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L Moretta

Publications and source records attributed to L Moretta.

At least 55 records · Page 3Linked to original sources
PubMed2000

Phenotypic and functional analysis of the HLA-class I-specific inhibitory receptors of natural killer cells isolated from peripheral blood of patients undergoing bone marrow transplantation from matched unrelated donors.

INTRODUCTION: Limited information is available on the natural killer cell reconstitution after bone marrow transplantation and on the possible role of these cells in graft-versus-host-disease. MATERIALS AND METHODS: Blood samples were collected at different time intervals after transplantation. Lymphocytes were analyzed for informative markers by immunocytofluorimetric analysis. Natural killer cells derived from patients undergoing matched unrelated donor transplant were cloned by limiting dilution in the presence of phytohemoagglutinin and IL2. The natural killer cell clones were analyzed for cytolytic activity. RESULTS: In the nine patients analyzed undergoing transplantation from sibling donors, the majority of peripheral blood lymphocytes during the first 80 d after BMT were represented by T lymphocytes, while in the 15 patients undergoing matched unrelated donor transplant natural killer cells consistently outnumbered T lymphocytes. During the early phases after transplantation, most CD56+CD3- natural killer cells did not express CD16 which was expressed at later intervals. Analysis of the inhibitory receptors specific for HLA-class I molecules showed that CD94/NKG2A, specific for HLA-E, unlike normal donors, was expressed by all natural killer cells including the early appearing CD16-negative ones. Killer inhibitory receptors of the Ig superfamily were expressed late and in low percentages after transplantation and were always coexpressed with CD94/NKG2A. Natural killer-cell clones efficiently lysed the HLA-class I-negative cell lines K562 and 721-221. Natural killer-cell populations or clones isolated from patients with graft-versus-host-disease, failed to lyse donor or recipient derived phytohemoagglutinin-induced lymphoblasts. CONCLUSION: Our analysis shows that (1) recipients of matched unrelated donors transplants exhibit a high proportion of NK cells (2) all NK cells express CD94/NKG2A while the HLA-class I-specific inhibitory receptors of Ig superfamily appear at later stages and (3) donor NK cells do not lysed donor or recipient target cells.

Adolescent↗
PubMed2000

Increased expression of non-functional killer inhibitory receptor CD94 in CD8+ cells of myeloma patients.

Different MHC class I-specific killer inhibitory receptors (KIRs) are expressed in vivo by a minor fraction of activated memory CD8+ cells. It has been postulated that KIRs may 'fine-tune' specific responses by altering their threshold of activation by the TCR-CD3 complex. We have previously shown that, in multiple myeloma (MM) patients, a large fraction of peripheral blood CD8+ cells display the phenotype of chronically activated memory T cells (CD38+, HLA-DR+, CD25-, CD45R0+, CD28-). We investigated the expression of KIRs on MM T cells and determined their possible influence on cytolytic responses elicited via the CD3-TCR complex. The expression of CD94, a molecule that is part of a heterodimeric KIR recognizing the non-classical MHC surface HLA-E molecule, was almost threefold higher in MM T cells than in age-matched normal control subjects (P < 0.0001). CD94 expression was preferentially confined to CD8+ cells but not restricted to activated (HLA-DR+) and/or memory (CD45R0+) T cells. Unlike normal T cells, in which CD94 is assembled with glycoproteins of the NKG2 family to form functional receptors with activating or inhibitory properties, most CD94+ MM T cells were devoid of both the NKG2-A and NKG2-C glycoproteins detected in the inhibitory or activating form respectively. CD94 blockade did not significantly affect either T-cell proliferation or cytotoxic T-lymphocyte generation induced by the myeloma-derived cell lines NCI and RPMI 8226. Similarly, the cytolytic activity induced by direct anti-CD3-mediated targeting of MM T cells to FCR+ P815 target cells was unaffected by the addition of anti-CD94 and/or anti-NKG2-A/C monoclonal antibodies (mAbs). These data indicate that the large majority of MM CD8+ cells do not express a functional CD94 receptor. Thus, their ability to 'fine-tune' an appropriate immune response against tumour cells can be impaired.

