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Takaaki Hato

Publications and source records attributed to Takaaki Hato.

17 recordsLinked to original sources
PubMed2006

Cappuccino mutation in an autoimmune-prone strain of mice suggests a role of platelet function in the progression of immune complex crescentic glomerulonephritis.

OBJECTIVE: Crescent formation in the renal glomerulus is a typical manifestation of progressive glomerulopathy associated with fatal renal failure; therefore, its prevention is of clinical importance. Little is known about the pathogenic mechanism for crescent formation. This study was undertaken in an attempt to identify the events that are critical for crescent formation in immune complex crescentic glomerulonephritis (CGN) by analyzing a novel mutant strain of mice. METHODS: A spontaneous mutant strain of mice was isolated from the autoimmune-prone strain EOD, which stably develops fatal CGN. The mutant phenotypes were assessed histopathologically, hematologically, and immunologically. The mutation was searched for with positional cloning using microsatellite markers. RESULTS: Compared with wild-type EOD (WT-EOD) mice, mutant EOD (mut-EOD) mice showed marked improvement in CGN in conjunction with an improvement in spontaneous mortality. In WT-EOD mice, an inverse correlation between blood urea nitrogen concentration and blood platelet count and massive accumulation of platelets in the glomerulus were evident, suggesting that an accumulation of platelets in the glomerulus contributes to the progression of CGN. The mutant platelets showed an abnormal aggregation in response to collagen and thrombin, associated with a bleeding tendency in mut-EOD mice. Genetic analysis revealed a deleterious mutation in the cappuccino gene (cno), which encodes a protein that belongs to a complex called the biogenesis of lysosome-related organelle complex 1 and is profoundly involved in platelet function. Morphologic examination revealed a partial defect in dense body formation in the delta-granule of platelets. CONCLUSION: The present findings suggest that platelet functions have a critical role in crescent formation in autoimmune GN.

Amino Acid Sequence↗
PubMed2006

Human herpesvirus 6 impairs differentiation of monocytes to dendritic cells.

OBJECTIVE: Monocyte-derived dendritic cells (DCs) play important roles in the immune response against infections and malignancies. Human herpesvirus 6 (HHV-6) infects monocytes and is reactivated in immunodeficient patients. To clarify the mechanisms of HHV-6-induced immunodeficiency, we investigated the effect of HHV-6 infection on differentiation of monocytes to DCs. METHODS: Monocytes were inoculated with or without HHV-6 and then allowed to differentiate to myeloid DCs in culture medium containing granulocyte-macrophage colony-stimulating factor and interleukin (IL)-4. The expression of cell surface molecules on DCs and the capacity of the DCs for antigen capture were examined by flow cytometric analysis. Alteration of antigen-presenting capacity induced by HHV-6 infection was examined. RESULTS: The morphology of HHV-6-infected monocyte-derived DCs was distinctly different from that of the DCs derived from mock-infected monocytes. Although expression levels of DC-associated surface antigens, including CD80, CD83, and CD86, were significantly higher on HHV-6-infected monocyte-derived DCs than on DCs derived from mock-infected monocytes, antigen-presenting capacity was significantly lower in the former group. Addition of culture supernatant of HHV-6-infected monocytes resulted in suppression of the T-lymphocyte proliferative response, and anti-IL-10 neutralizing antibody partly inhibited this suppressive effect. The antigen-presenting capacity of DCs generated from a patient with severe HHV-6 reactivation was significantly lower than that of DCs generated from the same patient in the recovery phase. CONCLUSIONS: HHV-6 infection induces immunodeficiency via impaired differentiation of DCs. These results present a new concept for the pathogenesis of HHV-6-induced immunodeficiency.

Base Sequence↗
PubMed2005

Direct recognition and lysis of leukemia cells by WT1-specific CD4+ T lymphocytes in an HLA class II-restricted manner.

