Granulocytes without degranulation: neutrophil function in granule-depleted neutroplasts

Abstract

Neutroplasts, which are vesicles consisting of cytoplasm enclosed by plasmalemma, have been prepared and found to be incapable of degranulation in response to f-Met-Leu-Phe. However, neutroplasts generate superoxide anion in response to f-Met-Leu-Phe and PMA, and therefore, degranulation is not essential for superoxide anion generation. In addition, neutroplasts aggregate and show shape changes in response to f-Met-Leu-Phe and PMA, and thus degranulation is not essential for aggregation. Neutroplasts take up the carbocyanine dye DiOC6(3), thereby providing evidence for ionic gradients. Dye-loaded neutroplasts show fluorescence changes in response to a variety of stimuli. This response is not CN--inhibitable; therefore, activation of neutroplasts is associated with changes in membrane potential at the plasmalemma, suggesting a role for ion fluxes in the activation sequence for aggregation and superoxide anion generation.