Independent trafficking of flavocytochrome b558 and myeloperoxidase to phagosomes during phagocytosis visualised by energy ‐filtering and energy‐dispersive spectroscopy‐scanning transmission electron microscopy

Summary When polymorphonuclear leukocytes (PMNs) phagocytose opsonised zymosan particles (OPZ), free radicals and reactive oxygen species (ROS) are formed in the phagosomes. ROS production is mediated by NADPH oxidase (Nox), which transfers electrons in converting oxygen to superoxide (O2−). Nox‐generated O2− is rapidly converted to other ROS. Free radical‐forming secretory vesicles containing the Nox redox center flavocytochrome b558, a membrane protein, and azurophil granules with packaged myeloperoxidase (MPO) have been described. Presuming the probable fusion of these vesicular and granular organelles with phagosomes, the translation process of the enzymes was investigated using energy‐filtering and energy‐dispersive spectroscopy‐scanning transmission electron microscopy. In this work, the primary method for imaging cerium (Ce) ions demonstrated the localisation of H2O2 generated by phagocytosing PMNs. The MPO activity of the same PMNs was continuously monitored using 0.1% 3,3′‐diaminobenzidine‐tetrahydrochloride (DAB) and 0.01% H2O2. A detailed view of these vesicular and granular structures was created by overlaying each electron micrograph with pseudocolors: blue for Ce and green for nitrogen (N). Lay description Energy‐filtering transmission and energy‐dispersive spectroscopy‐scanning transmission electron microscopic observation of free radicals formed in human leukocytes engaged in phagocytosis When polymorphonuclear leukocytes (PMN) perfo...
Source: Journal of Microscopy - Category: Laboratory Medicine Authors: Tags: Letter to the Editor Source Type: research