Wilms tumor gene 1 product (WT1) has been recognized as an attractive target antigen of immunotherapy for various malignancies including leukemia. Because tumor-associated antigen-specific CD4+ T lymphocytes undoubtedly play an important role in the induction of an antitumor immune response, we attempted to generate WT1-specific CD4+ T lymphocytes in vitro and examined their antileukemia functions. A CD4+ T-cell line, designated NIK-1, which proliferated and produced Th1 cytokines specifically in response to stimulation with the WT1-derived peptide, WT1(337-347) LSHLQMHSRKH, in an HLA-DP5-restricted manner was established. NIK-1 exhibited cytotoxicity against HLA-DP5-positive, WT1-expressing leukemia cells but did not lyse HLA-DP5-negative, WT1-expressing leukemia cells or HLA-DP5-positive, WT1-negative cells. NIK-1 did not inhibit colony formation by normal bone marrow cells of HLA-DP5-positive individuals. This is the first report to describe WT1-specific and HLA class II-restricted CD4+ T lymphocytes possessing direct cytotoxic activity against leukemia cells.

Amino Acid Sequence↗
PubMed2005

Novel RUNX1-PRDM16 fusion transcripts in a patient with acute myeloid leukemia showing t(1;21)(p36;q22).

The t(1;21)(p36;q22) is a recurrent chromosome abnormality associated with therapy-related acute myeloid leukemia (AML). Although involvement of RUNX1 has been detected by fluorescence in situ hybridization analysis, the partner gene has not been reported previously. We identified a novel RUNX1 partner gene, MDS1/EVI1-like-gene 1 (PRDM16), in an AML patient with t(1;21). Alternative splicing of the fusion gene generates five different fusion transcripts. In two of them, the PRDM16 reading frame is maintained in the fusion with RUNX1, suggesting that the RUNX1-PRDM16 gene fusion results in the production of a protein that is highly homologous to the RUNX1-MDS1/EVI1 chimeric protein. It is suggested that PRDM16 and MDS1/EVI1 share a common molecular mechanism for the leukemogenesis of RUNX1-associated leukemia. Characterization of the RUNX1-PRDM16 fusion protein and comparison with the RUNX1-MDS1/EVI1 protein will facilitate the understanding of the mechanisms underlying RUNX1-associated leukemia.

Aged↗
PubMed2005

Differential regulation of perforin expression in human CD4+ and CD8+ cytotoxic T lymphocytes.

OBJECTIVE: Because perforin is an essential cytolytic mediator of cytotoxic T lymphocytes (CTLs), it is important to understand the regulatory mechanisms of perforin expression in CTLs. In the present study, we investigated the relationship between cytotoxic activity, perforin expression, and cell-activated status of CD4(+) and CD8(+) CTLs. METHODS: Herpes simplex virus-specific CD4(+) CTL clones and Epstein-Barr virus-specific CD8(+) CTL clones were established, and their cytotoxic activities were examined in both the activated and resting phases. Perforin mRNA expression was examined by reverse transcriptase polymerase chain reaction quantitatively. Transcriptional regulation of perforin was examined by electrophoretic mobility shift assay. RESULTS: The degrees of cytotoxic activity of CD8(+) CTLs did not differ significantly between the two phases; however, CD4(+) CTLs in the activated phase appeared to be significantly more cytotoxic than those in the resting phase. Similarly, expression levels of perforin mRNA in activated and resting CD8(+) CTLs did not differ significantly, but activated CD4(+) CTLs appeared to express perforin more abundantly than resting CD4(+) CTLs. In addition, it appeared that binding of STAT5 to the perforin gene promoter was increased in activated CD4(+) CTLs compared to resting CD4(+) CTLs; however, there was no significant detectable difference of STAT5 binding activity to the perforin gene promoter between activated and resting CD8(+) CTLs. CONCLUSIONS: The present study has revealed a difference in the control of perforin expression between CD4(+) and CD8(+) CTLs; that is, perforin is expressed constitutively in memory CD8(+) CTLs, but is dependent on cell activation in memory CD4(+) CTLs.

