Youichi Tatsumi

Kinki University, Ōsaka, Ōsaka, Japan

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Publications (4)24.67 Total impact

  • Choonpa Igaku 01/2007; 34(1):65-68.
  • Akihisa Kanamaru, Youichi Tatsumi
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    ABSTRACT: The pattern of bacterial infections and antimicrobial susceptibility has changed significantly during the past 20-30 years. The causative organisms for bacteremia or fungemia identified at Kinki University Hospital in 1985-1996 were compared with the isolates identified during 1997-2002. The prevalence of gram-negative organisms decreased, whereas the prevalence of gram-positive organisms increased. Staphylococcal species predominated in the second period, accounting for 22% of isolates, and methicillin-resistant Staphylococcus aureus (MRSA) increased from 5% to 14% of isolates. Pseudomonas aeruginosa ranked second, although the prevalence decreased in the second period compared with the first. Candida species were also relatively frequent (11%). Enterococcal species had an 8% prevalence. A comparison of all culture isolates showed that gram-negative isolates still predominated among the general patient population, whereas almost equal prevalence was observed in patients with hematological diseases. MRSA was the organism most frequently isolated in the general patient population, followed by P. aeruginosa. Among staphylococcal species, MRSA accounted for as much as 90% of isolates.
    Clinical Infectious Diseases 08/2004; 39 Suppl 1:S7-S10. · 9.37 Impact Factor
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    ABSTRACT: We systematically examined the repertoire of chemokine receptors expressed by human plasma cells. Fresh bone marrow plasma cells and myeloma cells consistently expressed CXCR4, CXCR6, CCR10, and CCR3. Accordingly, plasma cells responded to their respective ligands in chemotaxis and very late Ag-4-dependent cell adhesion to fibronectin. Immobilized CXC chemokine ligand (CXCL)16, a novel transmembrane-type chemokine and CXCR6 ligand, also directly induced adhesion of plasma cells without requiring G(alpha i) signaling or divalent cations. Furthermore, we revealed consistent expression of CXCL12 (CXCR4 ligand), CXCL16 (CXCR6 ligand), and CC chemokine ligand 28 (CCR10 and CCR3 ligand) in tissues enriched with plasma cells including bone marrow, and constitutive expression of CXCL12, CXCL16, and CC chemokine ligand 28 by cultured human bone marrow stromal cells. Collectively, plasma cells are likely to be recruited to bone marrow and other target tissues via CXCR4, CXCR6, CCR10, and CCR3. CXCR6 may also contribute to tissue localization of plasma cells through its direct binding to membrane-anchored CXCL16.
    The Journal of Immunology 03/2003; 170(3):1136-40. · 5.52 Impact Factor
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    ABSTRACT: Chemokines and chemokine receptors play important roles in migration and tissue localization of various lymphocyte subsets. Here, we report the highly frequent expression of CCR4 in adult T-cell leukemia (ATL) and human T-cell leukemia virus type 1 (HTLV-1)-immortalized T cells. Flow cytometric analysis revealed that ATL and HTLV-1-immortalized T-cell lines consistently expressed CCR4. Inducible expression of HTLV-1 transcriptional activator tax in a human T-cell line Jurkat did not, however, up-regulate CCR4 mRNA. In vitro immortalization of peripheral blood T cells led to preferential outgrowth of CD4(+) T cells expressing CCR4. We further demonstrated highly frequent expression of CCR4 in fresh ATL cells by (1) reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of CCR4 expression in peripheral blood mononuclear cells (PBMCs) from patients with ATL and healthy controls; (2) flow cytometric analysis of CCR4-expressing cells in PBMCs from patients with ATL and healthy controls; (3) CCR4 staining of routine blood smears from patients with ATL; and (4) an efficient migration of fresh ATL cells to the CCR4 ligands, TARC/CCL17 and MDC/CCL22, in chemotaxis assays. Furthermore, we detected strong signals for CCR4, TARC, and MDC in ATL skin lesions by RT-PCR. Collectively, most ATL cases have apparently derived from CD4(+) T cells expressing CCR4. It is now known that circulating CCR4(+) T cells are mostly polarized to Th2 and also contain essentially all skin-seeking memory T cells. Thus, HTLV-1-infected CCR4(+) T cells may have growth advantages by deviating host immune responses to Th2. CCR4 expression may also account for frequent infiltration of ATL into tissues such as skin and lymph nodes.
    Blood 04/2002; 99(5):1505-11. · 9.78 Impact Factor