The increase in intracellular free calcium associated with IgG gamma 2b/gamma 1 Fc receptor-ligand interactions: role in phagocytosis.
The concentration of cytosolic free calcium, [Ca2+]i, was measured in J774 mouse macrophages by use of the fluorescent indicator quin-2. Resting [Ca2+]i was 87 nM. Addition of a number of specific ligands to the immunoglobulin gamma 2b/gamma 1 Fc receptor resulted in a transient increase in [Ca2+]i, the magnitude of which depended on the extent of receptor aggregation. Monovalent ligands gave only a small Ca2+ signal but blocked cell response to subsequent addition of multivalent ligands. Incubation with antibody-coated erythrocytes raised macrophage [Ca2+]i to micromolar levels. [Ca2+]i changes were only partially inhibited by the absence of external Ca2+, suggesting the release of Ca2+ from internal stores in addition to an influx of external Ca2+. These internal stores were not limited to mitochondria. An optimal range of [Ca2+]i was required for phagocytosis. Buffering [Ca2+]i with quin-2 and treating cells with quinine in the absence of external Ca2+ resulted in inhibition of phagocytosis. Increasing [Ca2+]i to micromolar levels with the calcium ionophore A23187 also resulted in similar inhibitory effects. We suggest the involvement of localized cytosolic Ca2+ gradients in generating the signals necessary for phagocytosis.
D000634:Aminoquinolines; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004912:Erythrocytes / Q000502:physiology; D005456:Fluorescent Dyes; D007141:Immunoglobulin Fc Fragments / Q000276:immunology*; D007128:Immunoglobulin Fragments / Q000276:immunology*; D007700:Kinetics; D008264:Macrophages; D051379:Mice; D010587:Phagocytosis / Q000187:drug effects; D011961:Receptors, Fc / Q000502:physiology*; D017452:Receptors, IgG; D013050:Spectrometry, Fluorescence
D000634:Aminoquinolines; D005456:Fluorescent Dyes; D007141:Immunoglobulin Fc Fragments; D007128:Immunoglobulin Fragments; D011961:Receptors, Fc; D017452:Receptors, IgG; D000001:Calcimycin; C035739:Quin2; D002118:Calcium