Antigens, CD↗
PubMed2005

Leukemoid reaction in association with bone marrow necrosis due to metastatic prostate cancer.

An 80-year-old man presented to the internist with fever, fatigue and leukocytosis up to 66.8 x 10(3)/microl. Although a chronic myelogenous leukemia was initially suspected, he was diagnosed as metastatic bone marrow tumor with bone marrow necrosis from primary prostate cancer on the basis of the clinical and pathological findings. The serum concentrations of IL-6 and TNF-alpha were mildly elevated to 65.0 pg/ml and, 54.0 pg/ml respectively. It is probable that these humoral factors were partially responsible for the leukemoid reaction although other factors induced by the bone marrow necrosis with bone marrow metastasis of prostate cancer are also likely involved.

Aged↗
PubMed2004

Suppression of integrin activation by the membrane-distal sequence of the integrin alphaIIb cytoplasmic tail.

Integrin cytoplasmic tails regulate integrin activation including an increase in integrin affinity for ligands. Although there is ample evidence that the membrane-proximal regions of the alpha and beta tails interact with each other to maintain integrins in a low-affinity state, little is known about the role of the membrane-distal region of the alpha tail in regulation of integrin activation. We report a critical sequence for regulation of integrin activation in the membrane-distal region of the alphaIIb tail. Alanine substitution of the RPP residues in the alphaIIb tail rendered alphaIIbbeta3 constitutively active in a metabolic energy-dependent manner. Although an alphaIIb/alpha6Abeta3 chimaeric integrin, in which the alphaIIb tail was replaced by the alpha6A tail, was in an energy-dependent active state to bind soluble ligands, introduction of the RPP sequence into the alpha6A tail inhibited binding of an activation-dependent antibody PAC1. In alphaIIb/alpha6Abeta3, deleting the TSDA sequence from the alpha6A tail or single amino acid substitutions of the TSDA residues inhibited alphaIIb/alpha6Abeta3 activation and replacing the membrane-distal region of the alphaIIb tail with TSDA rendered alphaIIbbeta3 active, suggesting a stimulatory role of TSDA in energy-dependent integrin activation. However, adding TSDA to the alphaIIb tail containing the RPP sequence of the membrane-distal region failed to activate alphaIIbbeta3. These results suggest that the RPP sequence after the GFFKR motif of the alphaIIb tail suppresses energy-dependent alphaIIbbeta3 activation. These findings provide a molecular basis for the regulation of energy-dependent integrin activation by alpha subunit tails.

Amino Acid Sequence↗
PubMed2004

Role of CD21 antigen in diffuse large B-cell lymphoma and its clinical significance.

Recent advances in immunological and molecular technology have prompted proposals to change tumour classification and treatment strategies. Cell surface antigens are now easy to access, and tumour origins and clinical characteristics are now readily identifiable. However, in diffuse large B-cell lymphoma (DLBCL), one of the heterogeneous forms of haematological malignancy, the clinical significance of tumour surface antigens has not been well documented. We analysed the tumour surface antigens of 50 tumours from newly diagnosed DLBCL patients by flow cytometry in accordance with their clinical characteristics and followed the patients for a median 3.7 years. Statistical analysis showed that CD21 expression was significantly negatively associated with mortality in DLBCL (CD21 negative versus positive; relative risk = 2.36, P < 0.05). As a result of these clinical observations, we generated CD21-overexpressed (CD21(+)) lymphoma cell lines after gene transfection and analysed tumour cell growth in vivo in immunocompromised mice. Mice challenged with vector-only transfectants and parental cells as controls died within 50 d. In contrast, mice injected with CD21(+) transfectants exhibited significantly reduced tumour growth and 83% survived long term (versus control groups; P < 0.05). Interestingly, all established CD21(+) transfectants (six clones from different bulks) showed homotypic aggregation during in vitro cell culture, and anti-CD21 antibodies did not block this aggregation. Expression of CD21 is strongly associated with increased survival in DLBCL in vivo. CD21 expression may be indirectly concerned with the expression of additional cell adhesion molecules.

