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Biomedical subjects

L L Lanier

Publications and source records attributed to L L Lanier.

At least 37 records · Page 2Linked to original sources
PubMed2001

Biphasic response of NK cells expressing both activating and inhibitory killer Ig-like receptors.

NK cells can co-express inhibitory and activating killer Ig-like receptors (KIR) recognizing the same HLA class I ligand. We present evidence from experiments with NK cells expressing both activating (KIR2DS2) and inhibitory (KIR2DL2 and KIR2DL3) receptors that the activating KIR can function without apparent interference from the inhibitory KIR. These studies used CD158b mAb that is equally reactive with KIR2DS2, KIR2DL2 and KIR2DL3. First, we show using plastic-immobilized CD158b mAb that the activating KIR2DS2 is stimulated, resulting in NK cell division and degranulation. Second, we show using soluble CD158b mAb and FcRII (+) P815 cells that high concentrations of CD158b mAb trigger the inhibitory KIR, whereas low concentrations stimulate the activating KIR2DS2 resulting in NK cell division and cytolysis. These results demonstrate that the activating KIR2DS2 can function on cells co-expressing the inhibitory KIR2DL2 and/or KIR2DL3, indicating the potential for independent function of activating KIR with natural ligand.

Animals↗
PubMed2000

Immune inhibitory receptors.

With the detailed description and analysis of several inhibitory receptor systems on lymphoid and myeloid cells, a central paradigm has emerged in which the pairing of activation and inhibition is necessary to initiate, amplify, and then terminate immune responses. In some cases, the activating and inhibitory receptors recognize similar ligands, and the net outcome is determined by the relative strength of these opposing signals. The importance of this modulation is demonstrated by the sometimes fatal autoimmune disorders observed in mice with targeted disruption of inhibitory receptors. The significance of these receptors is further evidenced by the conservation of immunoreceptor tyrosine-based inhibitory motifs during their evolution.

Abatacept↗
PubMed2000

DAP10 and DAP12 form distinct, but functionally cooperative, receptor complexes in natural killer cells.

Many of the activating receptors on natural killer (NK) cells are multisubunit complexes composed of ligand-binding receptors that are noncovalently associated with membrane-bound signaling adaptor proteins, including CD3zeta, FcstraightepsilonRIgamma, DAP12, and DAP10. Because the DAP10 and DAP12 genes are closely linked, expressed in NK cells, and have remarkably similar transmembrane segments, it was of interest to determine the specificity of their interactions with ligand-binding receptors and to examine their signaling properties. Despite their similarities, DAP10, DAP12, FcstraightepsilonRIgamma, and CD3zeta form specific receptor complexes with their ligand-binding partners in NK cells and transfectants. The transmembrane regions of DAP10 and DAP12 are sufficient to confer specific association with their partners. Although cross-linking of either DAP10- or DAP12-associated receptors has been shown to be sufficient to trigger NK cell-mediated cytotoxicity against Fc receptor-bearing cells, substantial synergy was observed in the induction of cytokine production when both receptors were engaged. Activation of the Syk/ZAP70 tyrosine kinases by the immunoreceptor tyrosine-based activation motif-containing DAP12 adaptor and of the phosphatidylinositol 3-kinase pathway by the YxNM-containing DAP10 adaptor may play an important role in the stimulation of NK cells and T cells.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Functional requirement for SAP in 2B4-mediated activation of human natural killer cells as revealed by the X-linked lymphoproliferative syndrome.

X-linked lymphoproliferative syndrome (XLP) is an immunodeficiency characterized by life-threatening infectious mononucleosis and EBV-induced B cell lymphoma. The gene mutated in XLP encodes SLAM (signaling lymphocytic activation molecule-associated protein)-associated protein (SAP), a small SH2 domain-containing protein. SAP associates with 2B4 and SLAM, activating receptors expressed by NK and T cells, and prevents recruitment of SH2 domain-containing protein tyrosine phosphatase-2 SHP-2) to the cytoplasmic domains of these receptors. The phenotype of XLP may therefore result from perturbed signaling through SAP-associating receptors. We have addressed the functional consequence of SAP deficiency on 2B4-mediated NK cell activation. Ligating 2B4 on normal human NK cells with anti-2B4 mAb or interaction with transfectants bearing the 2B4 ligand CD48 induced NK cell cytotoxicity. In contrast, ligation of 2B4 on NK cells from a SAP-deficient XLP patient failed to initiate cytotoxicity. Despite this, CD2 or CD16-induced cytotoxicity of SAP-deficient NK cells was similar to that of normal NK cells. Thus, selective impairment of 2B4-mediated NK cell activation may contribute to the immunopathology of XLP.

