Neutrophil activation

Neutrophils are mature immune cells with a very short life in vitro and have a pivotal role in innate immune responses. As typical BD lesions such as pustular folliculitis, pathergy reactions, and hypopyon have significant neutrophil infiltrations, neutrophil functions and activation status have been extensively investigated.1 ,2 Conflicting reports of increased, normal, or decreased basal and fMLP stimulated superoxide productions, phagocytosis, chemotaxis, and neutrophil-endothelial adhesion in BD may reflect the status of clinical activity, in vivo neutrophil activation, drug effects, or just methodological problems of investigating neutrophils.3-9 In a recent study, which showed decreased fMLP stimulated superoxide production in BD and patients with sepsis, consecutive restimulations of prestimulated BD neutrophils produced a smaller increase in superoxide production than in healthy controls, implying a state of in vivo neutrophil preactivation.9 An in vivo “primed” state of neutrophils with a dual signalling system for activating neutrophil oxidase has been suggested previously.10 Agents such as fMLP or the cytokines, tumour necrosis factor α (TNFα) and granulocyte monocyte colony stimulating factor, have been shown to increase tyrosine phosphorylation of various intracellular proteins and to prime neutrophils in vivo without full activation, which might also be the case in BD with its proinflammatory cytokines. In HLA-B51 transgenic mice, a presumed model for BD, the only abnormality seen is increased superoxide …