearing protein tyrosine phosphatases SHP-1 and SHP-2 in vitro. Using chimeric receptors having an intact intracytoplasmic KIR domain bearing both ITIMs (N + C-KIR), a deleted domain containing the N-terminal ITIM only (N-KIR), or a deleted domain containing the C-terminal ITIM only (C-KIR), we examined the respective contributions of the two ITIMs in the inhibition of cell activation in two experimental models (a rat mast cell and a mouse B cell line) that have been widely used to analyze KIR functions. We found that the two KIR ITIMs play distinct roles. When coaggregated with immunoreceptor tyrosine-based activation motif-bearing receptors such as high-affinity IgE receptors or B cell receptors, the N + C-KIR and the N-KIR chimeras, but not the C-KIR chimera, inhibited mast cell and B cell activation, became tyrosyl-phosphorylated, and recruited phosphatases in vivo. The N + C-KIR chimera recruited SHP-1 as expected, but also SHP-2. Surprisingly, the N-KIR chimera failed to recruit SHP-1; however, it did recruit SHP-2. Consequently, the N-terminal ITIM is sufficient to recruit SHP-2 and to inhibit cell activation, whereas the N-terminal and the C-terminal ITIMs are both necessary to recruit SHP-1. The two KIR ITIMs, therefore, are neither mandatory for inhibition nor redundant. Rather than simply amplifying inhibitory signals, they differentially contribute to the recruitment of distinct phosphatases that may cooperate to inhibit cell activation.

Differential regulation of killer cell Ig-like receptors and CD94 lectin-like dimers on NK and T lymphocytes from HIV-1-infected individuals.

Abstract: NK and T lymphocytes share various cell surface receptors, including NK receptors for MHC class I molecules (NKR). NKR include killer cell Ig-like receptors (KIR) and lectin-like dimers which are composed of the invariant CD94 associated with a variety of NKG2 molecules. The combination of KIR and CD94/NKG2 dimers expressed on NK and T cell subsets defines a repertoire of MHC class I recognition. Engagement of NKR by cognate MHC class I molecules governs T and NK cell activation. We investigated the NKR distribution on NK and T cell subsets from uninfected and HIV-infected individuals, according to the clinical status, the absolute numbers of CD4+ T cells as well as the plasmatic viral load of the patients. We show that the KIR distribution on NK cells is not affected by HIV-1 infection, whereas the absolute numbers of T cells expressing specific KIR members (CD158b, p70) transiently increase in early stages of HIV infection. By contrast, the percentages of NK and T cells which express CD94 dimers increase in parallel with the disease. These results document a differential regulation of KIR and CD94 lectin-like dimers during the course of a chronic viral infection in humans and further suggest that both types of NKR are independently regulated.

Biology of immunoreceptor tyrosine-based inhibition motif-bearing molecules.

Abstract: The term “immunoreceptor tyrosine-based inhibition motif” (ITIM) was coined after the term “immunoreceptor tyrosine-based activation motif” (ITAM) to designate molecular motifs that antagonize ITAM-dependent cell activation (Daeron et al. 1995a; D’Ambrosio et al. 1995). The concept of ITIM lies on the coexpression by single cells of “on” and “off” molecules which, when kept in close proximity, transduce intracellular signals that interfere with each other. On and off receptors can be constitutively associated at the cell membrane, such as B Cell receptors (BCR) and CD22 on B lymphocytes (Law et al. 1996) or high-affinity IgE receptors (FcɛRI) and mast cell-associated function antigen (MAFA) on mast cells (Guthmann et al. 1995); or they can be coaggregated by extracellular ligands. Thus, ITIM-bearing low-affinity receptors for IgG (FcγRIIB) and ITAM-bearing receptors are coaggregated by IgG antibodies or soluble immune complexes (Amigorena et al. 1992; Daeron et al. 1995b; Daeron et al. 1995a). Although the spatial relationship established between MHC class I-specific killer cell Ig-like receptors (KIRs) and receptors that trigger cytotoxicity (Moretta et al. 1997) is unclear, KIRs needed to be coligated with FcɛRI by the same soluble molecules in order to inhibit the activation of mast cells in a reconstitution model (Blery et al. 1997). Following aggregation or coaggregation of the receptors, both ITAMs and ITIMs are tyrosyl phosphorylated by src family protein tyrosine kinases and, once phosphorylated, they recruit cytoplasmic molecules having SH2 domains (Cambier 1995; Burshtyn and Long 1997; Vivier and Daeron 1997).

