Koho Iizuka

University of Minnesota Duluth, Duluth, Minnesota, United States

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Publications (14)145.69 Total impact

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    ABSTRACT: NK cell responses are regulated by a balance of inhibitory and activating signals, reflecting the net effect of interactions between receptors and ligands on target and effector cell surfaces. The identification of ligands for orphan NK cell receptors is key to enhancing our understanding of NK cell biology. Here we describe a strategy (protocol) for the identification of ligands for orphan NK cell receptors using signaling reporter cells in combination with a virus rescue system.
    Methods in molecular biology (Clifton, N.J.) 01/2010; 612:285-97. · 1.29 Impact Factor
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    ABSTRACT: NK cells use surface NK receptors to discriminate self from non-self. The NK receptor ligand-binding domain (NKD) has been considered the sole regulator of ligand binding. Using a prototypic murine NK receptor, Ly49A, we show that the membrane proximal nonligand binding ecto-domain (the stalk region) is critical to ligand binding and signaling. The stalk region is required for receptor binding to ligand on target cells (trans interaction), but is dispensable for receptor binding to ligand on the same cell (cis interaction). Also, signaling in a trans manner depends on the stalk region mediating the formation of the immunological synapse. Thus, our data modeling receptor function at the cellular level reveal an essential role for the stalk region as a specific mediator of receptor signal integration, by which NKD-ligand interactions at the interface initiate and deliver information to the spatially separated cytoplasmic domain.
    Proceedings of the National Academy of Sciences 07/2009; 106(27):11264-9. · 9.81 Impact Factor
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    ABSTRACT: Host NK cells can reject MHC-incompatible (allogeneic) bone marrow cells (BMCs), suggesting their effective role for graft-vs leukemia effects in the clinical setting of bone marrow transplantation. NK cell-mediated rejection of allogeneic BMCs is dependent on donor and recipient MHC alleles and other factors that are not yet fully characterized. Whereas the molecular mechanisms of allogeneic MHC recognition by NK receptors have been well studied in vitro, guidelines to understand NK cell allogeneic reactivity under the control of multiple genetic components in vivo remain less well understood. In this study, we use congenic mice to show that BMC rejection is regulated by haplotypes of the NK gene complex (NKC) that encodes multiple NK cell receptors. Most importantly, host MHC differences modulated the NKC effect. Moreover, the NKC allelic differences also affected the outcome of hybrid resistance whereby F1 hybrid mice reject parental BMCs. Therefore, these data indicate that NK cell alloreactivity in vivo is dependent on the combination of the host NKC and MHC haplotypes. These data suggest that the NK cell self-tolerance process dynamically modulates the NK cell alloreactivity in vivo.
    The Journal of Immunology 04/2008; 180(5):3260-7. · 5.52 Impact Factor
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    ABSTRACT: CMV infection is one of the most common complications in immunocompromised individuals, such as organ and bone marrow transplant patients. Both innate and adaptive immune responses are required for defense against CMV infection. In murine CMV (MCMV) infection, strains harboring the MCMV-specific NK cell activation receptor, Ly49H (Klra8), are resistant. In contrast, MCMV infection of mice lacking Ly49H gene causes early mortality due to uncontrolled viral replication. In this study, we report the successful protection of mice from lethal MCMV infection with gene-transferred polyclonal CD8 T cells. CD8 T cells expressing a chimeric receptor comprising Ly49H extracellular and CD3zeta cytoplasmic domains are capable of killing target cells expressing the MCMV protein, m157. CD8 T cells expressing the chimeric receptor protect mice in vivo from lethality in the acute phase of MCMV infection, leading to the establishment of long-term protection. These data provide proof-of-principle evidence that a novel strategy for harnessing CD8 cytolytic function through TCR-independent yet pathogen-specific receptor can result in effective protection of hosts from pathogens.
