Development of TVEs was confirmed by scanning electron microscopy. TVEs were disrupted following removal of inductors and biochemical, high-performance liquid chromatography and mass spectrometry investigations were employed to characterize the proteins within the incubation media.
TVE disruption released (a) the granular bactericides lactoferrin, lipocalin, myeloperoxidase, cathepsin G and defensins; (b) energy metabolism enzymes; (c) actin cytoskeleton proteins; (d) S100 proteins; and (e) annexin 1.
The data confirm that TVEs represent a means of secretory bactericide trafficking, where the protrusions fuse with the plasma membrane upon neutrophil adhesion or extend from the cell surface when fusion is impaired. It is proposed that proteins abundantly presented in TVE (energy metabolism enzymes, actin cytoskeleton and S100 proteins, annexin 1) play an important role in fusion of TVE with the plasma membrane.
Our study confirms TVEs as neutrophil secretory protrusions that make direct contacts with cells and bacteria over distance. The membrane-packed content and outstanding length of TVEs might allow targeted neutrophil secretion of aggressive bactericides over a long distance without dilution or injury to surrounding tissues.