Animals↗
PubMed2004

Critical residues for ligand binding in blade 2 of the propeller domain of the integrin alphaIIb subunit.

Ligand binding to integrin alphaIIbbeta3 is a key event of thrombus formation. The propeller domain of the alphaIIb subunit has been implicated in ligand binding. Recently, the ligand binding site of the alphaV propeller was determined by crystal structure analysis. However, the structural basis of ligand recognition by the alphaIIb propeller remains to be determined. In this study, we conducted site-directed mutagenesis of all residues located in the loops extending above blades 2 and 4 of the alphaIIb propeller, which are spatially close to, but distinct from, the loops that contain the binding site for an RGD ligand in the crystal structure of the alphaV propeller. Replacement by alanine of Q111, H112 or N114 in the loop within the blade 2 (the W2:2-3 loop in the propeller model) abolished binding of a ligand-mimetic antibody and fibrinogen to alphaIIbbeta3 induced by different types of integrin activation including activation of alphaIIbbeta3 by beta3 cytoplasmic mutation. CHO cells stably expressing recombinant alphaIibbeta3 bearing Q111A, H112A or N114A mutation did not exhibit alphaIibbeta3-mediated adhesion to fibrinogen. According to the crystal structure of alphaVbeta3, the alphaV residue corresponding to alphaIIbN114 is exposed on the integrin surface and close to the RGD binding site. These results suggest that the Q111, H112 and N114 residues in the loop within blade 2 of the alphaIIb propeller are critical for ligand binding, possibly because of direct interaction with ligands or modulation of the RGD binding pocket.

Alanine↗
PubMed2004

Existence of leukemic clones resistant to both imatinib mesylate and rituximab before drug therapies in a patient with Philadelphia chromosome-positive acute lymphocytic leukemia.

Imatinib mesylate and rituximab are molecularly targeted drugs against the BCR-ABL fusion protein and the CD20 antigen, respectively. Although these drugs have excellent anticancer effects, a major concern is drug resistance. We have investigated the case of a patient with Philadelphia chromosome-positive and CD20+ acute lymphocytic leukemia who acquired resistance to imatinib and rituximab. Imatinib therapy resulted in prompt cytogenetic remission, but resistance developed shortly thereafter. Sequencing of the kinase domain of the ABL gene and allele-specific polymerase chain reaction analysis revealed a point mutation resulting in an E255V substitution that was present before the therapy. After the patient received mild chemotherapy followed by rituximab administration, hematologic and cytogenetic remission was sustained for 5.5 months. The recurrent leukemic cells after the rituximab therapy showed not only the E255V mutation in the ABL gene but also loss of the CD20 antigen due to impaired transcription of the CD20 gene. The results of 2-color flow cytometry analysis showed that a small population of CD20(-) leukemic cells existed before the imatinib therapy. These results suggest that leukemic subclones carrying a genetic perturbation of the targeted molecules for both imatinib and rituximab were present before the therapies. The preexistence of primary resistant clones suggests the inability of combination therapy with 2 molecularly targeted drugs to overcome drug resistance in leukemia.

Aged↗
PubMed2004

Rupture of the gallbladder in a patient with acquired factor VIII inhibitors and systemic lupus erythematosus.

A 54-year-old woman with a 21-year history of systemic lupus erythematosus (SLE) was admitted to the Matsuyama Red Cross Hospital due to subcutaneous and gingival hemorrhaging. She was diagnosed with acquired factor VIII inhibitors based on a prolonged activated partial-thromboplastin time (APTT) and factor VIII inhibitors. Steroid pulse and factor VIII plasma concentrate were administered to her, not long after which she was transferred to Ehime University Hospital due to gallbladder hematoma. Although her APTT and factor VIII activity were improved after treatment with human factor VIII, she died of multiple organ failure. The autopsy demonstrated a ruptured gallbladder.

Autoantibodies↗
PubMed2003

Non-Hodgkin's lymphoma developing in a pacemaker pocket.