Animals↗
PubMed2000

Transgenic expression of Ly-49A in thymocytes alters repertoire selection.

A T cell-specific Ly-49A transgene inhibits TCR-mediated activation in the presence of H-2Dd. Expression of this transgene by developing thymocytes impairs negative selection evidenced by a failure to delete potentially autoreactive T cells and development of a graft-vs-host-disease-like syndrome. In mice carrying both the Ly-49A and a class II-restricted TCR transgene, positive selection was lost, but only when H-2Dd was present on thymic epithelium. These results are consistent with models suggesting that thymic selection is dependent on the perceived intensity of TCR signaling. More interestingly, these results show that Ly-49A does not simply provide a strict on/off switch for T cell responses. Since Ly-49A may shift the signaling threshold of TCR-induced triggering, inducible expression of Ly-49A may regulate peripheral memory/activated T cells by raising the threshold for T cell reactivation.

Animals↗
PubMed2000

The CD2-subset of the Ig superfamily of cell surface molecules: receptor-ligand pairs expressed by NK cells and other immune cells.

The CD2-subset of the immunoglobulin superfamily of cell surface receptors is an emerging family of proteins involved in cellular activation. Members of this family are CD2, CD48, CD58, CD84, signaling lymphocytic activation molecule (SLAM), 2B4 and Ly-9. These proteins are expressed on different leukocyte populations and the receptors of this family, specifically CD2, 2B4 and SLAM, contribute to the activation of T cells and natural killer cells. 2B4 and SLAM associate with a protein termed SLAM-associated protein that is the genetic defect in the immunodeficiency X-linked lymphoproliferative syndrome. Impaired signaling via these receptors may contribute to this often-fatal immunodeficiency.

Antigens, CD↗
PubMed2000

Molecular cloning, gene structure, and expression pattern of pig immunoreceptor DAP12.

Natural killer (NK) cells express receptors for MHC class I that contain immunoreceptor tyrosine-based inhibitory motif (ITIM) sequences in their cytoplasmic domain. Whereas these receptors inhibit NK cell cytotoxicity, certain isoforms of these NK receptors (e.g., KIR2DS, CD94/NKG2C, and Ly49D) do not have ITIMs, but associate with DAP12 and activate NK cell function. We cloned pig DAP12 cDNA from a pig peripheral blood lymphocyte (PBL) cDNA library using human DAP12 cDNA as a probe. The length of the pig DAP12 cDNA is 526 bp and contains an open reading frame of 324 bp. It has 79% identity with the human DAP12 cDNA sequence in the coding region and 73% identity with mouse DAP12 cDNA. The predicted polypeptide sequence of pig DAP12 is 108 amino acids, being composed of a 23-amino acid leader, a 14-amino acid extracellular domain, a 24-amino acid transmembrane segment, and a 47-amino acid cytoplasmic region. The amino acid sequence of pig DAP12 has 74% and 71% sequence identity with human DAP12 and mouse DAP12, respectively. Pig DAP12 has a conserved aspartic acid in the transmembrane region, and two conserved cysteine residues in the extracellular domain. It also contains an immunoreceptor tyrosine-based activation motif sequence in the cytoplasmic region. Genomic organization reveals that pig DAP12 consists of five exons and four introns. Southern blot analysis of pig genomic DNA revealed that DAP12 is a single-copy gene. In Northern blot analysis, DAP12 transcripts were detected in spleen, liver, thymus, and lymph node. DAP12 transcripts are expressed not only in PBLs, but also in granulocytes, macrophages, and monocytes.

Adaptor Proteins, Signal Transducing↗
PubMed2000

2B4-mediated activation of human natural killer cells.

2B4 is a member of the CD2 subset of the immunoglobulin superfamily of cell surface receptors. Other members of this family include CD2, CD48, CD58, CD84, signaling lymphocytic activation molecule and Ly-9. Some of these molecules are activating structures expressed by natural killer cells and T cells. We have recently cloned and characterised the human homologue of 2B4 and found that the cytoplasmic domain of 2B4 can interact with SAP, a signaling adaptor protein that is mutated in the immunodeficiency X-linked lymphoproliferative disease (XLP). Additionally, the natural ligand of 2B4 has been identified as CD48. These findings have facilitated the investigation of the functional role of this receptor-ligand pair, and associated signal transduction pathways, on immune cells. In this study, it was found that the interaction between 2B4 on effector cells and CD48 on target cells induced NK-cell activation, as evidenced by increased cytotoxicity and secretion of IFN-gamma. The responses induced by ligation of 2B4 could be reduced by the co-ligation of inhibitory receptors expressed by NK cells, demonstrating that activation signals delivered via 2B4 can be regulated by the action of certain inhibitory receptors. Because the signalling pathway of 2B4 involves SAP, it is possible that 2B4-mediated NK-cell activation may be compromised in patients with XLP due to mutations in SAP. This may contribute to the phenotype and progression of this disease.