Antibodies, Monoclonal↗
PubMed1999

Engagement of p75/AIRM1 or CD33 inhibits the proliferation of normal or leukemic myeloid cells.

P75/AIRM1 is a recently identified surface molecule that belongs to the sialoadhesin family and displays homology with the myeloid cell antigen CD33. In lymphoid cells, p75/AIRM1 is confined to natural killer cells and mediates inhibition of their cytolytic activity. In this study, we show that p75/AIRM1 is also expressed by cells of the myelomonocytic cell lineage, in which it appears at a later stage as compared with CD33. In vitro proliferation and differentiation of cord blood-derived CD34(+) cells (induced by stem cell factor and granulocyte-macrophage colony-stimulating factor) were consistently inhibited by the addition of anti-p75/AIRM1 mAb. Engagement of CD33 led to inhibition in some experiments. A sharp decrease of cell proliferation/survival was detected in all three p75/AIRM1+ chronic myeloid leukemias analyzed when cultured in the presence of either anti-p75/AIRM1 or anti-CD33 mAbs. Thus, the present study suggests that p75/AIRM1 and CD33 may play a regulatory role in normal myelopoiesis and may be viewed as suitable target molecules to counteract the proliferation/survival of chronic myeloid leukemias.

Antibodies, Monoclonal↗
PubMed1999

Identification and molecular characterization of NKp30, a novel triggering receptor involved in natural cytotoxicity mediated by human natural killer cells.

Two major receptors involved in human natural cytotoxicity, NKp46 and NKp44, have recently been identified. However, experimental evidence suggested the existence of additional such receptor(s). In this study, by the generation of monoclonal antibodies (mAbs), we identified NKp30, a novel 30-kD triggering receptor selectively expressed by all resting and activated human natural killer (NK) cells. Although mAb-mediated cross-linking of NKp30 induces strong NK cell activation, mAb-mediated masking inhibits the NK cytotoxicity against normal or tumor target cells. NKp30 cooperates with NKp46 and/or NKp44 in the induction of NK-mediated cytotoxicity against the majority of target cells, whereas it represents the major triggering receptor in the killing of certain tumors. This novel receptor is associated with CD3zeta chains that become tyrosine phosphorylated upon sodium pervanadate treatment of NK cells. Molecular cloning of NKp30 cDNA revealed a member of the immunoglobulin superfamily, characterized by a single V-type domain and a charged residue in the transmembrane portion. Moreover, we show that NKp30 is encoded by the previously identified 1C7 gene, for which the function and the cellular distribution of the putative product were not identified in previous studies.

Animals↗
PubMed1999

Identification and molecular cloning of p75/AIRM1, a novel member of the sialoadhesin family that functions as an inhibitory receptor in human natural killer cells.

In this study, by the generation of a specific monoclonal antibody, we identified p75/AIRM1 (for adhesion inhibitory receptor molecule 1), a novel inhibitory receptor that is mostly confined to human natural killer cells. p75/AIRM1 is a 75-kD glycoprotein that, upon sodium pervanadate treatment, becomes tyrosine phosphorylated and associates to src homology 2 domain-bearing protein tyrosine phosphatase (SHP)-1. The p75/AIRM1 gene is located on human chromosome 19 and encodes a novel member of the sialoadhesin family characterized by three immunoglobulin-like extracellular domains (one NH(2)-terminal V-type and two C2-type) and a classical immunoreceptor tyrosine-based inhibitory motif (ITIM) in the cytoplasmic portion. The highest amino acid sequence similarity has been found with the myeloid-specific CD33 molecule and the placental CD33L1 protein. Similar to other sialoadhesin molecules, p75/AIRM1 appears to mediate sialic acid-dependent ligand recognition.

