F-Met-Leu-Phe and echo 9 virus interaction with human granulocytes. Changes of cell membrane structure

Biophysical and biochemical methods were applied for investigation of cell membrane properties of human polymorphonuclear leukocytes (PMNs) exposed to the chemotactic peptide N-formylmethionyl-leucylphenylalanine (f-Met-Leu-Phe) and echovirus type 9, strain A, Barty. Steady-state fluorescence depolarization with diphenylhexatriene demonstrated no gross changes of the total membrane fluidity under the different experimental conditions. However, by means of the monomer-excimer technique with pyrenedecanoic acid (PDA), significant changes of the local membrane structure were detected for both agents. As demonstrated by a higher excimer ratio, the membrane area available for the PDA molecules was restricted by f-Met-Leu-Phe. This effect was dependent on the dose and on the time of interaction of the chemotactic peptide. These experimental findings were explained by the formation of functional receptor units ("activated membrane"). Echo 9 virus exhibited the opposite effect, characterized by a higher ratio of monomers, which also depended on the viral dose and the time of virus-PMN interaction. These virus-induced findings were explained by the dissolution of functional receptor units. Consecutive exposure of the PMNs to f-Met-Leu-Phe and echovirus, or vice versa, demonstrated a virus-predominant effect on the membrane structures.