    The Journal of Immunology 08/2007; 179(2):1122-8. · 5.52 Impact Factor
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    ABSTRACT: Natural killer (NK) cell development in the bone marrow is not fully understood. Following lineage commitment, these cells appear to advance through a series of developmental stages that are beginning to be characterized. We previously reported a selective deficiency of NK cells in a C57BL/6 mouse with a transgenic construct consisting of the cDNA for the Ly49A major histocompatibility complex (MHC) class 1-specific inhibitory receptor driven by the granzyme A gene. This mouse has few NK cells in peripheral tissues with relative preservation of other immune cells, including T and B cells. Herein we demonstrate that these mice have an accumulation of NK cells with an immature phenotype in the bone marrow, consistent with a block at a previously proposed stage in normal NK-cell development. The phenotype is associated with transgenic insertion into Atf2, the gene for the basic leucine zipper (bZIP) transcription factor family member ATF-2. Although analysis of Atf2-null NK cells shows no defect, the transgenic mice express abnormal truncated Atf2 transcripts that may mediate a repressor effect because ATF2 can heterodimerize with other bZIP molecules. The defect is cell intrinsic, suggesting that certain bZIP molecules play significant roles in NK-cell development.
    Blood 03/2006; 107(3):1024-30. · 9.78 Impact Factor
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    ABSTRACT: The natural killer (NK) gene complex (NKC) encodes orphan lectin-like NK cell receptors that may explain uncharacterized NK cell specificities. Unlike other NKC-encoded receptors that recognize molecules with major histocompatibility complex (MHC) class I folds, here we show that mouse Nkrp1d and Nkrp1f bind specific C-type lectin-related (Clr) molecules. Nkrp1d mediated inhibition when recognizing Clrb, a molecule expressed in dendritic cells and macrophages. Nkrp1 (official gene name, Klrb1) and Clr are intertwined in a genetically conserved NKC region showing recombination suppression, reminiscent of plant self-incompatibility loci. Thus, these findings broaden the 'missing-self' hypothesis from solely involving MHC class I to including related NK cell receptors for lectin-like ligands, and reflect genetic strategies for biological self-recognition processes in other species.
    Nature Immunology 09/2003; 4(8):801-7. · 26.20 Impact Factor
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    ABSTRACT: Mouse NK cells express inhibitory NK receptors that recognize target cell MHC class I molecules and activation receptors that are less well defined. The Ly-49D activation receptor on C57BL/6 NK cells recognizes Chinese hamster ovary cells and triggers natural killing. In this study, we demonstrate that a Chinese hamster classical MHC class I molecule is the ligand for Ly-49D in a reporter gene assay system as well as in NK cell killing assays. Ly-49D recognizes the Chinese hamster class I molecule better when it is expressed with Chinese hamster beta(2)-microglobulin (beta(2)m) than murine beta(2)m. However, it is still controversial that Ly-49D recognizes H-2D(d), as we were unable to demonstrate the specificity previously reported. Using this one ligand-one receptor recognition system, function of an NK activation receptor was, for the first time, investigated in NK cells that are tolerized in beta(2)m-deficient mice. Surprisingly, Ly-49D-killing activity against ligand-expressing targets was observed with beta(2)m-deficient mouse NK cells, albeit reduced, even though "tolerized" function of Ly-49D was expected. These results indicate that Ly-49D specifically recognizes the Chinese hamster MHC class I molecule associated with Chinese hamster beta(2)m, and indicate that the Ly-49D NK cell activation receptor is not tolerized in beta(2)m deficiency.
    The Journal of Immunology 08/2002; 169(1):126-36. · 5.52 Impact Factor
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    ABSTRACT: Natural killer (NK) cells develop in the bone marrow, but their in vivo stages of maturation, expansion and acquisition of receptors that guide target cell specificity are not well defined. We describe here such stages of development. We also show that developing NK cells actively proliferate at a phenotypically distinguishable immature stage after they have acquired expression of Ly49 and CD94-NKG2 receptors. These studies provide a developmental framework for NK cell maturation in vivo and suggest the possible involvement of the Ly49 and CD94-NKG2 receptors themselves in modulating expansion of NK cell populations with a given NK cell receptor repertoire.
