Interactions of immunoglobulins with liposomes: an ESR and diffusion study demonstrating protection by hydrocortisone.

Heat-aggregated IgG, used as a surrogate for immunoglobulin configuration in immune complexes, mobilized a hydrophobic spin probe within bilayers of anionic liposomes, whereas native IgG was ineffective. Hydrocortisone, preincorporated into liposomal bilayers, both prevented the perturbation of nonpolar membrane regions and reduced the accelerated rate of solute diffusion from liposomes provoked by aggregated immunoglobulin. The capacity of aggregated, but not native, IgG to initiate membrane responses of living cells may therefore be due to its ability to alter surface bilayers or similar configurations of plasma membrane Fc receptors, events antagonized by corticosteroids.