Killing of Gram-Negative Bacteria by Neutrophils: Role of O2- Independent System in Intracellular Killing and Evidence of O2-Dependent Extracellular Killing
The cytotoxic capabilities of the neutrophil have long been recognized, particularly in relation to this cell’s function against invading microorganisms (1). Two events central to the mobilization of the cytotoxic function of the neutrophil are: 1) the respiratory burst, a prompt and marked rise in O2 consumption generating, de novo, several toxic metabolites of reduced O2 (2); and 2) degranulation, the fusion of cytoplasmic granules with plasma membrane sites proximate to the target delivering pre-existing cytotoxic proteins into the space surrounding the microbe (3). Both granule proteins and O2 metabolites can be released outside the neutrophil and damage extracellular tissues and large non-ingested cells and parasites (4). However, substantial extracellular killing of bacteria has not been found under normal circumstances. Hence, it is generally believed that intracellular sequestration of the bacterium is required for effective killing by neutrophils (5).
KeywordsOuter Membrane Respiratory Burst Bacterial Killing Intracellular Killing Hexose Monophosphate
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