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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 14 (1981), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: IgM antibodies have previously been reported to either inhibit or induce antibody-dependent lymphocyte cytotoxicity (ADCC). Here we show that human lymphocytes lyse bovine erythrocytes (Eb) in the presence of either IgM or IgG anti-Eb from rabbits. Seven out of 20 IgM preparations (Sephadex G-200) were ADCC-active. IgG-dependent ADCC was inhibited by human IgG but not by IgM. In contrast, IgM ADCC was inhibited by both IgG and IgM. The effector cells in IgM ADCC were a subpopulation of lymphocytes with distinct Fc receptors for both IgG and IgM. Most of them also had sheep erythrocyte receptors. Extensive purification of the ADCC-active IgM antibody preparations indicated that very small amounts of contaminating IgG anti-Eb were responsible for ADCC induction. When purified and ADCC-inactive IgM antibodies were mixed with suboptimal concentrations of IgG antibodies, a strong enhancement of ADCC was found. To achieve enhancement, the two antibody isotypes had to be present on the surface of the same target cells, and the IgM effect was not due to the release of soluble ADCC-enhancing factors. Thus, in this system, IgM antibodies are not capable of inducing ADCC on their own. However, they enhance ADCC by improving the contactual interaction between target cells and a special subset of effector cells.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: To characterize the effector cells (K-cells) in antibody-dependent cellular cytotoxicity (ADCC) against a nucleated target cell (El 4), human peripheral blood lymphocytes (PBL) were fractionated by roseue sedimentation into subpopulations differing in avidity for sheep erythrocytes (E). The fractions obtained were assayed for surface markers, and as a functional T cell marker, for responsiveness to the mitogen leucoagglutinin (La). By depleting PBL of E-receptor-bearing cells (El+), approximately half of the cytotoxic potential was found in the EL+-depleted fraction. While the EL+ fraction had low activity on a per cell basis, it nevertheles contained a significant proportion of the original cytotoxicity. By sequential E-rosetting, fractions binding E with high avidity (EL+), low avidity (EL+) or not at all (E -) were obtained. Both E-binding fractions consisted primarily of T-cells, as judged from their surface marker profiles. Both fractions responded well to La, but with different dose optima. The E- fraction contained primarily B-and null cells and did not respond to La. Significant K-cell activity was foundl in all these fractions. The results show that a significant fraction of the K-cells have receptors for E and these can be of either high or low avidity. Since both EH+ and EL+ fractions respond well to La and contain K-cells, a T-cell origin of the later is suggested. However, whether or not cytotoxicity and La-responsiveness are functions of the same cells remains to be established.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 5 (1976), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract. Treatment of human blood lymphocytes with neuraminidase has previausly been shown to uncover receptors for the A haemagglutinin of the snail Helix pomatia (HP). Neuraminidase-treated lymphocytes were now fractionated on columns charged with large Sepharose particles to which HP had been coupled covalently. HP-receptor negative (HP-) lymphocytes passed the columns while HP-receptor positive (HP+) lymphocytes were retained. The latter cells were eluted by addition of the competitive hapten N-acetyl-D-galactosamine (D-GalNAc). The total yield of cells recovered after fractionation was 60-80% Surface marker studies indicated that there was no selective loss of any of the major lymphocyte subpopulations. The fraction that passed the columns (fraction I) consisted of approximately 10% of all lymphocytes. It contained ˜ 1% HP+ cells and ˜3% of all lymphocytes forming rosettes with sheep erythrocytes (E+ cells) present before fractionation. 50-55% of the lymphocytes in this fraction had surface-bound immunoglobulin (SIg+ cells) and complement receptors (EAC+ cells). Of the SIg+ cells, ˜60% were true B cells while the remaining 40% had IgG adsorbed to their surface. The majority of the B cells were recovered in this fraction. The lymphocytes of this fraction responded poorly to T-cell mitogen but had an enhanced K-cell activity to chicken erythrocytes. Elution of the cells retained on the column with 0.1 mg/ml D-GalNAc gave a fraction II, consisting of, ˜15% of all lymphocytes. This fraction had a mixed composition. The majority of the cells (˜45%) were recovered by subsequent elution with 1.0 mg/ml D-GalNAc. This fraction III was strongly enriched with HP+ and E+ cells (T cells). About 10% of the HP+ cells in this fraction were SIg+. However, on the majority of these cells this surface-bound immunoglobulin was probably externally adsorbed IgG. These HP+-SIg+ cells were also EAC+ and had Fc receptors, as shown by rosette formation with IgG-coated bovine erythrocytes. The lymphocytes of fraction III responded most strongly to T-cell mitogen while their K-cell activity was weak.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 56 (2002), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: We have investigated the possible associations between polymorphisms in two interleukin-1 (IL-1) genes and severity of Plasmodium falciparum malaria in Ghanaian children with cerebral malaria, severe anaemia or uncomplicated malaria and controls. There was no significant difference in genotype and allele frequencies in IL-1β exon 5 or interleukin-1 receptor antagonist (IL-1ra) polymorphisms between the studied groups, suggesting that the two polymorphisms may not be involved in the pathogenesis of severe malaria. When parasitaemias in uncomplicated malaria patients were evaluated, a significantly higher level of parasitaemia was observed among carriers of IL-1β A2 allele as compared with noncarriers of this allele (P = 0.01). The mean parasitaemia in an age-matched asymptomatic group did not reveal such associations. These data suggest that IL-1β exon 5 allele 2 may play a possible role in the clinical outcome of uncomplicated malaria.