Antigens, CD↗
PubMed2000

The ITAM-bearing transmembrane adaptor DAP12 in lymphoid and myeloid cell function.

DAP12, an ITAM-bearing transmembrane adaptor protein, associates non-covalently with receptors in natural killer (NK) and myeloid cells, and provides signaling function via the Syk and ZAP-70 tyrosine kinase activation pathways. Humans and mice lacking DAP12 (DAP12(-/-)) show normal development of hematopoietic cells. However, DAP12(-/-) humans develop presenile dementia and bone cysts, and DAP12(-/-) mice show impaired immune responses.

Adaptor Proteins, Signal Transducing↗
PubMed2000

NK cell activation: distinct stimulatory pathways counterbalancing inhibitory signals.

A delicate balance between positive and negative signals regulates NK cell effector function. Activation of NK cells may be initiated by the triggering of multiple adhesion or costimulatory molecules, and can be counterbalanced by inhibitory signals induced by receptors for MHC class I. A common pathway of inhibitory signaling is provided by immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in the cytoplasmic domains of these receptors which mediate the recruitment of SH2 domain-bearing tyrosine phosphate-1 (SHP-1). In contrast to the extensive progress that has been made regarding the negative regulation of NK cell function, our knowledge of the signals that activate NK cells is still poor. Recent studies of the activating receptor complexes have shed new light on the induction of NK cell effector function. Several NK receptors using novel adaptors with immunoreceptor tyrosine-based activation motifs (ITAMs) and with PI 3-kinase recruiting motifs have been implicated in NK cell stimulation.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Differential effects of interleukin-3, interleukin-7, interleukin 15, and granulocyte-macrophage colony-stimulating factor in the generation of natural killer and B cells from primitive human fetal liver progenitors.

The regulatory roles of a number of early-acting growth factors on the generation of natural killer (NK) cells and B cells from primitive progenitors were studied. Experiments focused on the contributions of granulocyte-macrophage colony-stimulates factor (GM-CSF) and interleukin-3 (IL-3) to the regulation of the early events of lymphopoiesis.Two progenitor populations isolated from human fetal liver were studied, CD38(-)CD34(++)lineage(-) (Lin(-)) cells (candidate hematopoietic stem cells [HSCs]) and the more mature CD38(+)CD34(++)Lin(-) cells. The effects of different cytokines on the generation of CD56(+)CD3(-) NK cells and CD19(+) B cells were studied in serum-deprived cultures in the absence of stroma.NK cells generated in vitro were able to kill NK-sensitive target cells, expressed NK-associated marker CD161 (NKR-P1A), but exhibited little or no expression of CD2, CD8, CD16, CD94/NKG2A, or killer cell inhibitory receptors (KIRs). Among the cytokine combinations tested, kit ligand (KL) and IL-15 provided the best conditions for generating CD56(+) NK cells from CD38(+)CD34(++)Lin(-) cells. However, either flk-2/flt3 ligand (FL), GM-CSF, IL-3, or IL-7 could partially substitute KL. All of these cytokines also supported the growth of NK-cell progenitors from candidate HSC, with the combination of IL-15, KL, GM-CSF, and FL generating the greatest number of CD56(+) cells. B cells were generated from both progenitor populations in response to the combined effects of KL, FL, and IL-7. Both B and NK cells were generated with the further addition of IL-15 to these cultures. The in vitro generated B cells were CD10(+), CD19(+), HLA-DR(+), HLA-DQ(+), and some were CD20(+), but no cytoplasmic or surface immunoglobulin M expression was observed. In contrast with NK lymphopoiesis, GM-CSF, IL-3, and IL-15 had no effect on the generation of B cells from CD38(-)CD34(++)Lin(-) cells, and GM-CSF inhibited B-cell generation from CD38(+)CD34(++)Lin(-) progenitors. These findings indicate a differential regulation of NK and B lymphopoiesis beginning in the early stages of hematopoiesis as exemplified by the distinctive roles of IL-7, IL-15, GM-CSF, and IL-3.

ADP-ribosyl Cyclase↗
PubMed2000

DAP12-deficient mice fail to develop autoimmunity due to impaired antigen priming.

