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  • 1
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: On activation of cells membrane-associated proteases—including serine esterases known to cleave the third component of complement (C3)—become expressed. In this paper it is shown that as a consequence of this enzyme activity isolated native human C3 added to concanavalin A (Con A)-activated human lymphocytes is cleaved on the surface of the blast cell. This enables the immediate fixation of nascent C3b (C3bx) through its short-lived metastable biinliniisite to Oh acceptors (C3bA's) newly expressed on Con A-stimulaled cells. Aeceptor-bound C3b is detected by the immune adherence rosette formation of the O-treated Con A blasts with the C3b receptor (C3bR)-bearing O. Rh+ erythroeytes (32 ± 4%). The cleavage of C3 and the covalent fixation of C3b are shown to he inhibited hy phenylmethylsulphonyl fluoride and methylamine, respeclively. As a functional consequence of the covalent fixation of C3b to the mitogen-activatcd lymphocytes it is demonstrated that the antibody-dependent cellular cytotoxicity (ADCC) of these cells against O. Rh erythrocytes sensitized with anti-D IgG is significantly enhanced. The C3 specificity of the process and the role of C3bR's of the target cells: are proved. It is postulated that effector cell-bound C3b amplifies ADCC by improving effector cell-target cell contact.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 35 (1992), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The effect of murine IgG isotypes on the gene expression and secretion of the third component of complement (C3) has been studied using the monocytoid cell line P388DI and oil-elicited mouse peritoneal macrophages. It is demonstrated that the binding of IgG2a and IgG2b but not IgG1 and IgG3 augments the biosynthesis of C3 both in the presence and in the absence of the phorbol ester. phorbol myristate acetate in the case of both cell types. The multifunctional cytokine inlerleukin-6 (IL-6) alone reveals no effect on the gene expression of C3, but increases the effectiveness of mouse IgG2a and IgG2b. Confirming the role of FcγRII, a strong up-regulation of C3 gene expression and C3 secretion was found when macrophages were cultured with the F(ab')2; fragment of the FcγRII-specific monoclonal antibody 2.4G2.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 22 (1985), S. 0 
    ISSN: 1365-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Macrophages have been shown to produce C3 and to hear Fc receptors (FcR). and besides The various C3 receptors, they possess C3b acceptors (C3bA) as well as surface proteases capable of cleaving C3. Using the immune adherence method, we demonstrated that the amount of covalently fixed (i.e., C3bA-bound) C3h is markedly increased upon cell stimulation by phorbol myristate acetate or aggregated IgG. even in the absence of C3. The enhancement of nascent C3b (C3bx) binding to C3bA on these cells could be reversed by inhibiting the process at different stages, using either cycloheximide. phenyl-methyl-sulphonyl-fluoride, salycil hydroxamic acid, or methylamine. On the basis of our present results and earlier results, we propose a self-regulatory mechanism by which activated. C3-producing macrophages cleave C3 by their surface proteases. C3bx generated in this way fixes covalently to C3bA of the producer cells, resulting in the inhibition of FcR on these cells.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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