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 6 (1977), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Thirty-two percent of neuraminidase-treated DA rat spleen lymphocytes and 18% of lymph node lymphocytes possess receptors for Helix pomatia hemagglutinin (HP). Moreover, these HP-receptor-bearing cells can be separated from B cells by affinity chromatography on HP-Sepharose columns. The virtual absence of immunoglobulin (Ig) receptors and the close correlation with reported T-cell content of these lymphoid tissues surest that HP-receptor lymphocytes are probably T cells and that HP may provide a convenient marker, for both the identification and the purification of rat T lymphocytes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Scandinavian journal of immunology 61 (2005), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Iron deficiency has been reported to affect both malaria pathogenesis and cell-mediated immune responses; however, it is unclear whether the protection afforded by iron deficiency is mediated through direct effects on the parasite, through immune effector functions or through both. We have determined cytokine mRNA expression levels in 59 children living in a malaria endemic area on the coast of Kenya who we selected on the basis of their biochemical iron status. Real-time quantitative reverse transcriptase polymerase chain reaction analysis of cytokine mRNA levels of peripheral blood mononuclear cells (PBMC) obtained from these children showed an association between interleukin-4 (IL-4) mRNA levels and all the biochemical indices of iron that we measured. Furthermore, IL-10 mRNA was higher in parasite blood smear-positive children than in blood smear-negative children irrespective of their iron status. This study suggests that IL-4 expression by PBMC may be affected by iron status.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 5 (1976), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract. In this article we present methods for the purification and fractionation of human blood lymphocytes, which have been used in our laboratory to characterize antibody-dependent cytotoxic effector cells (K cells). The assay system consists of highly purified lymphocytes, 51Cr-labelled chicken erythrocytes (Ec) and IgG rabbit anti-Ec in high dilutions. Various ways of comparing K-cell potentials of different lymphocyte preparations in this system are discussed. When purified lymphocytes are partially depleted (60-85% depletion) of cells forming rosettes with sheep erythrocytes (E+ cells), the K-cell activity of the depleted fraction is increased, indicating that the majority of the E+ cells are inactive in this assay. Depletion of EAC-rosette-forming cells shows that most or all K cells have complement receptors. For depletion of B cells, the lymphocytes may be passed through glass bead columns, charged with F(ab')2 fragments of human IgG and F(ab')2 fragments of rabbit antibodies to the F(ab')2 part of human IgG. These columns give high yields of B-cell depleted fractions. These preparations are rich in E+ cells and contain ˜80% of the Fc-receptor lymphocytes which form rosettes with bovine erythrocytes, coated with IgG antibodies. Their K-cell activity is unchanged or slightly elevated, indicating that mature B cells, i.e. SIg+ cells, have little or no K-cell activity. In contrast, passage of the lymphocytes through immune complex columns (ovalbumin/anti-ovalbumin) leads to ˜ 70% depletion of Fc receptor-bearing cells, while most of the B cells (SIg+ cells) pass through the columns. The relative frequency of E+ cells in the passed fraction frequently shows a slight reduction. These preparations have a very low K-cell activity, indicating that K cells are lymphocytes with Fc receptors of relatively strong avidity.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 15 (1982), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: IgM antibodies, by themselves unable to induce human K-cell-mediated cytotoxicity, enhanced the lysis of TNP-coated bovine erythrocytes (TNP-Eh) induced by suboptimal concentrations of IgG antibodies. The antibodies used were directed against either TNP or intrinsic Eb antigens. The best enhancement of antibody-dependent ceal-mediated cytotoxicily (ADCC) was obtained when IgG and IgM antibodies had different specificities. IgM antibodies with specificity similar to that of the IgG antibodies often inhibited rather than enhanced cytolysis. By using 125I-labelled anti-DNP IgG. the number of IgG/TNP-Eb was determined. Under the present conditions, at least 9000 IgG molecules/TNP-Eb were required for K-cell-mediated lysis in the absence of IgM. In the presence of IgM antibody concentrations optimal for enhancement of ADCC, the minimal number of IgG molecules required for induction of ADCC was 30–100 times lower. No enhancement of cytotoxicity was seen with more than the optimal concentration of IgM even when IgG binding to the target cells was not reduced by IgM. This suggested that induction of ADCC was dependent on contiguous IgG-Fc receptor interactions, which were inhibited owing to steric hindrance by excessive amounts of IgM in the critical contact areas between effector cells and target cells.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Experimental Cell Research 13 (1957), S. 475-487 
    ISSN: 0014-4827
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Experimental Cell Research 13 (1957), S. 454-474 
    ISSN: 0014-4827
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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