Search PubMed⌕ Search

Biomedical subjects

T Tadakuma

Publications and source records attributed to T Tadakuma.

At least 37 records · Page 2Linked to original sources
PubMed1995

Single-cell observation of calcium signals in T cells and antigen-presenting cells during antigen presentation.

Intracellular calcium ion mobilization in T-cell hybridomas and antigen-presenting cells (APC) during the interaction was observed using confocal fluorescence microscopy. No calcium signal was detected in non-activated T-cell hybridomas by antigen presentation. However, in activated T-cell hybridomas, intracellular calcium ion concentration rapidly increased by antigen presentation and thereafter apoptosis was induced. On the contrary, during the interaction with T-cell hybridomas, calcium signal was induced in APCs irrespective of the activation of T-cell hybridomas. Chemical modification of APCs with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, which is known to induce T-cell unresponsiveness during antigen presentation, inhibited cap formation of surface MHC class II molecules and suppressed calcium signals during the interaction with T-cell hybridomas.

Animals↗
PubMed1995

Antibody specific for phosphorylated AMPA-type glutamate receptors at GluR2 Ser-696.

Possible phosphorylation sites on the Purkinje cell alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-type glutamate receptor subunits were identified using in vitro kinase assays of 17 synthetic peptides derived from the transmembrane-3 (TM3) domain to the end of C-terminal of a rat glutamate receptor 2 (GluR2). Only two peptides containing Ser-662 and Ser-696 were found to be efficiently phosphorylated by protein kinase C (PKC). The peptide including Ser-696 was also phosphorylated by protein kinase G (PKG). Another peptide containing Thr-692 of a rat GluRA, clone almost identical to GluR1, was phosphorylated by PKC but not by PKG. Antisera recognizing phosphorylated AMPA receptor subunits at GluR2 Ser-696 or the homologous sites of GluR1/3/4 were produced, and the specificity of one of them, named 12P3, was established by enzyme-linked immunosorbent assay (ELISA), immunoblot and immunoprecipitation analyses. 12P3-immunocytochemistry on cerebellar slices demonstrated an AMPA-induced transient AMPA receptor phosphorylation, which appeared in Purkinje cell dendrites as well as somata immediately after AMPA treatment and disappeared after 20 min. This antibody may be a useful tool to study the role of AMPA receptor phosphorylation in producing synaptic plasticity.

Amino Acid Sequence↗
PubMed1995

In vivo function of homing receptors participating in lymphocyte recirculation: transfer analysis in SCID mice.

In order to examine the in vivo function of the adhesion molecules implicated in lymphocyte homing, blocking effects of antibodies against various adhesion molecules on lymphocyte migration were tested in SCID mice into which BALB/c donor splenocytes had been transferred. It was proved that the transferred donor splenocytes migrated to peripheral lymph nodes (LNs) of SCID mice. T and B lymphocytes were distributed in the specialized compartments as seen in the LNs of normal mice. Migration of lymphocytes to the local LNs was accelerated by stimulation with ovalbumin and complete Freund's adjuvant. This experimental system with accelerated migration was applied to analyze the in vivo function of adhesion molecules, and the following findings were obtained. Combined use of antibodies against lymphocyte-function-associated antigen 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1) strongly inhibited the migration of T lymphocytes to the peripheral LNs. Antibodies against very late antigen 4 (VLA-4) and vascular cell adhesion molecule 1 (VCAM-1) led to diminished B lymphocyte migration and disturbed compartmentalization of T lymphocytes in the paracortex. Migration of both T and B lymphocytes to the LNs was completely inhibited by the antibody against L-selectin. These results indicate that L-selectin plays an essential role in migration of both T and B lymphocytes into peripheral LNs but LFA-1/ ICAM-1 and VLA-4/VCAM-1 play different roles in compartmentalization of T and B lymphocytes in the peripheral LNs. In contrast, these adhesion molecules were not involved in lymphocyte migration to the splenic white pulp, indicating that the mechanisms for lymphocyte homing to the white pulp are quite different from those to the peripheral LNs.

Animals↗
PubMed1994

Naive T cells can mediate delayed-type hypersensitivity response in T cell receptor transgenic mice.

We produced transgenic mice expressing T cell receptor-alpha beta chain genes, derived from the chicken ovalbumin (OVA)-specific I-Ad-restricted CD4+CD8- T helper cell clone 7-3-7. In transgenic mice with H-2d genetic background (Tg-d mice), delayed-type hypersensitivity (DTH) was induced in the hind footpad by one inoculation with OVA without any previous sensitization, suggesting that naive T cells have the potential to be involved in DTH response. Spleen cells from nonimmunized Tg-d mice showed a strong T cell proliferative response to in vitro stimulation with OVA. Furthermore, these spleen cells produce cytokines including interleukin(IL)-2, IL-3, interferon-gamma, granulocyte/macrophage colony-stimulating factor, macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta, which may play an important role in the attraction of mononuclear cells to an antigen-challenging site.