A 29-year-old man developed diffuse large B-cell lymphoma in a subpectoral pacemaker pocket that 6 years previously had been created in the chest for a titanium-covered pulse generator. The patient had an 8-cm-diameter dark red tumor with necrotic tissue on a keloidal surgical scar in the left side of the chest. Left axillary lymphadenopathy also was present. Laboratory studies showed an increased level of soluble interleukin 2 receptor and a normal level of lactose dehydrogenase. A biopsy specimen showed a diffuse large B-cell phenotype and monoclonal immunoglobulin H gene rearrangement. A gallium scintigraphy study showed abnormal accumulation in the left chest and left axilla. On the basis of these findings, we diagnosed diffuse large B-cell lymphoma, stage II. The patient received THP-COP chemotherapy (pirarubicin, cyclophosphamide, vincristine, and prednisolone) and radiotherapy, achieved complete remission, and was free of disease for 16 months after treatment. This case suggests that there was a relationship between the development of non-Hodgkin's lymphoma and the presence of chronic inflammation in the pulse generator pocket.

Adult↗
PubMed2003

Mesenteric venous thrombosis in hereditary protein C deficiency with the mutation at Arg169 (CGG-TGG).

A 39-year-old man with no significant medical history was admitted to our hospital with severe abdominal pain and melena. Computed tomographic (CT) scans demonstrated superior mesenteric venous thrombosis. Although thrombolysis and anticoagulant therapy was started immediately, symptoms of strangulation ileus developed. Laparotomy was therefore performed and revealed necrotic stenosis of the ileum. The patient, his father and sisters showed low protein C levels. Direct sequencing analysis of their protein C gene revealed a heterozygous mutation at codon 169 corresponding to the cleavage site of the activation peptide, which was referred to as protein C Tochigi.

Adult↗
PubMed2002

Identification of critical residues for ligand binding in the integrin beta3 I-domain by site-directed mutagenesis.

To define the structural basis of ligand recognition by alphaIIb beta3, we conducted site-directed mutagenesis of residues located on the top surface of the beta3 I-domain that is homologous to the I-domain of several alpha subunits and contains a putative ligand binding site. Here we identify D158 and N215 in beta3 as novel residues critical for ligand binding. Alanine substitution of D158 or N215 abolished binding of a ligand-mimetic antibody and fibrinogen to alphaIIb beta3 induced by different types of integrin activation. CHO cells expressing recombinant alphaIIb beta3 bearing D158A or N215A mutation did not adhere to fibrinogen. These mutations had the same effect on ligand binding to another beta3 integrin, alphaVbeta3. Compared to the alphaI-domain structure, the betaB-betaC loop containing D158 in the beta3 I-domain is quite different in length and sequence. These results suggest that the structure for ligand recognition is different in the betaI- and alphaI-domains.

Animals↗
PubMed2002

[Epstein-Barr virus-associated posttransplant lymphoproliferative disease after renal transplantation].

A 24-year-old Japanese male was admitted to our hospital because of lymphadenopathy in his left neck. He had a nine-year history of chronic renal failure, and had received an ABO-mismatched renal allograft and splenectomy in August 2000 after one year of hemodialysis treatment. After renal transplantation, he was treated with FK506, methylprednisolone (mPSL), and mycophenolate mofetil (MMF) as an immunosuppressants for his graft maintenance. On admission, April 2001, he underwent lymphadenectomy, and the immunohistochemical studies revealed that the tumor cells expressed EBV-LMP and EBNA-2 antigens with the histology of diffuse large B-cell lymphoma. Our diagnosis was an Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disease (PTLD), and we reduced the dose of immunosuppressive agents and treated the patient with rituximab. In this case, there may have been two principal risk factors associated with PTLD: first, the patient was treated with higher levels of immunosuppressive agents because of the ABO-mismatched transplantation, and second, he was an EBV-seronegative recipient at the time of pretransplantation.

ABO Blood-Group System↗