Amino Acid Sequence↗
PubMed1999

Inhibitory receptors sensing HLA-G1 molecules in pregnancy: decidua-associated natural killer cells express LIR-1 and CD94/NKG2A and acquire p49, an HLA-G1-specific receptor.

Trophoblastic cells lack classical HLA class I and class II molecules but express HLA-G1. Although this may prevent allorecognition by maternal T cells, it renders trophoblastic cells potentially susceptible to lysis by natural killer (NK) cells. As shown here, only a fraction of peripheral-blood NK cells in pregnant women express the HLA-G1-specific CD94/NKG2A and/or LIR-1 receptors. However, all NK cells isolated from maternal decidua during the first trimester expressed either one or both of these receptors. Perhaps more importantly, a fraction of cells expressed p49, an HLA-G1-specific inhibitory receptor, undetectable in peripheral-blood NK cells. p49 was expressed on virtually all NK cells isolated from placenta at term. Functional analyses revealed that the HLA class I-negative 221 lymphoblastoid cell line transfected with HLA-G1 was only partially protected from lysis by peripheral-blood NK cells isolated from pregnant women, whereas it was fully protected from decidual NK cells. As indicated by the addition of specific antibodies to cytolytic tests, all the above receptors contributed to HLA-G1 recognition by decidual NK cells, although p49 would appear to play a predominant role.

Animals↗
PubMed1999

NKp44, a triggering receptor involved in tumor cell lysis by activated human natural killer cells, is a novel member of the immunoglobulin superfamily.

Surface receptors involved in natural killer (NK) cell triggering during the process of tumor cell lysis have recently been identified. Of these receptors, NKp44 is selectively expressed by IL-2- activated NK cells and may contribute to the increased efficiency of activated NK cells to mediate tumor cell lysis. Here we describe the molecular cloning of NKp44. Analysis of the cloned cDNA indicated that NKp44 is a novel transmembrane glycoprotein belonging to the Immunoglobulin superfamily characterized by a single extracellular V-type domain. The charged amino acid lysine in the transmembrane region may be involved in the association of NKp44 with the signal transducing molecule killer activating receptor-associated polypeptide (KARAP)/DAP12. These molecules were found to be crucial for the surface expression of NKp44. In agreement with data of NKp44 surface expression, the NKp44 transcripts were strictly confined to activated NK cells and to a minor subset of TCR-gamma/delta+ T lymphocytes. Unlike genes coding for other receptors involved in NK cell triggering or inhibition, the NKp44 gene is on human chromosome 6.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Transforming growth factor-beta-induced expression of CD94/NKG2A inhibitory receptors in human T lymphocytes.

Different HLA class I-specific killer inhibitory receptors (KIR) are expressed in vivo by a fraction of activated T cells, predominantly CD8+, in which they may inhibit TCR-mediated cell functions. In an attempt to identify mechanisms leading to KIR expression in T cells, we analyzed the effect of transforming growth factor-beta (TGF-beta) in T cells responding to bacterial superantigens in vitro. We show that TGF-beta induces the expression of CD94/NKG2A in cells responding to toxic shock syndrome toxin 1 or to other staphylococcal superantigens. Remarkably, maximal CD94 expression occurred at (low) TGF-beta concentrations which have no substantial effect on lymphocyte proliferation. Maximal CD94 expression occurred when TGF-beta was added shortly after the cells were placed in culture. No expression could be induced in CD94/NKG2A-negative T cell clones. Although both CD4+ and CD8+ expressed CD94, the simultaneous expression of NKG2A was mostly confined to CD8+ cells. Monoclonal antibody-mediated cross-linking of CD94/NKG2A led to an impairment of T cell triggering via CD3, as determined in a redirected killing assay using the Fcgamma receptor-positive P815 murine target cells.

