PubMed Health⌕ Search

Biomedical subjects

T Takemori

Publications and source records attributed to T Takemori.

At least 37 records · Page 2Linked to original sources
PubMed1998

Detection of HIV-Gag p24-specific antibodies in sera and saliva of HIV-1-infected adults and in sera of infants born to HIV-1-infected mothers.

Secretory immunoglobulin A (IgA) is known to play an important role in the mucosal defense against a variety of pathogens. Although the role of IgA antibodies during sexual transmission of HIV is not clear, HIV-specific IgA antibodies have been detected in various mucosal secretions of HIV-infected individuals. Using a monoclonal antibody against human IgA, we established an ELISA system to detect anti-HIV p24 IgA antibodies in sera and saliva. We have analyzed the levels of anti-HIV p24 IgG and IgA antibodies in sera and saliva of 107 and 119 adults, respectively, with HIV infection at different clinical stages, and in the sera of 13 infants born to HIV-infected mothers. The level of anti-HIV p24 IgA antibodies was lower in sera and higher in saliva as compared to that of anti-HIV p24 IgG antibodies. Where the percentage of HIV-specific serum antibody-positive cases decreased with disease progression, that of saliva antibody-positive cases increased in AIDS patients. Among the 13 infants born to HIV-infected mothers, 7 infants were HIV-p24-specific serum IgA positive. These sera were negative for anti-HIV p24 secretory IgA, suggesting that some infants develop their own immune responses against HIV infection. Thus, the detection of HIV-specific IgA antibodies, especially in saliva, could be a simple and reliable test for the diagnosis of HIV infection.

AIDS Serodiagnosis↗
PubMed1998

Expression of cellular adhesion regulatory molecule in hepatocellular carcinoma.

Cellular adhesion regulatory molecule (CMAR) enhances the adhesiveness of cells to collagen and laminin and is considered to be a candidate anti-oncogene. The purpose of the present study was to investigate the relationship between the expression of CMAR and clinical features of hepatocellular carcinoma (HCC). Small amounts of liver tissue were obtained from HCC and non-cancerous portions of the liver in 29 patients and from normal liver in seven patients with metastatic liver tumour by biopsy under ultrasound guidance. RNA was extracted with acid guanidinium thiocyanate-phenol-chloroform. Expression of CMAR was assessed by quantitative PCR using beta-actin as an internal standard. A 4 b.p. insertion polymorphism at nucleotide 241 of the CMAR coding region was then investigated using extracted RNA to assess the relationship between the expression of variant mRNA of CMAR and HCC carcinogenesis. The relative expression of CMAR was significantly reduced in HCC compared with non-cancerous and normal livers and had a relationship with certain clinical background factors. The reduced expression of CMAR was thought to be closely associated with the progression of HCC. However, the 4 b.p. insertion polymorphism pattern of CMAR was the same between HCC and non-cancerous liver in all cases in which it was found. These results suggest that progression of HCC may be predicted based on the relative expression of CMAR.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1998

Footprint analysis of the RAG protein recombination signal sequence complex for V(D)J type recombination.

We have studied the interaction between recombination signal sequences (RSSs) and protein products of the truncated forms of recombination-activating genes (RAG) by gel mobility shift, DNase I footprinting, and methylation interference assays. Methylation interference with dimethyl sulfate demonstrated that binding was blocked by methylation in the nonamer at the second-position G residue in the bottom strand and at the sixth- and seventh-position A residues in the top strand. DNase I footprinting experiments demonstrated that RAG1 alone, or even a RAG1 homeodomain peptide, gave footprint patterns very similar to those obtained with the RAG1-RAG2 complex. In the heptamer, partial methylation interference was observed at the sixth-position A residue in the bottom strand. In DNase I footprinting, the heptamer region was weakly protected in the bottom strand by RAG1. The effects of RSS mutations on RAG binding were evaluated by DNA footprinting. Comparison of the RAG-RSS footprint data with the published Hin model confirmed the notion that sequence-specific RSS-RAG interaction takes place primarily between the Hin domain of the RAG1 protein and adjacent major and minor grooves of the nonamer DNA.

Animals↗
PubMed1997

Efficient virus transmission from dendritic cells to CD4+ T cells in response to antigen depends on close contact through adhesion molecules.

