The plasma membrane of rat peritoneal exudate cells was spin labelled with fatty acid spin probes and structural changes induced by ligand binding to Fc and C3b receptors were followed. Neither antigens, nor monovalent immune complexes were capable of inducing any change. Multivalent ligands, both in soluble and particulate form, and to a lesser extent uncomplexed immunoglobulins were very effective in inducing membrane re-ordering, i.e. a decrease in fluidity. The phase transition region markedly broadened upon binding of multivalent immune complexes, indicating phase separation. There was a time lag of 5-10 min before the onset of lipid re-ordering was observed. We suggest that multivalent binding that is capable of cross-linking surface receptors initiates lateral phase separation and lipid re-ordering due to receptor aggregation.
ASJC Scopus subject areas
- Molecular Biology