    Nature Immunology 07/2002; 3(6):523-8. · 26.20 Impact Factor
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    ABSTRACT: Natural killer (NK) cells express inhibitory and activation receptors that recognize MHC class I-like molecules on target cells. These receptors may be involved in the critical role of NK cells in controlling initial phases of certain viral infections. Indeed, the Ly49H NK cell activation receptor confers in vivo genetic resistance to murine cytomegalovirus (MCMV) infections, but its ligand was previously unknown. Herein, we use heterologous reporter cells to demonstrate that Ly49H recognizes MCMV-infected cells and a ligand encoded by MCMV itself. Exploiting a bioinformatics approach to the MCMV genome, we find at least 11 ORFs for molecules with previously unrecognized features of predicted MHC-like folds and limited MHC sequence homology. We identify one of these, m157, as the ligand for Ly49H. m157 triggers Ly49H-mediated cytotoxicity, and cytokine and chemokine production by freshly isolated NK cells. We hypothesize that the other ORFs with predicted MHC-like folds may be involved in immune evasion or interactions with other NK cell receptors.
    Proceedings of the National Academy of Sciences 07/2002; 99(13):8826-31. · 9.81 Impact Factor
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    ABSTRACT: Integrin-associated protein (CD47) is a broadly expressed protein that costimulates T cells, facilitates leukocyte migration, and inhibits macrophage scavenger function. To determine the role of CD47 in regulating alloresponses, CD47+/+ or CD47−/− T cells were infused into irradiated or nonconditioned major histocompatibility complex disparate recipients. Graft-versus-host disease lethality was markedly reduced with CD47−/− T cells. Donor CD47−/− T cells failed to engraft in immunodeficient allogeneic recipients. CD47−/− marrow was unable to reconstitute heavily irradiated allogeneic or congenic immune–deficient CD47+/+ recipients. These data suggested that CD47−/− T cells and marrow cells were cleared by the innate immune system. To address this hypothesis, dye-labeled CD47−/− and CD47+/+ lymphocytes or marrow cells were infused in vivo and clearance was followed. Dye-labeled CD47−/− cells were engulfed by splenic dendritic cells and macrophages resulting in the clearance of virtually all CD47−/− lymphohematopoietic cells within 1 day after infusion. Host phagocyte-depleted CD47+/+ recipients partially accepted allogeneic CD47−/− T cells. Thus, dendritic cells and macrophages clear lymphohematopoietic cells that have downregulated CD47 density. CD47 expression may be a critical indicator for determining whether lymphohematopoietic cells will survive or be cleared.
    Journal of Experimental Medicine 08/2001; 194(4):541-550. · 13.21 Impact Factor
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    ABSTRACT: This unit describes the isolation of natural killer (NK) cells from mouse spleen. The basic protocol describes a method for preparing a highly purified NK cell population from mouse spleen by cytotoxic depletion of contaminating cells with selected monoclonal antibodies (MAbs), complement lysis, and density-gradient centrifugation to eliminate dead cells. The advantage of this negative selection process is that the NK cells are not coated with antibody and, therefore, are not at risk of activation by antibody cross-linking. Purity can then be assessed by cell surface phenotype.
    Current protocols in immunology / edited by John E. Coligan ... [et al.] 06/2001; Chapter 3:Unit 3.22.