Monocyte-derived cultured dendritic cells (DCs) are potent antigen-presenting cells (APCs) and are susceptible to HIV-1Lai infection. Compared to the low level of virus production by HIV-1-infected DCs alone, a level of virus two to three orders of magnitude higher was produced by cocultivation of HIV-1-infected DCs with autologous resting CD4+ T cells in the presence of a nominal antigen. In this coculture system, direct contact of HIV-1-infected DCs with T cells was crucial for efficient virus transmission and subsequent virus production. Blocking of the LFA-1/ICAM-1 or LFA-3/CD2 interaction between these cells substantially reduced virus production, without influence or IL-2 production by activated T cells. In contrast, cell-cell transmission of HIV between non-APCs and activated T cells was not blocked by an antibody against LFA-3. Since a low level of virus production by HIV-infected DCs was upregulated by cross-linking of CD40, it was suggested that not only focal adhesion, but also mutual activation of HIV-infected DCs and T cells through adhesion molecules, may potentiate virus transmission and production and that such activation signals to HIV may be distinct from signals responsible for IL-2 production in activated T cells.

Antigen Presentation↗
PubMed1997

The PU.1 binding site is a cis-element that regulates pro-B/pre-B specificity of Vkappa-Jkappa joining.

We have previously shown that the PU.1 binding motif (GAG GAA) in the 3'-enhancer region in the Ig kappa gene is responsible for the negative regulation of tissue (B/T)-specific Vkappa-Jkappa joining. Here we report that the PU.1 binding site also regulates the stage (pro-B/pre-B) specificity of Vkappa-Jkappa joining. In the substrate with base substitutions in the PU.1 binding motif, recombination took place in both pro-B (B220dull/CD43+) and pre-B (B220dull/CD43-) cells. In the transcriptional regulation, the PU.1 motif acts in a positive manner cooperatively with the nuclear factor-EM5 (or PIP) motif (GAAAAC), which is located 2 bp downstream from the PU.1 motif. Interestingly, base substitutions in the nuclear factor EM5 (PIP) motif did not affect the pro-B/pre-B specificity of Vkappa-Jkappa joining. Thus, the PU.1 motif regulates both temporal and tissue-specific rearrangements, while nuclear factor-EM5 is not involved in the regulation of Ig kappa recombination.

Animals↗
PubMed1997

Accumulation of somatic hypermutation and antigen-driven selection in rapidly cycling surface Ig+ germinal center (GC) B cells which occupy GC at a high frequency during the primary anti-hapten response in mice.

Well-developed germinal centers (GC) contain rapidly dividing surface immunoglobulin-negative (sIg-) B cells (centroblasts), and most of their progeny are sIg+ B cells (centrocytes) in a resting state. It has been predicted that somatic hypermutation occurs in centroblasts, whereas antigen-driven selection takes place in centrocytes. The present analysis indicates that murine GC B cells bearing sIg with specificity for an immunizing antigen are in a rapidly cycling state and increase exponentially in number to occupy spleen GC at high frequency during the 1st week after primary immunization; however, the number of these cells is significantly reduced in the 2nd week of immunization. During that period, these proliferating sIg+ GC B cells accumulate somatic hypermutations with nucleotide exchanges indicative of affinity maturation. These sIg+ GC B cells co-express B7-2, ICAM-1, and LFA-1, and have potent antigen-presenting activity which results in T cell activation in vitro. These observations indicate that the sIg+ GC B cells accumulate somatic hypermutations and undergo antigen-driven selection through proliferation, probably upon activation by T cells. This sIg+ GC B cell population may represent cell cycling centrocytes; however, the possibility that these may represent centroblasts undergoing re-expression of sIg could not be excluded.

Amino Acid Sequence↗
PubMed1997

Mouse germinal center B cells with the xid mutation retain responsiveness to antimouse CD40 antibodies but diminish IL-5 responsiveness.

The germinal center (GC) develops in secondary lymphoid tissues in response to thymus-dependent (TD) antigens. To investigate the molecular mechanism of B cell differentiation in GC, we enriched GC B cells from spleen of TD antigen-immunized wild-type and X-linked immunodeficient (XID) mice, and examined the differentiation of GC B cells into antigen-specific IgG1 antibody-forming cells (AFC) in response to anti-CD40 mAb and cytokines. A significant proportion of freshly purified GC B cells expressed receptors for IL-4 and IL-5. Anti-CD40 mAb sustained the viability of GC B cells and IL-4 co-operated with anti-CD40 mAb for further enhancement of the cell viability. Anti-CD40 mAb and IL-4 were essential for inducing differentiation of GC B cells into antigen-specific IgG1-AFC and IL-5 efficiently enhanced their differentiation. GC B cells with the xid mutation responded for proliferation to CD40 ligation to a lesser extent and for the IgG1-AFC response to anti-CD40 mAb together with IL-4, but they showed impaired responsiveness to IL-5, regardless of enhanced expression of IL-5R in response to anti-CD40 mAb and IL-4. These results suggest that anti-CD40 mAb, IL-4 and IL-5 play a critical role in the differentiation of mouse GC B cells. The GC B cells from XID mice show a functional defect with respect to IL-5-mediated differentiation.