The PEN5 epitope identifies an oligodendrocyte precursor cell population and pilocytic astrocytomas.

Abstract: PEN5 is a sulfated polylactosamine carbohydrate epitope first described in a subpopulation of mature natural killer cells. Here we report that it is also expressed in a developmentally regulated fashion in human and rat central nervous systems and that its protein carrier is P-selectin glycoprotein ligand-1 (PSGL-1), a ligand for selectins. In rat neural primary cultures, PEN5 is transiently and selectively expressed by oligodendrocyte precursor cells and marks the transition from proliferative to postmitotic stages. In concordance, in human central nervous system tumors, PEN5 is observed in a subset of oligodendrogliomas and in all pilocytic astrocytomas, a class of tumor of uncertain histogenesis. These data suggest that PEN5-PSGL-1 plays a role in the differentiation of oligodendrocytes and that pilocytic astrocytomas are likely to result from a dysregulation occurring in oligodendrocyte precursor cells at the crucial stage of exit from the cell cycle.

Engagement of natural cytotoxicity programs regulates AP-1 expression in the NKL human NK cell line.

Abstract: NK cell cytotoxicity is a fast and efficient mechanism of target cell lysis. Using transcription analysis, such as multiplex messenger assays, we show here that natural cytotoxicity exerted by the human NKL cell line correlates with mRNA accumulation of very early activator protein (AP)-1 transcription factor genes such as JunB, FosB and c-Fos. In addition, DNA-binding activities of Jun-Fos heterodimers were observed by electrophoretic mobility shift assays during the course of natural cytotoxicity. Interaction between immunoglobulin-like transcript-2/leukocyte Ig-like receptor 1 on NKL cells and HLA-B27 on target cells leads to an impairment of NKL natural cytotoxicity, which correlates with an absence of JunB, FosB, and c-Fos transcription, as well as an absence of their DNA-binding activity. Our studies thus indicate that, despite the rapidity of NK cell-mediated lysis, AP-1 transcription factor is activated during the early stage of NK cell cytolytic programs and that engagement of NK cell inhibitory receptors for MHC class I molecules impairs the very early activation of AP-1.

How to extinguish lymphocyte activation, immunotyrosine-based inhibition motif (ITIM)-bearing molecules a solution?

Abstract: ITIM-bearing molecules represent a novel family of inhibitory receptors expressed widely through the hematopoietic compartment. These molecules share certain features such as the presence in their intracytoplasmic domain of the so-called motif ITIM (ImmunoTyrosine-based Inhibition Motif). These molecules are able to recruit phosphatases on their phosphorylated ITIM and thus mediate a localized inhibition of the transduction pathways. The molecular basis of this inhibitory pathway is discussed below.

The enigma of activating isoforms of ITIM-bearing molecules.

