Biological activities of murine low-affinity Fc receptors for IgG.
Murine low-affinity Fc receptors for IgG (Fc gamma RIIb 1, Fc gamma RIIb2, and Fc gamma RIII) bind the same IgG subclasses and are not distinguished by available anti-Fc gamma RII/III mAbs (2.4G2). They trigger various biological activities, among which are the internalization of soluble and particulate immune complexes, cell activation, and its regulation. To determine the biological properties of the three murine receptors, each was expressed by stable transfection of corresponding cDNAs in two model cells: the murine lymphoma B cell IIA1.6 and the rat basophilic leukemia cell RBL-2H3. Biological activities of recombinant receptors were triggered with soluble immune complexes or 2.4G2 IgG in IIA1.6 cells, which express no Fc gamma R, and with 2.4G2 Fab or F(ab')2, cross-linked with mouse anti-rat F(ab')2 in RBL, which express rat Fc gamma R. Conditions for studying cell activation and endocytosis in both cell models are described, as are conditions for studying phagocytosis in RBL cells and antigen presentation or regulation of cell activation in IIA1.6 cells. Internalization of immune complexes was triggered by Fc gamma RIIb2 and Fc gamma RIII, but not by Fc gamma RIIb1. Intracytoplasmic sequences required for phagocytosis and endocytosis could be distinguished in Fc gamma RIIb2, but not in Fc gamma RIII. Cell activation was restricted to Fc gamma RIII. Fc gamma RIII-mediated endocytosis, phagocytosis, and cell activation involved the consensus tyrosine-containing activation motif found in the intracytoplasmic domain of the gamma subunit. Regulation of cell activation was induced by both Fc gamma RII isoforms and depended on the same sequence as endocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Bonnerot
C
C
Laboratoire d'Immunologie Cellulaire et Clinique, INSERM U255, Institut Curie, Paris, France.
Daëron
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M
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D002460:Cell Line; D007074:Immunoglobulin G / Q000502:physiology*; D051379:Mice; D051381:Rats; D017452:Receptors, IgG / Q000502:physiology*
D007074:Immunoglobulin G; D017452:Receptors, IgG