Animals↗
PubMed1996

Activation of mitogen-activated protein kinases via CD40 is distinct from that stimulated by surface IgM on B cells.

CD40 plays critical roles in B cell proliferation and differentiation in response to T cell-dependent antigenic stimulation. It has been suggested that CD40-mediated biological activities are transduced by a CD40 receptor-associated factor, CRAF1 and probably by protein tyrosine kinase Lyn and its substrates, phospholipase C gamma (PLC gamma) and phosphatidylinositol-3 kinase (PI-3 kinase). Here, we describe the novel finding that a mitogen-activated protein kinase (MAPK) extracellular signal-regulated protein kinase (ERK) cascade is involved in CD40 signaling in mouse B cells. Analysis of ERK activities in the B cell lymphoma cell line WEHI 231, which shows an increase in DNA synthesis or arrest of the cell cycle by cross-linking of CD40 or surface IgM (sIgM) cross-linking, respectively, indicated that one of the ERK isoforms, ERK2, was preferentially and rapidly activated after CD40 cross-linking. The CD40-mediated ERK2 activation was comparable to that after sIgM stimulation, although the activity was reduced toward the basal level within several minutes after stimulation. In contrast, ERK1 and ERK2 were activated to a similar extent by sIgM cross-linking, and the activities remained stable for at least 10 min. Furthermore, similar features of differential activation of ERK isoforms were observed in normal resting B cells in CD40 and sIgM signaling. These results suggest divergent regulatory pathways for ERK1 and ERK2 activation, and they support the notion that CD40 signaling may utilize a limited set of elements in the ERK cascade. Co-stimulation of WEHI 231 cells with anti-CD40 mAb rescues the cells from anti-IgM-mediated apoptosis, whereas this co-stimulation resulted in activation of ERK isoforms comparable to that in sIgM stimulation, without a synergistic effect. This result indicates the dominance of ERK activation in sIgM signaling over that of CD40, and it suggests that ERK activation may not be linked to the biological effect that CD40 stimulation in this cell line.

Animals↗
PubMed1996

CD43 expression in a B cell lymphoma, WEHI 231, reduces susceptibility to G1 arrest and extends survival in culture upon serum depletion.

CD43 is a major surface sialoprotein on hemopoietic cells, whose extracellular domain is heavily O-glycosylated. The functional role of CD43 in the hemopoietic system is not fully understood; however, it has been suggested that CD43 may have a role in cell-cell repulsion and in modifying T cell proliferation and activation. CD43 is expressed in immature B cells in the bone marrow, but not by peripheral B cells, except for B-1 B cells and plasma cells. To analyze the biological effect of CD43 in B-lineage cells, we transfected mouse CD43 cDNA into a CD43- B cell lymphoma, WEHI 231, and the growth and survival in culture were compared to those of a parental cell line, human CD8 transfectants, and CD43- revertants established from CD43+ clones. We observed that CD43 expression supported cell growth in culture upon serum reduction, whereas growth of CD43- cell lines was barely detected under this condition. CD43- cell lines accumulated in G1 phase of the cell cycle, and the numbers of viable cells were greatly reduced during culture upon serum depletion, whereas expression of CD43 reduced the susceptibility to G1 arrest and temporarily retarded the apoptotic process, which, in turn, resulted in an increase and maintenance of the number of viable cells in culture. The results suggest that CD43 may have some role in the survival and expansion of B-lineage cells. The biological effect of CD43 was initiated without stimulation by cross-linking and was significantly impaired by replacement of the extracellular domain by the human CD8 extracellular domain. The basis of these regulatory processes is discussed.

Animals↗
PubMed1996

Expression of Vpre-B3 (8HS-20) molecules by alternative RNA processing.