Animals↗
PubMed1994

Preferential induction of IL-4 is determined by the type and duration of antigenic stimulation.

The transition of lymphokine production from IL-2 to IL-4 was investigated with antigen-primed lymph node cells (LNC) by observing cytokine release following sequential cycles of antigen exposure in vitro. LNC from mice infected with Nippostrongylus brasiliensis (Nb), Trichinella spiralis, or primed with giant ragweed pollen demonstrated a pattern of dominant IL-2 production at 24 hr; however, there was a switch to predominantly IL-4 production within 72 hr following the first cycle of in vitro antigenic stimulation. In addition, repeated antigenic stimulation with these antigens shifted the pattern to IL-4 production. In contrast, only IL-2 production was observed after a single cycle of in vitro antigenic challenge with haptens (e.g., NP-O-succinimide or trimethylammonium hapten) or the naive allogenic spleen cells. Thereafter, the lymphokine production pattern gradually changed from IL-2 alone to mixtures of IL-2 and IL-4, and finally to predominant IL-4 secretion. In contrast, following priming with purified protein derivatives (PPD), it was difficult to detect IL-4 release even after nine successive weekly stimulations. However, activation of PPD-primed cells with anti-CD3 antibody resulted in IL-4 secretion. Furthermore, Nb-primed T cells, which produced IL-4 alone after repeated antigenic stimulation, produced IL-2 when stimulated in the presence of cycloheximide. These results suggest that (1) immune populations regulate cytokine production, (2) the IL-2/IL-4 profile is dependent on the type and duration of antigenic stimulation, and (3) production or accumulation of cycloheximide-sensitive proteins is critical for the switch from IL-2 to IL-4 secretion.

Animals↗
PubMed1994

Acceleration of diabetes in young NOD mice with peritoneal macrophages.

To elucidate the roles of macrophages in the pathogenesis of NOD murine diabetes, peritoneal macrophages from NOD mice were injected into young NOD mice. We used 12 to 20 week-old NOD mice of both sexes as donors, and sex-matched 2-week-old NOD mice as recipients. Cyclophosphamide (CY), 200 mg/kg, was intraperitoneally injected into the donors. Two weeks later, peritoneal exudate cells (PEC) were collected from the diabetic donors. Macrophage-rich fractions (MRF) were collected by adherence. Then PEC(5-8 x 10(6)) or MRF(3-7 x 10(6)) were transferred, intraperitoneally, to the recipients. Two weeks later, some of the recipients were killed in order to perform immunofluorescent analysis of splenocytes and to assess pancreatic histology. Mac 1 positive splenocytes were increased in PEC- and in MRF-injected recipient mice. Insulitis was seen in PEC- and MRF-injected mice, but not in controls. Some of the recipients were injected with CY, 200 mg/kg, intraperitoneally, at two weeks post cell transfer. Two weeks after CY injection, the animals were examined for the presence of diabetes. The incidences of diabetes were 67% in PEC-injected mice, 40% in the MRF-injected group, and 3% in the controls. These results suggest that peritoneal macrophages accelerate the disease process in NOD mice.

Animals↗
PubMed1994

Improvement of therapeutic effect by using Fab' fragment in the treatment of carcinoembryonic antigen-positive human solid tumors with adriamycin-entrapped immunoliposomes.

To improve the therapeutic efficiency adriamycin entrapped in antibody-conjugated liposomes, Fab' fragment was used instead of the whole antibody molecule. The murine monoclonal antibody, 21B2, against human carcinoembryonic antigen (CEA) was digested with pepsin, and the thiol residue of intra-heavy chain produced by reduction of F(ab')2 with dithiothreitol was conjugated to liposomes containing adriamycin. The tissue distribution of adriamycin delivered with these liposomes was studied in BALB/c nu/nu female mice bearing CEA-positive human gastric cancer strain MKN-45. An increase in delivery of adriamycin to the tumor was observed in the mice given liposomes with Fab' fragment as compared to those given liposomes with whole antibody. However, the preferential distribution of adriamycin in liposomes to the reticuloendothelial cells remained the same regardless of the use of Fab' fragment. For investigation of in vivo therapeutic effect, three i.v. injections of free adriamycin or adriamycin in liposomes equivalent to 5 mg/kg were given, and adriamycin in Fab' fragment-conjugated liposomes was found most effective in the inhibition of tumor growth. This was confirmed in terms of actual tumor weights excised and CEA concentration in the blood, as well as by pathological observations. The advantages of using Fab' fragment instead of whole antibody are discussed.

Animals↗
PubMed1994

[Apoptosis in immunology].