Animals↗
PubMed1999

The murine homologue of the human NKp46, a triggering receptor involved in the induction of natural cytotoxicity.

The NKp46 molecule has been proposed to play the role of triggering receptor in the natural cytotoxicity mediated by human NK cells. In this study we have identified the gene encoding the murine NKp46 homologue that we termed MAR-1. The MAR-1 gene is localized on chromosome 7 that is synthenic to the human chromosome 19 where the NKp46 gene is located. MAR-1 encodes a type I transmembrane glycoprotein belonging to the immunoglobulin (Ig) superfamily that, like human NKp46, is characterized by two C2-type Ig-like domains, a transmembrane portion containing a positively charged residue and a cytoplasmic tail lacking the immunoreceptor tyrosine-based activation motif (ITAM). The MAR-1 protein is expressed on the surface of cell transfectants and displays a molecular mass of approximately 46 kDa similar to that of its human counterpart. Semiquantitative RT-PCR analysis showed that MAR-1, similar to the human NKp46, is selectively expressed by NK cells. The MAR-1 protein displays 58 % identity with the human NKp46 receptor. This high homology together with the presence of a charged amino acid (Arg) in the transmembrane portion suggest that MAR-1 may associate at the cell membrane into a multimeric complex with ITAM containing polypeptides.

Amino Acid Sequence↗
PubMed1999

NKp46 is the major triggering receptor involved in the natural cytotoxicity of fresh or cultured human NK cells. Correlation between surface density of NKp46 and natural cytotoxicity against autologous, allogeneic or xenogeneic target cells.

NKp46 is a novel triggering receptor expressed by all human NK cells that is involved in natural cytotoxicity. In this study we show that the surface density of NKp46 may vary in different NK cells and that a precise correlation exists between the NKp46 phenotype of NK clones and their natural cytotoxicity against HLA-class I-unprotected allogeneic or xenogeneic cells. Thus, NKp46bright clones efficiently lysed human and murine tumor cells while NKp46dull clones were poorly cytolytic against both types of target cells. We also show that the NKp46 phenotype of NK clones correlates with their ability to lyse HLA-class I-unprotected autologous cells. Finally, NKp46 was found to be deeply involved in the natural cytotoxicity mediated by freshly derived NK cells. This was indicated both by the inhibition of cytolysis after monoclonal antibody-mediated masking of NKp46 and by the correlation existing between the natural cytotoxicity of fresh NK cells derived from different donors and their NKp46 phenotype. In conclusion, these studies strongly support the concept that NKp46 plays a central role in the physiological triggering of NK cells and, as a consequence (in concert with killer inhibitory receptors), in the NK-mediated clearance of abnormal cells expressing inadequate amounts of HLA-class I molecules.

Cells, Cultured↗
PubMed1999

Molecular and functional characterization of IRp60, a member of the immunoglobulin superfamily that functions as an inhibitory receptor in human NK cells.

In this study we describe the functional and molecular characterization of IRp60 (inhibitory receptor protein 60), an inhibitory receptor expressed on all human NK cells. The IRp60 molecule has been identified by the generation of three novel monoclonal antibodies (mAb). Cross-linking of IRp60 by specific mAb strongly inhibits the spontaneous cytotoxicity of NK cells as well as the NK-mediated cytolytic activity induced via different non-HLA-specific or HLA-specific activating receptors. IRp60 is a 60-kDa glycoprotein that, upon sodium pervanadate treatment, becomes tyrosine phosphorylated and associates with the SH2-containing phosphatases SHP-1 and SHP-2. The IRp60 gene is located on human chromosome 17 and encodes a molecule belonging to the immunoglobulin (Ig) superfamily characterized by a single V-type Ig-like domain in the extracellular portion. The cytoplasmic tail contains three classical immunoreceptor tyrosine-based inhibitory motifs. Southern blot analysis revealed cross-hybridization with monkey and mouse genomic DNA, thus suggesting that IRp60 may be conserved among different species. Moreover, based on the use of different anti-IRp60 mAb, we could identify two IRp60 allelic variants. Since IRp60 is also expressed by other cell types, including T cell subsets, monocytes and granulocytes, it may play a more general role in the negative regulation of different leukocyte populations.

