Fc-mediated binding of IgG to vimentin-type intermediate filaments in vascular endothelial cells.

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Abstract
Vascular endothelial cells bind circulating IgG intracellularly during cell death. All endothelial cells have intracellular binding sites for IgG and these binding sites are exposed to circulating IgG only if the plasma membrane is damaged. The binding sites are located on the cytoskeletal intermediate filaments and can be detected also in other cells containing vimentin-type intermediate filaments. Monoclonal human IgG1 exhibited saturable, high-affinity binding to vimentin-enriched cytoskeletons [of bovine aortic endothelial cells]. Binding was inhibited by Fc fragments but not by Fab, F(ab'')2 or pFc'' fragments, suggesting that the binding site on IgG is located in the C.gamma.2 domain [2nd domain of the constant region of IgG] of the Fc fragment. Binding of IgG to intermediate filaments may be important for the destruction and removal of damaged cells.