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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 28 (1988), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: T lymphocytes provide a major line of defence against many protozoan parasites. The aim of this work was to determine the role of T-cell helper/inducer subset (T h/i) in the resistance to Trypanosoma cruzi in a murine model. The imponatance of natural killer (NK) cells in the resistance to the parasite was also evaluated. BALB/c and C57BL/6 mice were injected with either monoclonal antibodies against L3T4, Thy 1.2, NK1.1, or with a polyclonal rabbit antiserum against NK cells (anti-asialo GM-1). The effect of in vivo administration of these antibodies was tested in separate functional assays. Alter antibody treatment, mice were infected with a low dose of T. cruzi in the bloodstream form. Mice depleted of, or reduced in T, T h/i, or NK cell activity all developed higher parasitaemia and had higher mortality than their control counterparts. Mice injected with anti-L3T4 monoclonal antibodies were unable to generate a specific antibody response to the parasite. Treatment of mice with alpha/beta interferon, which is known to boost NK cell activity, resulted in an enhanced resistance to the parasite. Our data indicate that T h/i cells as well as NK cells are of vital importance in controlling parasitaemia and reducing mortality in T. crazi-infected mice. Finally, We also demonstrate that the production of antibodies specific for T. cruzi is strictly T helper cell dependent.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Subclasses of lymphocytes can be separated on gradients of non-toxic polyvinylpyrrolidone-coated colloidal silica (Percoll) by virtue of differential densities. Such gradients can yield functionally active lymphocyte populations after brief centrifugation. Gradients can he generated in a discontinuous step fashion and centrifuged in standard table-top laboratory centrifuges or as self-generating gradients duriny ultracentrifugation. The density medium has low viscosity and can be made isotonic for virtually any use. Gradients have proved useful in both human and experimental animal studies, and high percentage yields allow for separations from small cell numbers. Methods are described for separation of whole blood and lymphotd subpopulations. including blasts stimulated with mitogens or in mixed lymphocyte reactions. The cytotoxic capability of various density fractions was evaluated for mixed lymphocyte culture-induced allogeneic killing and spontaneous, so-called ‘natural’ killer cell activity. The lower density associated with blast transformation allows for significant enrichments of stimulated cells from in vitro cultures. Higher thymidine incorporation, restimulation in mixed lymphocyte reactions, and greater cytotoxic capacity are associated with these‘blast’fractions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 30 (1989), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A massive activation of T cells takes place during the early stages of a Trypanosoma cruzi infection in mice. We present data indicating that substantial amounts of Interleukin 2 (IL-2) are secreted and IL-2 receptors are expressed during the period of increased proliferation (4–7 days post infection). Both concanavalin A-induced proliferation and IL-2 production are markedly decreased later in the acute infection (around 3 weeks post infection). This proliferation cannot be restored by externally added IL-2 Simultaneously, there is a drastic reduction in the number of both high-and low-affinity IL-2 receptors. The reduction is not attributable to the elimination of a particular T-cell population. In vivo administration of recombinant IL-2 failed to improve resistance to T. cruzi parasites as measured by parasitaemia and mortality.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 29 (1989), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Phosphatidylinositol-specific phospholipase C (PI-PLC) treatment of the human natural killer (NK) target cells Molt-4, Jurkat, and U937 reduced their susceptibility to killing by human NK cells in a dose-dependent fashion. This indicates that a cell surface Structure, anchored by a glycosyl-Phosphatidylinositol (G-P1) moiety, is important in NK cytotoxicity. In contrast, another common NK target cell line, K562, remained susceptible to NK killing after enzyme treatment, suggesting that distinct target structures are expressed by this cell line. PI-PLC treatment of Molt-4 cells also reduced their sensitivity to human lymphokine activated killer (LAK) cells, suggesting that NK and LAK cells share common specificity in the killing of Molt-4. In contrast, PI-PLC had no effect on the killing of the LAK target cell line. Daudi, which is only weakly sensitive to unactivated NK cells. Killing of a variety of murine target cells by murine NK cells was not affected by PI-PLC treatment, but cross-species killing of Molt-4 by murine NK cells was inhibited by PI-PLC, suggesting a common mechanism in the killing of this human target cell line. The PI-PLC treatment of effector cells from either species did not reduce their NK activity. The reduction in sensitivity of the Molt-4, Jurkat, and U937 target cells probably results from a loss of a target specific G-PI linked membrane molecule, but other possible explanations for these results are also discussed.