Apoptosis is the physiological cell death, and recent studies have revealed that apoptosis plays an important role in the various fields of immunology. Especially, in the formation of T or B cell repertoires, the cells reactive to self antigens are eliminated by the induction of apoptosis, whereas the cells competent to react against foreign antigens are saved for survival by the suppression of apoptosis. Furthermore, apoptosis is employed as the destruction mechanism of target cells in killer T cells or NK cells. The disturbance of apoptosis-mechanism, therefore, will be strongly relevant for the etiology of autoimmune diseases and carcinogenesis.

Animals↗
PubMed1994

[The role of apoptosis in the development of T cells].

T cells are responsible for the discrimination of self and nonself. To acquire such activities, however, T cells must encounter two selections in the thymus, namely positive and negative selections. Recent data from in vivo and in vitro experiments strongly indicated that apoptosis is involved in these selections, especially in the elimination of the cells reactive to self antigens. This article briefly reviewed the roles of apoptosis in the development of T cells in the thymus.

Animals↗
PubMed1993

Topoisomerase inhibitors induce apoptosis in thymocytes.

The effects of the inhibitors of topoisomerase I and II, camptothecin and etoposide, as well as novobiocin and adriamycin, on the DNA fragmentation and viability of mouse thymocytes in primary culture were examined. All inhibitors were shown to produce dose-dependent internucleosomal DNA cleavage by resolving isolated DNA by agarose-gel electrophoresis. The DNA fragmentation seemed to precede cell death, determined on the basis of LDH release, by a few hours. Etoposide-induced DNA fragmentation progressively increased after incubation and was enhanced by pretreatment with phorbol 12,13-dibutyrate, a phorbol ester capable of activating protein kinase C, whereas camptothecin-induced DNA fragmentation increased progressively after 12 h incubation and was unaffected by phorbol 12,13-dibutyrate-pretreatment. The process was also energy-dependent and required RNA and protein synthesis and protein phosphorylation, since it was inhibited by sodium azide, actinomycin D, cycloheximide and 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine hydrochloride, a protein kinase inhibitor. DNA fragmentation was also inhibited by zinc ions, suggesting the involvement of a specific endonuclease in DNA cleavage. These phenomena are similar to those detected in thymocytes undergoing apoptosis following exposure to glucocorticoids (Cohen, J.J. and Duke, R.C. (1984) J. Immunol. 132, 38-42). Considering that topoisomerases function in cellular proliferation and differentiation by altering DNA topology, the results suggest that topoisomerases have important roles in T-lymphocyte ontogeny in the thymus and are in part involved in the elimination of autoreactive or harmful cells by an apoptotic process.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Tumour necrosis factor-alpha enhances cAMP-induced programmed cell death in mouse thymocytes.

During T-lymphocyte differentiation in the thymus, the majority of thymocytes die by apoptosis in situ. This process is characterized by internucleosomal DNA fragmentation and is induced by a number of stimuli including glucocorticoids, calcium ionophore, cAMP and 12-o-tetradecanoylphorbol 13-acetate (TPA). In this study, the effect of cytokines tumour necrosis factor-alpha (TNF-alpha) and interferon gamma (IFN-gamma) on the programmed cell death of thymocytes was examined by measuring DNA fragmentation and LDH release. TNF-alpha and IFN-gamma had no effect on DNA fragmentation in control and TPA, or A23187-treated thymocytes. Both human and murine rTNF-alpha enhanced cAMP-induced programmed cell death dose-dependently, but IFN-gamma had no effect on the process. TNF-alpha did not stimulate cAMP accumulation in control or 2-chloroadenosine-treated thymocytes. TPA markedly stimulated cAMP-induced DNA fragmentation as a result of 6 h incubation, whereas TNF-alpha did not. Thus TNF-alpha did not appear to activate protein kinase C directly. The effect of TNF-alpha was observed in the cell preparations from which adherent cells had been removed, suggesting that cytokines secreted by adherent cells in response to TNF-alpha are not involved in the process. The enhancement of cAMP-induced DNA fragmentation was observed in CD4+CD(8+)-double positive cells, but not in CD4+CD(8-)-single positive cells. The results of the present study indicate that a physiological cytokine, TNF-alpha, may modulate programmed cell death in immature thymocytes in concert with cAMP.

2-Chloroadenosine↗
PubMed1993

Possible application of the laser in immunobiology.