Amino Acid Sequence↗
PubMed1999

Natural killer cell-mediated recognition of human trophoblast.

Large numbers of natural killer cells are present within the maternal decidua close to the extravillous trophoblast cells. Most of these natural killer cells express high levels of inhibitory NK receptors (KIR) specific for HLA class I molecules. Since trophoblast cells only express HLA-C and HLA-G, the KIR expressed by decidual NK cells can only recognize these HLA class I molecules in order to avoid NK-mediated rejection of fetal tissues. We show that HLA-C recognition by decidual NK cells can be mediated by p58, LIR-1 and (indirectly) by CD94/NKG2A receptors. On the other hand, HLA-G recognition is not only mediated by LIR-1 and (indirectly) by CD94/NKG2A but also by a newly identified receptor termed p49. The p49 receptor, unlike the other KIR, appears to be selectively expressed by decidual NK cells.

Alleles↗
PubMed1999

P49, a putative HLA-G1 specific inhibitory NK receptor belonging to the immunoglobulin Superfamily.

NK cells display several killer inhibitory receptors (KIRs) specific for different alleles of major histocompatibility complex (MHC) class I molecules. A family of KIRs are represented by type I transmembrane proteins belonging to the Immunoglobulin Superfamily (Ig-SF). In the present study we describe a cDNA, termed cl.15.212, that encodes for a type I transmembrane protein displaying approximately 50% sequence homology with other Ig-SF members. The protein encoded by cl.15.212 (termed p49 according to its apparent molecular weight of 49 kDa) is characterized by two extracellular Ig-like domains, a 115-amino acid cytoplasmic tail containing a single immuno-receptor tyrosine-based inhibitory motif (ITIM) typical of KIR. Different from the other KIRs, the cl.15.212 transcript is expressed by all NK cells and by a fraction of T-cell clones expressing KIR. To determine the specificity of the cl.15.212-encoded receptor, we generated a chimeric protein, formed by the ectodomain of p49 and the Fc portion of human IgG1 (p49-Fc). Soluble molecules bound efficiently to LCL721.221 (221) cells transfected with HLA-G1, -A3, -B46 alleles and weakly to the -B7 allele. On the other hand, they did not bind to 221 cells either untransfected or transfected with HLA-A2, -B51, -Cw3, or-Cw4.

Alleles↗
PubMed1999

Human gamma delta T cells that inhibit the in vitro growth of the asexual blood stages of the Plasmodium falciparum parasite express cytolytic and proinflammatory molecules.

The functional properties, regarding parasite growth inhibition in vitro, the cytotoxic potential and cytokine profiles of human gammadelta+ and alphabeta+ T cells, T-cell lines and clones stimulated with Plasmodium falciparum-antigen-or T-cell mitogen in vitro were investigated. Using reverse transcriptase-polymerase chain reaction (RT-PCR) and specific primers, mRNA for the cytolytic molecules perforin, granzyme A and B, Fas and Fas ligand (FasL) were detected in both the gammadelta- and the alphabetaT cells. Despite this fact, only gammadeltaT cells inhibited, both Vdelta1+ and Vdelta2+, the in vitro growth of the asexual blood stages in a dose dependent manner. The inhibition required cell-to-cell contact and was not observed until the second parasite replication implied that the likely gammadeltaT-cell target was the extracellular merozoite or schizont. The failure of alphabetaT cells to inhibit the growth of the parasite suggests requirement of additional cytolytic molecules/signals or different receptor specificities exhibited by the gammadeltaT cells. Both the gammadelta- and alphabetaT cells expressed mRNA for a large number of cytokines. Interferon (IFN)-gamma, interleukin (IL) IL-5, IL-6, IL-8, tumour necrosis factor alpha (TNFalpha), tumour necrosis factor beta (TNF-beta)/lymphotoxin (LT) and T-cell growth factor beta-1 (TGF-beta1) were observed in all activated clones tested. No IL-3 was detected, while IL-1beta, IL-2, IL-4, IL-10 and GM-CSF were variably expressed. In conclusion, our data show that gammadeltaT cells in malaria nonimmune individuals inhibit the asexual blood stages of P. falciparum malaria, while similarly activated alphabetaT cells do not. Thus, it is likely that the gammadeltaT cells could play a mandatory role in the elimination of parasites and/or the regulation of the early immune response to malaria infection.