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The impact of five pigment mutations in the mouse on natural killer (NK) activity was examined in inbred strains congenic for the respective mutation. Whereas the nature of pigmentation disorder was similar in the five mutant strains (beige, pallid, reduced pigmentation, pale ear, and sepia), all mutations except sepia also led to a significant change in lysosomal enzyme activities in the kidney. A significant reduction in NK activity was observed in the four strains with lysosomal impact, whereas homozygous sepia mice displayed normal NK activity. The pigment mutations analysed are located on different chromosomes and fail to cross-interact negatively with each other in the heterozygous mice. This would indicate that pigment mutations with a parallel impact on lysosomal enzyme activities probably always result in a reduction in natural killer cell activity.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 31 (1990), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Male CBA/SU mice were exposed to ionizing radiation by intraperitoneal injection of the boneseekiag β-emitter 90Sr, NK-cell lytic activities in spleen, peripheral blood, and lymph nodes were severely depressed or completely abolished. In contrast, production of the NK regulatory proteins alpha interferon (IFN-x) and interleukin 2 (IL-2) was normal 5–8 weeks after 90Sr injection. IFN-x, produced in vivo or in vitro by cells from injected mice, was able to enhance strongly NK lytic activities. These data indicate that 90Sr acts on the bone marrow, where it interferes with ihe maturation and seeding of NK precursor cells. The mechanisms regulating NK activities in peripheral organs remained relatively unchanged. Finally, we did not detect any major organ redistribution of NK cells as a result of 90Sr irradiation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 12 (1980), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The enhancement of the lytic capacity of mouse splenic ‘natural killer’ (NK) cells by interferon has been studied in vitro as a model for NK cell differentiation from inactive immediate precursors. We show that the increased cytotoxicity is a function of interferon concentration, and that two stages in the NK cell differentiation pathway can be distinguished. The first, very brief, can he performed at 0°C and without protein synthesis and probably corresponds to the fixation of interferon on its cell surface receptors. The second, resulting from the inductive signal given by interferon, proceeds for several hours and requires both RNA and protein synthesis. Our results also indicate that target cells for interferon-induced cytotoxicity are cells for interferon-induced cytotoxicity arc cells with ‘null’ characteristics, similar to the mature NK cells. Finally, they suggest that no soluble Intermediary factor other than interferon is involved in the enhancing of NK cell cytotoxicity.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 41 (1995), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The expression of lymphokine genes during infection of virulent (Tulahuén) or mild (CA-I) strains of T. cruzi was studied in mice lacking CD4 and/or CD8 molecules. The increased susceptibility of CD4− and CD4−CD8− mice to infection with CA-I or Tuiahuen was parallelled by diminished IFN-γmRNA levels. Nitric oxide release and inducible nitric oxide synthase mRNA accumulation by cells from Tulahuen infected CD4− mice was also diminished. CD8− (but not CD4−CD8− mice) showed an increased IL-4 and IL-10mRNA accumulation upon infection with both strains of T. cruzi. A Th2-like’ response (higher IL-4 and IL-10mRNA to IFN-γmRNA ratio), was also observed when cells from non-infected CD8- mice were stimulated with T cell mitogens.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 40 (1994), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In the present study we describe the production and characterization of a panel of monoclonal antibodies (MoAbs) directed against cruzipain (Crz), the major cysteine proteinase from Trypanosoma cruzi. The five MoAbs, BD6, BF2, CG2, CH8, and DC10 were analysed with respect to affinity and specificity. None of the MoAbs cross-reacted with papain, which has regions of high homology with Crz. Treatment of the antigen with periodate did not affect the binding of the MoAbs. suggesting that they bind to the polypeptide moiety of Crz. CH8 recognized a continuous epitope located at the C-terminal extension of the proteinase that appeared to be highly immunogenic. Although the rest of the MoAbs recognized epitopes located in the catalytic domain, the enzymatic activity of Crz was not impaired by the binding of the MoAbs. Characterization of the antibody-binding sites revealed the presence of at least four separate epitopes.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 37 (1993), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have studied the expression of IFN-γ, IL-2 and IL-2 receptor (IL-2R) at the mRNA and protein levels in spleen and lymph node cells from Trypanosoma crizi-infected BALB/c mice. At 21 days post infection (dpi) (peak of parasitaemia), spleen cells stimulated with Con A for 16 h showed a reduced IFN-γ, IL-2 and IL-2R mRNA production compared with non-infected controls. Lymph node cells obtained at 4, 21 or 60 dpi produced similar amounts of IFN-γ, IL-2 or IL-2R transcripts after mitogen stimulation as uninfected controls.Spleen cells obtained at 21 dpi showed a lower Con A proliferative response and IL-2R expression compared with non-infected controls, while the proliferation and IL-2R expression of lymph node cells at 21 dpi was unaltered. Supernatantsfrom 48 h Con A-stimulated spleen and lymph node cells from mice at 21 dpi had very low levels of IL-2 but contained significantly higher levels of IFN-γ compared with the supernatants of cells from non-infected mice. The latter phenomenon correlates with an accelerated rate of IFN-γ mRNA accumulation.
    Type of Medium: Electronic Resource
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