In pre-B cells, mu chains are expressed in association with "surrogate' L chains encoded by the lambda 5 and Vpre-B1 genes. In addition to their association with lambda 5 and Vpre-B1, mu chains in pre-B cells are associated with the products of the Vpre-B3 gene (formerly designated 8HS-20), which display a distinct association with mu chains and biochemical properties in terms of mol. wt, pI value and glycosylation. However, the mechanism of the generation of Vpre-B3 isoforms has been unknown. The present study indicates that the Vpre-B3 gene transcript underwent alternative RNA processing in normal B cells, in a pre-B cell lymphoma and in a mature B cell lymphoma, WEHI 231, that was transfected with the Vpre-B3 genomic clone. Vpre-B3 isoforms were expressed in a WEHI 231 cell line transfected with the Vpre-B3 genomic clone, comparable in biochemical nature to those expressed in a pre-B cell lymphoma. In contrast, expression of one of the isoforms was missing in a cell line transfected with the Vpre-B3 cDNA clone. These results suggest that Vpre-B3 isoforms with distinct biochemical characteristics are derived from alternatively processed Vpre-B3 mRNA.

Alternative Splicing↗
PubMed1995

Suppression of HIV replication in human monocyte-derived macrophages induced by granulocyte/macrophage colony-stimulating factor.

Susceptibility to HIV infection was examined in macrophages differentiated from human monocytes by macrophage colony-stimulating factor (M-CSF) or granulocyte/macrophage colony-stimulating factor (GM-CSF). The replication of macrophage-tropic human immunodeficiency virus type-1 (HIV-1), which was determined by reverse transcriptase (RT) activity, was significantly suppressed in macrophages induced by GM-CSF (GM-type macrophages) but not in those induced by M-CSF (M-type macrophages). Multinucleated giant cells were formed only in M-type macrophages after HIV infection. However, the expression of CD4 molecules on the surface of both types of macrophages was similar and the proviral DNA was detectable in cell lysates of both macrophages, although the amount of proviral DNA in M-type macrophages was higher than that in GM-type macrophages. Many steps have been defined in HIV infection and replication, such as adsorption of HIV to the cell surface, internalization of the viral core into the cytoplasm, uncoating of viral RNA, reverse transcription and integration of proviral DNA into cellular DNA, transcription and translation of proviral DNA, assembly of viral components, and budding of virus particles. Our findings suggested that the suppression of HIV-1 replication in macrophages induced by GM-CSF is mainly due to a disturbance at certain steps of replication after synthesis of the proviral DNA. Thus, the suppression of HIV replication in GM-type macrophages may provide a model of the latency of HIV infection in vivo.

Antigens, Surface↗
PubMed1995

Monocyte-derived cultured dendritic cells are susceptible to human immunodeficiency virus infection and transmit virus to resting T cells in the process of nominal antigen presentation.

The susceptibility of monocyte-derived cultured dendritic cells (DCs) to human immunodeficiency virus (HIV) infection and their role in viral transmission in the immune response were studied in detail. We observed that highly purified cultured DCs were infected with the T-tropic Lai strain of HIV type 1 (HIV-1Lai) via the CD4 receptor, and this was followed by formation of the complete provirus as detected by PCR. HIV mRNAs were transcribed at only low levels, and virus production was undectable; however, the addition of the purified protein derivative antigen of tuberculin and of autologous resting T cells to HIV-1Lai-infected DCs but not to HIV-1Lai-infected macrophages led to massive HIV transmission and production. These data suggest that the interaction of infected DCs with T cells during the normal immune response could play an important role in the activation and expansion of HIV.

Antigen Presentation↗
PubMed1994

Molecular components and assembly of mu.surrogate light chain complexes in pre-B cell lines.

We describe the molecular components, subunit assembly, and cell surface expression of mu-chain complexes in mu+kappa- pre-B cell lines as revealed by two-dimensional gel electrophoresis. The mu-chain complexes of these cell lines contain several previously unreported components, p42(6.4), p39(6.7), p18(8.6), and p14(7.0), in addition to lambda 5, VpreB1, VpreB3 (formerly named 8HS20), MB-1(Ig-alpha), and B29(Ig-beta). These new components are not detected in mu+kappa+ immature B cell lines. The mu-chain associates with lambda 5, VpreB3, and p56(5.0) at an early phase of assembly, preceding the association of other molecules. mu-Associated VpreB3 decreased during assembly as the association of VpreB1 became dominant, suggesting that the change in the ratio of these two VL-like surrogate light chains is involved in the mechanism of assembly. Lambda 5, VpreB1, p56(5.0), p32(5.0), p36(5.5), and p14(7.0) were shown to be expressed on the cell surface in association with mu-chain. The association of the other molecules with mu-chain is most likely restricted to the intracellular compartment. An interaction between VpreB1 and VpreB3 was also suggested. These findings might be important for understanding the function of mu-chain complexes in pre-B cells. A possible signaling mechanism of mu/surrogate light chain complexes is discussed.