Abstract: A novel family of inhibitory receptors has been described recently Vivier and Daeron 1997) based on the presence of a conserved immunoreceptor tyrosine-based inhibition motif (ITIM) in the intracytoplasmic portion. The first ITIM-bearing receptors were identified, in cells of hematopoietic origin, as the low affinity receptors for immunoglobulins, FcγRIIB, in B cells (Amigorena et al. 1992; Daeron et al. 1995) and the killer cell Ig-like receptors (KIR) for MHC class I molecules in natural killer (NK) cells (Olcese et al. 1996; Burshtyn et al. 1996). Subsequently, other ITIM-bearing molecules have been described in both hematopoietic cells [PIR-B, (Kubagawa et al. 1997), ILT-2 and -3, (Cella et al. 1997; Samaridis and Colonna 1997), LIR molecules (Borges et al. 1997), MIR molecules, (Wagtmann et al. 1997), CD22, (Sato et al. 1998), and CD72, (Wu et al. 1998)] and nonhematopoietic cells [SIRPα, (Kharitonenkov et al. 1997)]. All these molecules are characterized by the presence of one or more ITIM sequences in their intracytoplasmic portions. This motif is responsible for the transduction of inhibitory signals inside the cells. The ITIM-bearing receptors belong to two families: the immunoglobulin superfamily (IgSF) and the lectin-like superfamily (LSF).

Les cellules NK

Abstract: Resume Les cellules NK representent le troisieme type de lymphocyte avec les lymphocytes T et B. Leur definition peut etre morphologique, phenotypique et fonctionnelle. Au niveau morphologique, ce sont de grands lymphocytes granuleux comme les lymphocytes T cytotoxiques CD8+. Au niveau phenotypique, ils se caracterisent par l'absence de recepteur pour l'antigene et par la presence d'un recepteur de basse affinite pour le fragment Fc des IgG, CD16, et d'une isoforme d'une molecule d'adherence neuronale N-CAM, CD56. Sur un plan fonctionnel, ce sont des cellules cytotoxiques capables de lyser les cellules recouvertes d'anticorps par une cytotoxicite dependante des anticorps, et de lyser egalement par un mecanisme de cytotoxicite naturelle, par exemple, des cellules infectees par des virus ou des cellules tumorales. Une nouvelle famille de recepteurs, exprimes sur des cellules NK et une sous-population de cellules T memoires, assurent une regulation negative de la cytotoxicite et de la production de cytokines de ces cellules. Ces recepteurs reconnaissent les molecules du CMH de classe I classiques et non classiques. Ils appartiennent soit a la superfamille des immunoglobulines et sont appeles KIR, soit a la superfamille des lectines de type C, et sont representes par les heterodimeres CD94-NKG2. Apres reconnaissance de leur ligand, ces recepteurs sont phosphoryles sur un residu tyrosine present dans leur partie intracytoplasmique au sein d'un motif appele ITIM (Immunoreceptor tyrosine-based inhibition motif). La phosphorylation de ce motif permet le recrutement de proteines tyrosine phosphatases SHP-1 et/ou SHP-2 responsables par leur activite enzymatique du pouvoir inhibiteur de ces recepteurs. L'etude de l'implication des cellules NK in vivo dans l'elimination des processus tumoraux et des infections microbiologiques necessite une etude plus approfondie du repertoire et de la fonctionnalite de ces recepteurs pour les molecules de classe I.

Determining repertoire of natural killer receptors useful for monitoring resistance to infection

Abstract: In vitro method for determining a repertoire of natural killer (NK) receptors (NKR), particularly KIR p58.1, p58.2, p70.INH, p140.INH or receptors NKG2A or B and/or a repertoire of counterparts to NKR, particularly KAR p50.1, p50.2, p70.ACT, p140.ACT or receptors NKG2C, D, E and F, is new. The method comprises incubation of (c)DNA from a human or animal sample with an excess of at least one pair of oligonucleotides (ON) and detecting hybrids formed. Each ON in a given pair can hybridize to the (c)DNA of either an NKR or its counterpart, but not with both. Incubation is for 1 min at about 50-65 deg C in buffer, pH 8.4, containing 20 mM Tris hydrochloride, 50 mM potassium chloride and 2.5 mM magnesium chloride. An Independent claim is also included for kits containing at least one pair of ON and other reagents, e.g. buffers and markers, optionally coupled to ON.