DAP12 is an ITAM-bearing membrane adaptor molecule implicated in the activation of NK and myeloid cells. In mice rendered DAP12 deficient by targeted gene disruption, lymphoid and myeloid development was apparently normal, although the activating Ly49 receptors on NK cells were downregulated and nonfunctional. To analyze the consequences of DAP12 deficiency in vivo, we examined the susceptibility of DAP12-/- mice to experimental autoimmune encephalomyelitis (EAE). DAP12-/- mice were resistant to EAE induced by immunization with myelin oligodendrocyte glycoprotein (MOG) peptide. Resistance was associated with a strongly diminished production of IFNgamma by myelin-reactive CD4+ T cells due to inadequate T cell priming in vivo. These data suggest that DAP12 signaling may be required for optimal antigen-presenting cell (APC) function or inflammation.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Rapid evolution of NK cell receptor systems demonstrated by comparison of chimpanzees and humans.

That NK cell receptors engage fast-evolving MHC class I ligands suggests that they, too, evolve rapidly. To test this hypothesis, the structure and class I specificity of chimpanzee KIR and CD94:NKG2 receptors were determined and compared to their human counterparts. The KIR families are divergent, with only three KIR conserved between chimpanzees and humans. By contrast, CD94:NKG2 receptors are conserved. Whereas receptors for polymorphic class I are divergent, those for nonpolymorphic class I are conserved. Although chimpanzee and human NK cells exhibit identical receptor specificities for MHC-C, they are mediated by nonorthologous KIR. These results demonstrate the rapid evolution of NK cell receptor systems and imply that "catching up" with class I is not the only force driving this evolution.

Animals↗
PubMed2000

Retinoic acid early inducible genes define a ligand family for the activating NKG2D receptor in mice.

Here we describe a family of GPI-anchored cell surface proteins that function as ligands for the mouse activating NKG2D receptor. These molecules are encoded by the retinoic acid early inducible (RAE-1) and H60 minor histocompatibility antigen genes on mouse chromosome 10 and show weak homology with MHC class I. Expression of the NKG2D ligands is low or absent on normal, adult tissues; however, they are constitutively expressed on some tumors and upregulated by retinoic acid. Ectopic expression of RAE-1 and H60 confers target susceptibility to NK cell attack. These studies identify a family of ligands for the activating NKG2D receptor on NK and T cells, which may play an important role in innate and adaptive immunity.

Amino Acid Sequence↗
PubMed2000

Loss-of-function mutations in TYROBP (DAP12) result in a presenile dementia with bone cysts.

Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL; MIM 221770), also known as Nasu-Hakola disease, is a recessively inherited disease characterized by a combination of psychotic symptoms rapidly progressing to presenile dementia and bone cysts restricted to wrists and ankles. PLOSL has a global distribution, although most of the patients have been diagnosed in Finland and Japan, with an estimated population prevalence of 2x10-6 (ref. 2) in the Finns. We have previously identified a shared 153-kb ancestor haplotype in all Finnish disease alleles between markers D19S1175 and D19S608 on chromosome 19q13.1 (refs 5,6). Here we characterize the molecular defect in PLOSL by identifying one large deletion in all Finnish PLOSL alleles and another mutation in a Japanese patient, both representing loss-of-function mutations, in the gene encoding TYRO protein tyrosine kinase binding protein (TYROBP; formerly DAP12). TYROBP is a transmembrane protein that has been recognized as a key activating signal transduction element in natural killer (NK) cells. On the plasma membrane of NK cells, TYROBP associates with activating receptors recognizing major histocompatibility complex (MHC) class I molecules. No abnormalities in NK cell function were detected in PLOSL patients homozygous for a null allele of TYROBP.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Fc alpha/mu receptor mediates endocytosis of IgM-coated microbes.

IgM is the first antibody to be produced in a humoral immune response and plays an important role in the primary stages of immunity. Here we describe a mouse Fc receptor, designated Fc alpha/microR, and its human homolog, that bind both IgM and IgA with intermediate or high affinity. Fc alpha/microR is constitutively expressed on the majority of B lymphocytes and macrophages. Cross-linking Fc alpha/microR expressed on a pro-B cell line Ba/F3 transfectant with soluble IgM or IgM-coated microparticles induced internalization of the receptor. Fc alpha/microR also mediated primary B lymphocyte endocytosis of IgM-coated Staphylococcus aureus. Thus, Fc alpha/microR is involved in the primary stages of the immune response to microbes.

Amino Acid Sequence↗