Animals↗
PubMed1999

The leukocyte Ig-like receptor (LIR)-1 for the cytomegalovirus UL18 protein displays a broad specificity for different HLA class I alleles: analysis of LIR-1 + NK cell clones.

Leukocyte Ig-like receptor (LIR)-1 is a member of the Ig superfamily which has been shown to bind the human cytomegalovirus MHC class I homologue UL-18 protein. In this study, we have analyzed the expression and function of LIR-1 in human NK cells. We show that LIR-1 is expressed by a subset of NK cells variable in size among different donors. When compared to the known HLA class I-specific NK receptors, the expression of LIR-1 was found to be partially overlapped with that of CD94-NKG2A or with that of killer inhibitory receptors (KIR) belonging to the Ig superfamily. The use of the soluble form of UL-18 molecule revealed, in double fluorescence analysis, a selective binding to LIR-1 + cells while no correlation was observed between expression of either KIR or CD94-NKG2A molecules and ability to bind UL18. We further determined whether LIR-1 could also function as receptor for HLA class I molecules. To this end, we assessed the capability of LIR-1 + NK cell clones of lysing HLA class I- target cells transfected with different class I alleles, including HLA-A, -B, -C and -G alleles. Data revealed that LIR-1 functions as a broad HLA class I-specific inhibitory receptor recognizing different alleles coded for by different HLA loci.

Alleles↗
PubMed1998

Molecular cloning of NKp46: a novel member of the immunoglobulin superfamily involved in triggering of natural cytotoxicity.

NKp46 has been shown to represent a novel, natural killer (NK) cell-specific surface molecule, involved in human NK cell activation. In this study, we further analyzed the role of NKp46 in natural cytotoxicity against different tumor target cells. We provide direct evidence that NKp46 represents a major activating receptor involved in the recognition and lysis of both human and murine tumor cells. Although NKp46 may cooperate with other activating receptors (including the recently identified NKp44 molecule) in the induction of NK-mediated lysis of human tumor cells, it may represent the only human NK receptor involved in recognition of murine target cells. Molecular cloning of the cDNA encoding the NKp46 molecule revealed a novel member of the immunoglobulin (Ig) superfamily, characterized by two C2-type Ig-like domains in the extracellular portion. The transmembrane region contains the positively charged amino acid Arg, which is possibly involved in stabilizing the association with CD3zeta chain. The cytoplasmic portion, spanning 30 amino acids, does not contain immunoreceptor tyrosine-based activating motifs. Analysis of a panel of human/hamster somatic cell hybrids revealed segregation of the NKp46 gene on human chromosome 19. Assessment of the NKp46 mRNA expression in different tissues and cell types unambiguously confirmed the strict NK cell specificity of the NKp46 molecule. Remarkably, in line with the ability of NKp46 to recognize ligand(s) on murine target cells, the cDNA encoding NKp46 was found to be homologous to a cDNA expressed in murine spleen. In conclusion, this study reports the first characterization of the molecular structure of a NK-specific receptor involved in the mechanism of NK cell activation during natural cytotoxicity.

Amino Acid Sequence↗