The human immune system acts a defence mechanism against exogenous or indigenous potentially harmful bodies, such as bacteria and viruses. The major histocompatibility complex (MHC class I and class II antigens) form key elements of legitimate body components, and the organization of MHC molecules allows T-lymphocytes to distinguish between legitimate and foreign bodies. On detection of a foreign component, T-cells activate the necessary pathways for destruction of the foreign body. Occasionally however the system breaks down and the result is a disease of an autoimmune nature. Both visible light and infrared low reactive-level laser therapy (LLLT) has been shown to act on immune system cells in a number of ways, activating the irradiated cells to a higher level of activity. Infrared LLLT has been shown to increase both the phagocytic and chemotactic activity of human leukocytes in vitro, for example. This is an example of photobiological activation. Photobiological cell-specific destruction is also possible using doses of low incident laser energy on cells which have been photosensitized for the specific wavelength of the laser, such as in photodynamic therapy (PDT) for superficial cancers. LLLT has also been shown to act directly and selectively on the autoimmune system, restoring immunocompetence to immunocompetence cells. Although much more research needs to be done, there are enough experimental and clinical data to show that the laser, and LLLT in particular, has a possibly exciting role both in immunobiological therapy for diseases of the immune system, and to activate and boost the normal reaction of the immune system components against harmful foreign bodies.

Animals↗
PubMed1992

Effect of liposomal interleukin-2 on ascites-forming rat hepatoma.

Interleukin-2 was entrapped in liposomes (Lip-IL-2) and injected into rats. The intraperitoneal injection of Lip-IL-2 into rats bearing an ascites-forming rat hepatoma (AH-66) significantly increased the survival time when compared with rats administered free IL-2 or saline-containing liposomes. The number of peritoneal exudate cells (PEC) increased markedly after intraperitoneal injection of Lip-IL-2 and consisted mainly of macrophages. The level of tumor necrosis factor alpha (TNF-alpha) and the intensity of free radicals increased in the ascites at 48 hrs after Lip-IL-2 administration, whereas TNF-alpha was not detected and the intensity of free radicals did not increase after free IL-2 administration. Our findings suggested that entrapment of IL-2 into liposomes enhanced its potential for cancer therapy, presumably by activating macrophages to produce TNF-alpha and free radicals.

Animals↗
PubMed1992

Inhibition of programmed cell death by cyclosporin A; preferential blocking of cell death induced by signals via TCR/CD3 complex and its mode of action.

Cyclosporin A (CsA) is reported to inhibit programmed cell death. We confirmed this by using T-cell hybridomas which are inducible to programmed cell death by activation with immobilized anti-CD3 antibody or with anti-Thy 1.2 antibody. Cell death and DNA fragmentation, characteristic features of programmed cell death, were almost completely blocked by CsA or FK506. To investigate whether CsA inhibits only the cell death through the signals via the TCR/CD3 complex or all of the programmed cell death induced by various reagents, we further established CD4+8+ thymic lymphomas which result in programmed cell death after activation with calcium ionophore, dexamethasone, cyclic AMP or anti-CD3 antibody. It was revealed that CsA could block only the cell death mediated by the TCR/CD3 complex. For the clarification of the site of action of CsA, Ca2+ influx and endocytosis of receptors after stimulation with anti-CD3 antibody were monitored in the presence of CsA, and no significant effects of CsA were observed. Furthermore, prevention of cell death was examined by adding CsA at various periods of time after initiation of culture. CsA was found to exert its effect even when added after 4 h of cultivation, and the kinetic pattern of suppression was similar to that of the suppressive effect on IL-2 production. These observations indicate that in the events of programmed cell death, the major site of action of CsA will not be the inhibition of the immediate membrane events after activation of the TCR/CD3 complex but rather the interference in the function of molecules that transmit signals between membrane events and the activation of genes in the nucleus.

Animals↗
PubMed1991

Modulation of thymocyte apoptosis by isoproterenol and prostaglandin E2.

Isoproterenol and prostaglandin E2 increased cAMP levels in mouse thymocytes transiently, but failed to induce significant internucleosomal DNA fragmentation in thymocytes with a 24-hr incubation. However, these substances showed synergistic interaction with forskolin in the accumulation of cAMP and DNA fragmentation. The addition of 12-O-tetradecanoyl 13-acetate, an activator of protein kinase C, with isoproterenol or particularly with prostaglandin E2 enhanced DNA fragmentation. These results indicate that an increase in cAMP mediated by isoproterenol or prostaglandin receptor is involved in thymocyte apoptosis through internucleosomal DNA fragmentation in concert with a second signal, the activation of protein kinase C.

Animals↗
PubMed1991

Inhibition of growth of rat hepatoma by local injection of liposomes containing recombinant interleukin-2. Antitumor effect of IL-2 liposome.

Human recombinant interleukin-2 (IL-2) was entrapped in liposome, consisting of egg phosphatidylcholine (PC) and cholesterol. The peri-tumor injections of IL-2 liposome inhibited significantly the growth of solid tumor and prolonged the survival time of rats with solid tumors which were induced by a subcutaneous (s.c.) inoculation of AH-66 cells. Immunohistochemical staining of peritoneal exudate cells and tumor tissues revealed a marked accumulation of activated macrophages in and around the tumor tissues induced by the local injections of IL-2 liposome.

Animals↗