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  • Title: Desensitization of macrophage oxygen metabolism on immobilized ligands: different effect of immunoglobulin G and complement.
    Author: Valletta EA, Berton G.
    Journal: J Immunol; 1987 Jun 15; 138(12):4366-73. PubMed ID: 2953806.
    Abstract:
    During adhesion and spreading to immobilized immune complexes, casein-elicited mouse peritoneal macrophages produced superoxide anion. This production was time-dependent, ceased after a couple of hours, and was due to interaction with immunoglobulins G (IgG) because neither immobilized antigen alone nor immunoglobulins M with or without complement-derived fragments were efficient stimuli. Cultivation of macrophages on immobilized IgG for 24 hr caused desensitization of the response to an unrelated stimulus like zymosan. Desensitization was due neither to inhibition of binding and uptake of zymosan nor to alterations of NADPH oxidase. In fact, macrophages cultivated on immobilized IgG bound and internalized zymosan and responded to PMA with production of superoxide anion normally. Desensitization was not specific for casein-elicited macrophages because both resident peritoneal and Corynebacterium parvum-activated macrophages underwent desensitization if cultivated for 24 hr on immobilized immune complexes. Desensitization on immobilized IgG was maximal after 24 hr, lasted up to 3 days in culture, and was reversed by detaching macrophages from the IgG surface and further cultivating them in normal tissue culture plastic. Scavengers of products of the oxygen metabolism such as superoxide dismutase and catalase and inhibitors of arachidonic acid metabolism such as indomethacin and nordihydroguaiaretic acid did not prevent desensitization. In addition, the zymosan-stimulated release of arachidonic acid was suppressed after cultivation on immobilized IgG for 24 hr; also in this case, the response to PMA was conserved. Contrary to cultivation on immobilized IgG, cultivation of macrophages on fragments derived from C3 was not accompanied by desensitization of the response to zymosan. These results indicate that although the interaction of Fc receptors with their ligands does not impair binding and uptake of zymosan, alterations in the sequence of signals which leads to the activation of the oxygen metabolism can occur, causing a complete dissociation between phagocytosis and stimulation of the oxygen metabolism.
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