Animals↗
PubMed1994

Analysis of function of a human antigen-presenting cell by xenogeneic interaction with mouse T cells.

A human B cell line, ARH, was transfected with a murine major histocompatibility complex class II gene (I-A(k)). One of the transfectants, ARH5.5, which strongly expresses I-A(k) molecules was found to be capable of presenting soluble antigens to I-A(k)-restricted, antigen-specific murine helper T cell (Th) clones. When ARH5.5 was treated with either chloroquine or paraformaldehyde prior to the antigen pulse, it failed to present a protein antigen, ovalbumin, but retained the ability to present a peptide, indicating that the presentation was dependent on processing. The xenogeneic interaction of co-stimulatory molecules on the human antigen presenting cell (APC) and the murine Th cell was assessed by using antibodies against adhesion molecules. We found that the xenogeneic interaction of LFA-1/ICAM-1 acted as a strong co-stimulator of the antigen presentation by ARH5.5, while that of CD2/LFA-3 had only little stimulatory effect. These results suggest that the interaction between some of the adhesion molecules on APC and Th can cross the species barrier. The experimental system presented here is simple and useful for analyzing human APC function, separately from T cell function, especially when the dysfunction of APC associated with viral infection with human tropism is considered.

Amino Acid Sequence↗
PubMed1993

A novel gene product associated with mu chains in immature B cells.

A previously unreported B cell specific gene, which we have named 8HS-20, was isolated from the cDNA library of a pre-B cell clone by subtraction and differential hybridization. This gene is selectively expressed as a 0.75 kb transcript in pre-B and bone marrow-derived B cell lines; a transcript of the same size is also found in bone marrow and, albeit at low levels, in spleen. The deduced amino acid sequence of the 8HS-20 cDNA displayed homology to a B cell specific gene, VpreB-1, and to members of the immunoglobulin supergene family including V lambda, V kappa, VH, TCRV alpha, V beta and CD8. Biochemical analysis using purified antiserum against 8HS-20 oligopeptides indicates that the gene encodes proteins with mol. wts of 13.5, 14, 15.5 and 16 kDa, which associate with mu chains in pre-B cell lines, and that these molecules are expressed concomitantly with VpreB-1 and lambda 5 gene products in the same cell lines.

Amino Acid Sequence↗
PubMed1993

Factors affecting tensile bond strength of composite to dentin.

Five factors which might affect the tensile bond strength of an experimental dentin bonding system to extracted human dentin were evaluated. Flat dentin surfaces of extracted human teeth were cleaned with 0.5 mol/L EDTA and pretreated with 35% glyceryl methacrylate solution. A commercial light-activated composite was then bonded using a commercial bonding agent. The five evaluated factors were: 1) embedding or not embedding the specimens in an epoxy resin, 2) thickness of the specimens, 3) crosshead speed during measurement, 4) storage time of the specimens, and 5) dentin substrate depth. Measurements were made of the bond strengths that resulted from the effects of these varied factors. These measurements were compared to a control group. Only the specimen thickness significantly affected the measured bond strength, and extremely thin specimens (about 1 mm) showed the lowest bond strength.

Composite Resins↗
PubMed1993

The fetal thymus stores immature hemopoietic cells capable of differentiating into non-T lineage cells constituting the thymus stromal element.

Immature hemopoietic cell lines were established by transforming fetal thymocytes in vitro with a ts mutant of Abelson murine leukemia virus. They are positive for c-kit and IL-2R alpha but negative for lineage specific markers. Their TCR and Ig heavy chain genes are in germline configuration, and are expressed as germline gene transcripts. When these cell lines were stimulated in vitro with IL-1 their morphology changed into that of typical macrophages (M phi). Subsequent analysis of a particular clone, which displayed the morphological change at the highest efficiency among established cell lines, indicated that the clone possesses the capacity to differentiate into I-A-M phi capable of secreting several cytokines, and supporting the proliferation of fetal and adult thymocytes in vitro. If their surface markers are considered, their normal counterparts would be present in a minor subset of CD4-CD8- double-negative cells in the thymus in early development. The results raise the possibility that the thymic organ at an early stage of development stores immature hemopoietic cells capable of differentiating into a non-T lineage constituting the thymic stromal elements.

Abelson murine leukemia virus↗