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    ABSTRACT: Studies of natural killer (NK) cell function in vivo have been challenging primarily due to the lack of animal models in which NK cells are genetically and selectively deficient. Here, we describe a transgenic mouse with defective natural killing and selective deficiency in NK1.1(+) CD3(-) cells. Despite functionally normal B, T, and NK/T cells, transgenic mice displayed impaired acute in vivo rejection of tumor cells. Adoptive transfer experiments confirmed that NK1.1(+) CD3(-) cells were responsible for acute tumor rejection, establishing the relationship of NK1.1(+) CD3(-) cells to NK cells. Additional studies provided evidence that (i) NK cells play an important role in suppressing tumor metastasis and outgrowth; (ii) NK cells are major producers of IFNgamma in response to bacterial endotoxin but not to interleukin-12, and; (iii) NK cells are not essential for humoral responses to T cell-independent type 2 antigen or the generalized Shwartzman reaction, both of which were previously proposed to involve NK cells.
    Proceedings of the National Academy of Sciences 04/2000; 97(6):2731-6. · 9.81 Impact Factor
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    ABSTRACT: Development of natural killer (NK) cells is thought to depend on interactions between NK progenitors and the bone marrow (BM) microenvironment; however, little is known about the molecular signals involved. Here we show that lymphotoxin (LT) provides an important signal for the development of both NK cells and NK/T cells. LTalpha-/- mice show marked reduction in splenic and BM NK and NK/T cell numbers and dramatically impaired NK and NK/T cell function. Mice deficient in either tumor necrosis factor receptor (TNFR)-I or TNFR-II have normal numbers of NK and NK/T cells, implying that neither of the TNFRs nor soluble LTalpha3 is required for development of these cell types. Reciprocal BM transfers between LTalpha-/- and wild-type mice suggest that close interactions between membrane LT-expressing NK cell precursors and LT-responsive radioresistant stromal cells are necessary for NK cell development. When LT-deficient BM cells are incubated with IL-15, NK cells are formed. In addition, LT-deficient BM cells produce IL-15 after activation. Thus, membrane LT appears to deliver a signal for NK cell development that is either independent of IL-15 or upstream in the IL-15 pathway. These results reveal a novel function for membrane LT in NK and NK/T cell development. They also support a cellular and molecular mechanism by which NK cell precursors themselves deliver essential signals, through the membrane ligand, that induce the microenvironment to promote further NK cell and NK/T cell development.
    Proceedings of the National Academy of Sciences 06/1999; 96(11):6336-40. · 9.81 Impact Factor
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    ABSTRACT: The molecular mechanisms underlying target recognition during natural killing are not well understood. One approach to dissect the complexities of natural killer (NK) cell recognition is through exploitation of genetic differences among inbred mouse strains. In this study, we determined that interleukin 2-activated BALB/c-derived NK cells could not lyse Chinese hamster ovary (CHO) cells as efficiently as C57BL/6-derived NK cells, despite equivalent capacity to kill other targets. This strain-determined difference was also exhibited by freshly isolated NK cells, and was determined to be independent of host major histocompatibility haplotype. Furthermore, CHO killing did not correlate with expression of NK1.1 or 2B4 activation molecules. Genetic mapping studies revealed linkage between the locus influencing CHO killing, termed Chok, and loci encoded within the NK gene complex (NKC), suggesting that Chok encodes an NK cell receptor specific for CHO cells. In vivo assays recapitulated the in vitro data, and both studies determined that Chok regulates an NK perforin-dependent cytotoxic process. These results may have implications for the role of NK cells in xenograft rejection. Our genetic analysis suggests Chok is a single locus that affects NK cell-mediated cytotoxicity similar to other NKC loci that also regulate the complex activity of NK cells.
    Journal of Experimental Medicine 01/1999; 188(12):2243-56. · 13.21 Impact Factor

Publication Stats

1k Citations
145.69 Total Impact Points

Institutions

  • 2007–2010
    • University of Minnesota Duluth
      • Medical School
      Duluth, Minnesota, United States
  • 2007–2009
    • University of Minnesota Twin Cities
      • • Division of Hematology, Oncology and Transplantation
      • • Department of Medicine
      Minneapolis, MN, United States
  • 1999–2008
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States
    • Icahn School of Medicine at Mount Sinai
      Manhattan, New York, United States
  • 2002
    • Barnes Jewish Hospital
      San Luis, Missouri, United States